Foiler Americas Cup

[Doug Lord]

A historic Cup is in the works-now that Alinghi has been confirmed to use lifting hydrofoils both Challenger and Defender will be depending on hydrofoils for speed. This will mark the first use of two multihulls in the Cup and the first use of lifting hydrofoils in an America's Cup. Can't get more exciting than this!
The "S" shaped board is Alinghi's-how do you put that in a trunk??!

[TeddyDiver]

Looks smth like keel-hydrofoil-hybrid.. canting maybe?

[Chris Ostlind]

The "S" shaped board is Alinghi's-how do you put that in a trunk??!




How shocking!!!!!!!

You mean that you really don't know this?

Imagine the horror across the foiling world when they all find out that Doug doesn't have a clue about Alinghi's curved foil and how it works...?

Stepping away from the WebTV keyboard might be a good starting point.

[yipster]

http://www.boatdesign.net/forums/attachments/multihulls/33036d1246969371-foiler-americas-cup-alinghi-board-3.jpg
so how does this work ?

[Chris Ostlind]

My $5 in the office pool says this...

Pivoting trunk entry box. Pivoting trunk exit box. Both boxes slide fore and aft independently to adjust pitch of the foil while underway.

In between a flexible Kevlar braided belt encased in heavy duty tire rubber and connected to each box with triple clamping system. The belt length is sized to accomodate all of the possible radius related movements.

Water-tight, fully flexible and easily maintained in a boat that size.

Send your cashier's checks and money orders in US funds, please.

[TeddyDiver]

Both boxes slide fore and aft independently to adjust pitch of the foil while underway.
I'll bet a beer it's canting, not fore-aft adjusted :)

[Chris Ostlind]

Canting, Teddy? As in canting side to side?

However the super secret turns-out, I'll be happy to buy you a beer when we get to meet.

[TeddyDiver]

:D yup! they allready have experience of a bending keel and how to control it so this could work as canting keel/foil with some controlled twist.. me thinks..

[Chris Ostlind]

With a cant, you can adjust the relative exposure of the lifting forces of the board to the oncoming flow.

With the ability to adjust rake, you get angle of attack adjustment that allows controllable lift through a wider range of boat speeds.

Looking at the ORMA tris, you see a fixed daggerboard slot that locks the angle of attack of the board relative to the hull, as well as locking any thought of a canting of the lifting surface exposure at optimal board surface areas. You can dial-in the amount of lift by raising and lowering the exposed board and/or adjusting boat speed.

With this boat, as a next generation, I'm thinking that the board, with an ability to be raked according to the boat speed, offers greater versatility for reducing wetted surface through a wider range of boat speeds. They don't have obvious movable surfaces, though that might be in the mix if one looks at the photos as dangling bait for the BMWO gang.

With the resources these dudes have, I don't think it would be too tough to build a foil with a moveable surface that is fully controllable by either auto, or manual, means. If this is the case, it's going to require a damn lot of practice to make sure one knows how to trim the foil for every possible scenario on the race course.

As usual, in every respect, it's all about tossing money at the place where it can do the most good for the end result desired.

Stay tuned.

[Doug Lord]

:D yup! they allready have experience of a bending keel and how to control it so this could work as canting keel/foil with some controlled twist.. me thinks..
------------------------------------------------------
I think the angle of incidence and the "cant" of the alinghi foil could both be controlled. Cant would allow the proportion of the foil that lifts to be controlled independently of the angle of heel of the boat. Angle of attack of the foil is going to be set by the pitch response of the boat so by adjusting the angle of incidence of the foil(relative to the hull) pitch changes can be compensated for. However it works there is certain be quite a story behind it.

[Chris Ostlind]

One of the guys over at Sailing Anarchy put together a nice graphic representation of the curved foil sliding through the hull.

Very interesting and it shows how the daggerboard arcs, when combined with movable exit/entry points, offers some curious options.

When you couple this feature with any kind of ability to adjust angle of attack, you have a pretty cool range of adjustments... if it all works as planned, that is.

[schakel]

About the Alinghi cat: In Sailing anarchy I asked where the reverse bow was good for, I got the following answer:

reverse bows allows the forward sections to drive through the waves therefore less drag - esp with hull lengths this long ( longer than the waves) can cause major engineering issues though - as per Team Philips. but as these are designed to fly a hull maybe not so much..

So what I make of it is that it is planning capabilities against ability to puncture a wave. Why not do the thing in between and have a torpedo shaped bow.
It's and wave puncturing and can lift the bow out of the water in various stages of planning.

What I always thought is the most dangerous about high speed cats is that they dive.
Doesn’t a reverse bow increase the chance of diving? And I know that that is one of the reasons where they use the banana- foiler for. But still:
I don't know: reverse bow a mostly designed to impress or to be extravagant. But that's only my humble opinion.

Here is a picture of the bow of the Alinghi cat that we were talking about:

http://www.bymnews.com/images/homepage/big/alinghi-bow.jpg

[yipster]

nice pics schakel, looks (http://www.bymnews.com/photos/displayimage.php?album=246&pid=95832) like a wavepiercer, LWL, windage etc probable reasons for the bow shape

Cris, i get the pic and thinks the hydrofoil may also be coupled to a computer flying a leg

one hell of a AC coming up

[bad dog]

I get a "Forbidden" message to that photo link Schakel - is there another? Thanks!

[TeddyDiver]

A long foil (like Alinghi's) is very prone to flutter.. Maybe this curved design has some additional advantages avoiding such thing..

[Chris Ostlind]

I stumbled onto this bit this evening and liked it a lot.

http://www.sail-world.com/USA/Americas-Cup:-Steve-Clark-on-Bows,-Stress-and-Weight/58754

[schakel]

I get a "Forbidden" message to that photo link Schakel - is there another? Thanks!


The last photo was on the front page of BYM and they change that every day.

Here is the permanent gallery:
http://bymnews.com/photos/thumbnails.php?album=246

Very nice and enthusiastic pictures: Huge crowds, happy faces. Especially of Rolf Vrolijk (the head designer of this project of Judel & Vrolijk)

[schakel]

A very good interview on the design of the Americas Cup multis:

http://www.bymnews.com/americas-cup-33/nigel-irens.php

And what I make of it:

He leaves awful lot in between:

About the bows that both changed into wave piercing: An inshore bow instead of a classic of shore bow.
Well they both adapted to Valencia as sailing water. I still find it strange because on the other hand the Tornado is being called as most successful catamaran ever. And those bows are slightly upward. I do not know I would not be surprised if both team shows up at the real cup with conventional bows.

About cavitations: He admits that when a hydrofoil starts to cavitate it loses its lifting power and then the whole thing ends up in a big crash. Game over!
Believe me: that is a very likely outcome of the match. And when the Multi is bigger the chance that this will happen is greater from my intuition.
But I will have to do some calcs on that.

About the motor: Both teams really push the envelope in their designs so why not. On the other hand: I would be surprised if you hardly need them. Those who ever compared the amount of power on the sheets between a cat and a mono know a cat is almost nothing in sheet tensions. My guess is both team leaves them out.

About trimaran versus catamaran: He points out that speed is more important then manouverability. But when it comes to the last part: Then the tri will win.
My guess Alinghi wins with 5 minutes in advance in the first race. Then the second race is the same. Then BMWO throws the towel. Until it starts to blow real hard: The team that keeps the boat together and doesn't lose much speed will win. In that case the tri might have an advantage.
The legal part about the maximum amount of wind will be a mess.... I am looking forward to that part as well.

But there is nothing much to be said in advantage of this match except that the most part of the match will be about design and not about tactics.
We will see:
I know there were speculations about the date of the match and since both multi's are not in Valencia I guess the date will be far of.

Can’t wait to see that happen

[xarax]

when a hydrofoil starts to cavitate it loses its lifting power and then the whole thing ends up in a big crash. Game over!
Believe me: that is a very likely outcome of the match.
Why is this so ? The whole structure can not withstand the fall so that cat continue sailing on both hulls until it is lifted up again?

[schakel]

Why is this so ? The whole structure can not withstand the fall so that cat continue sailing on both hulls until it is lifted up again?

In a previous discussion with Rhough he pointed me out that the banana-foils are for about 40 % responsible for the uphold of the bow. The buoyancy is by far not enough to withstand the load and unless the crew doesn't react instantly by easing the sheet the chance of the whole thing flipping over is possible and fatal for the match. So this is the case where the cat is with one hull out the water.

As you point out this is changed as the cat is out of the water on both hull and drives entirely on the foils
This is the case in this movie of Hydroptère where you can see the cat going nearly horizontal when on both foils:
http://www.youtube.com/watch?v=xFJocBvj-_w
But when it lands on both hulls however the decrease of speed might be fatal.

These are the dimensions of both competitors:

SUI100 lenght 25m, mast length 32.5m (top to deck (strange) instead keel)
gives:
A5 length (LOA hulls) around 36.65m 120'
mast around 54.3m 178'.

Somewhere in these forums I read that an increase of 1 ,5 % is calculated as fatal But the chance increases when the size is bigger. And of course I can start of the changes in the Reynolds numbers in case of turbulent or laminar but I guess we all know that.
I am pretty sure we are not going to get to see the calculations both teams made.

I have a feeling the bigger guy doesn't win this race. But I heard they have until February 2010 to fine-tune the whole thing. Where replacement of hulls and masts are within the rules of the game.

[Doug Lord]

She sailed today first time:

[TeddyDiver]

I love gaff cutters :D Thou a "bit" modernized version.. But seriously, I wouldn't call these mains as a "bermudan" anymore..

[Doug Lord]

Another spectacular picture from SA:

[EdgewaterMD]

i understand wave piercer to have benefits of reducing pitching of boat and resultant variations in apparent wind over sails. in monohull speak, this is popularly known as 'mmmmmm,..., flap,flap,flap,flap,mmmmm,..., flap,flap,flap,flap,flap,'.

fast multihulls' lee bow may want to dive/trip as opposite-direction hull drag and sail's lift forces increase with speed.
but let's separate 'diving' from 'tripping' bow.

now, imagine designing/trimming the boat to handle the diving problem for the design speed in flat water. but then, here comes a wave,..., trip. with a large bow having lots of 'reserve' flotation in its flare (to correct a diving problem that should have been dealt with in design/trim as noted above), the boat may have a Large increase in the skin,wave,and shape drag as the oversized bow hits the wave! just the opposite of what we want whereas reverse bow has more modest increase in each drag component as it punches through the wave. no trip, no problem. but who knows, maybe destructive wave interference (think Inui bulbous bow) has some effect?

a-class catamarans have been abuzz with this for some years now. the nacra a2 site has some content and a-class racing results back up the talk.

[Doug Lord]

The gist of the judges ruling today is that-apparently-Alinghy's engine is legal. I think it is a positive development for high performance big boats-and as Hydroptere has shown can lead to extraordinarily high performance.

[EdgewaterMD]

couple questions - i've seen that trend has been for increasing percentages for the amount weight carried by foils of ORMA 60's for example. i saw mention of a number above, and would not expect either BMW or Alinghi to even consider getting lee hull out of the water, onto foil. is that correct?

i liked the link to sail world article above. if everything i said regarding piercer bow is true, wouldn't it apply to monohulls? someone go out on a limb here if that's what it takes and say when or why not fast monhulls will have the reverse bow!

is there an 'easy' link to the rules regarding design of the AC boats? besides overall dimensions, various mentions of rigid wing and water ballast, the engine thing has me pretty confused.

re revolution - i think best part is the well-deserved attention that it will bring to multihulls. of course the flipping over and breaking up thing may be hard to swallow, but what the heck - it's time for everyone to find out about multihulls and for every reputable YC to support a multihull fleet.

[Doug Lord]

EMD- SA is rough compared to most other forums but the AC section is frequented by very knowledgeable people-you can learn about applicable rules there:
http://forums.sailinganarchy.com/index.php?showforum=23
============
The last batch of ORMA 60's had the curved foils lift about 70% of the total weight. Speculation has the percentage a bit higher on DZ and CZ.
This type of foil system does not use an altitude control system and so could theoretically lift the whole boat. If it did that there would be a much greater chance of the foil ventilating and a crash. The likelyhood of a crash resulting from such an event is even more likely since if the hulls are out of the water there is nothing providing pitch stability. Both these boats may be using some nifty technology that may allow them to reduce lift underway ,if necessary-but that is pure speculation. I would watch for changes in the foil systems as time goes by...
In the AC leadbelly days boats broke in half, masts failed etc.-wouldn't expect less from these extraordinary boats.

[EdgewaterMD]

thanks for the link but i couldn't really find a straightforward guide to any rules driving the design - particularly the rules that have allowed for multihulls or given them dimension. i've seen mention of 90'x90' is the thing but also speculation that A5 is actually 35mx25m.

i think the normal advantage of a tri is the extreme righting moment of a well-behaved boat that can be built to be square in LxW, whereas the cat should become directionally unstable as it exceeds W/L of 2/3. I imagine the torque inputs to steering if windward hull is not held steady out of water would be tough to deal with in a high efficiency world (hi aspect rudders for ex).

but Alinghi is not square and has been accumulating experience with the 40'x26' x40's and A5 is demonstrating sailing in flat water.

there is less heeling required for the cat but neglecting differences in mast height, SA, and effect of lifting foils, i would think a tri that is maxed out with resp to righting moment would still be able to have advantage over a cat that is pushing the stability issue, especially in an imperfect weather/water world.

but toss in the new-ish lifting foils, engine, water ballast and it makes me wonder if an Alinghi tri can pop out somewhere else? are they locked in to A5 in any respect?

[schakel]

When they started this,BMWO racing had the help of Frank Gammas and the crew of Groupama. Ernesto from Alinghi just hired Loic Peron who has extensive experience on Big catamarans like Gitana 13.
http://www.gitana-team.com/en/gitana2/gitana-team/bateaux/gitana-13.aspx

Both Groupama an Gitana team also experimented with trimarans and foils.
They are actualy very far and when it become stable it might be a huge improvement for the sport. Just as in the early days of the kanting keels things will break and even capzise. I was once worried that when at 40 knots this would mean serious danger for the crew when hitting a stay during a nose dive. The experts neglected this and I hope I will not have to say : "I told you so" when somebody dies in this new high velocity-cup.

Strange but I getting more and more aware of the fact that yachtsman aren't safety freaks at all. In holland 95 % of the time that sea rescue or coast guard had to take action it was for sailing yachts in trouble.On the other hand it is one sport after soccer where most revenue is made. And this is for private investors instead of FC Ajax Or Chelski.

The pitch stabillity is being obtained with waterballast in the stern compartments of the windward hull. At least that is the only solution that I can think of. Boy would I like to go with the Alinghi Cat. They have around 8 month to practice before the new America's Cup begins.

EMD- SA is rough compared to most other forums but the AC section is frequented by very knowledgeable people-you can learn about applicable rules there:
http://forums.sailinganarchy.com/index.php?showforum=23
============
The last batch of ORMA 60's had the curved foils lift about 70% of the total weight. Speculation has the percentage a bit higher on DZ and CZ.
This type of foil system does not use an altitude control system and so could theoretically lift the whole boat. If it did that there would be a much greater chance of the foil ventilating and a crash. The likelyhood of a crash resulting from such an event is even more likely since if the hulls are out of the water there is nothing providing pitch stability. Both these boats may be using some nifty technology that may allow them to reduce lift underway ,if necessary-but that is pure speculation. I would watch for changes in the foil systems as time goes by...
In the AC leadbelly days boats broke in half, masts failed etc.-wouldn't expect less from these extraordinary boats.

[Doug Lord]

On the S foils at the Daily Sail today by way of SA:
--

One of the most revolutionary features has been the S-bend shaped daggerboards. We assumed that the top of the S was simply there for engineering reasons, to enable each board to be cranked down. But Jones says this is not the case. “They are radical. That was part of the testing program we did last year in Valencia, sailing on the Alinghi 41, we built some boards of the same concept. A normal tri will have a centreboard and some C-foils. You can’t do that with a catamaran, so this is the solution and it gives us a lot of options. The concept is that when you are sailing downwind, the board is half up or reduced area, but because it is an S it is rotated inboard a lot, so it has got a lot of horizontal lifting capability when the board is half down. But when you push it all the way down, because of that top part of S, it cants it back out and makes it more vertical.”

[Indio]

My $5 in the office pool says this...

Pivoting trunk entry box. Pivoting trunk exit box. Both boxes slide fore and aft independently to adjust pitch of the foil while underway.

In between a flexible Kevlar braided belt encased in heavy duty tire rubber and connected to each box with triple clamping system. The belt length is sized to accomodate all of the possible radius related movements.

Water-tight, fully flexible and easily maintained in a boat that size.

Send your cashier's checks and money orders in US funds, please.

These pictures help you out?

[Chris Ostlind]

Interesting pics, Indio.

Has there been an accompanying discussion as to how the raking system works? Hydraulic actuators, pivoting points, waterproofing, etc., if applicable?

Thanks for the post.

[Indio]

Interesting pics, Indio.

Has there been an accompanying discussion as to how the raking system works? Hydraulic actuators, pivoting points, waterproofing, etc., if applicable?

Thanks for the post.

Our intrepid "reporter" Philippe in AC Anarchy shot those two photos, among many. The picture on the left shows a hydraulic ram which positions the foils sideways, while the shape of the foil mounting suggests the second actuator is a rotary actuator for canting the foil. The picture of the control panel below should give you an idea of how these actuators are manipulated.
Notice also the port and starboard ballast pump controls..something which Murray Jones is on record as denying (that Alinghi had water ballast) ;) .

[cristofa]

... This will mark the first use of two multihulls in the Cup and the first use of lifting hydrofoils in an America's Cup. Can't get more exciting than this!

... dipping back into boatdesin.net after quite a break, I was interested to read your comment, Doug.

You are probably right according to the letter, but in 1988 Stars and Stripes was a cat, and a British contender, Blue Arrow, was a radical tri/foiler. They never made the start line thanks, once again, to energetic legal wranglings on behalf of the defenders - lawyers have done very nicely out of the America's Cup over the years!

Christopher

[Doug Lord]

Christopher, "they" wouldn't let her in but Blue Arrow was surely interesting!

[cristofa]

Christopher, "they" wouldn't let her in but Blue Arrow was surely interesting!

... very interesting to see those pics - in fact, even if she had been allowed to participate, I gather she was a pig to sail - prone to digging the foil ends of the crossbeams and rapidly turning in a very inelegant fashion! But controversial and good for them for trying - gave the conservatives something to think about:)

[xarax]

Blue Arrow was much more interesting than Alinghi ! With both its foils working simultaneously to right up the craft, a symmetric most elegant solution for any future foiler trimaran...

[Gary Baigent]

Blue Arrow designers and hierachy had the problem of maintaining that the design was a monohull (to supposedly fit the DoG) - but it is/was a foil trimaran - now if they had just put a little more buoyancy; originally had a swelling shape at the foil tops, in the form of minimal floats, that boat would have been not only interesting but also successful (in sailing terms that is, not AC). However that windward foil needed to be lifted to reduce drag. The catenary wing mast by Barry Noble was a work of art.

[Doug Lord]

Mounted similarly to the way they do it on the International 14-this pix from SA and very poor:

From Catsailor
Stealth Marine comments on rudder t-foils:
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