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]

Originally Posted by Doug Lord

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]

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]

Originally Posted by Chris Ostlind

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]

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]

Originally Posted by TeddyDiver

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..

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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/homepa...linghi-bow.jpg

[yipster]

nice pics schakel, looks 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..