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So I'm building a 89er for myself, there is a possibility of a sister ship being built, but really, at my age, and with Covid and wanting to sial with mates around Australia, I'm doning this for me, myself and I along with maybe 6-8 sailing mates (inc females).

I have quite a few people asking whats happening, and 2 of those mates have been sending out photo's of the process, as we go along (about 1 month into it already) and that group of interested parties is getting bigger, so the queastion is do people want me to post it here, if so I can start that, from right back at the design stage, and go right through to the actual build process.     Finished the for-deck on Friday, we start on the cockpit plug today!    Hopefully finish this side of Christmas, just myself and Alex (my youngest son) are building it!    Few mates will jump in, when we need extra hands!

        jB

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Agreed. The 20+ Footer from Hawaii has been a popular thread because we all love the build process.

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Looking forward to follow your building process Julian. I have always loved the 89er and would love to build one myself given the chance.

 

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Julian, in case you need reinforcement that it's a good idea, look at the stats of the 20+ Footer from Jim Donovan.  745 replies, mostly Jim, 125,000 views.  It blows away most of the threads.  Free advertising.

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The one thing I don't need is free advertising and I am not contemplating even considering building another.   All ready been asked once and politely refused.

It's just not on my play list for the next 5 year, got way more than I could hope to have already.

This is very very much for me, myself and I!

But the inner circle that it's going around top has spread to about 40 people already and my mate in Adelaide, suggested I do this, so give me a few days, got a bit on, Wednesday is my sailing day so I should have some free time then.

But I'm spraying the cockpit plug today!

                jB

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The stuff is known as Basalt Fibre, but Granite is cute!

Glass fibre is just sand melted, Basalt is just Granite melted, same process, it's a very dark brown, almost olive-brown in colour.    Temp to generate Basalt is about double that of glass which is possibly one of the reasons it has a higher MPa.

It all started 2-3 years ago when I started looking into Flax, and it's impressive also, I happened to be invited to Albert Eisenstein’s supposedly favourite cafe in Zurich and this super cool guy told me all about Flax, and I tried a bit, initially in a 49er centreboard and it was impressive.

But something when wrong, possibly a 3rd party and I started looking around at other options (trying to reduce or remove the use of Carbon, because unless you get huge longevity out of it, it's really not very GREEN) anyway stumbled onto Basalt, did another 49er centreboard out of it, so if Carbon was good, and Flax was great then Basalt was sensational.    Thing about 49er foil is we define it's bend, everything has to bend so we require it to fall within a range, max and min bend.    All 3 fibre's can easily be used and comply with those bends, lightest was the Flax, Carbon is Carbon but Basalt just took so much abuse, far greater than either Flax or Carbon, so it's potential for longevity is extraordinary.

Then couple that with PET cores, so again being green but also being weight conscious and a tad misery on $$$, by upping the density of the PET, you can almost 1/2ve the weight of the skin's and end up with a tougher (& lighter) laminate.    And that's were, to date, in all our empirical testing, Basalt shines.

Before someone jumps down my throat, Carbon mast, near perfect use of the material, mostly because you can be pretty sure the mast will live and remain competitive for a ridiculously long period of time.   By that, on a boat like a 49er, or a 18teen Carbon mast, 5-6-7 years of sailing 6 days a week, on a Farr 40, 20 years, Farr 30 also 20 years.   Tomorrow I am sailing on Exile, (Farr 40) it has literally just had it's rod rigging replaced for a 3rd time, same mast, 21-22years old, no alloy mast would ever dream of seeing that sort of service.      When I sailed 18teen's we had 3 ALLOY masts with FRP tips, we sailed 4 days a week, and the alloy sections where done and dusted after 4-5 months, we started sailing with the 1st set, in July, we switched them out in September and raced through to February with the 2nd set.   (this was the early 90's)  The idea was if we broke one of our race masts (2nd set) we could grab it's twin (1st set) and be up and going with a mast that was near identical and not trashed.

Carbon boom and Carbon Spinnaker pole are also near perfect and very environmentally logical (because of longevity) use of the material.

But if you want to 1/2ve the amount of resin you need to build a boat, then you had better think about, say Carbon at 450-500gms/m² as a outer skin and be willing to put up with it's brittleness.    Just so people understand 450gms of any cloth thickness (excluding flax which is about 150% thicker) = 0.45mm of skin thickness.   One of the reasons Flax is so good is it's organic and like more things organic it's hollow tubes (thick Nano tubes, but don't by nature).    Exile (Farr 40) has approx. 3mm of outer skin (e-glass), then approx. 20mm of Balsa core, then 2mm of a inner skin.    That's a pretty standard racing laminate.    Most USA based boats would be double that thickness (of laminate, not core)  most racing European boats would be similar, but if you want to push the edges, then you had better get down to what you actually need to handle the loads.     The 18teens we talk of above (early 90s) had a outer laminate of 275gms so approx. ¼ mm thick, I14s have 200gms so less than ¼ mm, 29er has 525gms, so ½ mm thick and is now considered extraordinarily tough, my thinking come from Vivace!

Just to follow this logic, I designed Vivace in 2004 with Martin Billoch, Pierre Gal (the owner/sailmaker) use 20mm PVC foam core and 1 layer of 450gms Carbon on both sides, and that boat is still sailing today and still fetching a premium price.     If you use 450gms of Carbon then you had better expect to use 500-520gms of resin also to "wet it out".  So your total skin weight will end up 1kg/m².    ( In Pierre case, from memory, he did wet lay-up, but it was not Vacuum consolidated, he built the boat, amazingly well on a male open jig.    So he possible ended up at 1.3-1.5kgs/m².)

So a) I am a bit green, I don't have grand kids yet, but if I ever get any then I do worry about what we are doing to the planet (watch this space WRT the 49er/FX) so I really wanted to avoid PVC foam cores and Carbon skins. plus b) Vivace was 8m LOA, this boat, call it Don't Panic for now (because some of the crew are, and I'm a huge fan of Douglas Adams) is 8.5m LOA and as anyone who knows about these things, as you increase length, you increase depth and width and complexity so actual surface area goes up as  x³ law, it's not linear,  so I needed to get that skin weight down, and I need toughness, so I am investing in closed male plugs/moulds that are capable of Vacuum consolidation, and I have decide to use a 2 stage PET core, so the outer core is 3.5mm thick and P115 (115kgs/m³) and a inner core under the chine of 20mm thick P80 (80kgs/m³), so my outer skin/core density is P115 (rather than P80, and this is also either a x², possibly a x³ law) which has allowed me to reduce the skin laminate from what say the S8's used which was well over 1200gms/m² (with a corresponding 1600gms or resin) down to 200gm S-glass with a 370gm Basalt (twill) on the outer skin and a single layer of 370gm Basalt (Bi-Axial) as the inner layer.

We have built to date, the breast hook, the fore-deck and 2 flat panels, and all the weights are a little below target, so we are achieving or weights / m² which is really gratifying, the fore-deck which is the "full-monte" (so all s-glass/basalt, 3.5mm, 10mm and more basalt double sucked, is stupidly strong and stiff and tough),  I think it came in at 26kgs, that includes peel-ply, excess and Unies.     Target was 22.52kgs plus approx. 3kgs of unies, surface area is 6.88m²    (Peel-ply is about 220gms and soaks up about 300gms of resin/m²)

I am very big on empirical testing, we developed this ball peen hammer test, so what it is, you have a simple ball peen hammer on a pivot, you lift it up to a desired height and you let swing down and hit a panel that is mounted vertically just as the ball part of the hammer passed vertical.

You then put a test sample in front of the apparatus and count how many "swings" it takes before you get surface deformation, you then replace that test sample with another and count the next tranche of swing and so on.    Pretty basic stuff.     And my laminate not only "twangs" when you hit it (rather than thuds), it's about double the number of swings.

WRT the use of (or not) of Carbon in the hull.    Re rig loads, a extra 300mm wide layer of 300gm Unie locally around the chainplate negates any possibly disparity in MPa, if you actually think about the bit of wire (shroud (or Dynema)) and it's surface area, and then compare that to the amount of material available in the hull to resist that pull, it's a very lop-sided comparison, even if you have 1200gms of e-glass (most boats have 3000gms).     In terms of skin stiffness, thickness trumps MPa ever day of the week.    Pierre’s boats was 20-21 mm  mine is will be 23.5-25mm.    20.5² = 420,  24.25² = 590 so it's 150% up just as a starting point.

Glass is approx. 270 (MPa x 000???), S-Glass is about 420, Basalt is about 480 and Carbon is about 720, so sure, carbon would be marginally stiffer, but I will be infinitely tougher and last a lot longer, be less twitchy, (be far less expensive (about 1/2)) and I will be using PET (so net negative WRT environmental issues) and Basalt which is green, all the while using approx. 1/2 the resin which has to be better than using more.

Very happy with where I am at!

                jB

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Super interesting! Thank you!

However, is my understanding correct, that the 'green' of the basalt is mainly in longevity and additional strength compared to glass and carbon? Is it still better when factoring in the 2x energy use to produce it compared to glass? Sorry, probably a difficult question to answer.

Is the basalt recyclable?

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Correct, Basalt probably takes more energy than E-glass to make, probably similar energy to S-Glass to make and likely to be far less energy than Carbon to make.

All the fibres have similar UTS, what Carbon has is elongation or streach down around 0.7 - 1.5%, Basalt its between 1.5 -2.2%, S-Glass is 2 - 3% and E-glass it's upwards of 7%.   Now this is all from memory, and if someone can "refine those numbers" go for it.

Into that equation is the fact that if you plan to make a boat using minimal scantlings, in this case 570gms (200gm S-Glass + 370gm Basalt) outer skin then at that weight E-Glass really is not a option.   A 49er has about that weight of E-Glass on the outer surface (564gms/m²) and it weighs 275kgs all up, panel sizes are 1/4 or 1/8 of the size (and it's a x² law) and a well kept 49er stays Gold fleet competative for 3-4 years, and then has double that again as a silver fleeter (the 2008 Gold Medal boat is at my club, and is still just OK).     So if I want to build a hull using similar outer skin weigh, carrying 4 times the weight, traveling often at similar speeds, on panels double or 4 x the size, then E-glass is not a option.

So we have started this conversation mid way, really need to go back to the begining as to why we are building what we call a Sportsboat.

Let me go back to that, and then work forwards to your queastion so you get my thinking.

             jB

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2003 – 2014 I spent a lot of it towing Trilogy around Australia, 32ft Tri, 2.5 tonnes, tandem wheel electric braked trailer behind a Jeep Laredo.   Initially we needed a crane to get the 48ft mast up, but later we devised a A frame, but it still took all 4 crew 6 hrs to assemble it.

Also in 2004 Martin Billoch and I designed Vivace, a 8m Sportsboat that did rather well.

2006 Martin and I teamed up again and designed the SKUD that went on to become the Parra Olympic “lead assisted” skiff.

2017, my partner in “sailing” crime GT [Graham Turner] also a ex-skiffie brough a Farr 30, and after a rather successful season sailing it in the Super 30 series that happens on Sydney Harbour, a rush of blood to the brain, we all decide to sail the Farr 30 at Magnetic Island (2018).    That’s when reality hit the pavement.   Crane the mast out and then Sling the boat out at Hunters Hill in Sydney ($$$$$) Get it towed by a truck to Townsville, 35hr drive ($$$$$) the reverse in Townsville, Sling it in, then crane the mast in.  ($$$$$), 5 days sailing, but it was fabulous fun, we won Div 4 against mostly 40ft boats, so much fun we booked the same accom for the next 5 years. But then back to Townsville Sling & Crane ($$$$$) Truck back to Sydney ($$$$$) Sling and Crane at Hunters Hill ($$$$$) so we decided never to do that again.   As it was GT was offered a stupid price, so he sold the Farr.

2019 Maggie, we chartered a FE28R, much simpler, infinitely cheaper, lots of fun but a bit pedestrian.

GT was not finished buying boats, Hick 30 (for the Super 30 series) and a Thompson 8, ostensibly to do Maggie with, we called it “6 Pac” and latter a Fokboat.

On the way to Maggie  (2021) in Brisbane where the Sportsboat National Championships, so why not, we were going to be taking the boat through Brissy on the way to Maggie anyway.

As it turned out we won, but Covid struck. Maggie was cancelled and the boat is still in Brissy and has been there now for 12 weeks and we have no access.   To add to all that GT got elected to be the VP of the ASBA.   (Australian Sports Boat Association)

But that was a real eye opener, I have a very basic, ex-air-force Ford Territory with a 2.6lt Turbo Diesel.  6 Pac weighs 770kgs, and we tow it on a single axel, surge brake trailer. Brisbane is a 10 hr drive nth of Sydney, and the Territory did it without even breaking a sweat, let alone slowing down going up the hills, sat on 110kph the whole way, effortless drive.  Arrived early afternoon, then 3 of us basically rigged it in 2 ½ - 3 hrs and we were sailing that afternoon.

OK, Sportsboats in Australia can’t be longer than 8.5m, can’t be wider than 3.5m and max airdraft is 12.5m, they have to be capable of ramp launching, and they have to comply with Cat 5 or be ISO Certified.    I knew a bit about Sportsboats via Vivace and 6 Pac.

Super 30 in Sydney, and it’s a very Sydney thing, is 6 club all agreeing to race every 2 weeks, around the harbour anything that is longer than 8.5m shorter than 9.5m and it’s a monohull, really there are no other rules, Cat 7 is OK, some don’t even have bulbs or motors.    So there is a assortment of boats and the rules get stretched to allow MC32 to sail, Flying Tigers, a heavily modified Hick 30 tends to be the gun boat plus some very interesting concepts.

So we wanted a boat that had a foot in both camps, and the plan was and still is to do 8-12 Super 30 races each year along with maybe 6 travelling Sportsboat races per year.

Maggie is a definite, Port Lincoln (Sth Australia) is another (the seafood), and there are lots of possibilities in Victoria (Geelong, Marley Point), NSW (Port Stephens) and Queensland (Bay to bay, Gladstone.) we are spoilt for choices.

Super 30 racing is managed mostly through a historical PHRF system.

Most Sportsboat racing is managed via a simple PHRF process, so Port Stephens that we did earlier this year when we chartered another FE28R was PHRF.

But the Sportsboats have a SMS system mandated in their constitution.   And this is where it gets topical.

I am quite well know in the industry, and I had 3-4 quite high level people come up to me and warn me off Sportsboats because of SMS, and they quote what happened to various owner/boats who did exactly what I am doing, that is putting some effort in and with effort comes results and once you start doing well the “black box” SMS system simply rates you off the dial so that’s the end of doing well.   One even went to the extent of giving me one person name, and insisted I ring them, his boat, Sleuth was the last one this happened to and he simply up and left.

That’s possibly why we in 6 Pac, a 21 year old boat, won the Nationals on our 4th sail.

GT and I tend to have coffee most mornings, its become a bit of a ritual along with other friends, and he and I spoke about Sleuth, I am yet to ring the gentleman concerned, but we decided that most of the sailing we wanted to do was going to be PHRF, even the Sportsboat racing (like Port Stephens) and that even though he is a VP we may never apply for a SMS,  and that was infact a pretty big turning point.

So rather than design (barstardise) a boat for a rating, we just go and do what is

a)       best, b)   simplest and c)   fastest

So that is exactly what I have done.

Basically, I rang up my SKUD mate and he by chance had a pre-loved pre-used SKUD bulb, 140kgs, done. I then took Vivace, stretched it ½ m and applied all the advances that have manifested themselves over the last 18 years and applied those to the design.    And there have been a few.

Vivace had 450gms of Carbon both sides of a PVC H80 core.   We had know for a long time 450gms is about minimum, in-fact a tad border line WRT idiot factor, you can get away with it with a 18teen but not with a 49er (468gms), and certainly not with a 29er (525gms).   So I decided to play the 60-40 rule (60% of the laminate on the outside/compression side, 40% of the laminate on the inside/the tension side.

So by opting for 200gm S-Glass combined with 370gm of Basalt on the outside, and complimenting that with 370gm of Basalt bi-axial on the inside, I’m at 65-35, which is pretty dam close, also the inner layer is bi-axial so no crimp, so that pushes the % closer to 60-40.

If you want to get pedantic, sure Vivace has 900gms in total (both side) and Don’t Panic will have 940gms but Vivace was made wet layup, where as I am making vacuum capable moulds so my resin usage is likely to be around 210% (so 940gms of fibre, and I’m impregnating that, + the foam with about 1000gms of resin, and that’s an empirical number) where as Vivace was likely to be 250-280%.

So in terms of environmental impact, as compare to Vivace and it’s Carbon or if you wish to compare it to say a E-glass lay-up, I’m way ahead.

The we get into PET’s as opposed to PVC foam cores.

There is almost 100kgs of core material that will get used in Don’t Panic, so inside of creating another 100kgs of PVC, I am instead using 100kgs of re-cycled PET plastic.

So that’s a 200kg improvement in the environmental position.   I am probably pulling a few thousand soft drink or water bottle, plates and other plastic waste out of land fill.

But that is not actually the real benefit.    PET is quite plastic-ly, far more flexible.

Just about all foam, other than Polystyrene, get better and better as you increase the density, and they all pass a tipping point at about 65kgs/m³. At that density, most of them cross-link, and in simplest terms that mean they become impervious to water, but they also become more structurally stable.      80kgs/m³ is a point where most manufacturers believe they can be very confident that 99% of the foam has cross linked so H80 as it’s know has been sprouted as the duck-guts for years.

But what happen if you go a bit denser, and plenty of boat builder do just that.

In the case of a 49er, if we chose to use say P115 (PET people use P rather than H) then our testing has shown that we can drop the outer skin weight from around 564gms to approximately 300gms with the same idiot factor.     There is in-fact a net weight reduction, plus you end up using approximately 2/3’s of the resin, and of-course 2/3 of the fibre plus the boat is likely to last longer.

With Don’t Panic, the outer core layer will be 3.5mm (because they can’t cut any finer with accuracy) P115 PET foam, and then it will be “bulked out” with P80, 10mm (or 20mm) PET core.

So we should end up with a lighter boat, that has increase idiot factor, increase longevity and we need to use far less resin so we should just in the build process be that much more environmentally responsible.

And of-course it dose not end there!    Hitch a lighter boat on the back of the Territory and tow it Sydney to Townsville, we may increase fuel burn from 9lt/100km to 10.5lt/100km.    When we were towing Trilogy we were lucky to get 300km to a 65lt tank, (6 Pac was about 12.5lt/100km)

I get asked often how do you design a boat, and the very fist thing you do is a spread sheet with weights, and you track the weights.   I never try and do the whole thing initially, it’s in flux, I will try and come back on Saturday or Sunday with my spreadsheet and my actuals.

~~~~~~~~~~~~~~~~~~~~~~

I spoke earlier about running into GT for coffee most mornings.   This morning, both of us where early, and while sitting down, good mate who was in Garda in an infamous drinking hole looked up and there was a photo of Banana Republic taken in 1989 in Bandol Sth of France, GT saw the photo as it came in on WhatsApp, as I did and we both laughed a lot! He was the sheethand, I was the skipper.

 

image.png

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I don't think I've heard of sandwiching low density foam between higher density foam for panels before. Very interesting...

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Sailhmb, we keep 6 Pac in the same dry storage as Yorky's Reo-speedwagon, and where as we decided to do maybe 18 events a year, just about all of which would be judged on PHRF, Yorky, possibly because he is the Pres of ASBA has gone the other way and fully down the SMS route.   So it's fully optimised for SMS.   And good luck to him, it's not what I want, and the boat looks grossly under rigged.   In a breeze is amazing, tiny rig, lots of power, it goes up-wind about the same speed as everyone else in terms of VMG, but 10 deg lower and 2 knts faster, down wind, its doing 20+ knts, where as Tasty (the gun Super 30 boat which is a modified Hick 30)  is probably doing 12-13knts.    Yorky's big problem, and he may have just managed to solve it is to get everyone to satisfy Cat or ISO Cert, so we will all watch with interest as they actually go and do that (it's a physical actual test where they have to fully capsize the boat sails up, and get it back upright in 5 mins.

Looks like it highly possible that Don't Panic may get a sister ship, talking about borrowing the plugs, and if that happens that owner will go the opposite direction to Yorky, even bigger than what I am contemplating, because he says, he sails in predominately lighter winds.

Horse for courses.     Super 30 stretched the rule downwards to allow boats like Yorky's to compete as it's very much under length, and in a breeze, it win's, but it aint that often.

Jethrow, if I may give you a little picture.    And it is to approx scale.

image.png.104741c327613b2e9a5ed81459be17c7.png

White represents the S-Glass 200gm

Brown represents the Basalt 370gm

Red represents 3.5mm P115 PET outer core

Blue represents the 20mm P80 PET inner core

I would make the P115 outer core thinner if I could, optimum would be around 2.2mm, if I was a purest, but it's not feasible.

Think about it another way, your going from Water at a bit over 1000kgs/m-cu, to S-Glass/Basalt and Epoxy, possibly 1300-1500kgs/m-cu, then we are quite deliberate about the bog, the interface between the Basalt and the P115, it's probably 450kgs/m-cu, then to the P115 at 115kg/m-cu, then to the P80 at 80kgs/m-cu then to basalt/epoxy at 1300-1500kgs/m-cu.     It's very obvious where you may get sheer, and we do things like only use 75-80% of a Bar to suck it all together so we ensure that the bog remains viable and goes deep into the pores of the foam.    Also the mixture of the bog includes Aerocell/Carbosil along with Q-Cell, so it dose not all get sucked out under vacuum consolidation.

Not the first time we have done this and it won't be the last.   Also pretty common in the gliding industry to have feather laminates.

                           jB

 

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Hi all, couple of sideways questions so I will answer here because your probably all thinking them.

I have been at the Basalt thingy now for about 15 years and there are basalts and there are basalts.    Super interestingly, I spoke about been warned off SMS by some people hi up in the industry and being given someone’s name, to ring which I had yet to do, well he rang me yesterday out of the blue, and we spoke for about an hour, sure, he is not a fan of SMS, but more importantly he is in the composite industry and he also agrees with most of the things I have found out about basalt.    In his job he uses it extensively and has travelled to China many times to see it being made (along with std glass manufacture.)     Some hi end military applications you can’t use Carbon.

Some of you have gone to Wikipedia and 2006 contribution suggests that the MPa of Basalt is between 2-300MPa, where as the stuff I am using is about 480MPa.    Just FYI I happen to be using material that is made in either Russia or the Ukraine.     I do have some of the Chinese stuff and I am using it also in localised areas, but you need to do your research and you need to test your ideas.

To be honest whether it’s 300 or 480 is a little irrelevant to me.

We are talking about a 1 tonne boat, with a max un-supported span of 600mm and we are using a 25mm thick laminate (Chine downwards).

I have picked a laminate weight and composition a) because it’s about right, b) because it’s highly likely to be impervious (to water) without much trouble, c) it along with P115 outer core should give me way beyond ample “idiot factor” for that inevitable smack up against the dock (or another boat) so I have picked it knowing that structurally I could well ½ve it and still be pretty safe holding shrouds in the boat, rudders on the back and Fin not overly bending.

Most Sportsboats have 6mm shrouds, BS of 6mm 1:7 “dyform” is  3550kgs, very few boats use 5mm who’s BS is 2440kgs, No one carry's 7mm (BS of ½ tonne) so you can pretty safely say that if you stress the boat to carry 3550kgs you should be OK,   If you want double that to be conservative, great.    That’s a point load, normally on a 12mm (  ½ “ pin).   If you assume that only the top ½ of the pin is taking the load (the shroud is pulling upwards) then it’s a π(R/2)² equation/loading, so assume the chainplate is 4mm thick SS plate, you have 75mm² taking 3550 kgs so every 1mm² is handling 47kgs.

Go out 1 dia your at 150mm² and load per mm² 1/2ve’s to 23kgs.

At 36mm dia your down to 15kgs/mm², 48mm Dia, your down to 12kgs and so on.

200mm diameter away from the centre of the pin your loading is down to 2kgs/mm² and a bit of toilet paper impregnated with Epoxy is more than capable of managing that load without notable elongation.

So holding the mast up and the shrouds down is not really a big ask and some very well placed Unies, double, tripled and quadrupled 150mm away from your Chainplate pin is more than capable of managing the load.    Mast step, same story, max load down = max load up on the shrouds, you can argue its doble because punching into a wave at speed you could get to BS on both shrouds, but that’s still only 7,000kgs, so 100mm away your down to 4kgs/mm².

My point is this, if you are ever going to get anywhere near max elongation of the fibres, and to do that your probably need to ½ ve even your craziest lightest laminate it’s only going to happen within say 50m and at a max 100mm from the pin.    Max elongation of Carbon is about 1.2% x 50mm = 0.6mm, if you use Basalt, and you double the % then you get 1.2mm movement.  That’s assuming absolute minimum laminate, only just strong enough to hold the shroud in the boat.

 WRT the choice of material for use in a Sportsboat, with a well supported mast structure and well enclosed spans, with adequate (yes excessive) material then the numbers for Carbon will be 1/3rd maybe and likewise for Basalt.      Add another 1kg of either material all within 200mm of the pin you won’t be even able to measure it!

Salvation is in skin thickness and reducing un-supported spans.

 

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On 10/22/2021 at 12:56 PM, JulianB said:

Sailhmb, we keep 6 Pac in the same dry storage as Yorky's Reo-speedwagon, and where as we decided to do maybe 18 events a year, just about all of which would be judged on PHRF, Yorky, possibly because he is the Pres of ASBA has gone the other way and fully down the SMS route.   So it's fully optimised for SMS.   And good luck to him, it's not what I want, and the boat looks grossly under rigged.   In a breeze is amazing, tiny rig, lots of power, it goes up-wind about the same speed as everyone else in terms of VMG, but 10 deg lower and 2 knts faster, down wind, its doing 20+ knts, where as Tasty (the gun Super 30 boat which is a modified Hick 30)  is probably doing 12-13knts.    Yorky's big problem, and he may have just managed to solve it is to get everyone to satisfy Cat or ISO Cert, so we will all watch with interest as they actually go and do that (it's a physical actual test where they have to fully capsize the boat sails up, and get it back upright in 5 mins.

Looks like it highly possible that Don't Panic may get a sister ship, talking about borrowing the plugs, and if that happens that owner will go the opposite direction to Yorky, even bigger than what I am contemplating, because he says, he sails in predominately lighter winds.

Horse for courses.     Super 30 stretched the rule downwards to allow boats like Yorky's to compete as it's very much under length, and in a breeze, it win's, but it aint that often.

Jethrow, if I may give you a little picture.    And it is to approx scale.

image.png.104741c327613b2e9a5ed81459be17c7.png

White represents the S-Glass 200gm

Brown represents the Basalt 370gm

Red represents 3.5mm P115 PET outer core

Blue represents the 20mm P80 PET inner core

I would make the P115 outer core thinner if I could, optimum would be around 2.2mm, if I was a purest, but it's not feasible.

Think about it another way, your going from Water at a bit over 1000kgs/m-cu, to S-Glass/Basalt and Epoxy, possibly 1300-1500kgs/m-cu, then we are quite deliberate about the bog, the interface between the Basalt and the P115, it's probably 450kgs/m-cu, then to the P115 at 115kg/m-cu, then to the P80 at 80kgs/m-cu then to basalt/epoxy at 1300-1500kgs/m-cu.     It's very obvious where you may get sheer, and we do things like only use 75-80% of a Bar to suck it all together so we ensure that the bog remains viable and goes deep into the pores of the foam.    Also the mixture of the bog includes Aerocell/Carbosil along with Q-Cell, so it dose not all get sucked out under vacuum consolidation.

Not the first time we have done this and it won't be the last.   Also pretty common in the gliding industry to have feather laminates.

                           jB

 

Jethrow,  have been reminded that in 1982-3 we built the Prime mk3 18teen which had a hull weight of 45kgs (100lbs) and in that boat, I used 8mm strip-plank balsa as a core on the cockpit floor and we sucked down 1mm aircraft play where the "2" crew ran about (with a domestic vacuum cleaner).

So the balsa would have been 65-70kgs/m-cb and the aircraft play, think it was beech would have been 400+kgs/m-cb, so this is not the first time I have done this and Prime mk3 was still sailing 20 years latter, mostly as a 3 hander and the cockpit floor was still pristine. 

Sorry guys, been crazy few days, try and get you a update later today.

                    jB

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Thanks Julian, I remember the Duracore style stuff with the balsa inside the timber as another example. Your mentioning using a higher density foam sandwiching a lower density foam got my mind thinking about another project where this might be a low cost solution to a problem... ;)

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Duracore was developed by Arnie Duckworth, and he did exceptionally well out of it.    It was Arnie that pestered me so much that I sold off a 1/2 built PVC core Prime mkii (to Jermmy Sharp) and then went on to build the balsa strip-planked Prime that ened up on the front page of the Boston Globe, and had the first assymetric spinnaker system, back right before Australia won that cup.

And yes, that was a twin Core density system that has been responisble for many a fine boat.

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I said a bit back that the 1st thing you do and what I believe the most import part of a boats design process is a spreadsheet.   In the old days we did this all longhand, and if you designed 18teens, or Tasars or 49ers you did a lot of empirical testing.   So, you laid up a test panel.  I spoke of the Prime mkiii, and I remember well going to the local model shop, buying a few lengths of 8mm thick balsa and coming back to the factory and using a domestic vacuum cleaner to pull some skins on, then weighing it, and bashing it, to test the process.

But I lie, it’s not the first thing you do, the 1st thing you do, is what I have expressed previously, you work out what it is you want, what it is you trying and achieve and in my case that has included using things like basalt, PET, and racing under PHRF.    But (the spreadsheet) it is still the most important thing you will do!

2nd thing I do (in this world of 3D computer programs) was to take Vivace and stretch it to 8.5m, plug a rig on and look at what’s there.    This is super important from my POV, because it gives you areas and spans, and intuitively that allows you to effectively “allocate” loads.

3rd thing is generating the spreadsheet.

4th, 5th 6th 7th ---------20th thing you do is refine the spreadsheet.

So I have attached my spreadsheet for Don’t Panic.

I probably first did this in July, and last time I re-fined it was just before I posted it.

To digress momentarily, I have had people say I am crazy for doing this, why would you give your competitors access to this information, and there are 2 reasons,

1st , my dad said, best place to hide something is in plain sight, and the 2nd, Paul Elvstrøm who I had the very great privilege of meeting on a few occasions, “you have not won unless the guy you beat believes you have won.”    Most classes are riddled with people fiddling and not necessarily being up-front about what they are doing.    And a few classes are the antithesis of that.    I would like to think the 49er is one of those, (that don’t/can’t hide) surprisingly so is the 5o5, and I really like it.     I hate “black boxes”!   So 6 Pac’s SMS I posted on the web site some months back with GT’s blessing, and I have no issue being very public with this.

OK, to explain some of the spreadsheet,

Vivace had a 230kgs bulb and that was to satisfy Cat 5.    Pretty obviously the single biggest “opposing” force to the bulb is the rig.    Vivace started life with a 90mmID, approx. 2.6mm WT so 95.2mm OD carbon tube.    In Vivace’s case that tube weighed approx. 24kgs, and that’s very much in-line with what 6 Pac’s mast weighs, it was 12.3m high (off the deck).

So part of the refining process has been to look at masts, and yes I will more than likely use a 90mmID carbon tune, 2.6mm WT, 95.2mm OD but what is really surprising is that this mast now weighs 1.2kgs/m below the hound (taper) and 1.1kgs/m above the hound.   Now this new mast also has high stiffness cof, and because I plan to use a well-proportioned square head main I don’t need the length, so I am likely to come down to 11m off the deck.   I don’t have to decide this just yet, so I am not other than to be in the ballpark to do the maths.    8 x 1.2 + 3 x 1.1 = 12.9kgs.   Almost ½ ve.

Then you can see the maths WRT rigging, this boat will have all synthetic rigging, so saving 7-8kgs in that.   You can see the weights of the spreaders, they have ½ ved also, and this was true when we switched to Carbon spreaders on the 49er also, all that weight gone in the rig mean that we don’t need anywhere the weight in the blub.    Hence ringing up Chris Mitchel and buying a pre loved 140kgs SKUD bulb off him.   (plus it’s real cheap, and finished, (I’m lazy)).

When I did the initial displacement of Vivace in it’s stretched form, it came in at 1200+kgs.

So I needed to lose ¼ of a ton displacement.

This is where the magic comes in, this is where you incorporate all those things which you have learnt in the last 20 years to take a stretched Vivace to a refined Don’t Panic.

And no, I’m not going to tell you what that magic is, it may yet be a crushing failure, time will tell.

I know I am going to be asked, why target a weight less that what you expect to carry!

I learned this back in 18teen days, Prime mkiii (which was designed as a 2 hander) sailed extraordinarily well as a 3 hander also and became the route design for all the B18 series.

Took dad and me a bit to work it out, but at zero knts, if you weigh a tone, you will displace 1 tone.

As you start to move, some of your displacement will be carried dynamically, call it quasi planning, and at 5-6 knts (a 18teens hull speed [HS]) you still want full waterline length, and you want to be sailing on your marks.      If you initially design the boat to displace 1 tone at rest, then at HS your ends would be out, and you have lost full water line length, right when it’s most critical.

So we initially design our 18teens to be 19ft long and chop the back 1ft off.   The AAMI’s and the Nokia’s you see in the mid 90’s, where all designed to be about 22ft long, and we chopped the back 4 ft off.      It was interesting watching the max chine beam march back ad back and back.

Dad being dad, work all this out in ft/lbs and CoL’s of the hull, and we now have a formula, and we discount the displacement so as the boat will be optimum LOA at HS. 

Finally, I said “4th, 5th 6th 7th ---------20th thing you do is refine the spreadsheet.” Each time we do a part, we weigh it, and then go back and see if it agrees with what we calculated, In column N you will see some bold measurements, these are actual’s these are just those bits that we have made and gone back and seen it they agree with what we expected.    Basically, we are on target.

~~~~~~~~~~~~~~~~~~~

We did the initial laid up of the Cockpit on Tuesday, today we prepped to do the 2nd lamination that will happen tomorrow.    Monday or Tuesday that whole plug, with laminate on will go outside and be wrapped in a tarp.   It was 31c today, so we know inside the tarp it will get to 60-70c, maybe even as high as 80c.    Near perfect post-curing temp and very much at the right price both in terms of $$$ and cost to the environment!      Probably about Thursday, we will weigh the cockpit, refine column N again  and see where that sit with our calculations.

That’s the end of the little bits, hull plug gets starts Thursday also.

Hopefully rotate the hull early Dec, be out of there Mid Jan (I must spend most of Feb in Europe)

               jB

Weight Oct 2021.xlsx

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Julian, 

Thanks very much for sharing all this info in such detail. It's going to be a very educational thread. 

You referred the 'the magic' of refining Vivace to Don't Panic, I guess this is the bit that you'd really be crazy for giving away!? Are you willing to answer if 'the magic' is specifically with respect to design details or is it global hull shape too. You describe this time as stretching Is it ever a blank sheet of paper effort? 

Cheers

Andrew 

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Thanks Julian, my nephew is studying composites in college and your empirical approach is instructive. 
Can you elaborate on the interface adhesion between foam densities (how are they bonded) and the bog used for the skin attach process?  Our local big boat shop, Schooner Creek, punches reinforcing threads through the laminate before skinning but maybe it’s not an issue with smaller spans or better materials / processes?  I’ve found that the cheap spray adhesive (Elmer’s) roughens foam enough to get good adhesion (after having some skin blister in the hot sun) instead of sanding. 

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17 hours ago, JulianB said:

Now this new mast also has high stiffness cof, and because I plan to use a well-proportioned square head main I don’t need the length, so I am likely to come down to 11m off the deck. 

Presumably single spreader rig? How much SA are you planning to hang off the mast?

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Gone Ballistic, pretty hard to think of a situation where you don’t draw on previous experiences in designing something for the future.    In the case of Don’t Panic, a lot will come from the 49er/29er lineage as well as Vivace, the SKUD and looking around the fleet.

And Martin (Billoch) is keeping me in check~

I think it was Van Goh who said something like “big thing come from a series of little things done well”.

Maybe when we did the speed boat for Mahindra (India) or when we do the new PE/RM coach boats for PlusOne (China) we where very much blank sheet of paper.   The single hander we have just done is very much a bank sheet of paper approach, so that will be interesting.

But Don’t Panic is about 5 (really 4 and one young guy) old farts wanting to go sailing and see this fabulous country and drinking way too much Van Rouge!

 Kenny Dumas,  the late great Dave Ovington always thickened his initial coat of epoxy with 10% of Aerocell, because it stuck to the Polyester gelcoat better.     If you go to the experts they will tell you that you can never get Epoxy to stick to cured Polyester, I think 3,000 49ers later, those experts look a little stupid (and about 100 18teens)

He and I, and later Chris Turner, who brought Ovigy’s, have done a lot of tweaks, and played around a lot with different formulations, so absolutely, don’t trust your supplier because he is only reading the crap he is given and probably never got his hands dirty.

Theory has to equal fact!    How often are we told Fact must = Theory and normally by people who have never actually tried.     For me empirical testing is everything!

Sticking to PVC, and then there was this stuff “corecell” and now PET has required playing around to get additives in the right ratio, and not all epoxies are the same either, by any stroke of the imagination (+ Polyesters are a lot thinner so require a lot more additive.

We are presently putting about 4 expresso cups of AeroCell with 4 expressor cup of Q-Cell into 800gm of mixed epoxy and that seems to stay put, bind to the PET and also act as a good interface.

SideCar really don’t like the tree trunk masts and the single spreader rig, that a bit too much of the sailmaker and mast maker, say, hell you dumb-shit, you know no better, so this will do.

Now I may be a dumb-shit, but I like “well proportioned square heads, because empirically Dad and Simon Watin worked out how they work”, and I like to be able to move cambers and placements around, so I will have a double spreader rig, not to dissimilar to a 49er rig, Cap shrouds running to the deck and adjustable, along with primary shrouds, D2’s and D1’s.    Jury is out on a ram vang yet, it’s biggest advantage is it give the fwd-hand un-fettered access to get the spin down, and it lifts the D1’s and D2’s so you end up with better control of the mast.

But the plan is to use a 90mm ID base tube because it’s pretty resilient, at 2.6mm WT pretty idiot proof (remember 5 old guys, we don’t want to have to put off drinking and story telling time while we re-rig a mast) and to be honest the weight differential is only just over 0.1kg/m, so we may loose 1kg in total, (that’s a 80mm ID tube with 3.2mm WT), I think we are looking at a 12m² jib and a 29m² main.    Can’t carry a A1, the boat will be too fast for that in every thing above 5knts of WS, so probably a A1 ½ and a rope luff flatty as a #2.

But I will get to that in about a month, that whole decision making process is in-fact quite numbers driven and whether you chose to be a 95% boat or a 110% boat.

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Julian, love the thread so far but do you have any pics? I'm a huge fan of the building process. 

Your note about the sharing of information is so important. My father and his co-owner and crew used to tell everybody how they won their races. It builds the fleet and people appreciate the open discussions. It's also no guarantee that your competitors will know what to do with the information anyways so you look better simply for offering it. I have been and will be again a part of the 505 class and their post race debriefs are great. We also hold chalk talks after racing in our weekly Laser/ILCA series simply to bring the entire fleet up so that everybody is having fun.

 

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Pictures,

image.thumb.png.66fe3de9cb38b35e5646dfb94c27e0fb.png

image.thumb.png.ef7efb316268e26df3c20206d54311b1.png

image.png.66f9dd37fc60e7586aebb836d13fff5c.png

3D renders of what we are building, 1/2 model pretty obviously, this is probably the 3rd or 4th refinment.

You can see the reduction that happened when I took 1/4 tone of displacment away, the dark blue is the breast hook pre reduction.

Red & grey are the areas where we will have 3.5 + 20mm so approx 25mm skin thickness, Green and everywhere else it will be 3.5 + 10mm so approx 15mm skin thickness.

And yes we are toying with DSS, Martin's partner, in Benous Aries is Joaco Zerbo was involved in the Prada program and specializes in foils, so hopefully I will get to get some perals of wisdom from there also.

BTW, the boats is 3.5m wide, so we will do what Vivace and just about all the 79ers, and S8's did and effectively run the boat though a bandsaw, 1.2m off the CL and then bolt on "winglets".   So trailer towing width will be 2.4m (2.5m is AUST limit) while sailing width will be 3.5m.

Actual production photo's, most are on Alex's phone (my apprentice/son) and he is 4hrs nth of Syd with his brother and cousins right now, fishing on some river and swagging it out at nights but.

image.jpeg.fe694e13baf43f630401f7c7419f4140.jpeg

Foredeck mould starting, mould is 2600mm wide with 100mm flangs, you can also see the probably 30 year old vacuum pump directly behind the mould which so far has been faultless.

image.thumb.jpeg.da9be7418848d54ee3c05dbc462a9236.jpeg

Alex plating the mould, the one thing differently I would do next time is plate with 4.7 or 6mm MDF, (this is 3mm) but this was a 1 shot mould when we built it, looks like it will now be a 2 shot mould, so we would have been more liberal with glue (PVA) also, Cockpit, we used a lot more glue.

image.thumb.jpeg.74fff69589d20a3bf6d4017608d9978e.jpeg

Cockpit mould taking shape.

image.thumb.jpeg.d34d114b7b135b085224d74eb9fb056b.jpeg

Alex gelcoating the mould so we get a vacuum level of airtightness.   We initially glass the MDF using CSM and cloth (Polyester), then gelcoat, and that has been very effective.

image.thumb.jpeg.2bdfbfeb2447514eed1f8eb3dfde712c.jpeg

Partially inspired by Martin, this is him (standing) sailing his new creation on the River Plate in BA, it's IRC designed and he is doing very well with it.

 

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19 hours ago, JulianB said:

Pictures,

image.thumb.png.66fe3de9cb38b35e5646dfb94c27e0fb.png

image.thumb.png.ef7efb316268e26df3c20206d54311b1.png

image.png.66f9dd37fc60e7586aebb836d13fff5c.png

3D renders of what we are building, 1/2 model pretty obviously, this is probably the 3rd or 4th refinment.

You can see the reduction that happened when I took 1/4 tone of displacment away, the dark blue is the breast hook pre reduction.

Red & grey are the areas where we will have 3.5 + 20mm so approx 25mm skin thickness, Green and everywhere else it will be 3.5 + 10mm so approx 15mm skin thickness.

And yes we are toying with DSS, Martin's partner, in Benous Aries is Joaco Zerbo was involved in the Prada program and specializes in foils, so hopefully I will get to get some perals of wisdom from there also.

BTW, the boats is 3.5m wide, so we will do what Vivace and just about all the 79ers, and S8's did and effectively run the boat though a bandsaw, 1.2m off the CL and then bolt on "winglets".   So trailer towing width will be 2.4m (2.5m is AUST limit) while sailing width will be 3.5m.

Actual production photo's, most are on Alex's phone (my apprentice/son) and he is 4hrs nth of Syd with his brother and cousins right now, fishing on some river and swagging it out at nights but.

image.jpeg.fe694e13baf43f630401f7c7419f4140.jpeg

Foredeck mould starting, mould is 2600mm wide with 100mm flangs, you can also see the probably 30 year old vacuum pump directly behind the mould which so far has been faultless.

image.thumb.jpeg.da9be7418848d54ee3c05dbc462a9236.jpeg

Alex plating the mould, the one thing differently I would do next time is plate with 4.7 or 6mm MDF, (this is 3mm) but this was a 1 shot mould when we built it, looks like it will now be a 2 shot mould, so we would have been more liberal with glue (PVA) also, Cockpit, we used a lot more glue.

image.thumb.jpeg.74fff69589d20a3bf6d4017608d9978e.jpeg

Cockpit mould taking shape.

image.thumb.jpeg.d34d114b7b135b085224d74eb9fb056b.jpeg

Alex gelcoating the mould so we get a vacuum level of airtightness.   We initially glass the MDF using CSM and cloth (Polyester), then gelcoat, and that has been very effective.

image.thumb.jpeg.2bdfbfeb2447514eed1f8eb3dfde712c.jpeg

Partially inspired by Martin, this is him (standing) sailing his new creation on the River Plate in BA, it's IRC designed and he is doing very well with it.

 

Thank you so much for posting those pics...what a treat

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6 hours ago, sailhmb said:

no rake angle on the keel?  why not?

4 hours ago, JulianB said:

Why??

Sorry, a bit abrupt,

The fin dose 2 things, most importantly it is only one of 2 things driving the boat fwd, it and the sails (with a tad of input from the rudder if the boat is well balanced) are the only 2 things that make the boat go, so it should be 40-50% at least the focus of your attention.

The other thing it does is it's a structural beam, and by that, it needs to resist side force, and if there is a bit of lead hanging off the bottom, it needs to resist a canterliver force that the lead, and resulting crew members (in the event of a capsize) will exert.

The camber (read section) of the foil is pretty well defined, due to expected HS and therefore RN [Reynolds Number].

Area can be very well defined due to RM [Righting Moment], it is surprisingly small, and you can do empirical numbers based on similar boat doing similar speeds.

AR [Aspect Ratio] so the ratio of span (length) over cord (width) really does not factor into it, because you are going to effectively endplate the keel at the hull and also if you are using a "especially" T bulb then you will very effectively end plate there also.    When you end plate "well" you double AR, so you have a 2 x endplate so you have a 2 x 2 increase in AR so a say 1m span x 500mm cord = an effective 4m span over 500mm = 8:1 which is huge, think a glider wing.

But the other reason you make the fin longer is to get more RM from the bulb, but this boat is likely to be sailed flat (+/-10°) so on say 1m span you gain 173mm movement, 2m you get 340mm movement, far far better to get your crew to hick just that bit further out and you will get far more benefit from the shift in CoB of the hull.

As to Dihedral or Anhedral (and yes for-n-aft rake is also the same term) you can make a far greater argument from raking your LE fwd, “anhedral” than aft “dihedral”.    The major reason to rake it aft is to get weed to come off with greater ease, but if you actually do that experiment, and you only need look at an Optimist rudder to get your answer, there is a sweet spot around 27-30° were weed starts to move and your way outside the +/-7° minimal effect rake.

I have just about always put my fins in with the TE (Trailing edge) perpendicular to the keel-line aft, the rational being that as the nose lift once you start planning the LE dose not go past vertical, so it dose not go critical.  The reality is, its 3-4°aft.

But the Moths have put paid top all that, all their foils are raked 5-10° fwd to stop ventilation, so what do I know.  

Maybe, we make it vertical!

Get into the maths surrounding fin’s in a bit!   Need to position the fin, in the next 10 days, as we make the hull plug, and that could start as early as Thursday!

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4 hours ago, JulianB said:

Sorry, a bit abrupt,

 

The fin dose 2 things, most importantly it is only one of 2 things driving the boat fwd, it and the sails (with a tad of input from the rudder if the boat is well balanced) are the only 2 things that make the boat go, so it should be 40-50% at least the focus of your attention.

 

The other thing it does is it's a structural beam, and by that, it needs to resist side force, and if there is a bit of lead hanging off the bottom, it needs to resist a canterliver force that the lead, and resulting crew members (in the event of a capsize) will exert.

 

The camber (read section) of the foil is pretty well defined, due to expected HS and therefore RN [Reynolds Number].

 

Area can be very well defined due to RM [Righting Moment], it is surprisingly small, and you can do empirical numbers based on similar boat doing similar speeds.

 

AR [Aspect Ratio] so the ratio of span (length) over cord (width) really does not factor into it, because you are going to effectively endplate the keel at the hull and also if you are using a "especially" T bulb then you will very effectively end plate there also.    When you end plate "well" you double AR, so you have a 2 x endplate so you have a 2 x 2 increase in AR so a say 1m span x 500mm cord = an effective 4m span over 500mm = 8:1 which is huge, think a glider wing.

 

But the other reason you make the fin longer is to get more RM from the bulb, but this boat is likely to be sailed flat (+/-10°) so on say 1m span you gain 173mm movement, 2m you get 340mm movement, far far better to get your crew to hick just that bit further out and you will get far more benefit from the shift in CoB of the hull.

 

As to Dihedral or Anhedral (and yes for-n-aft rake is also the same term) you can make a far greater argument from raking your LE fwd, “anhedral” than aft “dihedral”.    The major reason to rake it aft is to get weed to come off with greater ease, but if you actually do that experiment, and you only need look at an Optimist rudder to get your answer, there is a sweet spot around 27-30° were weed starts to move and your way outside the +/-7° minimal effect rake.

 

I have just about always put my fins in with the TE (Trailing edge) perpendicular to the keel-line aft, the rational being that as the nose lift once you start planning the LE dose not go past vertical, so it dose not go critical.  The reality is, its 3-4°aft.

 

But the Moths have put paid top all that, all their foils are raked 5-10° fwd to stop ventilation, so what do I know.  

 

Maybe, we make it vertical!

 

Get into the maths surrounding fin’s in a bit!   Need to position the fin, in the next 10 days, as we make the hull plug, and that could start as early as Thursday!

 

I should have added to my original post that conventional wisdom around here prefers 6 degrees of dihedral to reduce induced drag.  I have never seen the data supporting this.  Your response was thought provoking.

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At the end of the day, that's roughly where I have my fin, but I can't see why that would reduce induced drag.

Love to hear the thinking on that, I get that you already commented you have not seen the data, but it would be interesting to see why someone thinks that?    Normally such things have a element of substance behind them, ofcourse Moths have anhedral which is therefore counter intuative even to me, and as I said before, what do I know, I have always just put my TE perpendicular to the keel line aft and worked around that.

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2 hours ago, sailhmb said:

I should have added to my original post that conventional wisdom around here prefers 6 degrees of dihedral to reduce induced drag.  I have never seen the data supporting this.  Your response was thought provoking.

Do you actually mean sweep? Dihedral/anhedral would be a canting keel in my opinion.

Anyway, conventional wisdom over here says straight wings have the lowest drag as sweep promotes spanwise flow which increases induced drag. There are some arguments for a forward swept fin promoting spanwise flow in the opposite direction and thus reducing induced resistance, but I do not think the concept ever got traction.

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^^^^ This.

Forward sweep has been tried many times on aircraft because theoretically it is more efficient for a given wing area, you are effectively preventing span wise flow because of the large fuselage/hull end plate. It also theoretically makes the wing and whatever it is attached to more manoeuvrable, but it tends to be more unstable and subject to structural flutter. Anhedral wings can have a similar effect.

And as previously mentioned, Moths have some forward sweep to prevent/minimise ventilation down the leading edge.

Sweep at large angles, can also help with longitudinal stability.

 

1D312F86-03D6-4B87-AD02-ABF66884A657.jpeg

43076A26-D9A9-47D7-8846-1E81F874C2FD.png

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Sorry peoples, very busy doing maths WRT the fin, ISO require you to get over 220% safety margin, I want to be up around 250-300% so we are just fiddling laminates, and staying away from Carbon.

Carbon, Lead and SS are not a good combination.

SS and Lead seam quite OK.    Basalt is inert.

Plus we pick up the hull frames tomorrow morning and one of the things we comit to quite early is the possition of the fin, so maths happening on that also.   Happy to share it all once we stop messing about.     With a boat that is designed to heel to get RM, you pull the fin a long way aft, because the WL as you heel get very round.

I also did a flexiable TE fin 5 years ago with great results, so I more than likely will do 2 fin's, one tacking and one not.

Martin Argentinian SportsBoat is 2 tonne and has 46m² working sail area.   The initial sums on Don't Panic is it's 1 tonne and has 41m² of working sail area.    One of us is wrong, very likely me, so that is consuming some grey matter.

Just tried to down load a Mp4 of us laying up the deck, but it's too big, I need to get Alex to reduce it's size, hope to have that up in a day or so.    There a even bigger one of us doing the cockpit, so that will require work also.

                      jB

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6 hours ago, JulianB said:

Sorry peoples, very busy doing maths WRT the fin, ISO require you to get over 220% safety margin, I want to be up around 250-300% so we are just fiddling laminates, and staying away from Carbon.

Carbon, Lead and SS are not a good combination.

SS and Lead seam quite OK.    Basalt is inert.

Plus we pick up the hull frames tomorrow morning and one of the things we comit to quite early is the possition of the fin, so maths happening on that also.   Happy to share it all once we stop messing about.     With a boat that is designed to heel to get RM, you pull the fin a long way aft, because the WL as you heel get very round.

I also did a flexiable TE fin 5 years ago with great results, so I more than likely will do 2 fin's, one tacking and one not.

Martin Argentinian SportsBoat is 2 tonne and has 46m² working sail area.   The initial sums on Don't Panic is it's 1 tonne and has 41m² of working sail area.    One of us is wrong, very likely me, so that is consuming some grey matter.

Just tried to down load a Mp4 of us laying up the deck, but it's too big, I need to get Alex to reduce it's size, hope to have that up in a day or so.    There a even bigger one of us doing the cockpit, so that will require work also.

                      jB

Concerning the sail area I think you might actually be OK. We are at approx. 1.4T and 43sqm on a much narrower boat than yours, so your crew weight should provide much more righting moment. We carry a heavy bulb, though. 

Edit: I just checked the rating certificate of Martin Billoch's design and it shows an upwind sail area of about 64sqm and displacement of 3433kg.

 

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OK, neuronz, we are at cross-purposes, Martin is about to start a whole new SportsBoat, not the one I sent you a photo of, it's 2 tonne and 46m².

Certinaly the sister ship to Don't Panic will have a big stick and big sails and power up very early in 5-6 knts.

I plan to target 8-9 knts fully wicked, I spoke before about 95 or 110% set-ups, just about everyone goes for 110%, but I'm a minimalist!

                jB

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52 minutes ago, JulianB said:

OK, neuronz, we are at cross-purposes, Martin is about to start a whole new SportsBoat, not the one I sent you a photo of, it's 2 tonne and 46m².

Certinaly the sister ship to Don't Panic will have a big stick and big sails and power up very early in 5-6 knts.

I plan to target 8-9 knts fully wicked, I spoke before about 95 or 110% set-ups, just about everyone goes for 110%, but I'm a minimalist!

                jB

I was actually expecting something like this as the weight was so far off. But still from my own experience on our boat, which is not extreme at all, 1.4T and 43sqm are very manageable. We are sailing double handed quite often without any issues. To me 2T and 46sqm sounds very conservative.

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Julian,

Thanks for being so open about the design process.  I am very appreciative of the time you are taking to post and answer questions. 

Ben 

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I have not been a very engaging storyteller, my apologies.

As you can see from the previous photograph, we are now at hull building stage. I expect this to take 10 days to develop the plug, and then another 10 days to develop the hull.  

As with the deck and the cockpit, I had all the frames CNC milled, sure you can do it yourself with a jig-saw, but the simplicity of getting the MDF frames CNC milled is well worth the $2k it cost.

Basically, Al and I initially got some 100 x 40 LVL’s 6m long (max length they had) but they were too bouncy, so we went back and got 150 x 45 x 6m LVL, and within 3 hrs we had set up all but the front 1.5m of the boat using a Laser light.   Some fine adjustment is needed, LVL’s even though being super straight and 150mm deep is very rigid, there is still tweaking, and the laser leveller exposes all sins.   That was Friday, Saturday morning I extended the LVL fwd 2.5m with some 95 x 45 DAR timber, simple plate sleave extension, and re positioning the laser (you can see it in the photo) shot it fwd and positioned the front 3 frames.    Frames are at 600mm centres, couple of reasons, the biggest being if you have a problem you can get up and in between them. 500mm is just too tight, and 750 - 1m is too flimsy.

Tomorrow, we will simply but joint and splice stringers together (max length timber we can get is 6m,) so we will have to make up some 8m stringers and strake up the hull,   Keel line is 42 x 19 material, chine/transition fwd is that also, everything else is 19 x 19.

While getting the frames CNC milled we also got side panels cut, so this is where we have “virtually” band-sawed the boat at 2.4m to meet AUS towing regs.

I commented before about upping the plating material from 3mm to 4.7mm (old 3/16”) MDF, that should allow for a far more stable plug and once the plating and then glassing is done, it should be very ridged, we could probably remove the LVL’s and be none the worst (and they are not cheap) (but we won't).

Last 2weeks have been interesting.

I may have commented before about the Issues surrounding the ABSA in Australia and the requirement that we meet Cat 5 or ISO cert regulations.    There has been a pretty profoundly advancement in this, and one has to credit the President (Andrew York) for finding, managing and doing a “Knock Down Test” [KDT] under ISO cert conditions.

https://www.youtube.com/watch?v=IcjkQPoHWxc

 

This will have an equally profound effect on the class here.   It’s simple, it can be down on the end of the jetty with all the deck chair commodores in witness in the event of dispute.

Credit where credit is due, I believe it’s important and great step in the right direction.

But what it does is re-set the bulb weight requirement, so whereas before I was guessing that I needed 140kgs on a 2m fin, to get Cat 5/ISO cert, to do the KDT and pass won’t require anything like 2m or 140kgs and probably less of both.

I spoke before about making sure you remain in flux and not locking down anything until you had to, this is exactly where the actions of “Yorky”, which I totally applaud, will have a significant bearing on what I am doing.

The first thing is that I can design and build a Fin which is Fit for Purpose” [FfP] rather than one that allows me to meet Cat 5/ISO Cert.

So I made some calculations and conferred with Martin in Argentina.

 In addition to that there are a suite of empirical “tweaks” which I had become aware off in Sportsboats where people modified their keels and in just about every case reduced span and area with great results.

I know people are going to ask me how I do this calculation, and I do have a formula which I have refined over the last 30 years, it did all my 18 teens, Vivace, OCL, 49er 29er SKUD etc etc etc.

The key element in Fin size is speed.  The ability for the fin to resist side load goes up as x² of the boat speed.    So if you have a boat that’s going to do 5knts with X sideload and another that’s going to operate at 7knts with the same sideload then the area of the fin in the 5knts boat needs to be almost exactly double the size of the board in the 7knts boat, and if the 7knts boat gets to 9knts, then it will have 165% the area it needs and that’s all parasitic drag, (plus weight and complexity).   Get to 12knts and it’s 3 times to big, get to 16knts (which we will) its 5 times too excessive.

Coming in very close 2nd in terms of importance is sideload which is a factor of RM (righting Moment) / Arm (distance between the CoE of the sails and the CLR of the hull (in my case the fin and rudder)).

I cheat and get the computer to find the CLR for me, and its 653mm below the keel.   Similarly It can find the CoE and that gives me an ARM of 6135mm

Boat is 3.5m wide, ½ ve that (CoB -> gunwale) so 1750mm, you then add on almost ¼ m for energetic hiking and shift in CoB to leeward of the CL as the boat heels even 5°, so KISS 2m.

500kgs of crew, x 2m = 1 tonne/m RM

1000kgs/6.135 = 162kgs sideload that the board must carry.

image.png.dfbfd9349497f71553f57d4ec11cca78.png

Pretty obviously I know the 49er very well, and it has undergone a range of refinements, and one of those is C’Board size, shape and section.    And it just happens to hit it’s “straps” at 7knts BS.

The area of a 49er Centreboard below the keeline is within 0.001% of 0.3m² (purely by chance)

49er is 3m wingtip to wingtip, so 1.5m CL to wingtip, add 1m toes to CoG of the crew, so 2.5m, and the mean crew weight is 165kgs so 412.5 kgs/m RM (approx. 40% of the 89er).

ARM is 4378mm (https://9eronline.com/library/49er%20working%20sail%20dynamics.jpg)

412 / 4.378 = 94kgs sideload.

162/94 x 0.3 = 0.51m² is the area needed by the 89er to resist expected sideload at 7knts hull speed.

And in some ways it is that simple, and we are extraordinarily lucky that we have such a great model with the 49er in that it has this sweet spot at 7knts which is the expected sweet spot of the 89er.

But, the 49er is far lighter, roughly ¼ of the weight of the 89er with ½ the power, so in the event of a change in circumstances, the 49er will accelerate or decelerate far faster to accommodate that change and you can cut the tolerance that much more. (in the case of the 49er to almost zero, 29er not so much)

89er is 5 fat old bastards out to have some fun, so we need some buffer room.

Cut a long story short, Martin suggests we go for 0.7 – 0.75m², I will probably target 0.68 -0.69m².

But we both agree that we don’t need any more than 1.5m below the keel and that in turn dramatically alters the construction and the weight of the fin.

Just as a cross reference, Vivace had a fin length of 1.8m which was latter cut done to 1.5m, and it started life with surface area at 0.72m² which was also cut back when they reduced span, (but they also increase cord, so not all that much).    Don’t Panic should be ½ knts at least faster than Vivace a) because it’s longer, b) because it’s probably going to end up lighter, but b)ii) a massive amount of that weight reduction will be in the rig, so inertia will be far lower and c) Don’t Panic is 20+ years younger and if we can’t do better than WTF are we doing.  (one of those things will be square head)

So Don’t Panic should hit 7 knts sooner, more simply and with less fuss, and therefore Fin area and Mast height can be (read should be) smaller, by definition!

That’s enough for now, but there are a whole bunch of other variables that come into play.

Possible reduction in bulb weight (to comply with Cat 5 /ISO post Yorky), but we have decided to stay put, a) because I have it and b) need to go play first.

Section shape, smaller span (down to 1.5m) means far less complexity WRT structure, in-fact even a moderate use of unies glass or Basalt will easily get us to 300% safety margin on the fin and that then allows us to set the section shape and % to what it should be rather than what it has to be.

The ability for the unies to completely resolve all the structural issue WRT the fin mean we can get rid of a SS spar, so away goes cost and away goes weight (about 16 kgs).

What I am trying to say here is that one unrelated action, in this case by Yorky, and again all credit to him, has sent me of on 2 weeks of maths and re-optimisation that will more than likely reduce totally system weight by atleast 50kgs possibly more (and that’s 5% and that’s massive) it has reduce price, probably reduce rig height, increased simplicity and just is going to make the boat that much more fun.

Still trying to get Al to convert Mp4 into YouTube, it should happen tomorrow plus I promise some photos of the Hull plug taking shape.

 

                    jB

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6 hours ago, JulianB said:

Promissed you a video of laying up the foredeck, it carries onto the 2nd skin and then the cockpit

 

Thank you so much for sharing the process, Julian. 

What is that green core that you're using. I'm assuming it's core. It's so flexible. One can see it bending easily in your hand around the 3:15 mark.

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It's PET foam, so recycled soft drink or mineral water bottels, no idea how many times it been recycled, don't really care, I expect this boat to last 20+ year.

It's trade name is Kerdyn Green, made by Gruit, in reality all foam, regardless of make or manufacture all comes from one region, about 2 hrs nth of Beijing.

I am using 80kgs/m³ and 115kg/m³ and have been playing with this stuff, mostly in Italy (Nautivela) for the last 4 years with great success.

Really tough, we have 1/2ved the laminate schedual and it's still tough, so to some extent I'm building the 89er out of it as a trial for future 9er building as we go green. 

It is a interesting material, yes flexiable prior to being skinned, but seriously tough once skinned.

One of the big reasons the sailors pick moulded mains and jib was they believed they would get far greater longivity, and alot of that feed back came from the Moths (mostly ex 9er sailors) with their 3Di sails, Slingsby said something like, "hammer them for a year and they are still just fine, sure, get a new one for the worlds but 4-5 days sailing a week for a year no problem."    If we can duplicate that with the 49er, then we will 1/4er our sail consumption.     I will be very happy with 1/2!

Same with the carbon mast, Southerns are fabulous and we are hugley indebited to them but I think that CST is the next step up again, and all my research into mast for the 89er bear that out, so where as now you have sailors going to their 3rd Olympics with the same mast, and they only carrying maybe a top-mast as a spare (especially with the FX) now every sailor will have one mast across 2-3 hulls.

The whole point of that, is the weak link is now the hull, so to speak, they are still good 10 years later for silver fleet racing, be nice if we could get longivity in the 49er hull up so those Silver fleet racers can take on and beat some gold fleet racers and not have the hull holding them back.

Spoke with Turner last night (Ovington) he is planning to make a OK out of it, and go thrash it himself, McMillian here in Australia has already started on that project (building a OK out of Kerdyn Green).

Maybe, once the 89er project is done, I will get onto my long awaited Bat-boat project and build a 49er type boat but with Kerdyn Green core, Basalt skins, 50mm OD mast, have the possibility of foiling because if you build a test bed, why not, and I have Joaquin Zerbo (Martin's design partner in ARG) to draw on ideas.

But there is a cost benifit basis to foil or not to foil, being 49er's already do 26-27knts down hill, and they do it with big bright colourful sails (spinnakers) so they tend to be the media darlings.   Put them up on foils and maybe you would have Cuban Fiber flatties as downwind sails and that aint fun.   And all for maybe at best 5 knts extra.

Actually the Bat-boat project is exciting on a range of fronts, also in class managment structure, could be a water shed.

Sorry to go off point, but it's what my brain dose!

                         jB

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7 hours ago, JulianB said:

It's PET foam, so recycled soft drink or mineral water bottels, no idea how many times it been recycled, don't really care, I expect this boat to last 20+ year.

It's trade name is Kerdyn Green, made by Gruit, in reality all foam, regardless of make or manufacture all comes from one region, about 2 hrs nth of Beijing.

I am using 80kgs/m³ and 115kg/m³ and have been playing with this stuff, mostly in Italy (Nautivela) for the last 4 years with great success.

Really tough, we have 1/2ved the laminate schedual and it's still tough, so to some extent I'm building the 89er out of it as a trial for future 9er building as we go green. 

It is a interesting material, yes flexiable prior to being skinned, but seriously tough once skinned.

One of the big reasons the sailors pick moulded mains and jib was they believed they would get far greater longivity, and alot of that feed back came from the Moths (mostly ex 9er sailors) with their 3Di sails, Slingsby said something like, "hammer them for a year and they are still just fine, sure, get a new one for the worlds but 4-5 days sailing a week for a year no problem."    If we can duplicate that with the 49er, then we will 1/4er our sail consumption.     I will be very happy with 1/2!

Same with the carbon mast, Southerns are fabulous and we are hugley indebited to them but I think that CST is the next step up again, and all my research into mast for the 89er bear that out, so where as now you have sailors going to their 3rd Olympics with the same mast, and they only carrying maybe a top-mast as a spare (especially with the FX) now every sailor will have one mast across 2-3 hulls.

The whole point of that, is the weak link is now the hull, so to speak, they are still good 10 years later for silver fleet racing, be nice if we could get longivity in the 49er hull up so those Silver fleet racers can take on and beat some gold fleet racers and not have the hull holding them back.

Spoke with Turner last night (Ovington) he is planning to make a OK out of it, and go thrash it himself, McMillian here in Australia has already started on that project (building a OK out of Kerdyn Green).

Maybe, once the 89er project is done, I will get onto my long awaited Bat-boat project and build a 49er type boat but with Kerdyn Green core, Basalt skins, 50mm OD mast, have the possibility of foiling because if you build a test bed, why not, and I have Joaquin Zerbo (Martin's design partner in ARG) to draw on ideas.

But there is a cost benifit basis to foil or not to foil, being 49er's already do 26-27knts down hill, and they do it with big bright colourful sails (spinnakers) so they tend to be the media darlings.   Put them up on foils and maybe you would have Cuban Fiber flatties as downwind sails and that aint fun.   And all for maybe at best 5 knts extra.

Actually the Bat-boat project is exciting on a range of fronts, also in class managment structure, could be a water shed.

Sorry to go off point, but it's what my brain dose!

                         jB

Thank you for the comprehensive response. I'm working on a new boat building plan/project, a couple actually, and thanks to you we're going to spec PET core on both of them.

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2 hours ago, JulianB said:

image.thumb.png.831e6c8b9327e1dfaf5243abf2e1cf31.png

image.thumb.png.fcd8db435ec25af857cd9403fa640759.png

Close to plating time.

 

Jealous of your work space too!

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We call it a WING   (my fathers name for it)

image.thumb.png.e39c0fa91bd37a208c9c9ec48e088123.png

image.thumb.png.e7e86ddf61df1df0bbf95100df27fd0c.png

This is me sailing a Ovington built hull, December 2018, in HK, (Clearwater Bay) with a W6m² rig in 5knts of wind.   (I'm way to fat, hence building a 89er)

It's what I have been playing with for the last 8 years, 4 of them in Italy with Paolo Portiglia at Nautivela where we developed all of our green technology, so PET foam cores and learning to use Basalt.

This rig is what became the C-Rigs (for the Laser/ILCA)

I will see if I can find the video from Italy (near Rome airport) that was taken January 2020, (right before Covid went crazy)

Bloody quick, it catch's a 29er going up-hill (in HK).

 

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On 10/21/2021 at 9:41 PM, JulianB said:

I spoke earlier about running into GT for coffee most mornings.   This morning, both of us where early, and while sitting down, good mate who was in Garda in an infamous drinking hole looked up and there was a photo of Banana Republic taken in 1989 in Bandol Sth of France, GT saw the photo as it came in on WhatsApp, as I did and we both laughed a lot! He was the sheethand, I was the skipper.

 

 

image.png

Here is one from 1990 tour, me Neil Mac and Aido

1691862192_18s_France1990.thumb.jpg.540cf5d5d60a1f21283e3f8cc7d8f712.jpg

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On 11/10/2021 at 7:35 AM, JulianB said:

image.thumb.png.831e6c8b9327e1dfaf5243abf2e1cf31.png

image.thumb.png.fcd8db435ec25af857cd9403fa640759.png

Close to plating time.

 

Looking great so far. Can see the cool curves and look forward to see the plating and further building.

 

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This is a male plug.

As I have been asked, the step that you can see fwd, is where the boat transitions from 25mm thick laminate to 15mm thick laminate.

The reasons for the slewed planks as to find the "line of least resistance"!  4.7mm has to be 3 times stiffer than 3mm, and I guess it's a x² law.

Had a very busy morning checking out the final variant of the new 49er and FX 3Di sails so I only got 1/2 day, and my mate was up the coast sunning himself with the GF.

Reason I'm doing a plug, is I can get vacuum consolidation rather than a un-consolidated wet layup.   I always liked pulling hulls down over a plug, you get so much more tension in the fibres, you end up with a far more even and closer to the correct resin ration, it’s just a better boat.

Plus you use far less resin, and sure you can vacuum, to a foam jig but it’s pretty arbitrary.

Again, because I have been asked, we can go close to 100% vacuum, but I hold it at about 80% of a atm. Reason, is you don’t pull all the solids out of the resin at 80%, you tend to get far more issues at 100% with additives exciting.

And I am hitting pretty good numbers, so why go further, it’s all a bit pointless.

                  jB

 

 

image.thumb.png.ef82211a47edabb4fafc0ee622e72ba8.png

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Hope to finish plating tomorrow, maybe even start planning, which is the bit I really love, turning all thise 2D planks into a 3D form.

                      jB

image.thumb.png.67fbf7dfc42153bed1eecb359cc63f3c.png

 

image.thumb.png.b70384bb8f47e5223b2465fb3fa4b4ea.png

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22 hours ago, JulianB said:

 

This is a male plug.

 

As I have been asked, the step that you can see fwd, is where the boat transitions from 25mm thick laminate to 15mm thick laminate.

 

The reasons for the slewed planks as to find the "line of least resistance"!  4.7mm has to be 3 times stiffer than 3mm, and I guess it's a x² law.

 

Had a very busy morning checking out the final variant of the new 49er and FX 3Di sails so I only got 1/2 day, and my mate was up the coast sunning himself with the GF.

 

Reason I'm doing a plug, is I can get vacuum consolidation rather than a un-consolidated wet layup.   I always liked pulling hulls down over a plug, you get so much more tension in the fibres, you end up with a far more even and closer to the correct resin ration, it’s just a better boat.

 

Plus you use far less resin, and sure you can vacuum, to a foam jig but it’s pretty arbitrary.

 

Again, because I have been asked, we can go close to 100% vacuum, but I hold it at about 80% of a atm. Reason, is you don’t pull all the solids out of the resin at 80%, you tend to get far more issues at 100% with additives exciting.

 

And I am hitting pretty good numbers, so why go further, it’s all a bit pointless.

 

                  jB

 

 

 

image.thumb.png.ef82211a47edabb4fafc0ee622e72ba8.png

Looking good and I agree with you on using a male mold on a low production boat and you will be able to see the shapes and ensure you are happy with the result. 

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image.thumb.png.920dabede3f67ac1582a8ad74c7341c8.png

And I am now a very happy boy, it's come out far better than I could have hoped for, clean up super easily, I will let all teh glue go hard tomorrow (Wednesday, while I go beer can racing) and then I will spend most of Thursday on it, 1/2 the time pulling out or whacking in staples, the rest of the time with a super sharp plane, I have a long probably 2ft (600mm) shooting plane that is perfect for this.

The 4.7mm (3/16") MDF is far harder to work withm we had to think very hard about the alignment of the strakes, and they are thin, but it all came together really well.

We get 3 chance to fair it, now, planning MDF, then after we glass we will still put a thin layer of slurry on it, maybe 1mm, and then after we suck on the 20 & 10mm PET P80 foam, but no, very gratifying, it's great!

Alex and I are super happy with the result!

                    jB

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2 hours ago, JulianB said:

image.thumb.png.920dabede3f67ac1582a8ad74c7341c8.png

And I am now a very happy boy, it's come out far better than I could have hoped for, clean up super easily, I will let all teh glue go hard tomorrow (Wednesday, while I go beer can racing) and then I will spend most of Thursday on it, 1/2 the time pulling out or whacking in staples, the rest of the time with a super sharp plane, I have a long probably 2ft (600mm) shooting plane that is perfect for this.

The 4.7mm (3/16") MDF is far harder to work withm we had to think very hard about the alignment of the strakes, and they are thin, but it all came together really well.

We get 3 chance to fair it, now, planning MDF, then after we glass we will still put a thin layer of slurry on it, maybe 1mm, and then after we suck on the 20 & 10mm PET P80 foam, but no, very gratifying, it's great!

Alex and I are super happy with the result!

                    jB

Lovely work JB. Particularly sweet looking chine definition.

Can you shed light on your rational as to staying with sharp narrow fore foot skiff bow? The fat nose Pogo 3 or Imoca Proboscis Monkey nose - are they purely a function of cutting & smoothing a longer hull shape into a restricted waterline length package? 

Is there any situation where you would go there?

I know that your design language is very recognisable with all your skiff and 9er designs showing evolution and refinement, but would be interested on your take.

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Boink, hi, mini transpac’s or transpac or that sled race going from USA to Mexico down the west side, it’s all about maximising down-hill speed.

I call those mini transpacs scows.

I learnt to sail in scows, proper scows, not Opie’s.

I started in NJ’s, progressed to J12’s then A12’s and had some legendary rides in Scow Moths.

I had the delightful experience of being shown over one of those super big Melges scows with 150-year-old runners by Buddy Melges, and Harry Melges has threatened to take me scow sailing but it never has quite happened.

Those mini transpacs (may have the name wrong but really don’t care) are extraordinary and if I where to design a boat to mostly go downwind, at 15+ knts most of the time, then that is what I would probably skew my design towards.

In about 2006, not sure when I also had a legendary ride in Vivace.  Not only did we capzise and had to get on the fin, but we won and we did about 25knts for a extended period of time down the full length of Lake MacQuarie.   29ers do 30+Knts, 49er do almost 30knts so moving at speed with long fine bows dose not seems to be an issue.

Planning up wind.  I have a real soft spot for 5o5’s and I14’s because they seem to be trigger boats, they spend lots of money and effort on Gybing center-board, because they can chose to plane or not to plane.  If you don’t plane, then a gybing board is great to zero yaw (or Yawl) drag, once your planning it’s a bit pointless.   Tasar’s can plane upwind and I have done it many times myself.

49er always plane up-wind, in anything over 8 knts of wind speed, 29er also simply transition to planning upwind, effortlessly, and this is where long fine bows come into play.

Just one step back, take a 5o5, go to https://www.sailing.org/classesandequipment/I505.php and you get the basic numbers of a 5O5, and again I consider this a trigger boat, so it’s is on the cusp of being able to plane up-wind effectively.

5m LOA, = 5 x 39.54/12 = 16ft, √16 = 4 x 1.4 = 5.6kts HS (same as a 49er)

All up weight, 127 hull weight, another 20 kgs in the rig/sails/crap + crew at say 180 = 327kgs

Max RM = crew at ½ beam + 1m + skipper at 1/2beam + 200mm = 100kgs x (½ 1.88 +1) + 80 x  (½ x 1.88 + .2) = 1.94x100 + 1.14 x 80 = 285kgs/m (I think that’s Newtons) RM

I’m guessing the mast is 7.5m, the fin is 1.2m so the arm, very triangular sails so the arm will be short plus as commented before, very cleaver design and a lot of effort put into the foils, so CLR of the fin will be high, so a guess, 49er arm is 4.4m, it has to be less, say 3.5m (happy for anyone to shed some light if they have more details)  285kgs/m / 3.5m  = 81 kgs of SCP [sail carrying power].   327kgs total weight / 81kgs SCP = 4  

Now my father would have done this in imperial (ft and lbs) but you will still come out with a number and if your below that, you can plane upwind effective, if your above it you can’t (if you assume as I have that the 5o5 is a trigger boat.

To verify that, 49er.  All up weight is 92 + 20 + 165 = 277kgs, RM I have calculated previously in this string is about 92, so you end up with a number around 3, and it planes just about all the time.

The 89er, all up weight is going to be best part of a tone, max RM is also about 1 tone, SCP is likely to be, again, did this sum before but arm is 6m-ish, so it’s about SCP is likely to be 1000/6 = 166, I think I previous worked it out to be 142, but same ball park 1000kgs (all up weight) / 166 SCP =  6

It will never plane upwind! End of story.     It will be displacment probably 80-90% of the time.

Then, this boat is about 4 fat old men (and one skinny young man) going out and having fun!

We will do passage races, and windward/ leeward races so ½ the course is going to be up-wind.

Think a bit more carefully, more than ½ the distance will be up-wind, in fact almost 60-65% of the distance sailed in any around passage or windward/leeward race is up-wind, and then factor that up by the simple fact that downwind you likely to be travelling faster than upwind, between 70-75% of the time you’re sailing a race or even going out having a good time is up-wind.

So if your thought process is not skewed 3:1 up-hill then you probably better have a good hard look at yourself.

Hence the long fine for-foot to the boat.

Bunch of other stuff that comes into it, dynamically humpless hull, even though we will never plane will allow us to exceed HS (√28 x 1.4 = 7.4knts) relatively easily, but we would be better off taking the height rather than the speed, better compromise.

Let me know if you need something expanded on.

That’s my rational anyway.              jB

 

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On 11/16/2021 at 6:51 AM, JulianB said:

image.thumb.png.920dabede3f67ac1582a8ad74c7341c8.png


This is the sexiest picture of a mold I've ever seen.

I don't really care if it floats or not.  You already won.

 

No idea how you have time for a project like this Julian.  Kudos.

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Mini Transat 650 is what you are almost describing........ ;)

Their biannual charge downwind across the Atlantic in 21ft boats to the Carribbean is just wrapping up. Fabulous opportunity for a bit of clever design. Can I tempt you? 

As to your rational, very illuminating. Thanks

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Just got asked about Froud angles, mine is almost exactly 10° and yes that's fine but not fine enough to enjoy a multihull or a destroyer type benifits.

The WING I showed you in previous post is about total is 13.5° so approx 7° and it is below the critical x°.      That critical number is when a hull dose noty baulk as it approached HS, it just transitions.

This is where you get into what Dad refered to as dynamically humpless hulls, and it all has to do with being "isoclynial" ( I have spelt that wrong no doubt) fwd, and maintaing a very defined and level of sharpness infront of the Fin.    So by playing with fwd sections you can get an effective reduction in Froud angle, and 1-2° is important.

There's this funny little group in southern UK called AYRS (https://www.ayrs.org/)  but Dad was pretty interested in some of the really quirky things they did, I remember one sparked his interest and we did a series of tow tests, and then some more, with small changes to frontal vee's.    (this was all NS14's BTW, but it works arcross the board.)

And even more interestingly, in the same vein, we chartered a FE28R few years back, (at Magnetic Island) and then did it again (at Port Stephens) and it has a really U shaped fwd sections.   I got the crew to hick infront of the shrouds to keep the bow in, because when it came out, it slapped a lot.   Cut a long story short, there where maybe 5 FR28R, and I think we where 1st in just about every race bare one, and in one of the races we where 1st in, we won by over an hour in a 4 hour race.

Now it may have nothing to do with us making sure the bow did not come out, but these other boats sailed the boats alot, and they all asked why we sailed nose down.

 

 

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1 hour ago, Boink said:

Mini Transat 650 is what you are almost describing........ ;)

Their biannual charge downwind across the Atlantic in 21ft boats to the Carribbean is just wrapping up. Fabulous opportunity for a bit of clever design. Can I tempt you? 

As to your rational, very illuminating. Thanks

Scow yes, but I would be working up something like the WING.  

21ft WING

Had someone what me to do a yacht like that, (which is I guess what you are thinking) still talking, who know's where that will land!

           jB

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3 hours ago, WestCoast said:


This is the sexiest picture of a mold I've ever seen.

I don't really care if it floats or not.  You already won.

 

No idea how you have time for a project like this Julian.  Kudos.

Thanks George, you owe me a phone call!!!!!!!!

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1 hour ago, JulianB said:

Just got asked about Froud angles, mine is almost exactly 10° and yes that's fine but not fine enough to enjoy a multihull or a destroyer type benifits.

The WING I showed you in previous post is about total is 13.5° so approx 7° and it is below the critical x°.      That critical number is when a hull dose noty baulk as it approached HS, it just transitions.

This is where you get into what Dad refered to as dynamically humpless hulls, and it all has to do with being "isoclynial" ( I have spelt that wrong no doubt) fwd, and maintaing a very defined and level of sharpness infront of the Fin.    So by playing with fwd sections you can get an effective reduction in Froud angle, and 1-2° is important.

There's this funny little group in southern UK called AYRS (https://www.ayrs.org/)  but Dad was pretty interested in some of the really quirky things they did, I remember one sparked his interest and we did a series of tow tests, and then some more, with small changes to frontal vee's.    (this was all NS14's BTW, but it works arcross the board.)

And even more interestingly, in the same vein, we chartered a FE28R few years back, (at Magnetic Island) and then did it again (at Port Stephens) and it has a really U shaped fwd sections.   I got the crew to hick infront of the shrouds to keep the bow in, because when it came out, it slapped a lot.   Cut a long story short, there where maybe 5 FR28R, and I think we where 1st in just about every race bare one, and in one of the races we where 1st in, we won by over an hour in a 4 hour race.

Now it may have nothing to do with us making sure the bow did not come out, but these other boats sailed the boats alot, and they all asked why we sailed nose down.

 

Obviously you were doing something different that worked very well, or a combination of 2 or 3 factors that each helped.

I can't believe other racing sailors would see you doing something fairly obvious, putting the crew forward, and winning... and not copying you immediately. When someone beats me, I study what they're doing harder than I ever studied in school.

- DSK

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12 hours ago, JulianB said:
13 hours ago, Boink said:

Mini Transat 650 is what you are almost describing........ ;)

Their biannual charge downwind across the Atlantic in 21ft boats to the Carribbean is just wrapping up. Fabulous opportunity for a bit of clever design. Can I tempt you? 

As to your rational, very illuminating. Thanks

Scow yes, but I would be working up something like the WING.  

21ft WING

Had someone what me to do a yacht like that, (which is I guess what you are thinking) still talking, who know's where that will land!

To continue the thread drift….. The most interesting scow developments are in Class40, here:

http://chevaliertaglang.blogspot.com/

English translations in the back half…… longest effective LWL has a whole new meaning!

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13 hours ago, JulianB said:

Scow yes, but I would be working up something like the WING.  

21ft WING

Had someone what me to do a yacht like that, (which is I guess what you are thinking) still talking, who know's where that will land!

           jB

Scow design definitely. This is very encouraging. The winner in the Prototype division was Pierre Le Roy on a David Raison designed scow called Teamwork. I think this is his 3rd or 4th win in a row......

The power of a scow is undeniable. This year was light by all accounts on the long Trade Wind leg, yet the low resistance, symmetrical waterlines and extra RM were clearly well corralled and balanced. Just not very aesthetic to the traditionalist......

Your Wing concept would slaughter them, but for the hollow sections rule, which I believe would view it as a multihull. Those French do like a good multihull....... Raison, Manuard and Verdier are all active in the class.

But a 21ft scow moth........ Let's talk :)

I suspect your careful trim on the F28 not only optimised the platform, with less slap, resistance and stern immersion and possible leeway reduction but also improved rig efficiency by reducing the hobby horsing that can sap away the power of the platform. A Lovely example of the virtuous circle. Agreed?

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2 hours ago, Bill E Goat said:

Bullshit

I think that it was a simple typo (3 instead of a 2) and I meant to ask if he was sure. 

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Here we go again.

This did not end well for you last time, but if you wish to be slammed again, so be it, your problem not mine.

#1, the reference to speed was purely in relation to the fact that a lot of long thin bowed boats are capable of quite extraordinary speeds and the inference was that whether the bow was a punt, a scow, or a long & thin, it did not seem detrimental to top end performance in sailing boats.

One could sight Wild Oat, Comanche, Itchy Ban, even Vesta Rocket.

But I chose 49er, 29er & Vivace, because they were more relevant.

#2, re top end speeds of 29ers.

Simple fact, 29er are capable of higher top end speed than 49er, they always have, and they always will.

If you now wish to dispute top end speed of a 49er, be my guess to slam you head against into the wall, (it’s always good when you stop) there are ample race recorder records to suggest that 49er can and do often achieve speeds in the hi 20 knts.     If you wish to dispute that, please do, I have better things to do than respond.   Suggest you start with Emmett late in the 2000’s.

WRT 29er.

Some time in the early 2000’s I got a very elated email from an American, saying he had broken the 30 knts barrier and he had ample proof to prove it, GPS, etc ete.    I congratulated him.

2005, I was at St Francis Yacht Cub, in a Protector, a few photo jornos, and one Janet Baxter who at the time was Pres of US Sailing.   It was the US 29er Worlds BTW, the sailor had come around a mark somewhere up off the GG, had gybed of StFYC and where heading for Alcatraz, some jurnos asked if we could format on some back markers in gold fleet, I remember it well as we formatted on Soren, a Norwegian team who where in about 15th at the time (they had stayed in my house a year earlier, so I knew them, Sister steering, Brother in the bow), now they were 15th, Silija Letiean (Finnish) who went on to win was gapping them, someone asked how fast we were going, every instrument in that boat was telling us we were doing hi 20’s (knts), and yes there was a universal comment of Bullshit, but it was more in awr than dis-belief.

Now I was driving and I did that and I was party to that and I knew they could be quick, but that was 1st hand and I was impressed.

Since then there have been about another 8 pretty well documented accounts of teams “joining the 30knt club”.   AND GOOD LUCK TO THEM.   They are kids having fun.    I am very well aware of one such sailor who over the last 2 months has tried to break into the club but missed out by only 0.5knts.     He was telling me this, to my face, I have little doubt he will get there.

And then there where the 2018-19 HK Worlds, a particularly breezy series, bruising to put it bluntly.

If the speed off the trackers out on the track where not enough, and again, I had heard this all before, it was impressive, but to then get back home, for any of you who know Middle Island in HK and the gutter between it and the mainland where the wind picked up another 20-25%, the kids had to sail through this and rather than being terrified, they where having a ball., most made it, some ended up in tears but the shrieks of joy and the smiles on these kids faces said it all, they were having a hoot, and I have rarely ever seen boats go quite so fast.

It is of no concern to me what you believe and what you wish to believe.   That’s your problem.

I know what the boats are capable of.

I am vey comfortable with my comments and have no real need to do any more.

 

                            jB

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On 10/31/2021 at 12:43 AM, JulianB said:

At the end of the day, that's roughly where I have my fin, but I can't see why that would reduce induced drag.

Love to hear the thinking on that, I get that you already commented you have not seen the data, but it would be interesting to see why someone thinks that?    Normally such things have a element of substance behind them, ofcourse Moths have anhedral which is therefore counter intuative even to me, and as I said before, what do I know, I have always just put my TE perpendicular to the keel line aft and worked around that.

FWIW, our 40’ cruising sled has a forward swept bulb keel initially inspired by Gutelle and dinghy class practice. David Vacanti was involved in the hydro. She’s not a racer, but based on feel, grip, smoothness, speed and height upwind, we’ve been happy, and she’s stable, never a twitch planing downwind.  Tiller driven.  ( On the other hand, Bob Perry, the designer, in his book ‘Perry on Yacht design’, written after Amati’s design, states he’s skeptical about forward sweep, so there you go….)

Always liked your balsa 18- Amati is constructed using Steve Rander’s COVE method- e glas, strip planked cedar, e glas, klegecell, e glas, cedar, e glas, all in epoxy. Deck uses e glas, plywood, e glas, klegecell, e glas, plywood e glas 20 years later, still stiff.  

Nice project of yours!
 

 

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Amati,  Moths (following in your footsteps) have proven that fwd sweep is not such a bit deal. Had a very interesting conversation WRT "to bulb or not to bulb" with Leon few days back. When I say no bulb, I'm talking lead in the fin rather than that in the bulb. 

If you assume that you are getting a endplate effect from the bulb, then my back of the envelope maths would suggest that you would have to increase the size of the fin and infact be at a greater disadvantage without the bulb than you would be with it.

Whole range of assumptions yad yad yad, but the reason I am saying this now, in reference to your fwd sweep is you fwd sweep to increase efficiency (as commented before by Sidecar) if you have a bulb (or a endplate) then KISS and just make it vertical or close to it.

Really appreciate your comments,  adds to the colour of the conversation.

      jB

BTW, given the developments in the ABSA, Leon and I will probably get small 70-80kg bulbs made.  One for him, one for me.

 

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Hi Julian B,

Thank you for continuing to post and comment on the 89er progress. I've read your book (and Frank's) and it's still very insightful to follow and appreciate the thought and science that goes into developing a new boat.

A little off topic but i wondered if you have/or could express your thoughts on the RS Aero? Is the design right? The class seems to be building towards success with growing fleet numbers (something lacking in my region of fragmented classes). 

 

Kind regards

Dave

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