89er

JulianB

Super Anarchist
1,162
1,550
Sydney mostly
It's happening,  jB 20211112_095409.jpg IMG-20211112-WA0002.jpeg

 

Ncik

Super Anarchist
2,180
396
Are you going for a male mould or will this be a plug?

Why aren't you doing the method with foam on the jig, then remove from jig, flip and laminate?

 

JulianB

Super Anarchist
1,162
1,550
Sydney mostly
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.png

 

JulianB

Super Anarchist
1,162
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Sydney mostly
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.png

image.png

 

stealth

New member
41
3
Singapore
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

View attachment 474091
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. 

 

JulianB

Super Anarchist
1,162
1,550
Sydney mostly
image.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

 

Boink

Super Anarchist
1,589
779
View attachment 474253

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.

 

JulianB

Super Anarchist
1,162
1,550
Sydney mostly
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

 

Boink

Super Anarchist
1,589
779
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

 

JulianB

Super Anarchist
1,162
1,550
Sydney mostly
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.

 

JulianB

Super Anarchist
1,162
1,550
Sydney mostly
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

 

Steam Flyer

Sophisticated Yet Humble
44,109
9,536
Eastern NC
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

 

Sidecar

…………………………
3,115
1,487
Tasmania
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!

 

Boink

Super Anarchist
1,589
779
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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