Dave_S

Foils / Wings - Aftermarket installation ?

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Just dreaming, looking for some interesting reading. 

If I were able to fit wings on my rudders and dagger boards I imagine it might easily create 400kgs lift @ 10kn....., 800kgs @ 15kn...., and 

Must be worth having ?

Anyone know of it being done to existing boats....... links ?

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What sort of boat is it?

Haeberlin Composites in Auckland have done more than their fair share of this type of conversion (mainly to SL33 cats) and might even have some old moulds sitting around.

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57 minutes ago, SCARECROW said:

What sort of boat is it?

Haeberlin Composites in Auckland have done more than their fair share of this type of conversion (mainly to SL33 cats) and might even have some old moulds sitting around.

Ah, sorry, used to having it posted.

A Schionning Waterline1480.

It would be nice to get a bit more boat out of the water. 

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Would be easier and cheaper to take 400kgs of gear out of the boat, swap to lithium batteries etc.

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33 minutes ago, SCARECROW said:

Would be easier and cheaper to take 400kgs of gear out of the boat, swap to lithium batteries etc.

I wish :-)

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Along with lift you've got to think about control. How will you keep the angle of attack correct? Pitch them for 2 degrees up and hope for the best?

I don't think inverted T foils are quite ready for mainstream big cats yet.

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Having gone through development cycles of various degrees of "lift fraction" I can say that, yes it could be a good idea. with a few qualifiers however.

For me my experience is obviously rooted in C-class, so your results may vary.

Our first foray into foiling was with off yer rocker, which was a full foiling platform, 2 main t-foils in the water at all times with flaps and wands, and two T-rudders, long ones in the water all the time as well. It flew, it was actually as stable as a truck, but it was not quick comparatively.

A few years later we started down the path again but a more incremental approach to flight, starting with "high lift fraction" sailing, This means not lifting 100% of the mass of the boat, maybe only getting up to say 80% of the mass of the boat on lift.

720620283_SunnyDayonFYH-01.thumb.jpg.7f4a3ef3fc4ca74d659ecf045b78d22d.jpg

This is a shot from a day of testing we did, one of hundreds. Here we had two foils to leeward for testing, one straight to keep the boat from going sideways and another curved one for lift. It was blowing 13 and we were rocking steady mid-20's without stressing at all. Like I really mean it was waaaay less stressful than it might normally have been in the boat. It felt super lively yet under control. Pitch is our big enemy and as you can see we had nice bow-up trim and only about 10' of boat touching the water which had the nice side effect of offering up some great pitch stability that can go away quickly in full foiling mode. I can honestly say that in ten years of sailing C-cats this day was indeed one of the most fun I ever had. It was absolutely glorious, sunny, warm, decent breeze, a bit of seas state and this gradual dissipation of the usual anxiety you might feel when a bit too wicked up in short chop downhill. We totally smoked Caanan in these test runs. We were exceeding our archemedian targets by easily 20% and maintaining those speeds steadily, not cycling up and down. just nice big beautiful grunty VMG. Had one or two of stepped out on the wire we easily could have 15% more of all the goodness we were getting.

A lot of the big tri's have gone through this development step recently before getting fully airborne. With good reason.

Now for us this was not a winning route, essentially because we didn't fly 100% and when we did it wasn't really under control. But if I were to be building a boat today for shits and giggles, I'd not hesitate to have t-foil rudders and some serious, though not 100% lift available from my main foils. It makes life more secure, fun and you're able to step on the gas peddle without hesitation in all manner of sea state.

You don't need tons of deck gear to control AOA of you're not trying to fly 100%. you can go with a progressive foil design that allows you to set lift simply by how much board you put down. For this you need curved foils however, so the more "down" they are, the more lift they offer while still offering side force. Likewise with t-foil rudders, if all you do is put them on and ensure they are tuned to zero AOA at zero pitch, they can work wonders in reducing pitching in sea state. No need for tricky AOA adjustment systems on the rudders. It is nice to have for sure, but it can be fussy to keep both rudders at the same angle, particularly if your platform is not very stiff.

Now I will caution you that we have a rule in Architecture (Buildings not boats) that "curves cost four times as much as right angles". This is pretty much true in building foils too. You need bigger tools to build them and they are harder to machine. I'd also advise that if you are adding 400KG of lift to the boat, you will be adding a bunch more weight to the boat to handle it. Heavier foils, like 2-4 times heavier than straight foils if not more. Our lightest Canaan foils were 6 lbs, our full lifting foils that didn't break in ten minutes were coming in closer to 24 lbs a piece. Suffice to say a fuck-ton more carbon. Our traditional straight foils were two halves of built up foam and carbon laminated together. by the time we were fully foiling successfully, they were solid high-mod carbon right the way through. Which also takes a good deal more time to lay up, consolidate, cook off and machine than old school foils, so there's cost with all that time too.

Not to mention extra bulkheads and strengthening around the board box as you're now lifting the boat, even partially by a point, not the comparatively uniformly loaded hull when floating or planing. Likewise for transoms if you add t-foil rudders. Make sure your rudder system and transom in totality is more strong than normal. You'll have up and down loads imparted to the system that were not there before t-foils.

I will add that even the addition of T-foils to Canaan made our lives very much easier simply by moderating pitch somewhat.

As with all things, you need to learn how to use them. We had one incident on PL at the beginning of a season on a blustery day before we had our wits about us. We went ripping off across the harbor at 20 plus knots with the banana boards fully deployed and all of a sudden found ourselves VERY fucking airborne in an entirely uncontrolled fashion. We should have been lifting the boards more as we got going pretty quick, instead we ended up in a very short positive feedback loop that ended ten feet above the water, then back in the water. It was a bit of a shocker.

885899980_Goddammitkenny002.jpg.f042c2061a391ec9d8432b853075bac3.jpg

Your results may vary

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@blunted, having first got into SA to track you and Fredo dueling with SHC and Cogito in Toronto what now seems like eons ago, I just gotta say: it is this kind of post that keeps me coming back.  Been there, done that, and here's the story.   (But Brexit?  On SA?  WTF indeed)

Moving on: to OP @Dave_S who I hope sees the humour, there are other ways to get a big cat out of the water and riding with a nice bow-up attitude:^_^
attachment.php?attachmentid=158674&d=150

"Looking for some interesting reading?": I have to recommend Dave Keiper's "Hydrofoil Voyager: WILLIWAW" if you can find a copy. 

Keiper was first guy to really cruise foils.  Blunted, Killing still has my copy.  I hope.  Link to vid:

https://www.foilingweek.com/blog/2015/04/williwaw-the-real-first-foiling-cruiser-20-000-miles-from-1970-to-1974/

Like MONITOR before him, Keiper used ladders, but then they didn't have the carbon we have today.  Gotta love the videos of Keiper sizzling across SF Bay... in the 70s... no flaps or moving parts for stability and dynamic AoA, just ladders.  At least ladders have decent inherent negative-feedback with less risk of total cavitation like that of angled surface-piercing foils, like, say Hydroptere.

Sorry, didn't mean to go all DLord on y'all from my armchair here, but you did ask for some reading material... 

cheers, ben

PS: I guess I am showing my age a bit, but FWIW Tom Speer did some thinking about foiling and cruising not being mutually exclusive: http://www.basiliscus.com/CSYSpaper.pdf 
One can find a lot worse people to read than Tom Speer on aero/hydrodynamics. 

PPS: I have to get down south where the water isn't all frozen pretty damn soon or I'll go nuts.  Or get a DN.  Must... stop... wasting time on SA...

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I am slowly building some c foils for a 50' cat, mould has to be done first.

(The foil cases are already in the boat.)

It will work on a big boat as well, exactly as blunted described. 

It will reduce pitch up wind and give the boat the performance of a 65' downwind.

Max lift from one foil will be about 3 ton at 25kn. (The boat weighs 7.5 ton sailing)

My foils will be going approx 2m in front of the dagger boards and can be fully retracted when not required.

We have already used T foils for the rudders but am having trouble keeping them on so currently don"t have them. We were putting them on the bottom of the rudder but could not stop the carbon from letting go. I now know how to fix that. I think from memory they create about 400kg of force each at 20kn so you need pretty strong rudder assemblies as well.

They make quite a bit of difference upwind and down for pitch reduction

In summary it will definitely work for my boat because it can happily sail at 20kn plus, but your boat is quite a bit slower so may not have the same result.

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Thanks all,

blunted, thanks for putting so much in, I think fitting C foils is beyond my retro-fitting ability, I was thinking of fitting a hull conforming inverted T shape on the bottom of the dagger boards. Maybe I should just start with the rudders, I hadn't considered the pitching aspect/benefit. I notice there is no one on the windward hull... did there used to be ?

bacq2bacq Love the pic, that was in the Kimberly where they have huge tides 12m+ (40') with lots of uncharted areas. Those early guys in the videos didn't mind going places to test it out !   I'll have good read through, thanks

bushsailor What sort of boat is yours, sounds fairly similar weight/length wise.

 

I might think about adding wings to the rudders as a start point. They are swing up rudders and the hinge for some reason seems overkill construction wise so I think it will have no issue with some reasonable loads. I'll measure it up and check though.

Can anyone point me in the right direction, From this I would hope to achieve less stress on the boat and better VMG. Does less pitching give me this or do I want some lift as well. If I am after less pitch only, then a wing that has smaller front aspect and trails longer might be a better design and lift might be wider with a shorter cord ?

I am thinking I can fit a cam closing on each rudder box and change the AOA manually by turning the cam down or up, if so what angle range do I want.

 

 

 

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I believe you will want the rudder elevators to be as neutral as possible for that situation.  No reason to change the attitude of the boat, just lessen the pitch right?  

In heavier air with C board A-Class boats, we would reduce rudder lift to let the bows come up a bit more.  Same thing is true on foiling boats where you need less lift at higher boat speeds in higher winds.  If you are stuffing all the time, you could prepare for that if the boat is up to it. 

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Still going through all the info... thanks, one link leads to another and another.

One piece I haven't found is where is 0* AOA. Say at a depth of 0.4m (1.5') is 0* a). parallel with the surface or b). to the hull or c). my guess somewhere in between but closer to the surface level.

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rudders set at O to the optimum waterline of the boat.

Foils should be down at least 1 metre. (ie near the bottom of the rudder.)

If you have the original schionning rudders they would need to be modified first. Then you will be able to steer the boat in rough conditions.

Do a search for Rushour

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On 2/18/2019 at 2:10 PM, bushsailor said:

rudders set at O to the optimum waterline of the boat.

Foils should be down at least 1 metre. (ie near the bottom of the rudder.)

If you have the original schionning rudders they would need to be modified first. Then you will be able to steer the boat in rough conditions.

Do a search for Rushour

rudders set at O to the optimum waterline of the boat.

Makes sense, how do I determine that. My gut says the bows and stern just in touch with the waterline at rest.

 

If you have the original schionning rudders they would need to be modified first.

They are original and are not 1m, more like 500mm, is it length or another factor.

 

Then you will be able to steer the boat in rough conditions.

Will wings degrade steering, I assumed little change but for the better.

Edited by Dave_S

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T foils I might do, but front foils, no..........but just humour me. I discounted the idea because of the complexity of retrofitting them but just for sh#ts and giggles why couldn't they fit in a similar way to the AC monos with arms pivoting from the deck height.

I'm not talking about an active set up remember we are just talking "assisted". If you want them put them down and fix them rigidly before heading out.

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2 hours ago, Dave_S said:

T foils I might do, but front foils, no..........but just humour me. I discounted the idea because of the complexity of retrofitting them but just for sh#ts and giggles why couldn't they fit in a similar way to the AC monos with arms pivoting from the deck height.

I'm not talking about an active set up remember we are just talking "assisted". If you want them put them down and fix them rigidly before heading out.

Well you could do but....

While moving the loads tend to get quite high quite quickly. So if you want to gybe or tack etc, You might find you need to slow down or stop to change their settings. sure in some cases the load helps, like you can "fly" your board up. do you plan on having both sides down at the same time? That's a different story too. On boats with both boards down at the same time you do need to be able to adjust them to get some differential.

 

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3 hours ago, Dave_S said:

rudders set at O to the optimum waterline of the boat.

Makes sense, how do I determine that. My gut says the bows and stern just in touch with the waterline at rest.

 

If you have the original schionning rudders they would need to be modified first.

They are original and are not 1m, more like 500mm, is it length or another factor.

 

Then you will be able to steer the boat in rough conditions.

Will wings degrade steering, I assumed little change but for the better.

"Optimum WL of the boat". It's a trick question / statement. WL at rest should do. Boat was designed to sit on its lines for a reason, optimal WL length. (Multihulls don't plane, regardless of how much we wish they did)

Length of rudder. If you are not flying completely, not a big deal. To make the wings effective, measure their chord (Front to back length at thickest point), the T-foil must be a minimum of two chord lengths below the water to be effective, more is better. If they are loaded up a lot they can ventilate down the length of the rudder quite easily. It's worse if they are operating in the downwash of the front foils. So, if possible, deeper is better, end plate is even better as its the lowest drag solution and has grip the longest.

Wings improve the hydrodynamic efficiency of the rudder for the most part if done properly as they act as an endplate for the rudder which makes it less draggy. However, if you ventilate, your rudder won't steer, it'll just make cool looking bubbles behind the boat. If this is happening you can moderate it with fences on the front of the rudder. Fences are there to stop entrained air from getting sucked down the edge of the foil to the low pressure area of the foil from the surface.

c-cats-0002.jpg.29aedeb81c7ee2c8aff29878a05e16e4.jpg

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56 minutes ago, blunted said:

Well you could do but....

While moving the loads tend to get quite high quite quickly. So if you want to gybe or tack etc, You might find you need to slow down or stop to change their settings. sure in some cases the load helps, like you can "fly" your board up. do you plan on having both sides down at the same time? That's a different story too. On boats with both boards down at the same time you do need to be able to adjust them to get some differential.

 

I didn't imagine adjustable, although rake would not be hard, depth harder without lots of hardware.

I imagined set and forget, inward facing foils that as the windward hull raised the foil would angle more to perpendicular and lose lift but the leftward hull would do the opposite.

I expect to lower them and lock them in place when you raise the sail and not touch them again

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On 2/18/2019 at 2:10 PM, bushsailor said:

rudders set at O to the optimum waterline of the boat.

Foils should be down at least 1 metre. (ie near the bottom of the rudder.)

If you have the original schionning rudders they would need to be modified first. Then you will be able to steer the boat in rough conditions.

Do a search for Rushour

Here's a pic with the rudder up. What are your thoughts ?

20190220_142443.jpg

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4 hours ago, Dave_S said:

Here's a pic with the rudder up. What are your thoughts ?

20190220_142443.jpg

your rudder needs to get longer or your transom shorter if its to have sufficient clearance for starters. Additionally you'll need something more substantial to keep your rudder locked down in place. Does your boat pitch a lot?

As for main foils, once they are under load, everything about them is hard to move. While the drag pushing the foil back may not be huge the friction between the trunk and the foil will be due to the side loads, thus adjusting rake can be hard on the fly. That and a little bit of adjustment can make a big difference in lift.

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They are the standard rudders. They are nowhere near big enough to effectively steer a 15m x 8 ton boat.

Nice kick up system though. Foils generate a lot of vertical load ie up and down so examination of the pivot point would also be required.

That boat is sitting low in the water, a way easier performance improvement would be to empty all  your cupboards out, and your water tanks etc etc

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How big would I need to go ?

The hinge system seems strong enough, I  haven't looked at the bearing thrust specifications. My thoughts were to mount across the top of the rudder box a shaft with two, off centre cams that pressed on top of the rubber box. This would give me the power to make small adjustments to the rudder on the fly. It would not be able to come up if I hit something though.

At 1 day cruising weight it sits on that water line across the back thats visable and the bows are just clear of the water. When the boats is completely empty, about 30mm below it. I have 100lt of buoyancy to put into the outboard wells which should make another 10mm, then synthetic rigging not sure how much gain there.

That's about it, without great expense.

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On 2/20/2019 at 5:24 PM, Dave_S said:

How big would I need to go ?

Eyeballing B53 (probably the tip of the spear of cruisable racer design currently), the rudders seem 5-5.5’ below waterline.

4776DE4F-7AA2-455D-ABAB-D32616B77B13.jpeg

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Thinking about a wing shape. I assume they are talking about the side profile when they talk about asymmetrical and symmetrical. 

I am leaning towards asymmetrical that generates neutral lift at no angle of attack and increases rapidly as angle of attack increases for the smallest leading edge profile.  But I don't know enough to know if the front profile area reduction is equal to, less than or greater than the extra drag created from having a more aggressive wing profile.

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7 hours ago, Bruno said:

No point in adding angled daggers?

I'm happy to do small projects but that's a major. I'm not sure of the benifit for me.

I did think of a swinging curved foil in front of the dagger boards, like the AC monohulls, but without the righting force. I'll never do it but it would be the simplest retrofit. 

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I have 1.2m rudders. You can extend the ones you have or build new ones.

I have a rudder mould and know someone who could make you a set if you wanted to go down that road. (I also have a T foil mould)

The T foil is symmetrical. That way when the angle of attack (water flow over the rudder T foil) changes the foil pulls either up or down reducing pitching.

I cant remember how much force but I seem to recall 300kg at 20kn

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Thanks bushsailor, 

I am concearned about the maths of the forces increasing ^2. I might be beating upwind at 8kn in to the swell when I need it, or on a reach at 18kn. Has anyone come up with a limiting system i.e. a sprung loaded foil that holds against 4500N then can reduce AOA against the spring over X° to 5500N.

 

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I'll jump in and offer my ill informed opinion. 

 

T-rudders, you'd want 0* AOA and a symmetric section. You'll also want the T as low as you can get it, but it doesn't have to be the bottom of the rudder. You'll probably want passive AOA adjustment so you can get to 0*, and zero is measured relative to the actual waterplane of the boat, not a designed waterplane. In flat water you don't want the T to do anything basically. If you want to go really fast, you'd set the rudder AOA to have differential, i.e. the windward rudder pulls down, leeward rudder pushes up, but you have to be built very strong and you have to go fast for it to work. 

We are doing T's on the daggerboards on our 57' cat. We are engineering for 8 tons of lift at 25 knots. We have an asymmetric section with active AOA adjustment on just the T with a push/pull rod inside the board and an electric actuator in the head of the board. Generically speaking, an asymmetric section produces zero lift at ~2*. Our range of motion is minus 2*-plus 5*. We want to avoid a situation where we can generate RM via windward board, and the associated loads on the...well..everything. 

We are targeting skimming, not full foiling. Anecdotally, the ORMA guys say they went from to speeds of 25 knots to top speeds of 35 knots in one generation when they added C's. Maserati has successfully proven that foiling isn't really faster on the MOD70 platform. The F4 has similarly made offshore foiling look like a parlor trick.  

One note: tris can really utilize c boards because they rely on their main hull daggerboard for leeway resistance, and their c boards for z (vertical lift). Cats that try to use c boards for leeway and Z end up with two much leeway resistance when sailing fast (reaching/running) so they pull up their c, giving up Z first and foremost. We are trying to decouple the Z from the leeway resistance. We'll carry the burden of the T foil upwind (@ -2* AOA) but we will be able to turn the Z on when sailing fast while reducing the leeway resistance. 

Hopefully it works...

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On 3/3/2019 at 8:42 PM, soma said:

Generically speaking, an asymmetric section produces zero lift at ~2*. Our range of motion is minus 2*-plus 5*. We want to avoid a situation where we can generate RM via windward board, and the associated loads on the...well..everything. 

....

We are trying to decouple the Z from the leeway resistance. We'll carry the burden of the T foil upwind (@ -2* AOA) but we will be able to turn the Z on when sailing fast while reducing the leeway resistance. 

Upwind @-2* AOA  on the windward foil? Wouldn’t it generate the RM you want to avoid?

other than drag, the RM from a neg. AOA windward foil looks risky — you lose the RM just as you lift the hull out of the water. 

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1 hour ago, EarthBM said:

Upwind @-2* AOA  on the windward foil? Wouldn’t it generate the RM you want to avoid?

other than drag, the RM from a neg. AOA windward foil looks risky — you lose the RM just as you lift the hull out of the water. 

-2 = no lift (up or down) so no extra RM. 

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Okay, so zero lift at -2* because of the asymmetric section (I interpreted ~2* as “approximately 2*”)

Fancy. May I ask who designed these foils?

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1 hour ago, EarthBM said:

Okay, so zero lift at -2* because of the asymmetric section (I interpreted ~2* as “approximately 2*”)

Fancy. May I ask who designed these foils?

Dirk Kramers and Steve Koopman. SDK

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2 hours ago, soma said:

Dirk Kramers and Steve Koopman. SDK

Bahh, what does THAT guy know?

 

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On 3/4/2019 at 11:42 AM, soma said:

I'll jump in and offer my ill informed opinion. 

 

T-rudders, you'd want 0* AOA and a symmetric section. You'll also want the T as low as you can get it, but it doesn't have to be the bottom of the rudder. You'll probably want passive AOA adjustment so you can get to 0*, and zero is measured relative to the actual waterplane of the boat, not a designed waterplane. In flat water you don't want the T to do anything basically. If you want to go really fast, you'd set the rudder AOA to have differential, i.e. the windward rudder pulls down, leeward rudder pushes up, but you have to be built very strong and you have to go fast for it to work. 

We are doing T's on the daggerboards on our 57' cat. We are engineering for 8 tons of lift at 25 knots. We have an asymmetric section with active AOA adjustment on just the T with a push/pull rod inside the board and an electric actuator in the head of the board. Generically speaking, an asymmetric section produces zero lift at ~2*. Our range of motion is minus 2*-plus 5*. We want to avoid a situation where we can generate RM via windward board, and the associated loads on the...well..everything. 

We are targeting skimming, not full foiling. Anecdotally, the ORMA guys say they went from to speeds of 25 knots to top speeds of 35 knots in one generation when they added C's. Maserati has successfully proven that foiling isn't really faster on the MOD70 platform. The F4 has similarly made offshore foiling look like a parlor trick.  

One note: tris can really utilize c boards because they rely on their main hull daggerboard for leeway resistance, and their c boards for z (vertical lift). Cats that try to use c boards for leeway and Z end up with two much leeway resistance when sailing fast (reaching/running) so they pull up their c, giving up Z first and foremost. We are trying to decouple the Z from the leeway resistance. We'll carry the burden of the T foil upwind (@ -2* AOA) but we will be able to turn the Z on when sailing fast while reducing the leeway resistance. 

Hopefully it works...

Rudder AoA differential and negative AoA on asymmetric winglets was used by the ETNZ boys in the last A Cat Worlds to control RM. 

A similarly what would they know?

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35 minutes ago, WetnWild said:

Rudder AoA differential and negative AoA on asymmetric winglets was used by the ETNZ boys in the last A Cat Worlds to control RM. 

A similarly what would they know?

Yeah, it's a potent "go fast" option. We opted to not utilize it. Rudder diff is a good way to generate RM, but it's also a good way to tear your boat apart. Dirk felt a tubby cruising boat has plenty of RM, and it would've given us a new failure point. We are doing enough edge-y stuff as is with the hybrid motors and 8 tons of lift on the dboards. Maybe we'll mod the boat and add rudder diff after the first season...

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Plus...developing a system to rake the rudders from tack to tack takes some effort. It's doable, but complexity goes up. 

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On ‎3‎/‎4‎/‎2019 at 11:42 AM, soma said:

I'll jump in and offer my ill informed opinion. 

 

T-rudders, you'd want 0* AOA and a symmetric section. You'll also want the T as low as you can get it, but it doesn't have to be the bottom of the rudder. You'll probably want passive AOA adjustment so you can get to 0*, and zero is measured relative to the actual waterplane of the boat, not a designed waterplane. In flat water you don't want the T to do anything basically. If you want to go really fast, you'd set the rudder AOA to have differential, i.e. the windward rudder pulls down, leeward rudder pushes up, but you have to be built very strong and you have to go fast for it to work. 

We are doing T's on the daggerboards on our 57' cat. We are engineering for 8 tons of lift at 25 knots. We have an asymmetric section with active AOA adjustment on just the T with a push/pull rod inside the board and an electric actuator in the head of the board. Generically speaking, an asymmetric section produces zero lift at ~2*. Our range of motion is minus 2*-plus 5*. We want to avoid a situation where we can generate RM via windward board, and the associated loads on the...well..everything. 

We are targeting skimming, not full foiling. Anecdotally, the ORMA guys say they went from to speeds of 25 knots to top speeds of 35 knots in one generation when they added C's. Maserati has successfully proven that foiling isn't really faster on the MOD70 platform. The F4 has similarly made offshore foiling look like a parlor trick.  

One note: tris can really utilize c boards because they rely on their main hull daggerboard for leeway resistance, and their c boards for z (vertical lift). Cats that try to use c boards for leeway and Z end up with two much leeway resistance when sailing fast (reaching/running) so they pull up their c, giving up Z first and foremost. We are trying to decouple the Z from the leeway resistance. We'll carry the burden of the T foil upwind (@ -2* AOA) but we will be able to turn the Z on when sailing fast while reducing the leeway resistance. 

Hopefully it works...

8 tons of lift, that's what worries me, while I expect to hit 20kn I don't want the lift to increase ^2 with it because the boats not made to take big loads but I want strong control at lower speeds. Without calculating it yet I guess my boat might be able to handle 4-500kgs per side on the rudders. My cunning plan #763 is to fit a pressure relief into the foils so I can hit 300kgs at 8 knots and thereafter bleed off the angle of attack up to X degrees at a max of 500kgs (10* shown in the image) up and down. I don't see why this wouldn't work providing the design doesn't run out of travel or jamb. I would appreciate comments from more cunning people than me on the principal. It's just a concept drawing of the spring action, don't get hung up on the details, proper design is a week+ work for me, and only after the principal and calculations are made.

T Foil Spring Release Rudder Test - +8deg.jpg

T Foil Spring Release Rudder Test - 0deg.jpg

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That glorious day I described above. One purpose of said day was to take video, tons of video of what we were doing and how the boat was behaving.

Before you draw any mods to the boat, do the same. Go sailing with regular configuration in lots of conditions and if you're serious about research, get video of the boat from off the boat. Go back and analyze it, if need be, frame by frame. We'd do this for foil testing all the time, and we'd have 4 cameras on the boat and one or two off the boat. In a perfect world you have someone abeam, who can see the whole hull and the horizon beyond, its not a model shoot, its research. Then you also have a camera behind tracking roll. In theory if you are measuring pitch, period and frequency you can do it from on board, just lock off some go pros looking off the boat at the horizon.

When you go through frame by frame, measure pitch. you have a horizon, you have a deck, you have a computer, it's easy to measure. It doesn't have to be perfect. You're looking for patterns and weird things happening. You'll discover that the boat perhaps doesn't pitch as much as you imagine it does, perhaps its more the speed or frequency at which the boat pitches that's a problem rather than how much it pitches. 

Now stick a dumb non-moving, easy to build symmetric foil on one rudder. It's the cheapest foiling experiment you can do at full scale. Go sail the boat, and VIDEO. Now compare the behavior of the two modes. Maybe you'll find that by slowing the rate at which the boat pitches it also has the effect of reducing the pitch. It could be that a little goes along way.

For the load stoppers / fuses above. Really cool, totally wouldn't do it myself. If I'm going down the mine, and my rudder foils are helping to keep the bow up, then all of a sudden when I need them most they let go. Fuck that, I already have the scars from a move like that. no, when I'm going down the mine, that's when I most want them to work. Likewise if the bow is way up in the air, I need to get my ass to follow, and full lift on my rudder foils is a great way to do that.

Assy foils on the rudder I think is good on a fully foiling boat, but then what you are asking of the rudders is rather different. If you have a largely archemedian boat, you simply need to dampen pitch and heave, you don't need to fly. As I mentioned on Canaan, the boat was very pitchy with straight foils and rudders. We ended up putting on tiny little wings on the rudders and it made a huge difference. Same thing, Symmetric, maybe 8-10" long in total with a 3" chord. It made a world of difference on the pitching and whatever drag they made was more than offset by the gains from reducing pitching. Keep in mind one of the biggest benefits of stabilizing pitch is that it stabilizes your sail plan. When you pitch in bad enough conditions in a light boat upwind in waves, at times the top of your rig could actually be going backwards relative to the boat, with greatly reduced AWS, then huge AWS, then tiny AWS. downhill, those little winglets give you a few precious extra moments to steer the boat before the bows push on down. They also dampen pitch and heave.

Also remember the momentum of pitch from a rig way up in the air in particular, its takes a lot of force to slow it down, stop it and then reverse it to equilibrium. It takes barely any force to keep it from getting started building momentum in the first place. Thus, a small foil can make a big difference.

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Another great post. I take your point about the research and cheap, quick test. I'll do that, thanks.

The model I drew doesn't release the pressure. It will continue to increase resistance but at a reduced rate. Where a fixed wing increases at ^2 of speed at all speeds, this will allow it to increase at ^2 of speed, but only up to 8 knots/6°, there after it will continue to increase but at a reduced rate as the wing is allowed to rotate against the spring up to a maximum of 500kgs. So at 20knots and 8° pitch I will only have 500kgs on the rudders.

It allows me to have a significant amount of pitch control at low speeds but without tearing my sugar scoops off at 20kn.

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12 hours ago, Dave_S said:

Another great post. I take your point about the research and cheap, quick test. I'll do that, thanks.

The model I drew doesn't release the pressure. It will continue to increase resistance but at a reduced rate. Where a fixed wing increases at ^2 of speed at all speeds, this will allow it to increase at ^2 of speed, but only up to 8 knots/6°, there after it will continue to increase but at a reduced rate as the wing is allowed to rotate against the spring up to a maximum of 500kgs. So at 20knots and 8° pitch I will only have 500kgs on the rudders.

It allows me to have a significant amount of pitch control at low speeds but without tearing my sugar scoops off at 20kn.

Nice engineering solution, but the argument from Blunted should be headed; you want the pitch dampening at speed!!

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14 hours ago, Dave_S said:

Another great post. I take your point about the research and cheap, quick test. I'll do that, thanks.

The model I drew doesn't release the pressure. It will continue to increase resistance but at a reduced rate. Where a fixed wing increases at ^2 of speed at all speeds, this will allow it to increase at ^2 of speed, but only up to 8 knots/6°, there after it will continue to increase but at a reduced rate as the wing is allowed to rotate against the spring up to a maximum of 500kgs. So at 20knots and 8° pitch I will only have 500kgs on the rudders.

It allows me to have a significant amount of pitch control at low speeds but without tearing my sugar scoops off at 20kn.

Decent thinking. Still seems more complicated to me that needed but to each his own.

Do you ever hit 8 degrees of pitch? Really? Here's a level C-class and 8 degrees in either direction. I suppose if I was frequently suffering that kind of pitch I'd want to dampen it too. Or take up golf.

If we ever hit 8 degrees of pitch in either direction, we'd be moments away from a very bad day indeed. you'll note at 8 degrees negative the rudder would likely be out of the water by then.

471372402_CAN102013GRAPHICPROFILE-01.jpg.da6cdbe09c5fdc5aefb550a5cc621292.jpg

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Also, if you just pitch the boat at 8 degrees while plowing it horizontally forward at 20kt the load would be high. However the movement is likely to be more fluid with the speed parallel to the hulls. Whatever wave forces caused the pitch are also the forces that redirected the boat movement momentum.

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I think sometime ago it was discussed that there are some  symmetric  foil shapes which have less lift at higher speeds, that would negate somewhat the engineering problems being discussed. 

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I chose 8* because it is just above the stall figure for the wing profile if it were fixed, and why I picked +/- 10* travel into the wing. They are just figures plucked out of nowhere at the moment. In saying that it often pulls one or the other rudder out of the water.

I get that it would be better to have maximum effort at maximum speed but the reality is my boat won't handle 2.5t smashing up and down on the rudder, I've picked 500kgs as a safe load, it maybe more or less.

I'd be interested to hear opinion of the effect of these numbers on the boat? Maybe I don't need all of that?

I have looked at two options

Option 1. Have a fixed wing with 500kgs +/- lift on the rudder at max speed/angle and 200kg when close hauled

Or

Option 2. A self regulating wing that gives me 300 when close hauled and a max of 500kgs at a lower speed than max. It's not a complex design, I was happy with it's simplicity.

I have assumed option 2 to be the best, but do you think option 1 is better ? It would have less drag.

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I get that it would be better to have maximum effort at maximum speed but the reality is my boat won't handle 2.5t smashing up and down on the rudder, I've picked 500kgs as a safe load, it maybe more or less.

This is why you shoot video. you really need to study the dynamic forces at work. Where does 2.5 tons come from? Is that maximum calculated load the foil will kick off at that speed and angle? Is that steady state loading? What about dynamic loading, If the boat is actually pitching, e.g. rotating through the water its potentially putting more force on the total rudder assembly pushing it down into the water column, which changes the AOA of the foil in practical terms.

From here we get into discussions of the actual sea state you sail in. Take some shots of your transoms as you sail through sea state, are they cycling between being underwater and clear of the water?

Do you know that water in a wave is a horizontal column of water that is essentially rolling in a circle, so there's circulation within the wave itself that affects the AOA constantly and dynamically as well?

I will admit, it gets stupid complicated once you start adding up all the forces and then when you move from a static condition to a dynamic conditions its gets stoooopid squared. At one point I did in fact write a simulation for the C-cat accounting for all the foils, wet and dry and the hull's floatation so we could try to gauge loads and balance the whole thing. It also takes into account crew weight as that is 50% of the boats mass or displacement. it was actually a pretty decent approximation of the loads. The lesson was frequently, speed is your friend and don't make anything to big as it can cause run away positive feedback loops.

Roll, pitch, heave, yaw, forces from 4 foils in a multitude of directions, then add in forces from the sail plan which are critical especially at speed. Nothing fucks up your foiling day more than letting go of your mainsheet that burps the bow up as you just took away a major pitch moment and then you add 4 degrees of AOA to all your wet foils nd kaboom, your flying clear of the water 2 seconds later.

I also note you spend a lot of time thinking about close hauled. In my experience none of the fun stuff happens upwind, rig tension aside all the loads are lower as you're going slower. That having been said, you experience pitch more bashing into a seaway with a big fat beast.

In all of these, the drag is totally marginal, until it picks up a shit ton of weed, then its meaningful and foils do love weed for lunch just like me.

Look at it this way, picture flat water, 12 knots breeze, steady state sailing. What should your rudder foils be doing? Answer? Being quiet and doing fuck nothing. The boat should already be sailing on its lines properly, if not, move the beer out of the transom and trim the boat properly. Now lets say you're going upwind into the waves, what's happening? Is the boat rocking back and forth a lot fore and aft? Then what should rudder foils be doing? Stopping that shit so you don't spill your beer right? Go back to what I said before about stopping momentum before it gets started. It's like an anti-perturbation. It's a condom for movement, it stops it before it can start in earnest.

Downhill, same thing, what is the precise problem you are solving for? Define it and the answer will be much more easy to solve for.

 

 

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On 2/11/2019 at 11:27 AM, bacq2bacq said:

@blunted, having first got into SA to track you and Fredo dueling with SHC and Cogito in Toronto what now seems like eons ago, I just gotta say: it is this kind of post that keeps me coming back.  Been there, done that, and here's the story.   (But Brexit?  On SA?  WTF indeed)

"Looking for some interesting reading?": I have to recommend Dave Keiper's "Hydrofoil Voyager: WILLIWAW" if you can find a copy. 

Keiper was first guy to really cruise foils.  Blunted, Killing still has my copy.  I hope.  Link to vid:

https://www.foilingweek.com/blog/2015/04/williwaw-the-real-first-foiling-cruiser-20-000-miles-from-1970-to-1974/

Like MONITOR before him, Keiper used ladders, but then they didn't have the carbon we have today.  Gotta love the videos of Keiper sizzling across SF Bay... in the 70s... no flaps or moving parts for stability and dynamic AoA, just ladders.  At least ladders have decent inherent negative-feedback with less risk of total cavitation like that of angled surface-piercing foils, like, say Hydroptere.

cheers, ben

PS: I guess I am showing my age a bit, but FWIW Tom Speer did some thinking about foiling and cruising not being mutually exclusive: http://www.basiliscus.com/CSYSpaper.pdf 
One can find a lot worse people to read than Tom Speer on aero/hydrodynamics. 

PPS: I have to get down south where the water isn't all frozen pretty damn soon or I'll go nuts.  Or get a DN.  Must... stop... wasting time on SA...

This is a note about my participation with Dave Keiper in his last foiling experience on this planet.  Keiper brought a Hobie18 to my home in Florida 20 years ago with this aluminum foil set.  A long story: I fixed these foils by filing the hell out of them,  because the sharp leading edges on his 008 struts split the water at speed, and his ClarkY lifters were incredibly draggy.  My conclusion was this foil set was too small for the Hobie 18: it would lift onto foils then crash, in a 7 second cycle.  Dave shipped cut foil sections of the same material but 10% larger, then, sadly departed the next day for a higher purpose.  So I put them all together after filing the crap out of them (as before), and they worked pretty well on the Hobie18.  The smaller set went onto my Hobie16, where it wasn't too bad, at least Sam Bradfield thought it worked pretty well at a big Hobie Regatta.  Then I dramatically reduced the boat weight by utilizing my wooden A-class cat, as shown above, adapting the original small foil set.  It worked well enough for me to take it to an A-cat winter regatta at RIck White's place in S. Florida at Key Largo, 2001.  After the races were over, I attached this foil set and went foiling around a small part of the bay within sight of Rick's dock and the other racers, all proud owners of new fiberglass A-cats.  Then apparently a critical meeting was called on-shore, and instantly, hydrofoiling for A-class was declared illegal.   AND unwanted in the USA.  This is before carbon fiber, a creative sailer might note.  

post-37839-078871600%201341007008_thumb.jpg             CatnipSMfoil2.thumb.jpg.2632a40c5f6c45ad50626f026ea422a2.jpg

Edited by dacarls
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1 hour ago, dacarls said:

This is a note about my participation with Dave Keiper in his last foiling experience on this planet.  Keiper brought a Hobie18 to my home in Florida 20 years ago with this aluminum foil set.  A long story: I fixed these foils by filing the hell out of them,  because the sharp leading edges on his 008 struts split the water at speed, and his ClarkY lifters were incredibly draggy.  My conclusion was this foil set was too small for the Hobie 18: it would lift onto foils then crash, in a 7 second cycle.  Dave shipped cut foil sections of the same material but 10% larger, then, sadly departed the next day for a higher purpose.  So I put them all together after filing the crap out of them (as before), and they worked pretty well on the Hobie18.  The smaller set went onto my Hobie16, where it wasn't too bad, at least Sam Bradfield thought it worked pretty well at a big Hobie Regatta.  Then I dramatically reduced the boat weight by utilizing my wooden A-class cat, as shown above, adapting the original small foil set.  It worked well enough for me to take it to an A-cat winter regatta at RIck White's place in S. Florida at Key Largo, 2001.  After the races were over, I attached this foil set and went foiling around a small part of the bay within sight of Rick's dock and the other racers, all proud owners of new fiberglass A-cats.  Then apparently a critical meeting was called on-shore, and instantly, hydrofoiling for A-class was declared illegal.   AND unwanted in the USA.  This is before carbon fiber, a creative sailer might note.  

post-37839-078871600%201341007008_thumb.jpg             CatnipSMfoil2.thumb.jpg.2632a40c5f6c45ad50626f026ea422a2.jpg

 

Cheers to Dave Keiper, who was way ahead of his time.  Cool story, thanks!  http://www.wingojo.com/dakh/

williwaw9-xl.jpg

https://www.foils.org/wp-content/uploads/2017/09/KEIPER-97-2000-1.pdf

Quote

Dave Keiper is best known and honored for having pioneered and developed the world's first hydrofoil sailing yacht, a 32- footer named WILLIWAW in which he cruised around the Pacific in the late1960s, early 1970s, sailing as far south as New Zealand. He loved the sea and designing smoother, faster sailing vessels.

 

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On 3/8/2019 at 10:57 AM, dacarls said:

After the races were over, I attached this foil set and went foiling around a small part of the bay within sight of Rick's dock and the other racers, all proud owners of new fiberglass A-cats.  Then apparently a critical meeting was called on-shore, and instantly, hydrofoiling for A-class was declared illegal.

Some more sweet (+sour?) history, thanks dacarls.  Never underestimate the self-interested efforts of an entrenched status quorum to screw things up for everyone else.  Feel free to generalize on that thought...

On 3/7/2019 at 10:58 AM, blunted said:

If we ever hit 8 degrees of pitch in either direction, we'd be moments away from a very bad day indeed.

Haha!  EXACTLY!  LMAO.

bb

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On 3/8/2019 at 11:41 PM, blunted said:

I get that it would be better to have maximum effort at maximum speed but the reality is my boat won't handle 2.5t smashing up and down on the rudder, I've picked 500kgs as a safe load, it maybe more or less.

This is why you shoot video. you really need to study the dynamic forces at work. Where does 2.5 tons come from? Is that maximum calculated load the foil will kick off at that speed and angle? Is that steady state loading? What about dynamic loading, If the boat is actually pitching, e.g. rotating through the water its potentially putting more force on the total rudder assembly pushing it down into the water column, which changes the AOA of the foil in practical terms.

From here we get into discussions of the actual sea state you sail in. Take some shots of your transoms as you sail through sea state, are they cycling between being underwater and clear of the water?

Do you know that water in a wave is a horizontal column of water that is essentially rolling in a circle, so there's circulation within the wave itself that affects the AOA constantly and dynamically as well?

I will admit, it gets stupid complicated once you start adding up all the forces and then when you move from a static condition to a dynamic conditions its gets stoooopid squared. At one point I did in fact write a simulation for the C-cat accounting for all the foils, wet and dry and the hull's floatation so we could try to gauge loads and balance the whole thing. It also takes into account crew weight as that is 50% of the boats mass or displacement. it was actually a pretty decent approximation of the loads. The lesson was frequently, speed is your friend and don't make anything to big as it can cause run away positive feedback loops.

Roll, pitch, heave, yaw, forces from 4 foils in a multitude of directions, then add in forces from the sail plan which are critical especially at speed. Nothing fucks up your foiling day more than letting go of your mainsheet that burps the bow up as you just took away a major pitch moment and then you add 4 degrees of AOA to all your wet foils nd kaboom, your flying clear of the water 2 seconds later.

I also note you spend a lot of time thinking about close hauled. In my experience none of the fun stuff happens upwind, rig tension aside all the loads are lower as you're going slower. That having been said, you experience pitch more bashing into a seaway with a big fat beast.

In all of these, the drag is totally marginal, until it picks up a shit ton of weed, then its meaningful and foils do love weed for lunch just like me.

Look at it this way, picture flat water, 12 knots breeze, steady state sailing. What should your rudder foils be doing? Answer? Being quiet and doing fuck nothing. The boat should already be sailing on its lines properly, if not, move the beer out of the transom and trim the boat properly. Now lets say you're going upwind into the waves, what's happening? Is the boat rocking back and forth a lot fore and aft? Then what should rudder foils be doing? Stopping that shit so you don't spill your beer right? Go back to what I said before about stopping momentum before it gets started. It's like an anti-perturbation. It's a condom for movement, it stops it before it can start in earnest.

Downhill, same thing, what is the precise problem you are solving for? Define it and the answer will be much more easy to solve for.

 

 

Great advice here Blunted - and wanted to ask you about the the bits  in bold.

Firstly, in post #31 Soma talks about T's being as low as possible - which is contrary to the I14's which run their Horizontal elements quite close to water surface. Now to qualify - their systems are hung on boxes behind the sterns - but the theory is related to operating the foils in the zone where the stern wave is rising - the foils are flying in this area of upward flow - there is both positive lift - reduced hull immmersion and reduced wave drag - the stern wake between foils and no foils is markedly flatter. But if you place your T foils at the bottom of the rudder then do you miss this zone of upward flowing energy? Or if the rudders are under the sterns (I think you run under stern rudders for endplating on Cannan & FYH). Any Thoughts or experience about this?

Secondly - do you cant your rudders outwards to be flying vertically when weather hull is clear? Because again anything other than vertical translates to some quirky traits in rudder feel - which would be most of the time in the C class, but not neceassrily the case for Dave S's boat.

Thirdly - How much range of rake change do you have on say Canaan or FYH?  (to account for those pesky dynamic changes that we kind of predict but are unsure about when it comes to having foils fixed to the rudder permamently) I speak from experience when we have used the foils to keep the bows up when it gets kind of sporty downhill - survival is faster than swimming in these episodes. You may have seeen the rudders on the new Sodebo Tri - well forward of stern (just behind rear beam)with ability to rake ~+/-5 degrees. Probable that this will give them rudder differential - not just trim changes, but too early to know for certain.

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On ‎3‎/‎10‎/‎2019 at 12:42 AM, Boink said:

Great advice here Blunted - and wanted to ask you about the the bits  in bold.

Firstly, in post #31 Soma talks about T's being as low as possible - which is contrary to the I14's which run their Horizontal elements quite close to water surface. Now to qualify - their systems are hung on boxes behind the sterns - but the theory is related to operating the foils in the zone where the stern wave is rising - the foils are flying in this area of upward flow - there is both positive lift - reduced hull immmersion and reduced wave drag - the stern wake between foils and no foils is markedly flatter. But if you place your T foils at the bottom of the rudder then do you miss this zone of upward flowing energy? Or if the rudders are under the sterns (I think you run under stern rudders for endplating on Cannan & FYH). Any Thoughts or experience about this?

Secondly - do you cant your rudders outwards to be flying vertically when weather hull is clear? Because again anything other than vertical translates to some quirky traits in rudder feel - which would be most of the time in the C class, but not neceassrily the case for Dave S's boat.

Thirdly - How much range of rake change do you have on say Canaan or FYH?  (to account for those pesky dynamic changes that we kind of predict but are unsure about when it comes to having foils fixed to the rudder permamently) I speak from experience when we have used the foils to keep the bows up when it gets kind of sporty downhill - survival is faster than swimming in these episodes. You may have seeen the rudders on the new Sodebo Tri - well forward of stern (just behind rear beam)with ability to rake ~+/-5 degrees. Probable that this will give them rudder differential - not just trim changes, but too early to know for certain.

1. Despite what I said about waves being rolling columns of water and despite most of the C-class team being made of 14 sailors, we never thought about upward energy at that point of the hull. We hung rudders under the boat for a variety of reasons. When it came to foiling, we wanted maximum possible immersion, because when a rudder lets go at speed its bad and its extra easy for the windward rudder to let go. so maximum immersion was required to keep it wet as long as possible.

2. Rudders canted out? Nope. Simply because of the box rule. In this shot below you can see on Cannan we had mid span winglets for a while. The rudders were square to the hulls but the hulls are canted out about 2-3 degrees themselves, so when the windward hull is just clear of the water, the lee hull sits on its lines. For bigger winglets, some were Assy due to the box rule, as the rudder is operated through its range it could not make the boat wider than 14'  

Some of our bigger winglets were assy as they needed to stay inside the box rule.

IMG_7653.thumb.JPG.314eb0599c1f2afc941fc5932a9473b2.JPG

3. Cannan, zero rake change, it was never designed for it. So Canaan winglets are set to be neutral on static waterline. FYH, had about 3 or four degrees on either side of "neutral". The bottom of the rudder shaft was a circle, the top was oval to allow it to track fore and aft. The whole contraption lead to a twisting tiller extension to allow the skipper the tune the rudder rake. But it was not a quick change, 3 degrees would be about 6 turns of the wrist.

c-cats-0010.jpg.e78e63a4fe15bcef91b6a83491b7bfc8.jpg

 

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1 hour ago, blunted said:

1. Despite what I said about waves being rolling columns of water and despite most of the C-class team being made of 14 sailors, we never thought about upward energy at that point of the hull. We hung rudders under the boat for a variety of reasons. When it came to foiling, we wanted maximum possible immersion, because when a rudder lets go at speed its bad and its extra easy for the windward rudder to let go. so maximum immersion was required to keep it wet as long as possible.

2. Rudders canted out? Nope. Simply because of the box rule. In this shot below you can see on Cannan we had mid span winglets for a while. The rudders were square to the hulls but the hulls are canted out about 2-3 degrees themselves, so when the windward hull is just clear of the water, the lee hull sits on its lines. For bigger winglets, some were Assy due to the box rule, as the rudder is operated through its range it could not make the boat wider than 14'  

Some of our bigger winglets were assy as they needed to stay inside the box rule.

3. Cannan, zero rake change, it was never designed for it. So Canaan winglets are set to be neutral on static waterline. FYH, had about 3 or four degrees on either side of "neutral". The bottom of the rudder shaft was a circle, the top was oval to allow it to track fore and aft. The whole contraption lead to a twisting tiller extension to allow the skipper the tune the rudder rake. But it was not a quick change, 3 degrees would be about 6 turns of the wrist.

Thanks for the reply.

Will you be running inward facing L's to overcome the box rule width restictions on future versions? Or setting the rudder placement on the most inward location of the hull (ie not on the true hull centreline) to allow some foil to be placed both sides of the rudder even if the layout remains assymetrical? (From the photos showing how skinny the hulls are, you would not be gaining much real estate by moving the rudderstocks inwards.......)

How much feel does Fred have on the tiller after all the foils and linkages? Sensitive or somewhat dead stick compared to the old simple unadorned variants?

 

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9 hours ago, Boink said:

Thanks for the reply.

Will you be running inward facing L's to overcome the box rule width restictions on future versions? Or setting the rudder placement on the most inward location of the hull (ie not on the true hull centreline) to allow some foil to be placed both sides of the rudder even if the layout remains assymetrical? (From the photos showing how skinny the hulls are, you would not be gaining much real estate by moving the rudderstocks inwards.......)

How much feel does Fred have on the tiller after all the foils and linkages? Sensitive or somewhat dead stick compared to the old simple unadorned variants?

 

Sterns might be skinny but they don't define the edge of the box, the beam is the fatter part of the boat.

No we liked the rudders in the middle of the hull under the hull for end plating effect which makes them less draggy and more effective. As I've said a couple of times now, we didn't need huge winglets to work, so we can fit happily enough inside the box rule with them as is. Symmetric has better structural loading.

The rudders are counterbalanced a reasonable amount so feel is light on the best of days. Generally we never had any complaints about losing feel besides the fact the rudders are simply tiny in the first place. Generally there was very little friction in the system over all. Everything had ball bearing universal joints. If you think about it, there is only four pins in the whole system, its elegant and simple and robust. Never broke a rudder or any rudder hardware except for one time we idiotically flew a hull over a coach boat forgetting about the rudder on Patient Lady, which whacked the coach boat plenty hard and made that rudder kick up.

On Canaan Fredo had a running competition with himself to see just how small we could make the rudders and still control the boat. I think we got some down to about a little tiny shade over a square foot of surface area. That was all fine and dandy going in a straight line at 16 knots, but when getting stalled up on a start line it was hellacious as its not like you can back the jib on that thing to complete a tack. the point of making the rudders tiny was to reduce wetted surface area by any means possible.

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On 3/9/2019 at 12:13 PM, bacq2bacq said:

Some more sweet (+sour?) history, thanks dacarls.  Never underestimate the self-interested efforts of an entrenched status quorum to screw things up for everyone else.  Feel free to generalize on that thought...

Haha!  EXACTLY!  LMAO.

bb

Here are thumbnail pix of Cheetalope (Catnip wooden A-cat), Jackalope (Hobie 16) and Kangalope (Hobie18) flying on Lake Santa Fe, Florida.  They never pitchpoled & never capsized.  If you flew out of the water, the boat would come down, reattach, rise up and away you go again.  Not really fast going hard upwind on foils but still above a beam reach,  beam reach all day long, and downwind was fast and fun.  

fly2.jpg

jacka1.jpg

jacka2.jpg

hydroplm.jpg

CatnipSMfoil5.jpg

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