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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, m

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.    T

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53 minutes ago, Varan said:

Why do American's (boats) have such short poles? 3m, now that is impressive.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

You haven't seen a Moore 30 then. Holy smokes that's a long sprit. It nearly doubles the length of the boat when launched.

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49er has a 2.3m pole, hangs out the bow 1.8m and is 16ft long so pro-rata the 89er pole should be 3.2m and the 49er has a short pole/length is you consider 18teens, or even more freakishly the 12ves.

But structural considerations come into it, to make it 500mm longer, you probably double the weight, plus the spinnaker is likely to lift up rather than pull fwd.

Thinking of a 86mm ID with a 6mm WT as it comes out of the bow.   Still lighter and more robust than a 90mm ID pole.

As I may have commented before, highly probably going to be using a A1.5 spinnaker, so we need separation from the jib, and therefore probably a 69-72% hounds height rather than a 75%+ so we will get separation.     Short windward-leewards you won't be dropping the jib downhill.

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2 hours ago, WCB said:

Looks mean...

Just pick a car full of MDF frames up, I get the spin pole recieving tube tomorrow, my guess, all decks will be on, pre NY, going together like a mechano set, bloody happy.   (sticking point will be the DSS horizontal case), can't put the cockpit floor down before that's gllassed in and I really want to play with that.

I can lift the bow, so I'm guessing I'm lifting 60kgs, (at my age, that's not bad) so if the whole thing is 120kgs, 3 sheets of 12mm MDF, thats 26 x 3 = 78, less say 30% so 55-56kgs of MDF, then maybe 10 kgs of other crap, say 65kgs, so that = 55kgs, and that's not possible, it's got to be heavier than that but the shell has to be 60-65kgs maybe and that's too light.   Anyway, super simply release and rotation, just 2 of us and not even sketchy, simply.

Popped the polyester tabs of the transom frame (so we know they will come off) and it sat right back down into them without issue.     Looking fwd to the next 3 days.

                      jB

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9 hours ago, JulianB said:

 Looking fwd to the next 3 days.

                      jB

As are we!

I forgot about the DSS foils. 

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Just starting a super (hopfully) interesting conversation about DSS, so be fasinating to see where that goes, but time is super short, 2 weeks max, but keep you posted on where that heads.

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3 hours ago, JulianB said:

Just starting a super (hopfully) interesting conversation about DSS, so be fasinating to see where that goes, but time is super short, 2 weeks max, but keep you posted on where that heads.

Was DSS part of the original SCP/stability strategy, or is it a way of lightening ship by getting rid of one old fat bastard?

More room in the cockpit as well?

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2 hours ago, Sidecar said:

Was DSS part of the original SCP/stability strategy, or is it a way of lightening ship by getting rid of one old fat bastard?

More room in the cockpit as well?

It's more about playing around and finding sweet spots.  playing with sections, etc etc. May simply put the case in place, and leave it plugged for 6 month to a year as we settle the boat in.

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2 hours ago, JulianB said:

Lots of MDF frames

20211220_165010.jpeg

Are the MDF frames there as templates for carbon/basalt frames or do they get put into use in the boat?

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1 hour ago, WCB said:

Are the MDF frames there as templates for carbon/basalt frames or do they get put into use in the boat?

Purely as templates, the only frames that we will Basalt is the X frames, they are the ones with the 1/2 oval cut into them, they, along with some FRP tubes carry the mast, the rest simple hold the skins apart.

1st 2 bogged in

image.png.2139e9216480a738647c0c7f645f721f.png

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16 minutes ago, JulianB said:

Purely as templates, the only frames that we will Basalt is the X frames, they are the ones with the 1/2 oval cut into them, they, along with some FRP tubes carry the mast, the rest simple hold the skins apart.

1st 2 bogged in

image.png.2139e9216480a738647c0c7f645f721f.png

Sorry, re-read that and it dose not make sense.

We have pre-laid-up some 8mm PET core with 250gms Bi-Axial cloth both side, I have a bit of "plate" glass, 2.8 x 1.6m x 10mm, absoutly prefect for pulling flat panels down onto and we pre-made 2 by 2.4 x 1.2m panels some time back, so we just jig-saw, rip the peel-ply off them and that's what you are seeing above. We locate them using "easy sand", I think it's a Pu putty, and it goes off in about 2mins in todays heat (34C), then we do the proper cove with thickened expoxy, tomorrow, very light sand and we will "tab" them in, so 50mm wide glass at 45-45°.

You can see the path of the front X frame, (bits of masking tape) all shot with a laser light, that will get laid up on the glass tomorrow, go in maybe in on Thursday!

               jB

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A couple of you have ask me about the bulb, so this is it, it's off a SKUD.   The plan is to use it on a short fin, maybe 1.4m effective ( between the bottom of the hull and the top of the bulb).   It's 138 kgs, that's just me using a pretty rough system but it's +/- 5kgs of that.  

Given Yorky's new ISO measurement process highly probable that we can 1/2ve that, but that's a year away.

         jB

20211223_102654.jpg

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I don’t know too much about bulb geometries, but I was watching this recent Excellence in Yacht Design episode with Kevin Dibley and both he and Bob Perry mention that they use a “beaver tail” for the trailing tip of their bulbs, and Kevin avoids too much rounding on the leading point to reduce the tendency of his boats tripping over themselves when accelerating:

https://youtu.be/uQNrB7sXyeM

Thoughts on that and how this might apply (or not) to the shape of your bulb?

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1 hour ago, JulianB said:

A couple of you have ask me about the bulb, so this is it, it's off a SKUD.   The plan is to use it on a short fin, maybe 1.4m effective ( between the bottom of the hull and the top of the bulb).   It's 138 kgs, that's just me using a pretty rough system but it's +/- 5kgs of that.  

Given Yorky's new ISO measurement process highly probable that we can 1/2ve that, but that's a year away.

         jB

20211223_102654.jpg

A shark/Messerschmitt 262 cross section with a beaver tail is where I would be heading for a bulb keel……

 

BE9996D3-0925-4FE2-A85E-043BF02B6FA9.png

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1 hour ago, atnan said:

I don’t know too much about bulb geometries, but I was watching this recent Excellence in Yacht Design episode with Kevin Dibley and both he and Bob Perry mention that they use a “beaver tail” for the trailing tip of their bulbs, and Kevin avoids too much rounding on the leading point to reduce the tendency of his boats tripping over themselves when accelerating:

https://youtu.be/uQNrB7sXyeM

Thoughts on that and how this might apply (or not) to the shape of your bulb?

My thoughts,

This is not a yacht, it’s a Sportsboat, and I know there is a long debate about what that is, but one thing it is not is a yacht.  I guess that opens a can of worms as to what a yacht is.    I did like Steve's definition because it was simple, so let’s stay with that, my one caveat is it has to be able to plane freely (not down the face of a wave or in 40 knots).  It's a bit like the planning up-wind debate, there is a trigger point, and in that case, it can be very well defined because of the amount of time and effort ($$$) spent by 2 boats (5o5 & I14), clearly defines the point at which that dose and does not happen.   (Nb1)

The above is important, because it defines what the purpose of the bulb is.

In 99% of yachts the purpose of a bulb is to give RM and Stability.   You want to maximise depth of the lead, and you want to maximise the amount of lead and we are talking about a lot of mass, 2-3 tonnes (50-60-70% of total system weight) in most cases, and it’s a significant part of the total system weight.

Also in a yacht the attitude of the boat in all but extreme cases (plunging down a wave or 40 knots) wont change all that much, it will just dig a deeper and deeper hole.

So using some hydronamic “dampers” reduce oscillations in a sizable chunk of lead is most likely a very smart thing to do.   Sure, they will generate drag, but the alternative is to up the structure in the fin, and that could mean lifting the CoG of the bulb/fin combination which is counter-productive.

In this boat, the bulb is likely to be 15% (maybe) of total system weight, and next year could be as little as 7-8%.

It’s primary function is to ensure a level of self-righting and to slow the reactions of the boat down far enough to allow "5 fat old bastards" to be able to have fun.

Add to that, that the difficulty of hanging onto 140kgs of lead via a 480mm (cord) fin is 1000 times easier than hanging onto 2 tonnes of lead with the same cord and 50% longer (span) fin that say a MC38 dose.

And even the MC38 has a far more symmetrical bulb, and its attitude dose alter as it dose get up and plane often, so it goes nose up.    A whale tail or beaver tail bulb would get to be pretty high drag 5° nose up, sure some lift, but it would be negligible compared to the drag!

Nb1, some years (5-10) back there was a debate about this, and I put it in graphical form, see if I can dig that out, it was published here on SA, probably in the dinghy section.  

It was “peer reviewed” so to speak!

     Maybe if we expanded that “graph” it would clearly define a Sportsboat??????

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They were talking about the Dibley FD 33 at the time, which is more of a sportboat. See below for an image of the shape. Discussion is at 53:30 in that video I linked to - Dibley’s bulb shape came from design work being done by Laurie Davidson on the Americas Cup boats.

I haven’t seen a bulb like this in the flesh, so it was interesting to hear the discussion and origin story.

D214EF2A-BD42-4186-8438-74083C116D6E.jpeg

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It's Christmas Day, not going to sit through sailing video today.  Maybe mid week, but a whale tail like that, I can't see much merit, but open to suggestions, flow ofcourse is skewed at 2-3⁰ and if designed well the fin will twist 1-2⁰ (nose down) to alleviate that.  Depends on the CoG/M of the bulb.  Flats on the side could be necking.

Red bulb is necked and CoM is fwd of CoS.

Triangles are obviously not as good as circles for packing mass in and minimising Surface Area, so I'm happy to stay with my elliptical sphere.  Maybe your video will change my POV.

         jB

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I think Julian is right in this one. With so little bulb weight the change in CoG is probably not worth the additional resistance, especially since the boat is designed to get its righting moment from the crew on the wings.

A quick approximate calculation. The bulb maybe has a diameter of 150mm. So the difference in CoG between circular and triangular cross sections would be at most 25mm. Multiply with bulb weight to overall displacement ratio of 0.15 to get the change in overall CoG and you end up with 3.75mm. Reduce this according to deviation from actual triangle shape and bulb share in overall weight.

Julian, what I find more interesting is the idea of the fin twisting. Especially since you derived fin area from experience with dinghies where there is no bulb. Or does the fin twist purely due to the sideforce acting on it? I understand that this would help aligning the bulb with the incoming flow, but it would also increase leeway and therefore angle of attack of the hull wouldn't it?

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51 minutes ago, neuronz said:

I think Julian is right in this one. With so little bulb weight the change in CoG is probably not worth the additional resistance, especially since the boat is designed to get its righting moment from the crew on the wings.

A quick approximate calculation. The bulb maybe has a diameter of 150mm. So the difference in CoG between circular and triangular cross sections would be at most 25mm. Multiply with bulb weight to overall displacement ratio of 0.15 to get the change in overall CoG and you end up with 3.75mm. Reduce this according to deviation from actual triangle shape and bulb share in overall weight.

Julian, what I find more interesting is the idea of the fin twisting. Especially since you derived fin area from experience with dinghies where there is no bulb. Or does the fin twist purely due to the sideforce acting on it? I understand that this would help aligning the bulb with the incoming flow, but it would also increase leeway and therefore angle of attack of the hull wouldn't it?

I'm on my 2nd halipion Margarita after bubbles and red. Talk tomorrow

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2 hours ago, neuronz said:

With so little bulb weight the change in CoG is probably not worth the additional resistance, especially since the boat is designed to get its righting moment from the crew on the wings.

Agree that the bulb is so small that the differences in CoG will be small, as will the extra resistance/increased surface area for the same reason. It is more about interference drag reduction (ie the intersection between the foil and the bulb) and maximising the end plate effect of a deliberately short foil.

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Hi guys, the graph I promissed

image.thumb.png.1c0b1ed5c6ec7e5e1fe8eac152c6db40.png

Started life on the back of a napkin, (WSC, 2014) trying to explain, initially to one mother, then to a group of parents what boat they should be choosing for their kids if they wanted to progress up from Opies into the higher reaches of the HP classes.   Blue is double handed, and the oval represent the effect of the spinnaker, not sure it adds to this debate.    But I need to stress all the info used comes from the WS web site, all the numbers as publish either in the classes’ rules or the tech-specs, so if your going to do this re SportsBoats, you really need to have a rock solid base line for your numbers or you will be pilloried!   (Base point is the 5o5)

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

Twisting foils.

We went down, I was going to say rabbit hole,  but it’s anything but!

Nicky (my sister) used it in the 470 in the Korean Olympics, we used it extensively in 18teens, early 80's to mid 90's and onwards), 49er do it, 29er (with FRP foils) do it and we tweaked a Cookson 12 by adding 750kgs of lead turning the L bulb, into a T bulb and adding area and strength to the TE of the fin, we added 0.75knts and 5° of height and went on to win Hamilton Island race week.

OK, the maths.   Let’s use a 49er, because it’s so well tested in so many countries it’s beyond reproach, you just can’t argue with the results.   And if you search the strings on SA, It’s all been said before.

image.png.1da3039191df83c46cda67f36e2d0cfc.png

Basic geometry of a 49er Centreboard!

image.thumb.jpeg.ccdd4b08ef1b83802d613f06f0490580.jpeg

The closest thing to the sectional shape of a 49er foil in my 60+ year-old NACA book of sections.   (using this because this is a worst case secnerio, new work tells us we are doing a lot better as is the emperical evidence)

And this board supports 165kgs of crew weight with their feet say 3m from the CL and the boats are ostensibly sailed flat.   ½ ve that 3m (Cl -> wing tip), add another 1m to get to the crews CoG, so 2.5m.   2.5 x 165 = 412.5kgs/m torque.  Go to 9erInc and get the arm, (4.378m) so

 412.5kgs-m/4.378m = 94.22kgs (force??).

So that board, outlined above is generating 94kgs resistance and at a guess 99% of the time.

OK that’s a fact, a empirically derived fact, happens every day of the week/year/decade in 50+ countries in the world and you can go down to your local boat park and come up with these numbers yourself.

Empirical evidence is also telling us that this foil is operating [in a] laminar flow "state", so if you look at the above NACA graph RHS, you can see the bucket in the graph, we are operating at a CoL, at say 5 knts (speed coming out of a tack) right in the corner, if not slightly outside the bucket, and by the time you hit cruise speed of about 7kts (nb1) it has to be operating well inside the bucket.

So pick a number inside or very close to the edgy of the bucket, I’m going to pick a CoL of 0.2 (across the bottom).

OK, now go to the graph on the LHS, go up or down (or both) the LHS numbers (CoL) and land on 0.2, run that across to the line in the middle and you will end up with a “angle of incidence” we call it a Angle of Attack [AoA] of approx. 2°! 

Again empirical evidence tells us that a 49er coming out of a tack at say 5 knts gets a yaw (or yawl) of 2-2 ½ ° but once it gets to 7 knts that AoA/yaw has dropped almost to 1°, and again you can go verify this on 50+ countries most days of the week.

OK, nb1, the reason 7 knts is important to me is that’s target speed of the 89er.

So if 0.3m² of area on a 49er can generate 95kgs then

89er, 500kgs of crew, 3.5m wide, ½ ve that so 1.75m + say 200mm (gunwale to CoG of crew) so 1.95m x 500kgs = 975kgs/m divide that by the arm, 6.165m  so 975kgs-m/6.165m = 158.15kgs.

So 158.15 (89er) /95 (49er) = 1.66 x 0.3008 = 0.5m² is need on a 89er if it is to operate laminar and at say 1° yaw.

0.5m² / 0.45m = 1.11279m so I am being conservative and opting for 1.4m.  (yes the foil tapers yad yad yad)

So in answer to your first part, I don’t think the fin is too small, in fact I believe I am being conservative, got a bit in the bank, and given this boats potential for high top end speed and that ostensibly all it RM will come from 5 “fat old barstards” on the gunwale then it’s pretty big/long!

Come back to stage 2 (twist) after you have absorbed all of that.

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2 hours ago, JulianB said:

Hi guys, the graph I promissed

image.thumb.png.1c0b1ed5c6ec7e5e1fe8eac152c6db40.png

Started life on the back of a napkin, (WSC, 2014) trying to explain, initially to one mother, then to a group of parents what boat they should be choosing for their kids if they wanted to progress up from Opies into the higher reaches of the HP classes.   Blue is double handed, and the oval represent the effect of the spinnaker, not sure it adds to this debate.    But I need to stress all the info used comes from the WS web site, all the numbers as publish either in the classes’ rules or the tech-specs, so if your going to do this re SportsBoats, you really need to have a rock solid base line for your numbers or you will be pilloried!   (Base point is the 5o5)

 

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

 

Twisting foils.

 

We went down, I was going to say rabbit hole,  but it’s anything but!

 

Nicky (my sister) used it in the 470 in the Korean Olympics, we used it extensively in 18teens, early 80's to mid 90's and onwards), 49er do it, 29er (with FRP foils) do it and we tweaked a Cookson 12 by adding 750kgs of lead turning the L bulb, into a T bulb and adding area and strength to the TE of the fin, we added 0.75knts and 5° of height and went on to win Hamilton Island race week.

 

OK, the maths.   Let’s use a 49er, because it’s so well tested in so many countries it’s beyond reproach, you just can’t argue with the results.   And if you search the strings on SA, It’s all been said before.

 

image.png.1da3039191df83c46cda67f36e2d0cfc.png

Basic geometry of a 49er Centreboard!

image.thumb.jpeg.ccdd4b08ef1b83802d613f06f0490580.jpeg

The closest thing to the sectional shape of a 49er foil in my 60+ year-old NACA book of sections.   (using this because this is a worst case secnerio, new work tells us we are doing a lot better as is the emperical evidence)

And this board supports 165kgs of crew weight with their feet say 3m from the CL and the boats are ostensibly sailed flat.   ½ ve that 3m (Cl -> wing tip), add another 1m to get to the crews CoG, so 2.5m.   2.5 x 165 = 412.5kgs/m torque.  Go to 9erInc and get the arm, (4.378m) so

 

 412.5kgs-m/4.378m = 94.22kgs (force??).

 

So that board, outlined above is generating 94kgs resistance and at a guess 99% of the time.

 

OK that’s a fact, a empirically derived fact, happens every day of the week/year/decade in 50+ countries in the world and you can go down to your local boat park and come up with these numbers yourself.

 

Empirical evidence is also telling us that this foil is operating [in a] laminar flow "state", so if you look at the above NACA graph RHS, you can see the bucket in the graph, we are operating at a CoL, at say 5 knts (speed coming out of a tack) right in the corner, if not slightly outside the bucket, and by the time you hit cruise speed of about 7kts (nb1) it has to be operating well inside the bucket.

 

So pick a number inside or very close to the edgy of the bucket, I’m going to pick a CoL of 0.2 (across the bottom).

 

OK, now go to the graph on the LHS, go up or down (or both) the LHS numbers (CoL) and land on 0.2, run that across to the line in the middle and you will end up with a “angle of incidence” we call it a Angle of Attack [AoA] of approx. 2°! 

 

Again empirical evidence tells us that a 49er coming out of a tack at say 5 knts gets a yaw (or yawl) of 2-2 ½ ° but once it gets to 7 knts that AoA/yaw has dropped almost to 1°, and again you can go verify this on 50+ countries most days of the week.

 

OK, nb1, the reason 7 knts is important to me is that’s target speed of the 89er.

 

So if 0.3m² of area on a 49er can generate 95kgs then

 

89er, 500kgs of crew, 3.5m wide, ½ ve that so 1.75m + say 200mm (gunwale to CoG of crew) so 1.95m x 500kgs = 975kgs/m divide that by the arm, 6.165m  so 975kgs-m/6.165m = 158.15kgs.

 

So 158.15 (89er) /95 (49er) = 1.66 x 0.3008 = 0.5m² is need on a 89er if it is to operate laminar and at say 1° yaw.

 

0.5m² / 0.45m = 1.11279m so I am being conservative and opting for 1.4m.  (yes the foil tapers yad yad yad)

 

So in answer to your first part, I don’t think the fin is too small, in fact I believe I am being conservative, got a bit in the bank, and given this boats potential for high top end speed and that ostensibly all it RM will come from 5 “fat old barstards” on the gunwale then it’s pretty big/long!

 

Come back to stage 2 (twist) after you have absorbed all of that.

 

Thanks for this rather detailed response Julian. I probably should have phrased my question differently. I was not actually questioning how you derived your foil area. I was more astounded that dinghy foils actually twist this much and then wondering how transferable this actually is to something with a lump of lead at the end.

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Stage #2 Twist, otherwise referred to as Gybing and Feathering.   Again, this has all been discussed in SA in the past, but I will try and make it relevant to yachts & Sportsboats.

Couple of huge differences between a 49er fin and a Sportsboat fin, the biggest one being no bulb and therefore the 49er has no lower endplate.

And there are even bigger difference’s between 49er-Sportsboat (fin) and a yacht (keel), a yacht needs to heel to generate RM to generate thrust.

WRT the 49er, we do 2 things to minimise drag from there being no lower endplate, #1 is we “feather off” the camber starting from about 250mm up (from the tip) we go from 9.5%ish which is approx. the camber coming out of the hull, all the way down to when we start to feather, we then feather that of 5.5-6%ish at the tip, and #2 we allow the board to naturally feather (twist).

Go back to the original diagram,

image.png.1da3039191df83c46cda67f36e2d0cfc.png

The CoE is above the CoA because of this feathering, the reduction in camber in the foil as you get closer to the tip. And represented by the blue line you have a line of the approx. pressure resolution.

So the placement of that blue line is defined by the sections of the foil.   This is very much an approximation, there is simply to little work done in this area for anyone to be definitive.    All our results are empirically driven.

You could now draw a 2nd line that is defined mostly by the placement of the unie directional reinforcements that you put in the board to resist the 95kgs of side load generated by RM/Arm but more so to resist the 2 gorilla’s jumping on the tip in the last race of the Olympics, it is in-fact 4-5 times the sailing load.

So now if that approx. structural resolution line is in front of the approx. pressure resolution line, then the board will feather, if it is behind it will gybe.

Don’t only think about that approx. structural resolution line being vertical, it can easily be at 30° so the whole tip blades of.   And the force that drives that tip movement is the arm between the approx. structural resolution line and the approx. pressure resolution line, and the force which is the approx. 95kgs coming from RM/Arm.

The amount you are looking for is not a lot, in the case of a 49er doing 7-8-9knts, ½ ° is a lot because yaw is approx. 1°.

 Just to hang a few added things here, in the case of a 49er or any HP skiff, all you really want is for it to go the right way, you don’t want it to gybe, and you want that for 2 reasons 1) if it feathers then the lift from the tip of the foil reduces and that rises the CLR and that increases available power because of the reduction in the arm and 2) if it feathers it reduces the load carrying capacity of the tip of the foil and that reduces the pressure differentials and that effectively endplates the foil and that leads to AR benefits.

But it’s very much self-limiting in that as the tip feather, the load at the tip reduces and that reduces the force needed to feather.

Some other boats, actively opt to gybe, the 2 most obvious are the 5o5 and I14 but there are others that do it without gybing the board in the case and they do it because the reduction in yaw drag outweighs the increase in tip-losses.

Just going back to the 30° approx. structural resolution line, it is also possible to “over-rotate” the tip so that it will over twist to either feather of gybe, and yes we have done it, but not to any great success.

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

I laboured on WRT 49ers and Sportsboats because if we have enough foil at 5knts, coming out of a tack, then we have excessive foil at 7 knts.

Unless you have a excess to “feather” then you can’t get a benefit, but just about all designers put foils on that are big enough to get the boat going and therefore by definition are too big once your going.

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

WRT the Sportsboat, there is far less need to feather, mostly because there is an endplate, so ½ the reason for doing it is negated.

But the lift in CLR is still significant so if you can engineer it via tapering of camber in the sections or via allowing it to feather, you probably should.

Just playing devil’s advocate for a second, you can equal make a case for gybing and reducing yaw and it’s likely to be effective because of the bulb/endplate!

I plan on making quite a few foils, for Don’t Panic, and I’m pretty sure the feathering ones will be popular.

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

WRT yachts, and this was also true of the SKUD, if you have the CoG of the bulb in front of that structural line, and that is very simple to do, far simpler than what we are doing in the 49er or the Sportsboats, then as soon as you start to heel, you have a significant torque from that displacement than can be use to great effect to feather the keel.

L bulbs are good for ensuring there is no weed but not a lot else.

L blubs everything goes the wrong way; you don’t even have enough volume forward to generate an effective enough endplate.

That being said, I have never designed a boat with a L bulb, so I know shit!

The other limiting factor is that most yacht keels are a significant % camber and the twist goes down as a X² law as the camber goes up.

To make this work you need max 11-12% camber foils on boats that move fast, and you need to design in twist.

All keels/fin/foils twist, just need to make it go the right way, and your ½ way there.

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

As a close, go look at http://airfoiltools.com/airfoil/details?airfoil=naca64a010-il simplify it by only clicking on RNs of ½ and 1 million.    Look at where the bucket is now compared to the graph in the previous post.    Need to stress this is aero, not hydro and it really is just a feel-good confirmation that we are heading in the right direction.   I also need to stress we are not using naca64a010 section but it’s a nice section and a great starting point.

 

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Hi, so a few are asking how we know its feathers or gybes, and what do I mean by empirical evidence.

Probably the best example is with the 470 centreboard, from memory it about 0.4m² in surface area (49er is 0.3m²) and it has to be because it’s,  a) not going nearly as fast (as a 49er, hull speed is mid 5knts) and the ability to resist sideload goes up as a X² of speed, b) it’s section is governed by class rules so the section can’t overly evolve but c) has only 1 on the wire, off the gunwale, so it dose not have the same side load and then again d) it’s Arm is 800mm less  (than a 49er), anyway, it has evolved just like every class evolves, as everyone chases an edge.

But at Nautivlea (Milan), they have a 20 tone press, so it’s pretty easy to put a centreboard in it and mimic a centre-case, also if you do the maths, Alberto (one of the owners) almost exactly equals (his body weight) the side load (hi 70’s to low 80’s) and we can also pretty accurately identify the CLR on that foil.

So to get Alberto to stand on a rubber stopper placed on the CLR and see what happens with tip deflection and resulting angle of the tip is very easy.

49er (& 29er) are a bit more complex, the rules governing the construction are similar, but the compliance is far far stricter.    We measure every foil before it’s IHC tagged, and the foil has to fall within a tight range, plus the foils come out of very controlled moulds, in the case of the 49er, there are only 3 of them, there will never be any more and they are within 0.25mm of each other.

But same – same!   Put the board in the jig and load it, I can’t mention the actual number or the amount of deflection allowed but its triple to quadruple the operating side load, it’s applied at the tip (rather than the CLR) and the range is small (what you would expect from a 470).

Equally easily, you can drop the test load back to the 95kgs mark and measure what happens to the tip, how far it moves and how far it twists.

Re CLR/Pressure line, we can deduce that from looking at balance, how much the rudder is carrying, and then make a alteration, say move the rig aft 20mm, and look at how much of a increase in weather helm you get.    I’m not mentioning numbers because these are closely guarded data held by most Olympic teams, but doing circular measurements you can identify with a high degree of accuracy what’s happening.

It’s also as simple as looking at the pivot line in a rudder, and the weight on the helm, and working out how far behind the pivot line is the pressure line.

Many years ago, with Dad, we hung foils over the side of a speed boat, and Comanche commented in SeaHorse, they mimicked Dad’s test of 20 years earlier when generating foils.    Though that is quite ancient, we very quickly found out resolutions of pressure/loads.

Of course there is a large amount of aerodynamically derived data, and the diagram above has been drawn based on that.  (the std 33% or rd)

Lots of ways of getting that position.   Hydrodynamically it’s often further aft, depending on section, using sections like the NACA-a60010 above it’s back in the hi 30% range.

Then, as outlined above, once you know the load and where to apply it, deriving a result is simple, and probably conservative!

 

 

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Hi peoples, ran into or have been contacted by quite a few of you over the Christmas/NY and it would appear that Alex’s video’s are a hit, so we will try and do a few more of those.  The reality is the big lay-ups are all done, but people seem to be interested in my Glass table and vacuum onto that, so I will try and video, the Aft X frames which should happen tomorrow or Friday.   Fitting decks, things like that we can video!

Yesterday, with GT, we got up at 3am, and drove to Brisbane (9hrs, wheels turning) packed up 6Pac and drive back (almost 10hrs) sitting on the speed limit because double demerits and all that stuff.

Arrived back home at 1am, so 22hr round trip which 19hrs wheels turning, big day!

Today is also a public holiday here, so we put the mast up, and plan to sail Saturday.   The really big thing is I now have my test bed back, so all those doubts and questions, I can get an immediate answer.   So feeling bullish.

Had the huge honour of Hugh Welbourn (conceptor of DSS) contacting me and we have exchanged a few emails, the big issue WRT DSS and the 89er, is I plan to sail it flat.   To get DSS to work you need to heel it to get ½ the foil 300mm down to make it work and if I do my numbers, it’s 12-15° and that sort of defeats what I am trying to do.

The 5 “fat old bastards” committee and pushing me very hard to get this finished, and GT seems to be selling off rides, not sure that will come to pass but we have decided to really go hard on the KISS principal, so I will build in the capacity to instal DSS later, and more interestingly the possibility to instal what sort of is being referred to as “quadrant” foils.   To me a quadrant is a 45° segment of a circle, and these foils could be 45° but more likely 40ish°, I know I am splitting hairs.   They would have a radius of about 1m, length of about 1900mm, you would carry a pair, so Pt & Stb, you obviously deploy the leeward one and at 8knts, if they are 400mm cord and 1540mm span, asymmetric section, they could lift the boat.   The big thing that came from Hugh of the upwind benefits, I was thinking of DSS to play foils and downwind when boat speeds are up there.   Maybe with Quadrants you would only ¾ deploy them downhill, but upwind, CoB/resolution (it’s not buoyance) is massive, you would go from about 1 tone of RM to just under 2 tones.   And lift the boat up and out in the process.

I hope to catch up with Hugh in UK in February over a very long drink and we will probably both leave with sore heads.

I can, with probably less than 1kg of additional weight future proof the structure so these can be added in 6-12-18 months’ time if ever.

Wednesday and Friday, I’m helping be part of the RM for the 29er nationals so it’s a short week, but lots of thinking happening.

Ciao, hope everyone stayed safe over the break!

 

 

image.png.777c666c9629b89cc08f87d7c3aa6fb0.png

Quadrant foil deploied, and you can see where the DSS would go.

image.png.935bd2a2a9d178494becd0bb366ee8cb.png

Quadrant foil raised.

Really interesting geometry, you have so many options, and Hugh was great with target AoA idea's especially on a boat like this where there will be more live/moving ballast than boat weight.

May take a few weeks (months or years) to get my head around it.

 

 

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5 hours ago, JulianB said:

Hi peoples, ran into or have been contacted by quite a few of you over the Christmas/NY and it would appear that Alex’s video’s are a hit, so we will try and do a few more of those.  The reality is the big lay-ups are all done, but people seem to be interested in my Glass table and vacuum onto that, so I will try and video, the Aft X frames which should happen tomorrow or Friday.   Fitting decks, things like that we can video!

 

Yesterday, with GT, we got up at 3am, and drove to Brisbane (9hrs, wheels turning) packed up 6Pac and drive back (almost 10hrs) sitting on the speed limit because double demerits and all that stuff.

 

Arrived back home at 1am, so 22hr round trip which 19hrs wheels turning, big day!

 

Today is also a public holiday here, so we put the mast up, and plan to sail Saturday.   The really big thing is I now have my test bed back, so all those doubts and questions, I can get an immediate answer.   So feeling bullish.

 

Had the huge honour of Hugh Welbourn (conceptor of DSS) contacting me and we have exchanged a few emails, the big issue WRT DSS and the 89er, is I plan to sail it flat.   To get DSS to work you need to heel it to get ½ the foil 300mm down to make it work and if I do my numbers, it’s 12-15° and that sort of defeats what I am trying to do.

 

The 5 “fat old bastards” committee and pushing me very hard to get this finished, and GT seems to be selling off rides, not sure that will come to pass but we have decided to really go hard on the KISS principal, so I will build in the capacity to instal DSS later, and more interestingly the possibility to instal what sort of is being referred to as “quadrant” foils.   To me a quadrant is a 45° segment of a circle, and these foils could be 45° but more likely 40ish°, I know I am splitting hairs.   They would have a radius of about 1m, length of about 1900mm, you would carry a pair, so Pt & Stb, you obviously deploy the leeward one and at 8knts, if they are 400mm cord and 1540mm span, asymmetric section, they could lift the boat.   The big thing that came from Hugh of the upwind benefits, I was thinking of DSS to play foils and downwind when boat speeds are up there.   Maybe with Quadrants you would only ¾ deploy them downhill, but upwind, CoB/resolution (it’s not buoyance) is massive, you would go from about 1 tone of RM to just under 2 tones.   And lift the boat up and out in the process.

 

I hope to catch up with Hugh in UK in February over a very long drink and we will probably both leave with sore heads.

 

I can, with probably less than 1kg of additional weight future proof the structure so these can be added in 6-12-18 months’ time if ever.

 

Wednesday and Friday, I’m helping be part of the RM for the 29er nationals so it’s a short week, but lots of thinking happening.

 

Ciao, hope everyone stayed safe over the break!

 

 

 

 

image.png.777c666c9629b89cc08f87d7c3aa6fb0.png

Quadrant foil deploied, and you can see where the DSS would go.

image.png.935bd2a2a9d178494becd0bb366ee8cb.png

Quadrant foil raised.

Really interesting geometry, you have so many options, and Hugh was great with target AoA idea's especially on a boat like this where there will be more live/moving ballast than boat weight.

 

May take a few weeks (months or years) to get my head around it.

 

 

Would it make sense to keep this boat in its original form and build a second boat down the road that is DSS specific and can be treated as a unique boat?  

I can appreciate the fatigue of a drive like that. When I bought my Melges 24 I drove up to Seattle and back. 28 hours driving solo, 30 hours total. I was supposed to go with a friend of mine but he was diagnosed with Covid the day before we were supposed to leave so it didn't leave any time for finding a co-driver and I even had to find a different tow vehicle.  Pretty funny looking back.  My wife was actually happier that I was driving solo because then we didn't have to worry about Covid as much.  Funny how one's priorities can shift.

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WCB, by far the biggest reason is I'm 65 this year, and I have wanted to do this for a very long time, but I simply don't have a 2nd boat in me.   So this boat has to be it!

The other reason is that with approx 1.5m² of basalt I can future proof some of the internal structure so that should I want to go for DSS or Quadrant foils I can!     I would add maybe 0.1m² of additional framing, right at the front of the centercase, and that's possibly a good thing anyway, so for max of 2kgs, if in 6-12-18months I want to play, I can!

So really looking forward to going back up there in a few hours, really enjoying working with Alex, really enjoying making this happen, but as a designer I am committed up to the wahozzie, and I can't ever see myself getting 6 months free again to indulge in a project like this again.

                          jB

I thought I was f--king mad, with 18hrs and a co-driver and a light boat, you are certifiable!   

Lucky we are all a bit crazy, life would be very boring if we where not!

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3 minutes ago, JulianB said:

WCB, by far the biggest reason is I'm 65 this year, and I have wanted to do this for a very long time, but I simply don't have a 2nd boat in me.   So this boat has to be it!

The other reason is that with approx 1.5m² of basalt I can future proof some of the internal structure so that should I want to go for DSS or Quadrant foils I can!     I would add maybe 0.1m² of additional framing, right at the front of the centercase, and that's possibly a good thing anyway, so for max of 2kgs, if in 6-12-18months I want to play, I can!

So really looking forward to going back up there in a few hours, really enjoying working with Alex, really enjoying making this happen, but as a designer I am committed up to the wahozzie, and I can't ever see myself getting 6 months free again to indulge in a project like this again.

                          jB

I thought I was f--king mad, with 18hrs and a co-driver and a light boat, you are certifiable!   

Lucky we are all a bit crazy, life would be very boring if we where not!

I admit that I completely agree with the idea of going back and adding the DSS later.  I'm working on a new powerboat company and our first idea was to create a day boat that could be modified to a foiler down the road a little. i.e. we would build in bulkheads and "trunks" for retractable foils but not install them initially so when the second version came out with the foils, customers who bought v1.0 could upgrade their boats to foil as well. So I get it...

Regarding the drive, I'm a bit crazy. I like to, or at least I'm pretty good at, rallying for long drives. Luckily for me the Melges 24 towed like a dream and there were zero issues.   Last March that same guy who came down with Covid and I drove the Melges 24 to Miami which was thirty eight hours straight.  No hotels, just naps in the passenger seat.  We were pretty happy to be done with that drive.  

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The speed boat issue is very real, re foiling, known power, known weight, known speed.

I'm doing 5 sailing boats and 3 speed boats in the next 3 years, one entity.

1st (sailing) will do the Asian shows in 3 months time.

Quadrant foils and electric motors for the power boats could be nice.

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1 hour ago, JulianB said:

The speed boat issue is very real, re foiling, known power, known weight, known speed.

I'm doing 5 sailing boats and 3 speed boats in the next 3 years, one entity.

1st (sailing) will do the Asian shows in 3 months time.

Quadrant foils and electric motors for the power boats could be nice.

I may as well spill the beans...I co-founded a company called Bonneville Boatworks.  We're working on all electric powerboats.  The first one was going to be a lot like Candela's C7 but they stole our thunder so we're going a different route with build #1. 

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17 hours ago, JulianB said:

They would have a radius of about 1m, length of about 1900mm, you would carry a pair, so Pt & Stb, you obviously deploy the leeward one and at 8knts, if they are 400mm cord and 1540mm span, asymmetric section, they could lift the boat.   The big thing that came from Hugh of the upwind benefits, I was thinking of DSS to play foils and downwind when boat speeds are up there.   Maybe with Quadrants you would only ¾ deploy them downhill, but upwind, CoB/resolution (it’s not buoyance) is massive, you would go from about 1 tone of RM to just under 2 tones.   And lift the boat up and out in the process.

So if the dynamic RM is (say) doubled at 8 knots due to the DSS foil and the heeling arm remains the same, or even reduced (due to dynamic hull lift), the SCP is halved from ~ 6 to ~ 3, the same as the 49’er. If the DSS foil produces ~ 250 kg lift at 8 knots, (Cl of ~1.0) the 89’er would also have a superior SA/Displ and Displ/L ratio to the 49’er.

All of which means that which means that the 89’er should plane upwind with a DSS foil?

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5 hours ago, Sidecar said:

So if the dynamic RM is (say) doubled at 8 knots due to the DSS foil and the heeling arm remains the same, or even reduced (due to dynamic hull lift), the SCP is halved from ~ 6 to ~ 3, the same as the 49’er. If the DSS foil produces ~ 250 kg lift at 8 knots, (Cl of ~1.0) the 89’er would also have a superior SA/Displ and Displ/L ratio to the 49’er.

All of which means that which means that the 89’er should plane upwind with a DSS foil?

I think the devil is in the detail.

Maybe this could do it, but at present it is not the driving force!

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6 hours ago, JulianB said:

Really like the motor on the Candela's C7, that is one neat bit of engenerring.

 

Agreed, it is beautiful.  I'm quietly hoping that they will sell that to competitors someday.  

I did receive your PM.  I will respond shortly with my email address.

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Julian, I found this thread a few days ago and have thoroughly enjoyed reading it. Quite informative. 

I am looking at the transom and the cockpit sole looks pretty low.

Just want to inform you of a little known rule in the Australian Sailing Special Regulations.

3.08.4 A cockpit sole shall be at least 2% LWL above LWL. For Cat 1-6 racing.

If Don't Panic is trimmed bow down without crew I would think you can easily achieve this. 

Glad to hear you got 6Pac back onto the hardstand.

Love Hitchhiker's Guide to the Galaxy.

See you Saturday.

Yorky

PS. Thanks for kudos on the ISO work!

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Hi

3 hours ago, tedrules said:

Julian, I found this thread a few days ago and have thoroughly enjoyed reading it. Quite informative. 

I am looking at the transom and the cockpit sole looks pretty low.

Just want to inform you of a little known rule in the Australian Sailing Special Regulations.

3.08.4 A cockpit sole shall be at least 2% LWL above LWL. For Cat 1-6 racing.

If Don't Panic is trimmed bow down without crew I would think you can easily achieve this. 

Glad to hear you got 6Pac back onto the hardstand.

Love Hitchhiker's Guide to the Galaxy.

See you Saturday.

Yorky

PS. Thanks for kudos on the ISO work!

Hi Yorky, I am aware of the rule, but the unloaded LWL is actually quite short, and the distance is from the LWL to the top of the cockpit sole, and I'm pretty sure we comply.

But we went low, just like we did with say the 29er, for reasons of safety, getting people back in, so 5 fat old bastards, just imagine GT trying to get me back onboard in the event of mis-adventure.  6Pac would be a struggle.

Plus 90% of the racing we will be doing wont be sports-boat and then if people get ancy, we just dam it up at the right height, blow a Pu core and Velcro it in place.

Dumb rules are just that, dumb rules and they need to be seen in that light.

Just like what you did with ISO, brought clarity to a dumb rule.

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27 minutes ago, Sidecar said:

Certainly is……

Obviously you want maximum lift at minimum AoA with minimum drag.

Best I could find in a cursory glance was Cl: 0.6-1.0, AoA 0-4 deg, Cd: 0.03-0.05>

http://airfoiltools.com/airfoil/details?airfoil=e214-il
 

Hugh obviously has better ones.

Sidecar, you are doing all my work for me and I am being very conservative, plus those are aero and hydro, you don't do hollows as a rule, but yes, if we get those numbers (CoL) then we can very easily get significant sifts in CoB/R.

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31 minutes ago, JulianB said:

Sidecar, you are doing all my work for me and I am being very conservative, plus those are aero and hydro, you don't do hollows as a rule, but yes, if we get those numbers (CoL) then we can very easily get significant sifts in CoB/R.

I enjoy learning……..

I don’t like hollows either, but they do seem to give you better Cl’s at lower AoA’s. Hugh seems to like them:

https://dynamicstabilitysystems.com/technology/

My fag packet tells me that using the numbers upthread, the CoB (dynamic) shift is ~ 1.25 metres to leeward from the centreline?

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3 hours ago, Sidecar said:

I enjoy learning……..

I don’t like hollows either, but they do seem to give you better Cl’s at lower AoA’s. Hugh seems to like them:

https://dynamicstabilitysystems.com/technology/

My fag packet tells me that using the numbers upthread, the CoB (dynamic) shift is ~ 1.25 metres to leeward from the centreline?

Hi Sidecar,

I'm still very much in development of the idea stage. Lots of options, AoA, rake, washout or washin and radius of the quadrant.  

Again, I will structurally beef up the frames that are there but outerwsie do little else.

If but yes, most likely a 1.2 -> 1.3m shift.

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7 hours ago, Sidecar said:

I enjoy learning……..

I don’t like hollows either, but they do seem to give you better Cl’s at lower AoA’s. Hugh seems to like them:

https://dynamicstabilitysystems.com/technology/

My fag packet tells me that using the numbers upthread, the CoB (dynamic) shift is ~ 1.25 metres to leeward from the centreline?

Horses for courses on sections...I've tried more than a few...and these days I design the foils to suit the boat and the speed regime.  So if the foil will be at times running more as a planing surface then they get pretty flat bottomed, but key to all this is to have the foil and hull trim dynamic combination naturally giving you the AoA that you want/need at any sailing point.

That was something I'd figured from the beginning and got sorted in the tank along with a raft of other small stuff.  As ever it's an efficiency game, but as it's over a wide spread of conditions then you have to choose the key areas.  

You also have to look at more than simple L/D ratios of a section to decide where to pin the tail on that particular donkey.

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I'm puzzled by the choice of a constant radius of curvature DDS.  Is that for ease of construction or is it a generation 1 placeholder for later tbd designs?

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6 hours ago, sailhmb said:

I'm puzzled by the choice of a constant radius of curvature DDS.  Is that for ease of construction or is it a generation 1 placeholder for later tbd designs?

It's for ease of retraction.

No idea what bearings I am going to need, milled Acetal/POM probably, probably need to be 20mm thick at least, but if we are talking about lifting a significant proportion of the weight of the boat, that's say 800kgs, 1/2 of the arm at 1200, so 600 and a bury of 300, so it's a 1600kg bearing load, and you are going to need to retract the windward one atleast.      DSS is easy, you tack and then heel the boat to leeward, the foil that was to leeward is now to windward in the breeze, (out of the water) so no load, single simple string, with a bit of inertia, you may get that 200-300mm extended to leeward, so you luff a bit and heel the boat to windward, extend it completely to leeward and then go back to a 12d heel.

Quadrant foils, don't know, because they will still be loaded, hopefully the new leeward foil will be heavily immersed and therefore "more" loaded, so that will take the load off the old windward one, and it can be retracted.   I simply don't know.

Re the radius, being approx 1m, just as I was playing with the 89er, it seemed like a good idea, I tried a bigger radius and a smaller, but you can't go much smaller because you loose to much surface area, and as you go bigger, the spans get difficult to manage,   These quadrants will be loaded to similar level to DSS, (far higher than say a fin/keel) so they will need W stringers inside pretty heavy skins, lots of unies.

You could go J foils but that's quite a step up in complication, and again, not looking to lift the boat clear of the water, just to alter the dynamics, this boat will already have more movable ballast that non movable, and there are very few boats that can claim that, even a 49er is 165/137 so about 120%, if we drop the bulb weight, then the 89er could be 111%, add a 6th "fat old bastard" and your at 128%.

It's like all evolution, today it seems a bit crazy, in 10 years it will be normal, just look at moths and the AC.

Plus the operative word is old, other than getting a young crazy guy fwd, at 65, I will be the youngest on the boat and we just want to have fun, not scare the shit out of ourselves!

Not going to get another chance to do this.

                 jB

 

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10 hours ago, JulianB said:

It's for ease of retraction.

No idea what bearings I am going to need, milled Acetal/POM probably, probably need to be 20mm thick at least, but if we are talking about lifting a significant proportion of the weight of the boat, that's say 800kgs, 1/2 of the arm at 1200, so 600 and a bury of 300, so it's a 1600kg bearing load, and you are going to need to retract the windward one atleast.      DSS is easy, you tack and then heel the boat to leeward, the foil that was to leeward is now to windward in the breeze, (out of the water) so no load, single simple string, with a bit of inertia, you may get that 200-300mm extended to leeward, so you luff a bit and heel the boat to windward, extend it completely to leeward and then go back to a 12d heel.

Quadrant foils, don't know, because they will still be loaded, hopefully the new leeward foil will be heavily immersed and therefore "more" loaded, so that will take the load off the old windward one, and it can be retracted.   I simply don't know.

Re the radius, being approx 1m, just as I was playing with the 89er, it seemed like a good idea, I tried a bigger radius and a smaller, but you can't go much smaller because you loose to much surface area, and as you go bigger, the spans get difficult to manage,   These quadrants will be loaded to similar level to DSS, (far higher than say a fin/keel) so they will need W stringers inside pretty heavy skins, lots of unies.

You could go J foils but that's quite a step up in complication, and again, not looking to lift the boat clear of the water, just to alter the dynamics, this boat will already have more movable ballast that non movable, and there are very few boats that can claim that, even a 49er is 165/137 so about 120%, if we drop the bulb weight, then the 89er could be 111%, add a 6th "fat old bastard" and your at 128%.

It's like all evolution, today it seems a bit crazy, in 10 years it will be normal, just look at moths and the AC.

Plus the operative word is old, other than getting a young crazy guy fwd, at 65, I will be the youngest on the boat and we just want to have fun, not scare the shit out of ourselves!

Not going to get another chance to do this.

                 jB

 

But what you learn here could be directly applicable to a Proto Mini Transat boat where the RM is replaced from 5 oldies to a canting keel solution.

It's a class that when they crack it will really lift the performance envelope. Tanguy hasn't quite cracked it yet with the Verdier Pogo Proto and the KISS scows with straight dagger boards still rule.

As you have identified full flight is not required for your goals, but that is probably where an offshore solution without flat water would get greatest gains (and under autopilot and shorthanded).

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37 minutes ago, Boink said:

But what you learn here could be directly applicable to a Proto Mini Transat boat where the RM is replaced from 5 oldies to a canting keel solution.

It's a class that when they crack it will really lift the performance envelope. Tanguy hasn't quite cracked it yet with the Verdier Pogo Proto and the KISS scows with straight dagger boards still rule.

As you have identified full flight is not required for your goals, but that is probably where an offshore solution without flat water would get greatest gains (and under autopilot and shorthanded).

We have spoken about Mini Transat before on this site.

Because it’s up and directly in your line of sight, sails, masts and sail makers have done a great job of selling themselves and I really do think that the advances in sail making have been quite extraordinary.

But as a ex glider pilot, I do always grimace at the roughness of a sails surface.   In the glider world you would not be seen dead with all those seams and seams perpendicular to the flow at that, the fittings on the mast and by far my biggest bug bear, all those halyards coming out of the mast, right where maximum airflow velocity is.

When I sailed Occasional Course Language, we had one of those 3Di mains with taffeta on one side. 99% of the time the performance with the taffeta to windward was better.  On the pressure surface it did not matter, and the smooth mylar-ish leeward surface held flow better and therefor bigger pressure differential with less drag.

But Newtons 3rd law, what’s in the air has to be balance by what’s in the water and if you do the sums, it’s about right (in terms of areas) but the advances in foils over the last 10-15 years has been dramatic, quite possibly out-striping the advance in masts and sails.

But, still, most money is spent on the bit of low drag flotation in the middle.

Look at Vesta Rocket, look at that new project out of Switzerland that wants to beat Vesta’s mark!

It’s all about the foil in the air and the foil in the water.

Probably without realising it, Hugh probably pushed me away from DSS, at heart, I’m a skiffy, and we sail boats flat, if not heeled to windward, look at the AC, look at the Moth, look at the 49er, in the case of the 49er even though they reduce their RM by heeling it to windward, they still all do it.

That must tell you something.    You simply don’t get that many rock star sailors being supported by that many smart coaches and support teams, + $m's  allowing their charges to do that if there is not a benefit!

Evolution is a bitch, everyone hates it even though everyone knows it’s inevitable!

Maybe what I am thinking of will find it’s way into other boats, very sure it will happen with power boats, hopefully electric support boats for training venues across Asia.     BWT sailing, this is very much were you need a Hugh because he has done the work and he is far more adept than someone like me to make it work.  I also can call on Joaquin (ARG – Prada) so I am in a good space.

But I do have one of those minds that takes a problem to bed (not talking about my wife) and wake up at 2am with a solution, have to run to the computer and 3 hrs later, I may get back to Deidre.

That has happened 3-4 times with these quadrants.

But, stage one, get the boat on the water, maybe after Maggie, (August) we may play quadrants.

Bit on between then and now, but I have no doubt that I will be waking up many times at 2-3am.

Sailing 6Pac on Saturday, get to play with my test bed!

 

 

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3 hours ago, JulianB said:

We have spoken about Mini Transat before on this site.

 

Because it’s up and directly in your line of sight, sails, masts and sail makers have done a great job of selling themselves and I really do think that the advances in sail making have been quite extraordinary.

 

But as a ex glider pilot, I do always grimace at the roughness of a sails surface.   In the glider world you would not be seen dead with all those seams and seams perpendicular to the flow at that, the fittings on the mast and by far my biggest bug bear, all those halyards coming out of the mast, right where maximum airflow velocity is.

 

When I sailed Occasional Course Language, we had one of those 3Di mains with taffeta on one side. 99% of the time the performance with the taffeta to windward was better.  On the pressure surface it did not matter, and the smooth mylar-ish leeward surface held flow better and therefor bigger pressure differential with less drag.

 

But Newtons 3rd law, what’s in the air has to be balance by what’s in the water and if you do the sums, it’s about right (in terms of areas) but the advances in foils over the last 10-15 years has been dramatic, quite possibly out-striping the advance in masts and sails.

 

But, still, most money is spent on the bit of low drag flotation in the middle.

 

Look at Vesta Rocket, look at that new project out of Switzerland that wants to beat Vesta’s mark!

 

It’s all about the foil in the air and the foil in the water.

 

Probably without realising it, Hugh probably pushed me away from DSS, at heart, I’m a skiffy, and we sail boats flat, if not heeled to windward, look at the AC, look at the Moth, look at the 49er, in the case of the 49er even though they reduce their RM by heeling it to windward, they still all do it.

 

That must tell you something.    You simply don’t get that many rock star sailors being supported by that many smart coaches and support teams, + $m's  allowing their charges to do that if there is not a benefit!

 

Evolution is a bitch, everyone hates it even though everyone knows it’s inevitable!

 

Maybe what I am thinking of will find it’s way into other boats, very sure it will happen with power boats, hopefully electric support boats for training venues across Asia.     BWT sailing, this is very much were you need a Hugh because he has done the work and he is far more adept than someone like me to make it work.  I also can call on Joaquin (ARG – Prada) so I am in a good space.

 

But I do have one of those minds that takes a problem to bed (not talking about my wife) and wake up at 2am with a solution, have to run to the computer and 3 hrs later, I may get back to Deidre.

 

That has happened 3-4 times with these quadrants.

 

But, stage one, get the boat on the water, maybe after Maggie, (August) we may play quadrants.

 

Bit on between then and now, but I have no doubt that I will be waking up many times at 2-3am.

 

Sailing 6Pac on Saturday, get to play with my test bed!

 

 

 

 

Insightful as ever. Thank you.

Are you in any way able to quantitatively express the difference in Performance with the Taffeta to Windward or Leeward?

And as a side bar, with exposed/uncovered GNAV arrangements; do you prefer the strut to be sitting in the slot, on Starboard or Port Tack?

Asking for a friend!

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1 hour ago, Boink said:

But what you learn here could be directly applicable to a Proto Mini Transat boat where the RM is replaced from 5 oldies to a canting keel solution.

It's a class that when they crack it will really lift the performance envelope. Tanguy hasn't quite cracked it yet with the Verdier Pogo Proto and the KISS scows with straight dagger boards still rule.

As you have identified full flight is not required for your goals, but that is probably where an offshore solution without flat water would get greatest gains (and under autopilot and shorthanded).

Mini's have a bunch of rules surrounding them that make foiling harder, such as that the boats must complete a pull down test with everything in the worst configuration from 90degrees and a 45kg weight on the masthead, and every proto must pass this, one of the other foilers actually failed an initial one of these due to water ingress from the bearing case and a new waterproofing solution was required.

Another is that the foils must retract inside the box rule, so to have a foil you have to have them protude from a slighly smaller than max beam point, and when both are fully extended they must not exceed 6.5m so you can't have any foil you like.

And of course if you can't foil for some reason (sea state / conditions etc) you need those foils to also act as dagger boards if you want the keel to work when canted, so its a very constricted design problem

(Apologies for the thread drift Julian)

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7 hours ago, Boink said:

Insightful as ever. Thank you.

Are you in any way able to quantitatively express the difference in Performance with the Taffeta to Windward or Leeward?

And as a side bar, with exposed/uncovered GNAV arrangements; do you prefer the strut to be sitting in the slot, on Starboard or Port Tack?

Asking for a friend!

Short answer is no, it was 2004, pretty sure the taffeta was to port, and the numbers where always better on port.

It dose not happen on the Farr 40, also 3Di but no taffeta.

WRT Ram vang, when it exposed on the windward side you should get improved performance!   That's assuming the mast-maker & sailmaker have done good jobs and the strut is not stupid.

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4 hours ago, JonRowe said:

Mini's have a bunch of rules surrounding them that make foiling harder, such as that the boats must complete a pull down test with everything in the worst configuration from 90degrees and a 45kg weight on the masthead, and every proto must pass this, one of the other foilers actually failed an initial one of these due to water ingress from the bearing case and a new waterproofing solution was required.

Another is that the foils must retract inside the box rule, so to have a foil you have to have them protude from a slighly smaller than max beam point, and when both are fully extended they must not exceed 6.5m so you can't have any foil you like.

And of course if you can't foil for some reason (sea state / conditions etc) you need those foils to also act as dagger boards if you want the keel to work when canted, so its a very constricted design problem

(Apologies for the thread drift Julian)

I think I may be more guilty of "thread drift/lateral thinking/going off on a tangent" than you.

One of the big things that Covid has highlighted, given the lack of oppotunities to "shoot the breeze/talk crap" over a beer with people from other regions is the lack of fermentation of ideas.   Really miss that!    Little pearls of wisdom that may spark a idea, like quadrant foils.   Don't even know where that came from, I did email the "5 fat old bastards" a render early in 2021, possibly lat in 2020, probably lamenting the cancelation of Maggie, and future dreams.   God knows what, how where, but I rejected it for DSS, tried to get hold of Hugh, but now, there are so many possibilities to that development, the big issue will be the detail, maybe I need to go look at a Nacra and see how they control incedence because I think that will be the key.

Back on target, just about all the frames are in, starts to get exciting when Alex and I get a full week on it, which may just be next week.

Off on a tanget, talking with Jack (who is the 25 year old buck we 4 fat old bastards drag around with us) while rigging 6Pac last Monday. 89er will have a 11m lightening rod (carbon mast) with absoutly no earthing! So even the shrouds are synthetic, so zero electrical conductivity to the water (earth).

Do I run some Carbon uines into the water so in the unlikely event the current has somewhere to go????

I do remember in 2000 a 49er was hit by lightening, threw a crew 20m away 10 m into the water, the boat that was actually hit, the current went down the mast into that Carbon unies and blew the gelcoat off the laminate under the water line.    It also seriously fried the foam core, it was the Ukrainian boat.

Anyone know that answer or do I just accept it's insulated!

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Sounds like a great reason to me to pull the pin if there's a thunderstorm coming! ;)

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On 1/4/2022 at 4:07 PM, Sidecar said:

If the DSS foil produces ~ 250 kg lift at 8 knots, (Cl of ~1.0) the 89’er would also have a superior SA/Displ and Displ/L ratio to the 49’er.

To finish off the numbers, there is a fag packet formula which predicts ball park “average flat water speeds” based solely on effective waterline length, sail area and displacement. Used for multihulls, the 89’er has similar ratios to many performance multihulls (especially mine), but has a little more wave drag. It is even intended to sail it (almost) horizontally all the time.

Planing aside, with the DSS foil lifting ~ 250 kg @ ~ 8 knots, the 89’er’s average speed would go up another ~ 0.8 knots. With that additional speed comes more lift, and if you factor that in, the overall increase is over a knot.

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13 hours ago, JulianB said:

I think I may be more guilty of "thread drift/lateral thinking/going off on a tangent" than you.

One of the big things that Covid has highlighted, given the lack of oppotunities to "shoot the breeze/talk crap" over a beer with people from other regions is the lack of fermentation of ideas.   Really miss that!    Little pearls of wisdom that may spark a idea, like quadrant foils.   Don't even know where that came from, I did email the "5 fat old bastards" a render early in 2021, possibly lat in 2020, probably lamenting the cancelation of Maggie, and future dreams.   God knows what, how where, but I rejected it for DSS, tried to get hold of Hugh, but now, there are so many possibilities to that development, the big issue will be the detail, maybe I need to go look at a Nacra and see how they control incedence because I think that will be the key.

Back on target, just about all the frames are in, starts to get exciting when Alex and I get a full week on it, which may just be next week.

Off on a tanget, talking with Jack (who is the 25 year old buck we 4 fat old bastards drag around with us) while rigging 6Pac last Monday. 89er will have a 11m lightening rod (carbon mast) with absoutly no earthing! So even the shrouds are synthetic, so zero electrical conductivity to the water (earth).

Do I run some Carbon uines into the water so in the unlikely event the current has somewhere to go????

I do remember in 2000 a 49er was hit by lightening, threw a crew 20m away 10 m into the water, the boat that was actually hit, the current went down the mast into that Carbon unies and blew the gelcoat off the laminate under the water line.    It also seriously fried the foam core, it was the Ukrainian boat.

Anyone know that answer or do I just accept it's insulated!

We had a J24 at out club, got a direct hit on the mast but the earth strap missing from keel to mast base track.
The lightning found 4 damp parts of balsa around the hull, even one aft and blew them out with fist size holes, left burn marks and down it went in 30 seconds.
Was on a mooring.
No marks on the mast at all.
Hard to insulate the mast in a salty environment so it means earth it.

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Lightening protection is hard but some say is possible. A simple strategy that might work and isn't much more work than doing nothing...

is to try to keep the charge on the surface of the vessel and to the water as directly as possible. Connecting the mast foot/base to conductors running along the surface ending just above the waterline would be the least that could be done in my opinion.

The idea is that electric charges from above and below have a simple non destructive path. There is also a notion that if the whole boat was equally conductive it will natural balance the charges from above or below.

I'm sure some disagree.

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One thing is for sure, the lightning will find a way into the water if it hits the mast, regardless if there is a designated path or not.

I think the topic has been discussed elsewhere around here as well. It seems if you create a path, then you have to do it properly, i.e. no bends and large cross sections. Otherwise the lightning will create additional cross section.

Will the boat be dry stored or moored in a marina or on a mooring? Our approach us to hide between the taller masts around us in the marina. We do not have a direct path from the mast to the water so it is theoretically insulated. However, I do not think you can insulate a keel stepped mast against lightning.

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The boat will spend most of its life sitting on it's trailer, on a hard stand.

I could use a bit of scrape carbon tube for a king-post but that would only extend conductivity down to the cockpit floor.

May just wing it.   Not about to run a copper earth, that would fizz.   Only Yorky will have a shorter mast.

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5 hours ago, JulianB said:

The boat will spend most of its life sitting on it's trailer, on a hard stand.

I could use a bit of scrape carbon tube for a king-post but that would only extend conductivity down to the cockpit floor.

May just wing it.   Not about to run a copper earth, that would fizz.   Only Yorky will have a shorter mast.

Isn't that your answer right there? Make sure to park between to keelboats who don't have retractable keels. 

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To some extent, what happens in the boat park is secondary, I'm concerned about what happens if we get a strike while sailing.

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7 minutes ago, JulianB said:

To some extent, what happens in the boat park is secondary, I'm concerned about what happens if we get a strike while sailing.

Unless you have a hand on the mast and in the water crew arent part of the circuit so its down the mast then out wherever it can.
 

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1 hour ago, JulianB said:

To some extent, what happens in the boat park is secondary, I'm concerned about what happens if we get a strike while sailing.

Had HiFi on the hard in Asia, lightning strike blew the top of the mast out, fried all the electrics, eventually grounded out through the transom onto the metal stairway and blew some of the transom out too...grounding straps are a good idea on trailers:)

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On 1/7/2022 at 10:45 AM, Sailabout said:

We had a J24 at out club, got a direct hit on the mast but the earth strap missing from keel to mast base track.
The lightning found 4 damp parts of balsa around the hull, even one aft and blew them out with fist size holes, left burn marks and down it went in 30 seconds.
Was on a mooring.
No marks on the mast at all.
Hard to insulate the mast in a salty environment so it means earth it.

That's an extreme solution to soggy core.

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10 hours ago, JulianB said:

To some extent, what happens in the boat park is secondary, I'm concerned about what happens if we get a strike while sailing.

Worth worrying about. Lightning strikes are really hard to predict but most cases it seems that the crew is safe enough if not in contact with a conductor.

The way I've studied it, it seems to work to try and bleed off differential charge so you are less likely to attract a strike. But the grounding straps (I like braided flat conductors, they also make great radio ground planes) are heavy and need a large area exposed to the water. Platinum is a nice low-resistance material

;)

- DSK

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On 11/20/2021 at 7:01 PM, JulianB said:

 

Saturday 27th got the 7 Islands race, so Stanno, if your at Hunter Hill you can bring me out a beer.

 

 

 

Dammit JB - just started reading this thread and saw this!!  Was actually down at the Club that day and saw the fleet go by!!!  Must catch up soon ... plenty going on at HHSC with another batch of older 49er hulls coming into the Club (with modern rigs (not HDi)) ... 

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2 hours ago, Stanno said:

Dammit JB - just started reading this thread and saw this!!  Was actually down at the Club that day and saw the fleet go by!!!  Must catch up soon ... plenty going on at HHSC with another batch of older 49er hulls coming into the Club (with modern rigs (not HDi)) ... 

Well you owe me a beer, Peroni please!

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55 minutes ago, JulianB said:

Well you owe me a beer, Peroni please!

But of course - will ring when I get back from Sail Melbourne

 

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19 hours ago, European Bloke said:

That's an extreme solution to soggy core.

I sanded the hull as it was painted and it was dodgy repairs only in those areas and were wet. Rest of the hull was dry and solid

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On 12/23/2021 at 6:58 PM, atnan said:

I don’t know too much about bulb geometries, but I was watching this recent Excellence in Yacht Design episode with Kevin Dibley and both he and Bob Perry mention that they use a “beaver tail” for the trailing tip of their bulbs, and Kevin avoids too much rounding on the leading point to reduce the tendency of his boats tripping over themselves when accelerating:

https://youtu.be/uQNrB7sXyeM

Thoughts on that and how this might apply (or not) to the shape of your bulb?

Funny, when we were designing Amati (1999), I was keen on a beaver tail, like our U20, but Vacanti made a great case for a rough water keel which has a rounder front end that doesn’t stick out much, and a stinger tail. Davidson thought we should have gone with the beaver tail.  We do have a forward swept keel though, and the shape of the front end of the keel, when you stare at it for a while, has very much the shape of how I imagine the water would smoothly pile up there.  Going upwind in chop Amati feels very glued to the water, but the motion is more fluid than our U20, but the U20 was fatter with a beaver tail.  When we do stuff the bow into a wave upwind, Amati doesn’t slide (get knocked off) off the leeward side, but tends to want to go to the windward side, which is a very cool thing and helps when steering through waves.  We don’t race, so I realize helm feel doesn’t count for much.  But damping longitudinal motion is a fascinating thing, especially coming from a dinghy background, where body input and hull motion are entangled.  Frankly, I find my body language (it’s not easy to undo that) sailing Amati more like my Finn than other dinghies.  If I didn’t have to have fucking lifelines and no hiking straps I’d have my butt over the edge hiking & moving with every wave.  So as it is, I move with every wave and tiller movement as much as I can.  It’s nice to feel a boat dancing with every wave, rather than having that feeling dampened by a horizontal tail.  But if the beaver tail is better than the stinger, wouldn't it stand to reason that it would be better to have horizontal fins on the bottom of a daggerboard of a dinghy?

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