Foiler Americas Cup

[Indio]

Originally Posted by 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.

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]

Originally Posted by 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.

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]

Originally Posted by Doug Lord

... 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]

Originally Posted by Doug Lord

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

[Doug Lord]

Check it out: http://morrellimelvin.wordpress.com/...peed-on-foils/


Excerpt:
"Both the BMW ORACLE trimaran and Alinghi catamaran use curved daggerboards (hydrofoils) to provide necessary lateral lift/resistance and they also lift the leeward hull up. The same board is used to reduce sliding to leeward or leeway and also provide vertical lift. The current variations that are being experimented with by both teams, tradeoff more vertical lift for less lateral lift or vice versa. Upwind these boats still need a fair amount of lateral lift/resistance to prevent excess leeway due to their enormous sail plans and the fact that they essentially are always going upwind! These boats sail at apparent wind angles downwind that are only about 10 degrees more than upwind! Downwind the sails are never really eased and the apparent wind never goes very far aft… the wind is always in your face on these boats! The apparent wind is so far forward on these boats that you always feel as if you are going upwind.

Combining both jobs, lateral resistance and lifting the boat into one board simplifies the boat but complicates the parts. Both teams are playing with variations of “J” or “L” boards, constant arc boards or even crazy looking “S” boards. Each shape has its slight advantages and disadvantages. They are also playing with different foil section shapes, which can produce better results at different speeds."

[brian eiland]

Originally Posted by Doug Lord

Check it out: http://morrellimelvin.wordpress.com/...peed-on-foils/

Yes I just saw that referenced by Scuttlebutt.

So many interesting things and I just haven't been in the mood to follow them lately. Maybe if they get all this legal wrangling out of the way, I could get interested again.

[Doug Lord]

Originally Posted by brian eiland

Yes I just saw that referenced by Scuttlebutt.

So many interesting things and I just haven't been in the mood to follow them lately. Maybe if they get all this legal wrangling out of the way, I could get interested again.

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Yeah, me too.