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Doug Lord

Rudder T-foils

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I thought this might happen and it is very, very interesting. The Stealth beach cat and a few others have used them for years. Anybody got good pictures yet? The pix in the other thread-very poor quality-and apparently from a video-show the rudder foil mounted like they are and not at the bottom of the rudder.

http://forums.sailinganarchy.com/index.php...p;#entry2470794 post 24

 

pix of Darrell's cat:

post-30-1253489696_thumb.jpg

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John Pierce of Stealth Marine comments on rudder t-foils on beachcats:

(from Cat Sailor)

 

I will add my experiences to this debate.

 

We first tried the T-foil rudders 5 years ago, it was immediately obvious that they completely altered the sailing characteristics of the boat.

 

This is not one of those changes that you make and you are not sure whether anything actually changes, I say again the boat is totally different with T-foil rudders.

 

Next we had to check whether or not the difference was fast. Like Darryl we carried out 2 boat tuning with identical boats except for the rudders. In no circumstances was the non T- foil rudder equipped boat any faster.

 

In any kind of wave pattern whatever the wind strength the T-foils were quicker both upwind and downwind and in winds > 12 knots the T-foils where again quicker.

 

We also tried them on our formula 18 HT boat and the effect was just as marked.

 

And more recently the current Sptfire European Champion purchased a set and tested them he also confirms my/Darryls comments

 

I have no idea how much drag the T-foils create, and quite frankly I don't care, catmarans go quicker with them on so whatever the figure it is less than the drag of a normally equipped hull travelling through the water.

 

We did no tank testing (I think you will find that not much tank testing time is bought by any beach catamaran manufacturer since it is cheaper to build 2 boats and do the job properly on the sea).

 

As to the weed question, obviously a dagger rudder is harder to clear than a kick up rudder, just as a dagger board is harder than a centreboard. Perhaps if your water is very weedy these are not for you.

 

My credentials for carrying out these tests are that I was a full time member of the British sailing Team racing Tornado, my ISAF World ranking got to 9th, I was paid to sail by the Royal Yachting Association and my job from 1997 to 2000 consisted of 9-5 most weeks 2 boat tuning, with 8 -10 regattas a year thrown in, I have done thousands of hours of this work.

 

I would entirely echo Darryls findings and since we are the only people I know of who have done this and we both completely agree the chances are that we are not mistaken.

 

There is one further effect that is also noticable although I didn't pick up on it for ages, and that is that not only is the boat smoother through the waves but it is also smoother through gusts. Put simply the T-foil equipped boat lifts a hull more slowly when the gust hits, we think that this is because as the gust hits and the rig drives harder, it tries to push the bows down, of course the T-foils resist this, and the windward t-foil obviously adds load to the windward hull slowing down the hull rise and so squirting the boat forwards.

 

--------------------

John Pierce

Stealth Marine

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I thought this might happen and it is very, very interesting. The Stealth beach cat and a few others have used them for years. Anybody got good pictures yet? The pix in the other thread-very poor quality-and apparently from a video-show the rudder foil mounted like they are and not at the bottom of the rudder.

http://forums.sailinganarchy.com/index.php...p;#entry2470794 post 24

 

pix of Darrell's cat:

Well Doug, after your many requests for better photos of the transom, and now foils; I kind of think it's your turn to go get them yourself! :P

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I thought this might happen and it is very, very interesting. The Stealth beach cat and a few others have used them for years. Anybody got good pictures yet? The pix in the other thread-very poor quality-and apparently from a video-show the rudder foil mounted like they are and not at the bottom of the rudder.

http://forums.sailinganarchy.com/index.php...p;#entry2470794 post 24

 

pix of Darrell's cat:

 

Well no better pics for the foils... But we are sure they have been tested!

 

It would explain this oversized and over-ingeneered carbon bottle holding the rudder, which wouldnt need to support any vertical force if not foil-equipped!

post-38390-1253570957_thumb.jpg

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@ Blackman

 

Great picture! I wonder what the pulley arrangement in the middle is for: it looks like a duplicate steering mechanism :blink: .

Ditto for the yellow wire - could it be electrical continuity between hull and rudder stock?

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@ Blackman

 

Great picture! I wonder what the pulley arrangement in the middle is for: it looks like a duplicate steering mechanism :blink: .

Ditto for the yellow wire - could it be electrical continuity between hull and rudder stock?

More likely a sensor to set off the claxton alarm just before it blows???

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@ Blackman

 

Great picture! I wonder what the pulley arrangement in the middle is for: it looks like a duplicate steering mechanism :blink: .

Ditto for the yellow wire - could it be electrical continuity between hull and rudder stock?

More likely a sensor to set off the claxton alarm just before it blows???

I think you are correct, in as far as it is almost certainly attached to a load sensor.

 

Whatever side you might be on (or even neutral ;) ), looking at this photo, you have to admire the detailing and engineering. For all that has been said about A5, she seems to be beautifully built, with some real attention to detail.

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@ Blackman

 

Great picture! I wonder what the pulley arrangement in the middle is for: it looks like a duplicate steering mechanism :blink: .

Ditto for the yellow wire - could it be electrical continuity between hull and rudder stock?

More likely a sensor to set off the claxton alarm just before it blows???

I think you are correct, in as far as it is almost certainly attached to a load sensor.

 

Whatever side you might be on (or even neutral ;) ), looking at this photo, you have to admire the detailing and engineering. For all that has been said about A5, she seems to be beautifully built, with some real attention to detail.

They are both mighty fine beasts. Anything rough, is a weakness, they certainly are a work of art

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I fully Support John's comments

 

I sail one of his Stealth F16's.

 

Before I sailed the F17 I had a EU spec Inter 17 and the F16 is more stable (even being 1 foot shorter) and far better in the bif stuff upwind and down.

 

If class rules allow I will never sail another catamaran without them.

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Doug:

 

Please explain why these two boats will use T-Foils? On the moth a T foil is used for lift. On I14s, etc a T foil is used to keep the ass down and to stop the bow submerging when going downwind in heavy weather on a monohull. All foils are draggy but are used because the benefit is worth it - either getting the whole hull out of the water or stopping a pitch pole.

 

Given that we have seen both DZ and CZ move from lifting (banana boards) board to much straighter boards and given that it will not be blowing much more than a fart in RAK, I am struggling to understand the need for T foil rudders. Tip votices? If that is the case, why not an L foil as is the norm?

 

Thanks,

Clancy

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The lift from the banana boards, or the inclined straight boards reduces the fore and aft stability of the boat.

That is unless they are sufficiently far in front of the LCG that the drive vector of the rig doesn't overcome the weight aft and tip the whole mess into the drink.

Xlot can tell you about how exciting Seignior G was on this account.

Both boats will use T foils to actively manage the fore and aft trim of the vessels.

Foils will also be used top dampen pitching, which given the size of the rigs they are putting on these things is a significant issue even in flat water.

Where the foils are located on the rudders is an open question. Dirk Kramers, with whom I have discussed this more than once, favors having the T relatively close to the surface such that when flying a hull, the weather T is clear of the water.

I think it is a drag having the T entering and exiting the surface ( at least it was on Cogito, PL6 and my A cat) so I favor putting the foil at the bottom of a deep rudder and trying to sail with the weather foil always in the water. By my thinking this means that the foils can be smaller, as I can count on both of them 100% of the time.

Time and testing will tell.

SHC

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Just a quick correction on Clancy's comment. yes, they help you send the 14 hard downwind. But they are very important upwind to LIFT the ass and dampen pitching. Boats are much faster upwind with the foil lifting the ass.

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I put my note up there half in jest, expecting Doug to start on about a monfoilingmaran where he has already done the math and proved out a new concept that will revolutionize the AC. But I'm glad I did as this is much more interesting.

 

Mitch - Agreed. It was just a short note where I was highlighting the difference between a foil designed to lift a hull clear of the water (moth, hydroptere, etc) and one like on a i14 which is about pitch control (both up and down) - again, expecting Doug to talk about DZ/CZ come Hydroptere.

 

SHC - even before DZ went wave piercing, there were two different approaches. CZ seems to have a lot more rocker and seemingly endless overhang at the bow. DZ did not even before the wave piercing bows.

 

Given that DZ seems to have gone after the pitching beast by narrowing out the pointy ends one would assume that there is less need for T foils on the rudders for pitch control, no?

 

Also, one of the things that struck me the first time I sailed a wing (your old PL, I am a buddy of Fred and Blunted's) was how much it increased pitch. With BOR strongly rumored to be winging it, what do you think the pitching will be like due to a wing? Yeah, I know, how much does M3 weight, how much does the rumored wing weigh, what boards will they use in the middle, etc.

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@ Blackman

 

Great picture! I wonder what the pulley arrangement in the middle is for: it looks like a duplicate steering mechanism :blink: .

Ditto for the yellow wire - could it be electrical continuity between hull and rudder stock?

 

Actually the radial is the steering mechanism. The tiller on top is the rudder "link".

The radial and cables lead forward to the wheel.

The tiller on top, and it's struts link the two rudders together.

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The lift from the banana boards, or the inclined straight boards reduces the fore and aft stability of the boat.

That is unless they are sufficiently far in front of the LCG that the drive vector of the rig doesn't overcome the weight aft and tip the whole mess into the drink.

Xlot can tell you about how exciting Seignior G was on this account.

Both boats will use T foils to actively manage the fore and aft trim of the vessels.

Foils will also be used top dampen pitching, which given the size of the rigs they are putting on these things is a significant issue even in flat water.

Where the foils are located on the rudders is an open question. Dirk Kramers, with whom I have discussed this more than once, favors having the T relatively close to the surface such that when flying a hull, the weather T is clear of the water.

I think it is a drag having the T entering and exiting the surface ( at least it was on Cogito, PL6 and my A cat) so I favor putting the foil at the bottom of a deep rudder and trying to sail with the weather foil always in the water. By my thinking this means that the foils can be smaller, as I can count on both of them 100% of the time.

Time and testing will tell.

SHC

 

Steve, Do you think that the trimaran/catamaran differences would possibly make the foil on the bottom of the rudder a better solution for the trimaran, as the entire windward rudder is out of the water all the time?

The catamaran on the other hand has part of the windward rudder in the water, unless the windward hull is flying quite high. The catamaran would possibly have the windward horizontal foil coming in and out of the water more often if it was located at the bottom of the rudder.

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The lift from the banana boards, or the inclined straight boards reduces the fore and aft stability of the boat.

That is unless they are sufficiently far in front of the LCG that the drive vector of the rig doesn't overcome the weight aft and tip the whole mess into the drink.

Xlot can tell you about how exciting Seignior G was on this account.

Both boats will use T foils to actively manage the fore and aft trim of the vessels.

Foils will also be used top dampen pitching, which given the size of the rigs they are putting on these things is a significant issue even in flat water.

Where the foils are located on the rudders is an open question. Dirk Kramers, with whom I have discussed this more than once, favors having the T relatively close to the surface such that when flying a hull, the weather T is clear of the water.

I think it is a drag having the T entering and exiting the surface ( at least it was on Cogito, PL6 and my A cat) so I favor putting the foil at the bottom of a deep rudder and trying to sail with the weather foil always in the water. By my thinking this means that the foils can be smaller, as I can count on both of them 100% of the time.

Time and testing will tell.

SHC

 

Steve, Do you think that the trimaran/catamaran differences would possibly make the foil on the bottom of the rudder a better solution for the trimaran, as the entire windward rudder is out of the water all the time?

The catamaran on the other hand has part of the windward rudder in the water, unless the windward hull is flying quite high. The catamaran would possibly have the windward horizontal foil coming in and out of the water more often if it was located at the bottom of the rudder.

I look forward to hearing Steve respond too.

 

But your premise here is that one of the trimaran/catamaran differences is in how high off the water the windward hull flies. Given how close they are in beam, do you mean to imply they will have different optimal heel angles? I think we determined that the float cant angle of DZ was at about 7 degrees and assumed it was their sweet spot even if the mast can cant about 9 degrees each way. But I don't recall us looking closely enough at CZ's hull cant angle to tell if it's exactly the same angle or not. We do have good pics of both somewhere, posted side by side, and they looked to be quite close.

 

It's an interesting subject, these T rudders an the fact the plane is so close to the surface. But that under-tramp 'sail' is still the biggest surprise to me so far. Steve - Any ideas on that too, please?

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The lift from the banana boards, or the inclined straight boards reduces the fore and aft stability of the boat.

That is unless they are sufficiently far in front of the LCG that the drive vector of the rig doesn't overcome the weight aft and tip the whole mess into the drink.

Xlot can tell you about how exciting Seignior G was on this account.

Both boats will use T foils to actively manage the fore and aft trim of the vessels.

Foils will also be used top dampen pitching, which given the size of the rigs they are putting on these things is a significant issue even in flat water.

Where the foils are located on the rudders is an open question. Dirk Kramers, with whom I have discussed this more than once, favors having the T relatively close to the surface such that when flying a hull, the weather T is clear of the water.

I think it is a drag having the T entering and exiting the surface ( at least it was on Cogito, PL6 and my A cat) so I favor putting the foil at the bottom of a deep rudder and trying to sail with the weather foil always in the water. By my thinking this means that the foils can be smaller, as I can count on both of them 100% of the time.

Time and testing will tell.

SHC

 

Steve, Do you think that the trimaran/catamaran differences would possibly make the foil on the bottom of the rudder a better solution for the trimaran, as the entire windward rudder is out of the water all the time?

The catamaran on the other hand has part of the windward rudder in the water, unless the windward hull is flying quite high. The catamaran would possibly have the windward horizontal foil coming in and out of the water more often if it was located at the bottom of the rudder.

I look forward to hearing Steve respond too.

 

But your premise here is that one of the trimaran/catamaran differences is in how high off the water the windward hull flies. Given how close they are in beam, do you mean to imply they will have different optimal heel angles? I think we determined that the float cant angle of DZ was at about 7 degrees and assumed it was their sweet spot even if the mast can cant about 9 degrees each way. But I don't recall us looking closely enough at CZ's hull cant angle to tell if it's exactly the same angle or not. We do have good pics of both somewhere, posted side by side, and they looked to be quite close.

 

It's an interesting subject, these T rudders an the fact the plane is so close to the surface. But that under-tramp 'sail' is still the biggest surprise to me so far. Steve - Any ideas on that too, please?

Probably the center hull flying with the trimaran is the critical drag issue, as the windward hull is always out. Whereas the catamaran must fly the windward hull to reduce drag. I think the trimaran dihedral, or that the windward hull on the trimaranis clear of the water would allow the windward rudder to be clear almost all the time. Even with the heel being equal.

 

My interest is that the two teams are dealing with the same problem in different ways. The dz has had the float hulls replaced with new hulls that have much less rocker, and a distribution of volume that reduces the effective rocker further. This was done to stabilize the boat, and reduce pitching. The cz has now started experimenting with horizontal foils on the rudder to produce the same effect.

Both are obviously band-aids. Design development being constant, which is the best solution? I'll go out on a limb, and say dz has the better fix.

Foils are great, up to a point, to counter act pitching. When you ventilate your foil, big problems! At the very least you have to re-attach the flow on the foil before any control is recovered.

Dz has been testing lifting foils on their dagger boards. What they may have found is that ultimate control of the boat at speed on a hull form that has high speed stability is a better solution than lifting, or horizontal foils.

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Where the foils are located on the rudders is an open question. Dirk Kramers, with whom I have discussed this more than once, favors having the T relatively close to the surface such that when flying a hull, the weather T is clear of the water.

I think it is a drag having the T entering and exiting the surface ( at least it was on Cogito, PL6 and my A cat) so I favor putting the foil at the bottom of a deep rudder and trying to sail with the weather foil always in the water. By my thinking this means that the foils can be smaller, as I can count on both of them 100% of the time.

Time and testing will tell.

SHC

 

One possible reason for using the shallower rudder foil would be to take energy from the stern wave. Another would be to make it work at a different flow direction, translating into a higher angle of attack with the same incidence. I really don't know if any of this true, but that is what I was told.

The rudder foils on my tri never leave the water, but being in the central hull, the situation is not comparable to a cat.

post-37428-1253664944_thumb.jpg

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Probably the center hull flying with the trimaran is the critical drag issue, as the windward hull is always out. Whereas the catamaran must fly the windward hull to reduce drag. I think the trimaran dihedral, or that the windward hull on the trimaranis clear of the water would allow the windward rudder to be clear almost all the time. Even with the heel being equal.

 

 

I think because of the max waterline beam issues of DZ the main hull and windward ama are in the water together and start to fly at virtually the same time. In this they are very similar in characteristics to CZ i.e the most important factor is what is the least wind speed can they fly a hull or in DZs case two.

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Some of the points have been made but having experimented with winged rudders for 15 years, here are my thoughts.

 

The first iteration of winged rudders I used were on my (lowrider) Moth and a UK specific class called National 12's. In this case, we used a t-foil (at the bottom of the rudder) with a fixed foil, and the angle of attack was set at neutral. The idea was 3 fold. First, it cut down pitching. Secondly, it reduced the tendency of both boats to nosedive and third, we believed that it interacted with the sternwave and, in effect, increased the waterline. To that last point, I can only offer anacdotal evidence as to the effect because there were too many other variables but in non planing conditions in the National 12, particularly upwind but also on a run, which are the situations where increased waterline might make a difference, we were consistantly fast, if not the fastest. However, there were potentially other factors, so who knows. It shoudl also be noted that we used significantly smaller rudders in these cases and in particular, they were less deep as the endplate effect of the t-foil helps reduce tip drag and therefore more of the foil actually works. This helped keep wetted surface to a reasonable amount.

 

Next, I used foiled rudders on Int. 14's. These were controllable for angle. The first one I had was a t-foil (foil on bottom of rudder). We had lots of issues with it, not least ebcause if we got weed on it, we had to capsize to clear it (or carry a long stick....!!). We also never got the same performance as the guys using wings half way up the rudder. We concluded that this was because it didn't work well with the sternwave. We changed to the same rudder/wing configuration as others were using and it worked fine. On the 14 we used the rudder to provide lift at the stern while going upwind and then went neutral downhill until we needed to lift the bow to stop going down the mine. We also began exerimenting with bow down offwind, which I think was fast but very dangerous!

 

Finally, I have come full circle to using a t-foil on the Moth, but that is to get the boat to lift oput of the water and isn't really relevent here.

 

WRT A5, I suspect that it was always intended to use a winged rudder. This would explain the stern down attitude at rest. Once moving, the rudder would lift the transom and push the bow down. IMO, that is clever as it isn't using balast to increase the waterline length. In addition to the actual increase in waterline length, I think that the smoothing out of the sternwave will have the effect of increasing the waterline even further. My only issue with all this is that in my experience, with this type of set up, you aim to sail the boat flat, otherwise it all gets pretty difficult as the baot begions to handle very strangely.

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Some of the points have been made but having experimented with winged rudders for 15 years, here are my thoughts.

 

The first iteration of winged rudders I used were on my (lowrider) Moth and a UK specific class called National 12's. In this case, we used a t-foil (at the bottom of the rudder) with a fixed foil, and the angle of attack was set at neutral. The idea was 3 fold. First, it cut down pitching. Secondly, it reduced the tendency of both boats to nosedive and third, we believed that it interacted with the sternwave and, in effect, increased the waterline. To that last point, I can only offer anacdotal evidence as to the effect because there were too many other variables but in non planing conditions in the National 12, particularly upwind but also on a run, which are the situations where increased waterline might make a difference, we were consistantly fast, if not the fastest. However, there were potentially other factors, so who knows. It shoudl also be noted that we used significantly smaller rudders in these cases and in particular, they were less deep as the endplate effect of the t-foil helps reduce tip drag and therefore more of the foil actually works. This helped keep wetted surface to a reasonable amount.

 

Next, I used foiled rudders on Int. 14's. These were controllable for angle. The first one I had was a t-foil (foil on bottom of rudder). We had lots of issues with it, not least ebcause if we got weed on it, we had to capsize to clear it (or carry a long stick....!!). We also never got the same performance as the guys using wings half way up the rudder. We concluded that this was because it didn't work well with the sternwave. We changed to the same rudder/wing configuration as others were using and it worked fine. On the 14 we used the rudder to provide lift at the stern while going upwind and then went neutral downhill until we needed to lift the bow to stop going down the mine. We also began exerimenting with bow down offwind, which I think was fast but very dangerous!

 

Finally, I have come full circle to using a t-foil on the Moth, but that is to get the boat to lift oput of the water and isn't really relevent here.

 

WRT A5, I suspect that it was always intended to use a winged rudder. This would explain the stern down attitude at rest. Once moving, the rudder would lift the transom and push the bow down. IMO, that is clever as it isn't using balast to increase the waterline length. In addition to the actual increase in waterline length, I think that the smoothing out of the sternwave will have the effect of increasing the waterline even further. My only issue with all this is that in my experience, with this type of set up, you aim to sail the boat flat, otherwise it all gets pretty difficult as the baot begions to handle very strangely.

 

Makes sense to me.

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WRT A5, I suspect that it was always intended to use a winged rudder. This would explain the stern down attitude at rest. Once moving, the rudder would lift the transom and push the bow down. IMO, that is clever as it isn't using balast to increase the waterline length. In addition to the actual increase in waterline length, I think that the smoothing out of the sternwave will have the effect of increasing the waterline even further. My only issue with all this is that in my experience, with this type of set up, you aim to sail the boat flat, otherwise it all gets pretty difficult as the baot begions to handle very strangely.

 

Are saying that the lwl is already at max (when at rest) so they apply some lift off the stern foil to increase lwl when underway?

 

The ass down appearance of CZ has always looked weird but there are far too many smart dudes working for Alinghi for this to have been anything but by design. Just seems like a big drag penalty to pay. And the present foils seem to be kinda small to do the job.

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WRT A5, I suspect that it was always intended to use a winged rudder. This would explain the stern down attitude at rest. Once moving, the rudder would lift the transom and push the bow down. IMO, that is clever as it isn't using balast to increase the waterline length. In addition to the actual increase in waterline length, I think that the smoothing out of the sternwave will have the effect of increasing the waterline even further. My only issue with all this is that in my experience, with this type of set up, you aim to sail the boat flat, otherwise it all gets pretty difficult as the baot begions to handle very strangely.

 

Are saying that the lwl is already at max (when at rest) so they apply some lift off the stern foil to increase lwl when underway?

That is exactly what I am saying. It explains a lot of stuff, such as the dragging arse when they first launched and the bad wake. I suspect they didn't want to use the foils initially as they wanted to understand how the boat handled and also the loads on it (in particular the rudder stock).

 

The ass down appearance of CZ has always looked weird but there are far too many smart dudes working for Alinghi for this to have been anything but by design. Just seems like a big drag penalty to pay. And the present foils seem to be kinda small to do the job.

We have found with the Int14's that the drag penalty is a fraction of the benefit. With the 14'ws I seem to remember we were running angle of attack somewhere in the region of 8 or 9 degrees withoiut penalty. And I wouldn't just be looking at increaseed LWL but also, effectively, decreased displacement and vastly improved drag from the stern wake. In fact, I suspect that the stern wake gains, even compared with a more "normal" boat, will more than offset the drag from the foils.

 

As for them not being very big, I thought they did look pretty big! They are certainly far bigger than we see on the 14's and A5 is going significantly faster. Last i heard with the 14's the suggestion was about 100kgs of lift at 10 knots. Double the speed and bigger wings, it is easy to guess lift is over 500 kgs. That would make a big difference.

 

I admit I could be off with the numbers and all that I am attributing to the foils. However, I wonder if it is a coincidence that Le Black's designer, Jo Richards, won the National 12 championships this year in a new design featuring a foiled rudder which was adjustable. One of the really interesting things about Jo's rudder was that the foils had some flex in them. In addition to the foiled rudder, Jo also used a centerboard with a trim tab, the first time I know of such a set up oin a dinghy like this. I wonder where he got his ideas from ;)

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some of it makes sense - i certainly agree with your i14 assertions. Where I begin to wonder is when you are flying a hull and the 1 t-foil is supposed to be giving enough lift to do the job. Big difference between a 160 lb i14 (can't remember min weight exactly) plus two blokes and a monster cat. The t-foil is not to sole piece of kit doing any lifting for sure (CZ seems to have some flat sections aft) and speed helps for sure (by the square).

 

All cool stuff and the fun part of this AC.

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John P (Designer of the Stealth F16) says that his foils provide about the same as an "extra bloke at the back" whenneeded down wind

 

36575d1246655970-what-did-you-do-last-weekend-back-2.jpg

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Some of the points have been made but having experimented with winged rudders for 15 years, here are my thoughts.

 

The first iteration of winged rudders I used were on my (lowrider) Moth and a UK specific class called National 12's. In this case, we used a t-foil (at the bottom of the rudder) with a fixed foil, and the angle of attack was set at neutral. The idea was 3 fold. First, it cut down pitching. Secondly, it reduced the tendency of both boats to nosedive and third, we believed that it interacted with the sternwave and, in effect, increased the waterline. To that last point, I can only offer anacdotal evidence as to the effect because there were too many other variables but in non planing conditions in the National 12, particularly upwind but also on a run, which are the situations where increased waterline might make a difference, we were consistantly fast, if not the fastest. However, there were potentially other factors, so who knows. It shoudl also be noted that we used significantly smaller rudders in these cases and in particular, they were less deep as the endplate effect of the t-foil helps reduce tip drag and therefore more of the foil actually works. This helped keep wetted surface to a reasonable amount.

 

Next, I used foiled rudders on Int. 14's. These were controllable for angle. The first one I had was a t-foil (foil on bottom of rudder). We had lots of issues with it, not least ebcause if we got weed on it, we had to capsize to clear it (or carry a long stick....!!). We also never got the same performance as the guys using wings half way up the rudder. We concluded that this was because it didn't work well with the sternwave. We changed to the same rudder/wing configuration as others were using and it worked fine. On the 14 we used the rudder to provide lift at the stern while going upwind and then went neutral downhill until we needed to lift the bow to stop going down the mine. We also began exerimenting with bow down offwind, which I think was fast but very dangerous!

 

Finally, I have come full circle to using a t-foil on the Moth, but that is to get the boat to lift oput of the water and isn't really relevent here.

 

WRT A5, I suspect that it was always intended to use a winged rudder. This would explain the stern down attitude at rest. Once moving, the rudder would lift the transom and push the bow down. IMO, that is clever as it isn't using balast to increase the waterline length. In addition to the actual increase in waterline length, I think that the smoothing out of the sternwave will have the effect of increasing the waterline even further. My only issue with all this is that in my experience, with this type of set up, you aim to sail the boat flat, otherwise it all gets pretty difficult as the baot begions to handle very strangely.

 

And not a hint of credit to Paul Bieker who designed the original T-foils for 14's and is working (I believe) for BMWO.

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WRT A5, I suspect that it was always intended to use a winged rudder. This would explain the stern down attitude at rest. Once moving, the rudder would lift the transom and push the bow down. IMO, that is clever as it isn't using balast to increase the waterline length. In addition to the actual increase in waterline length, I think that the smoothing out of the sternwave will have the effect of increasing the waterline even further. My only issue with all this is that in my experience, with this type of set up, you aim to sail the boat flat, otherwise it all gets pretty difficult as the baot begions to handle very strangely.

 

Are saying that the lwl is already at max (when at rest) so they apply some lift off the stern foil to increase lwl when underway?

 

The ass down appearance of CZ has always looked weird but there are far too many smart dudes working for Alinghi for this to have been anything but by design. Just seems like a big drag penalty to pay. And the present foils seem to be kinda small to do the job.

 

But why? Generating lift causes a drag penalty. Using foils on the rudders is beneficial only if you can benefit from the lift more than you lose from the drag. Designing a hull to float properly only from applied lift has no benefit as you do so at the cost of drag. Why not just design the sucker to float right to begin with?

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Obviously, because this way the said sucker will have a higher margin against a pitchpole

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i would be careful making to many i14 comparisons, when you boil it down they make a big diff to the 14 because they are too heavy for their size (crew and boat weight). Getting lift from the foil and hanging the crew close to it allows the boats to pop up and really plane upwind which they struggled to do before. Very hard finding similarities with A5.

 

I also find it hard to believe it was always designed to have them. There is no reason to think that these foils took longer to design/make than the previous ones (When you put it in context with the rest of the boat) so why not have them ready when the boat launched? Not saying they did not always plan to play with them but I dont see any reason (other than the odd trim but we are not at teh end of that story yet) why they would be this late if they where always planned.

 

Also, just looked at some more pics and it does not seem to do much to the trim as far as I can see. You would have to lift the stern a LONG way to get that bow in.

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Obviously, because this way the said sucker will have a higher margin against a pitchpole

 

Not disagreeing, and not being a multi sailor... but why would it give you margin?

 

Seems that pitchpole is only an issue at speed. And at speed, the foils would be pushing the bow down... just as 'proper' trim would. And if speed was 'overdone' it seems this solution could cause the pitchpole.

 

Now if they are adjustable, and connected to an emergency bailout system, then I get it, but if not, then how do they control pitchpole better than a neutral floating boat, or simply using the flat rear section to "plane" it down?

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Obviously, because this way the said sucker will have a higher margin against a pitchpole

 

Not disagreeing, and not being a multi sailor... but why would it give you margin?

 

Seems that pitchpole is only an issue at speed. And at speed, the foils would be pushing the bow down... just as 'proper' trim would. And if speed was 'overdone' it seems this solution could cause the pitchpole.

 

Now if they are adjustable, and connected to an emergency bailout system, then I get it, but if not, then how do they control pitchpole better than a neutral floating boat, or simply using the flat rear section to "plane" it down?

 

The flow of the water over the foil is always going to pretty much be horizontal but the attitude of the boat wont, in the same way the non foiling moths always used them, bow down causes negative lift on the rudder t-foil so the transom is pulled back down.

 

Obviously if you are set to generate lift when horizontal, you will not get negative lift until later in bow down movement but it will still provide stability there to some degree.

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Obviously, because this way the said sucker will have a higher margin against a pitchpole

 

Not disagreeing, and not being a multi sailor... but why would it give you margin?

 

Seems that pitchpole is only an issue at speed. And at speed, the foils would be pushing the bow down... just as 'proper' trim would. And if speed was 'overdone' it seems this solution could cause the pitchpole.

 

Now if they are adjustable, and connected to an emergency bailout system, then I get it, but if not, then how do they control pitchpole better than a neutral floating boat, or simply using the flat rear section to "plane" it down?

 

The flow of the water over the foil is always going to pretty much be horizontal but the attitude of the boat wont, in the same way the non foiling moths always used them, bow down causes negative lift on the rudder t-foil so the transom is pulled back down.

 

Obviously if you are set to generate lift when horizontal, you will not get negative lift until later in bow down movement but it will still provide stability there to some degree.

 

 

If the pitchpole is that inevitable, then the T-foils won't make much difference. In my A-class experience, when you get to that stage of trouble, the rudders aren't even in the water - they are wiggling around in the air!.

 

My bet will be they are mostly there to stop hobby-horsing and will be dialed to give a small incremental lift to the transom upwind, and neutral (low drag) ventilation stoppers downwind. Although, why make them that big then... (big boat I guess! Either way, nice to see a topic discussing the technology rather than slinging around useless crap.)

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Obviously, because this way the said sucker will have a higher margin against a pitchpole

 

Not disagreeing, and not being a multi sailor... but why would it give you margin?

 

Seems that pitchpole is only an issue at speed. And at speed, the foils would be pushing the bow down... just as 'proper' trim would. And if speed was 'overdone' it seems this solution could cause the pitchpole.

 

Now if they are adjustable, and connected to an emergency bailout system, then I get it, but if not, then how do they control pitchpole better than a neutral floating boat, or simply using the flat rear section to "plane" it down?

 

The flow of the water over the foil is always going to pretty much be horizontal but the attitude of the boat wont, in the same way the non foiling moths always used them, bow down causes negative lift on the rudder t-foil so the transom is pulled back down.

 

Obviously if you are set to generate lift when horizontal, you will not get negative lift until later in bow down movement but it will still provide stability there to some degree.

 

This makes a lot of sense.

 

But on a boat this long, it seems that the angle change in the foil from pushing the bow down would be minimal, and thus the anti pitchpoling effect unlikely to be valuable during the time the rudder is still in the water.

 

My guess is that they must then be adjustable, and probably 'fly by wire'.

 

They have the technology and the power.

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Obviously, because this way the said sucker will have a higher margin against a pitchpole

 

Not disagreeing, and not being a multi sailor... but why would it give you margin?

 

Seems that pitchpole is only an issue at speed. And at speed, the foils would be pushing the bow down... just as 'proper' trim would. And if speed was 'overdone' it seems this solution could cause the pitchpole.

 

Now if they are adjustable, and connected to an emergency bailout system, then I get it, but if not, then how do they control pitchpole better than a neutral floating boat, or simply using the flat rear section to "plane" it down?

 

The flow of the water over the foil is always going to pretty much be horizontal but the attitude of the boat wont, in the same way the non foiling moths always used them, bow down causes negative lift on the rudder t-foil so the transom is pulled back down.

 

Obviously if you are set to generate lift when horizontal, you will not get negative lift until later in bow down movement but it will still provide stability there to some degree.

 

 

If the pitchpole is that inevitable, then the T-foils won't make much difference. In my A-class experience, when you get to that stage of trouble, the rudders aren't even in the water - they are wiggling around in the air!.

 

My bet will be they are mostly there to stop hobby-horsing and will be dialed to give a small incremental lift to the transom upwind, and neutral (low drag) ventilation stoppers downwind. Although, why make them that big then... (big boat I guess! Either way, nice to see a topic discussing the technology rather than slinging around useless crap.)

 

But the T's KEEP the rudders in the water and so help to prevent the pitchpole. It will not stop it for ever, but it helps!

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Obviously, because this way the said sucker will have a higher margin against a pitchpole

 

Not disagreeing, and not being a multi sailor... but why would it give you margin?

 

Seems that pitchpole is only an issue at speed. And at speed, the foils would be pushing the bow down... just as 'proper' trim would. And if speed was 'overdone' it seems this solution could cause the pitchpole.

 

Now if they are adjustable, and connected to an emergency bailout system, then I get it, but if not, then how do they control pitchpole better than a neutral floating boat, or simply using the flat rear section to "plane" it down?

 

The flow of the water over the foil is always going to pretty much be horizontal but the attitude of the boat wont, in the same way the non foiling moths always used them, bow down causes negative lift on the rudder t-foil so the transom is pulled back down.

 

Obviously if you are set to generate lift when horizontal, you will not get negative lift until later in bow down movement but it will still provide stability there to some degree.

 

 

If the pitchpole is that inevitable, then the T-foils won't make much difference. In my A-class experience, when you get to that stage of trouble, the rudders aren't even in the water - they are wiggling around in the air!.

 

My bet will be they are mostly there to stop hobby-horsing and will be dialed to give a small incremental lift to the transom upwind, and neutral (low drag) ventilation stoppers downwind. Although, why make them that big then... (big boat I guess! Either way, nice to see a topic discussing the technology rather than slinging around useless crap.)

 

But the T's KEEP the rudders in the water and so help to prevent the pitchpole. It will not stop it for ever, but it helps!

Right- its not about stopping it once it has got to 'that stage' it will reduce its likelyhood of getting there in the first place. You dont need much angle to generate a significant amount of lift at the speeds these things will be going.

 

Reducing pitching if they put a hard rig on might be a good factor too.

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Obviously, because this way the said sucker will have a higher margin against a pitchpole

 

Not disagreeing, and not being a multi sailor... but why would it give you margin?

 

Seems that pitchpole is only an issue at speed. And at speed, the foils would be pushing the bow down... just as 'proper' trim would. And if speed was 'overdone' it seems this solution could cause the pitchpole.

 

Now if they are adjustable, and connected to an emergency bailout system, then I get it, but if not, then how do they control pitchpole better than a neutral floating boat, or simply using the flat rear section to "plane" it down?

 

The flow of the water over the foil is always going to pretty much be horizontal but the attitude of the boat wont, in the same way the non foiling moths always used them, bow down causes negative lift on the rudder t-foil so the transom is pulled back down.

 

Obviously if you are set to generate lift when horizontal, you will not get negative lift until later in bow down movement but it will still provide stability there to some degree.

 

 

If the pitchpole is that inevitable, then the T-foils won't make much difference. In my A-class experience, when you get to that stage of trouble, the rudders aren't even in the water - they are wiggling around in the air!.

 

My bet will be they are mostly there to stop hobby-horsing and will be dialed to give a small incremental lift to the transom upwind, and neutral (low drag) ventilation stoppers downwind. Although, why make them that big then... (big boat I guess! Either way, nice to see a topic discussing the technology rather than slinging around useless crap.)

 

But the T's KEEP the rudders in the water and so help to prevent the pitchpole. It will not stop it for ever, but it helps!

Right- its not about stopping it once it has got to 'that stage' it will reduce its likelyhood of getting there in the first place. You dont need much angle to generate a significant amount of lift at the speeds these things will be going.

 

Reducing pitching if they put a hard rig on might be a good factor too.

hard or soft rig, reducing pitching is a great way to increase speed with these boats. my experience is that ramping on waves, upwind and rhythmic pitching downwind are the big issues at speed. damping those tendencies will add control, and speed. also will make the sailpower of the rig more efficient, as the apparent wind will not be moving fore and aft, due to rig acceleration, deceleration. also adds a safety margin for the crew, as there is less acceleration, deceleration of the boat. also will make the lifting foils that are the daggerboards work better, as they will have a more constant angle of attack. lots of benefit to reduce pitching.

the pitching, and pitchpole, problem can be mitigated with volume distribution in hull design. with horizontal foils, the pitchpole problem can be delayed, but i don't think that is what they are being tested on cz for.

cz may have a trim problem, and a pitching problem, probably not a pitchpole problem.

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Obviously, because this way the said sucker will have a higher margin against a pitchpole

 

Not disagreeing, and not being a multi sailor... but why would it give you margin?

 

Seems that pitchpole is only an issue at speed. And at speed, the foils would be pushing the bow down... just as 'proper' trim would. And if speed was 'overdone' it seems this solution could cause the pitchpole.

 

Now if they are adjustable, and connected to an emergency bailout system, then I get it, but if not, then how do they control pitchpole better than a neutral floating boat, or simply using the flat rear section to "plane" it down?

 

The flow of the water over the foil is always going to pretty much be horizontal but the attitude of the boat wont, in the same way the non foiling moths always used them, bow down causes negative lift on the rudder t-foil so the transom is pulled back down.

 

Obviously if you are set to generate lift when horizontal, you will not get negative lift until later in bow down movement but it will still provide stability there to some degree.

 

 

If the pitchpole is that inevitable, then the T-foils won't make much difference. In my A-class experience, when you get to that stage of trouble, the rudders aren't even in the water - they are wiggling around in the air!.

 

My bet will be they are mostly there to stop hobby-horsing and will be dialed to give a small incremental lift to the transom upwind, and neutral (low drag) ventilation stoppers downwind. Although, why make them that big then... (big boat I guess! Either way, nice to see a topic discussing the technology rather than slinging around useless crap.)

 

But the T's KEEP the rudders in the water and so help to prevent the pitchpole. It will not stop it for ever, but it helps!

Right- its not about stopping it once it has got to 'that stage' it will reduce its likelyhood of getting there in the first place. You dont need much angle to generate a significant amount of lift at the speeds these things will be going.

 

Reducing pitching if they put a hard rig on might be a good factor too.

hard or soft rig, reducing pitching is a great way to increase speed with these boats. my experience is that ramping on waves, upwind and rhythmic pitching downwind are the big issues at speed. damping those tendencies will add control, and speed. also will make the sailpower of the rig more efficient, as the apparent wind will not be moving fore and aft, due to rig acceleration, deceleration. also adds a safety margin for the crew, as there is less acceleration, deceleration of the boat. also will make the lifting foils that are the daggerboards work better, as they will have a more constant angle of attack. lots of benefit to reduce pitching.

the pitching, and pitchpole, problem can be mitigated with volume distribution in hull design. with horizontal foils, the pitchpole problem can be delayed, but i don't think that is what they are being tested on cz for.

cz may have a trim problem, and a pitching problem, probably not a pitchpole problem.

Agreed, I was just responding to the 'why they help pitchpoling' comments. Not seen CZ look remotely like they might go bow down.

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yeah, quite the opposite. almost seems like cz was designed for a more powerful rig than it has in the images i've seen.

something else i've noticed is the wide sheeting angle of the whomper jib on cz. compare that to the narrow sheeting angle of the jibs i've seen in the dz images.

or, are there images of dz with a really big overlap wide sheeting angle jib on dz?

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Obviously, because this way the said sucker will have a higher margin against a pitchpole

 

Not disagreeing, and not being a multi sailor... but why would it give you margin?

 

Seems that pitchpole is only an issue at speed. And at speed, the foils would be pushing the bow down... just as 'proper' trim would. And if speed was 'overdone' it seems this solution could cause the pitchpole.

 

Now if they are adjustable, and connected to an emergency bailout system, then I get it, but if not, then how do they control pitchpole better than a neutral floating boat, or simply using the flat rear section to "plane" it down?

 

The flow of the water over the foil is always going to pretty much be horizontal but the attitude of the boat wont, in the same way the non foiling moths always used them, bow down causes negative lift on the rudder t-foil so the transom is pulled back down.

 

Obviously if you are set to generate lift when horizontal, you will not get negative lift until later in bow down movement but it will still provide stability there to some degree.

 

 

If the pitchpole is that inevitable, then the T-foils won't make much difference. In my A-class experience, when you get to that stage of trouble, the rudders aren't even in the water - they are wiggling around in the air!.

 

My bet will be they are mostly there to stop hobby-horsing and will be dialed to give a small incremental lift to the transom upwind, and neutral (low drag) ventilation stoppers downwind. Although, why make them that big then... (big boat I guess! Either way, nice to see a topic discussing the technology rather than slinging around useless crap.)

 

But the T's KEEP the rudders in the water and so help to prevent the pitchpole. It will not stop it for ever, but it helps!

Right- its not about stopping it once it has got to 'that stage' it will reduce its likelyhood of getting there in the first place. You dont need much angle to generate a significant amount of lift at the speeds these things will be going.

 

Reducing pitching if they put a hard rig on might be a good factor too.

hard or soft rig, reducing pitching is a great way to increase speed with these boats. my experience is that ramping on waves, upwind and rhythmic pitching downwind are the big issues at speed. damping those tendencies will add control, and speed. also will make the sailpower of the rig more efficient, as the apparent wind will not be moving fore and aft, due to rig acceleration, deceleration. also adds a safety margin for the crew, as there is less acceleration, deceleration of the boat. also will make the lifting foils that are the daggerboards work better, as they will have a more constant angle of attack. lots of benefit to reduce pitching.

the pitching, and pitchpole, problem can be mitigated with volume distribution in hull design. with horizontal foils, the pitchpole problem can be delayed, but i don't think that is what they are being tested on cz for.

cz may have a trim problem, and a pitching problem, probably not a pitchpole problem.

Agreed, I was just responding to the 'why they help pitchpoling' comments. Not seen CZ look remotely like they might go bow down.

 

Could it be that they are a response to a design problem not part of the original design i.e. that the CZ is bow high and the rudders are designed to lower the bow and increase water line length. I know we treat these designers as gods but they live in the real world and do make mistakes.

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Could it be that they are a response to a design problem not part of the original design i.e. that the CZ is bow high and the rudders are designed to lower the bow and increase water line length. I know we treat these designers as gods but they live in the real world and do make mistakes.

 

Not a mistake in the design, but a consequence. A5 is a very wide catamaran platform. I don't have the exact numbers but its beam is very large relative to its length. This gives the boat proportionately more lateral stability than fore and aft stability, which all means that it is easier to trip it up. Because this isn't usual, it will look different, and because it looks different, many will assume it is wrong.

So to the extent I understand the design....

Alinghi have gone as light as they dare.

In multi hulls being light reduces righting moment, so they have pushed the beam out as far as they dare to maximize sail carrying power. This increases their risk of pitch poling, so the design is loaded aft, with what may appear to be extended and unused waterline forward. This will be increasingly pressed into the water as the rig is increased and as speeds get higher. ( The force vector off the rig will drive the bow down.)

This also means that they can have a longer hull with a 90 foot waterline.

Alinghi may have water ballast forward to push the bow down in light air.

But there are some issues with taking on ballast ( or "bilge water") to alter a boat out of it's measurement trim even though this has been a common practice in the America's Cup for as long as anyone cares to admit.

They may use T foil rudders to actively manage the fore and aft trim and to make the boat less likely to go down the mine.

This does not have the ethical implications of the "bilge water".

This will be under development, but I don't believe for a moment that the boat floats anywhere but where they expected. The geometry is different than "normal" and this has consequences that makes some feel that the buoyancy or weight distribution is wrong. The design assumptions may or may not be correct, but I believe the Alinghi design team has done exactly what they intended.

SHC

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Could it be that they are a response to a design problem not part of the original design i.e. that the CZ is bow high and the rudders are designed to lower the bow and increase water line length. I know we treat these designers as gods but they live in the real world and do make mistakes.

 

Not a mistake in the design, but a consequence. A5 is a very wide catamaran platform. I don't have the exact numbers but its beam is very large relative to its length. This gives the boat proportionately more lateral stability than fore and aft stability, which all means that it is easier to trip it up. Because this isn't usual, it will look different, and because it looks different, many will assume it is wrong.

So to the extent I understand the design....

Alinghi have gone as light as they dare.

In multi hulls being light reduces righting moment, so they have pushed the beam out as far as they dare to maximize sail carrying power. This increases their risk of pitch poling, so the design is loaded aft, with what may appear to be extended and unused waterline forward. This will be increasingly pressed into the water as the rig is increased and as speeds get higher. ( The force vector off the rig will drive the bow down.)

This also means that they can have a longer hull with a 90 foot waterline.

Alinghi may have water ballast forward to push the bow down in light air.

But there are some issues with taking on ballast ( or "bilge water") to alter a boat out of it's measurement trim even though this has been a common practice in the America's Cup for as long as anyone cares to admit.

They may use T foil rudders to actively manage the fore and aft trim and to make the boat less likely to go down the mine.

This does not have the ethical implications of the "bilge water".

This will be under development, but I don't believe for a moment that the boat floats anywhere but where they expected. The geometry is different than "normal" and this has consequences that makes some feel that the buoyancy or weight distribution is wrong. The design assumptions may or may not be correct, but I believe the Alinghi design team has done exactly what they intended.

SHC

 

 

Thanks for the clear and easy to understand explanation SHC..

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Could it be that they are a response to a design problem not part of the original design i.e. that the CZ is bow high and the rudders are designed to lower the bow and increase water line length. I know we treat these designers as gods but they live in the real world and do make mistakes.

 

Not a mistake in the design, but a consequence. A5 is a very wide catamaran platform. I don't have the exact numbers but its beam is very large relative to its length. This gives the boat proportionately more lateral stability than fore and aft stability, which all means that it is easier to trip it up. Because this isn't usual, it will look different, and because it looks different, many will assume it is wrong.

So to the extent I understand the design....

Alinghi have gone as light as they dare.

In multi hulls being light reduces righting moment, so they have pushed the beam out as far as they dare to maximize sail carrying power. This increases their risk of pitch poling, so the design is loaded aft, with what may appear to be extended and unused waterline forward. This will be increasingly pressed into the water as the rig is increased and as speeds get higher. ( The force vector off the rig will drive the bow down.)

This also means that they can have a longer hull with a 90 foot waterline.

Alinghi may have water ballast forward to push the bow down in light air.

But there are some issues with taking on ballast ( or "bilge water") to alter a boat out of it's measurement trim even though this has been a common practice in the America's Cup for as long as anyone cares to admit.

They may use T foil rudders to actively manage the fore and aft trim and to make the boat less likely to go down the mine.

This does not have the ethical implications of the "bilge water".

This will be under development, but I don't believe for a moment that the boat floats anywhere but where they expected. The geometry is different than "normal" and this has consequences that makes some feel that the buoyancy or weight distribution is wrong. The design assumptions may or may not be correct, but I believe the Alinghi design team has done exactly what they intended.

SHC

Are you using the term "bilge water", as opposed to "water ballast", to make a distinction regarding lwl, and measurement trim?

If so do you feel there is a true distinction? Or do you feel that "water ballast" /"bilge water" are one, and the same?

I am curious, mostly about the viability, and enforceability of the ac measurement rules in general.

Also in regard to "sportsmanlike" behavior, and "friendly competition.

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What i am wondering is: could the t-foils shown on cz possibly be a red herring? As in install neutral t-foils that have little effect on trim, but would pull attention away from a "water ballast/bilge water" experiment?

I ask this because I do not see a flying moth, or i-14 style control to alter the t-foil's trim. You know, a method of altering the angle of attack. Or is this t-foil designed only to reduce pitching?

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Could it be that they are a response to a design problem not part of the original design i.e. that the CZ is bow high and the rudders are designed to lower the bow and increase water line length. I know we treat these designers as gods but they live in the real world and do make mistakes.

 

Not a mistake in the design, but a consequence. A5 is a very wide catamaran platform. I don't have the exact numbers but its beam is very large relative to its length. This gives the boat proportionately more lateral stability than fore and aft stability, which all means that it is easier to trip it up. Because this isn't usual, it will look different, and because it looks different, many will assume it is wrong.

So to the extent I understand the design....

Alinghi have gone as light as they dare.

In multi hulls being light reduces righting moment, so they have pushed the beam out as far as they dare to maximize sail carrying power. This increases their risk of pitch poling, so the design is loaded aft, with what may appear to be extended and unused waterline forward. This will be increasingly pressed into the water as the rig is increased and as speeds get higher. ( The force vector off the rig will drive the bow down.)

This also means that they can have a longer hull with a 90 foot waterline.

Alinghi may have water ballast forward to push the bow down in light air.

But there are some issues with taking on ballast ( or "bilge water") to alter a boat out of it's measurement trim even though this has been a common practice in the America's Cup for as long as anyone cares to admit.

They may use T foil rudders to actively manage the fore and aft trim and to make the boat less likely to go down the mine.

This does not have the ethical implications of the "bilge water".

This will be under development, but I don't believe for a moment that the boat floats anywhere but where they expected. The geometry is different than "normal" and this has consequences that makes some feel that the buoyancy or weight distribution is wrong. The design assumptions may or may not be correct, but I believe the Alinghi design team has done exactly what they intended.

SHC

Are you using the term "bilge water", as opposed to "water ballast", to make a distinction regarding lwl, and measurement trim?

If so do you feel there is a true distinction? Or do you feel that "water ballast" /"bilge water" are one, and the same?

I am curious, mostly about the viability, and enforceability of the ac measurement rules in general.

Also in regard to "sportsmanlike" behavior, and "friendly competition.

I believe he says "bilge water" to mean "unofficially" added water allowed to enter the boat that affects measurement trim. Ballast water I understood to mean water, or lead for that matter, that is included in the boat's measured trim.

 

The point is that it is very difficult to monitor how much bilge water enters and leaves the boat during a race, and if it is legitimately there from spray or games.

 

The Exposition above is very helpful... thanks SHC.

 

And I think most engineers would agree that the stance of the boat is intended. We may not know the full "why", but in this era of CAD design, it is too easy to get a center of gravity, center of buoyancy, and center of whatever you want with the push of a button, for them to not had a very close idea of how this was going to sit.

 

Furthermore, it would have been too easy for them to add ballast in the front of the boat if they wanted to "correct" this in the base case.

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Perhaps you should say instead that "it has not been a priority to monitor how much bilge water enters and leaves the boat during a race. Has there been a past ac boat that had declared water ballast as a part of the measurement. Sand bags for sure have been used, but they cannot be re-added after dumping so not important to monitor.

I think the inference is that there needs to be a system to identify any use of "bilge water" as opposed to ballast water, if the measurement of lwl is to have any meaning.

I don't think it is difficult to monitor water in the bilge.

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Perhaps you should say instead that "it has not been a priority to monitor how much bilge water enters and leaves the boat during a race. Has there been a past ac boat that had declared water ballast as a part of the measurement. Sand bags for sure have been used, but they cannot be re-added after dumping so not important to monitor.

I think the inference is that there needs to be a system to identify any use of "bilge water" as opposed to ballast water, if the measurement of lwl is to have any meaning.

I don't think it is difficult to monitor water in the bilge.

 

I agree. It shouldn't be difficult if a rule, and method of enforcement is put in place. Especially for these boats that have essentially closed hulls.

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Obviously, because this way the said sucker will have a higher margin against a pitchpole

 

Well - sure...that makes sense. But to design them to lift the sterns so the hulls go through the water at a proper attitude doesn't and is providing forces opposite to what you're looking for in an anti-pitchpole device.

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Obviously, because this way the said sucker will have a higher margin against a pitchpole

 

Well - sure...that makes sense. But to design them to lift the sterns so the hulls go through the water at a proper attitude doesn't and is providing forces opposite to what you're looking for in an anti-pitchpole device.

This is a misnomer. What foils are good at is helping to maintain a constant ride attitude. So, when the boat is sailing, it establishes an equilibrium and once that is reached, it is exactly the same as if the foils are fixed in neutral. If the bow begins to go down, it changes the angle of attack of the rudder foils, which then act to pull the back down. If the boat slows, as it would in a pitchpole, the amount of lift from the rudder foils is reduced which also has the effect of pulling the stern down.

 

However, no foils will work to eliminate pichjpoling and a point will be reached when, if the bow goes down enough, the forces are such that the rudders can no longer help. When conditions get to that, the Int14's then use their foils so as to lift the bow, goiving an extra margin for error

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Obviously, because this way the said sucker will have a higher margin against a pitchpole

 

Well - sure...that makes sense. But to design them to lift the sterns so the hulls go through the water at a proper attitude doesn't and is providing forces opposite to what you're looking for in an anti-pitchpole device.

This is a misnomer. What foils are good at is helping to maintain a constant ride attitude. So, when the boat is sailing, it establishes an equilibrium and once that is reached, it is exactly the same as if the foils are fixed in neutral. If the bow begins to go down, it changes the angle of attack of the rudder foils, which then act to pull the back down. If the boat slows, as it would in a pitchpole, the amount of lift from the rudder foils is reduced which also has the effect of pulling the stern down.

 

However, no foils will work to eliminate pichjpoling and a point will be reached when, if the bow goes down enough, the forces are such that the rudders can no longer help. When conditions get to that, the Int14's then use their foils so as to lift the bow, goiving an extra margin for error

 

Here ya go.

 

. . . dynamic length versus static length discussion anybody . . .

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I think that rudder t-foils work a lot better when they work in combination with forward lifting foils in "foil assist" applications-particularly when the CG of the whole boat is slightly aft of the center of lift of the forward foil. Having control of the angle of incidence(relative to the hull) of the foil seems to me to be indispensible especially on these big boats....

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Here ya go.

 

. . . dynamic length versus static length discussion anybody . . .

... But this Bieker guy is working for Oracle...

So how did his foils wind up on Alinghi ? :huh:

 

Next thing you know, you'll start seeing Swiss inventions on BOR90!

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There are no guarantees....

pix by Giles Martin Raget/Royale Production-www.wetasschronicles.com

post-30-1253834499_thumb.jpg

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There are no guarantees....

pix by Giles Martin Raget/Royale Production-www.wetasschronicles.com

Nice shot. pitchpole in mid gybe, probably not going full speed at the time with the main sheeted to center. Messing w/ the backstays perhaps?

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Obviously, because this way the said sucker will have a higher margin against a pitchpole

 

Not disagreeing, and not being a multi sailor... but why would it give you margin?

 

I should clarify that I was referring to a generic stern-down stance, without considering T-foils - and Steve Clark has replied much more eloquently than I could

 

.. almost seems like cz was designed for a more powerful rig than it has in the images i've seen.

 

Valid point, wasn't a mysterious 60-62 m M2 helicoptered to Genoa at the last minute before the ship sailed? Even from a static point, such heavier mast sits forward

 

I think that rudder t-foils work a lot better when they work in combination with forward lifting foils in "foil assist" applications-particularly when the CG of the whole boat is slightly aft of the center of lift of the forward foil. Having control of the angle of incidence(relative to the hull) of the foil seems to me to be indispensible especially on these big boats....

 

I have no experience with T-foils, but I do agree that they might have made a world of a difference had we had them on Signor G (see the picture in the Foils thread)

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Here ya go.

 

. . . dynamic length versus static length discussion anybody . . .

... But this Bieker guy is working for Oracle...

So how did his foils wind up on Alinghi ? :huh:

 

Next thing you know, you'll start seeing Swiss inventions on BOR90!

 

. . . well I s´pose the Bieker foils need to be cantilevered off the stern in order to be optimally positioned for the drag reduction benefits . . . of course if you thought that that was maybe a benefit and you could write your own rules . . . maybe you´d place some restrictions on LWL . . . ?? . . .

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Here ya go.

 

. . . dynamic length versus static length discussion anybody . . .

... But this Bieker guy is working for Oracle...

So how did his foils wind up on Alinghi ? :huh:

 

Next thing you know, you'll start seeing Swiss inventions on BOR90!

 

. . . well I s´pose the Bieker foils need to be cantilevered off the stern in order to be optimally positioned for the drag reduction benefits . . . of course if you thought that that was maybe a benefit and you could write your own rules . . . maybe you´d place some restrictions on LWL . . . ?? . . .

Those ama rudders on BOR90 are enough provocation, as it is. What overhanging extension behind the boat should the SNG be comfortable with; if 15 ft. why not 30?

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Here ya go.

 

. . . dynamic length versus static length discussion anybody . . .

... But this Bieker guy is working for Oracle...

So how did his foils wind up on Alinghi ? :huh:

 

Next thing you know, you'll start seeing Swiss inventions on BOR90!

 

. . . well I s´pose the Bieker foils need to be cantilevered off the stern in order to be optimally positioned for the drag reduction benefits . . . of course if you thought that that was maybe a benefit and you could write your own rules . . . maybe you´d place some restrictions on LWL . . . ?? . . .

Those ama rudders on BOR90 are enough provocation, as it is. What overhanging extension behind the boat should the SNG be comfortable with; if 15 ft. why not 30?

 

Not relevant - the deed is very clear that the only length of concern is LWL - overall length is not measured. Look at some of the early AC boats to see what extremes this has been taken to:

 

Here's a quote about Reliance: (from http://www.americascup.com/en/acclopaedia/...idContent=1743)

In 1903, the rule imposed only one major constraint on Herreshoff: the load waterline length of the boat couldn't exceed 27.43 metres. The designer modelled a flat and modestly deep hull, similar to that of a scow. The biggest surprise came from the long overhangs: 6.70 metres forward and 7.92 metres aft. Sailing close hauled, in seven or eight knots of breeze, the effective waterline length would stretche out from 27.43 metres to nearly 40-metres...a tremendous source of speed.

 

Her overall length was 43.79 m. L.W.L.: 27.32 m

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Not relevant - the deed is very clear that the only length of concern is LWL - overall length is not measured. Look at some of the early AC boats to see what extremes this has been taken to:

 

Here's a quote about Reliance: (from http://www.americascup.com/en/acclopaedia/...idContent=1743)

In 1903, the rule imposed only one major constraint on Herreshoff: the load waterline length of the boat couldn't exceed 27.43 metres. The designer modelled a flat and modestly deep hull, similar to that of a scow. The biggest surprise came from the long overhangs: 6.70 metres forward and 7.92 metres aft. Sailing close hauled, in seven or eight knots of breeze, the effective waterline length would stretche out from 27.43 metres to nearly 40-metres...a tremendous source of speed.

 

Her overall length was 43.79 m. L.W.L.: 27.32 m

Not relevant, or even on topic!

 

And where was the rudder on Reliance? 7.92 meters aft?

Anyway it sounded quite interesting, gearwise. Sort of like what we have now:

Due to the scale of the boat, and the loads on it, Nathanael fitted Reliance with uncountable innovations: Bronze Tobin hull, steel welded mast with a telescopic topmast sliding into the mainmast, two-speed winches, sheets and runners laid under an aluminium bridge covered with cork, a hollow rudder which could be filled or emptied of water depending on the point of sail. It would take all the effort and nautical wisdom of the incredible Charlie Barr to safely skipper Reliance through the Cup, along with a crew of 64.

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Not relevant - the deed is very clear that the only length of concern is LWL - overall length is not measured. Look at some of the early AC boats to see what extremes this has been taken to:

Not relevant, or even on topic!

 

And where was the rudder on Reliance? 7.92 meters aft?

Anyway it sounded quite interesting, gearwise. Sort of like what we have now:

Due to the scale of the boat, and the loads on it, Nathanael fitted Reliance with uncountable innovations: Bronze Tobin hull, steel welded mast with a telescopic topmast sliding into the mainmast, two-speed winches, sheets and runners laid under an aluminium bridge covered with cork, a hollow rudder which could be filled or emptied of water depending on the point of sail. It would take all the effort and nautical wisdom of the incredible Charlie Barr to safely skipper Reliance through the Cup, along with a crew of 64.

 

Agreed - Mea culpa - failure to review the context :( but at least I appear to have shared a useful bit of history...

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I'm delighted if we leave the rudder-altercations to others, TJ!

Speaking of Herreshoff, you may have seen there was photo of Amarylllis included in SNG court papers made public this morning.

Led me to looking for more photos or drawings, of which I didn't find all that many. Does anyone have other photos of f.ex. Amaryllis II up at the Herreshoff museum?

I wonder if Jo Richards ever happened to admire that boat, and even gained some inspiration toward the central beam and cable arrangements which he first installed on Ylliam and later on Le Black.

 

post-35861-1253889748_thumb.jpg

 

Back to the subject of foils. What Steve Clark posted above was very good. And I liked the 'as light as they dare' part.

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