T-foil rudder?

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mtaz
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Joined: Fri Jan 28, 2011 1:40 pm

T-foil rudder?

Post by mtaz » Thu Mar 03, 2011 4:12 pm

From the way i've read the rules, we are allowed to use T-foil rudders.
Has anyone ever tried one?

colinbrown
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Re: T-foil rudder?

Post by colinbrown » Thu Mar 03, 2011 6:33 pm

Yes, John Ellis

Rob
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Re: T-foil rudder?

Post by Rob » Thu Mar 03, 2011 9:21 pm

Yes, Lester Noble.

Alistair
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Re: T-foil rudder?

Post by Alistair » Fri Mar 04, 2011 8:06 am

Andy Paterson tried one on Tin Tear Drop

If you were to try one what would you hope it would do? It seems from people who have tried them, and I have spoken to, that they just add to drag. I think most other classes that have tried them either are a lot shorter or have a lot more sail area. There is actually nothing to stop you putting a foil on the dagger board, but the rule about being able to draw it out through the hull while sailing makes it a difficult one to achieve, and even if you did manage to work around that rule then there is a rule about no holes through the boat except for the dagger board or rudder, and no out riggers, so that means no control wand, (at least that's how I read the rules) I was going to try and work this one out ( I am sure there is a solution within the rules) but realised that it was prob better use of my time getting a new boat together and go sailing!
Alistair

mikeewart
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Re: T-foil rudder?

Post by mikeewart » Sun Mar 06, 2011 9:26 pm

Surely one of the main advantages of a T foil rudder is the end plate effect that most classes need to give them more effective rudders, on an IC we already have the end plate at the other end of the rudder so why bother?

jimc
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Re: T-foil rudder?

Post by jimc » Mon Mar 07, 2011 8:44 am

>end plate
AIUI the theory behind the things is that its a lot more efficient to lift the boat out of the water and reduce displacement with a 10:1 aspect ratio double sided rudder foil than it is with a 1:10 aspect ratio single sided planing surface.

bob
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Re: T-foil rudder?

Post by bob » Mon Mar 07, 2011 9:51 am

o jim you havnt learnt yet have you the idea is to keep the b....y thing in the water :lol: :lol: the our tiny rudders work on max efficiency :mrgreen:

bob
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Re: T-foil rudder?

Post by bob » Mon Mar 07, 2011 9:54 am

sorry forgot to add the major amount of rework unless you have an ellis hull or t :evil: ransom hung rudder to allow you to fit one :twisted: by the way hows your fat a...e affect :lol: ing stickiness :lol: :lol:

jimc
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Re: T-foil rudder?

Post by jimc » Mon Mar 07, 2011 11:57 am

bob wrote:o jim you havnt learnt yet have you the idea is to keep the b....y thing in the water
reduced displacement != boat out of water!
When planing dynamic lift from the hull shape reduced displacement of water and thus wave drag, also to an extent wetted area...
The theory of these foils, AIUI, is that you have a more efficient lifting device having the same effect. Naturally then weight has to be moved back to correct the trim, otherwise it will go bow down.
I think it ought to be possible to make it work, but I'm not at all convinced that its a complication that *I* want to get involved with! It seems possible, even probable that below a certain level of boat speed the extra dynamic lift won't compensate for the extra wetted area, and it seems likely that it would be quite easy to set the foil angle of incidence such that the boat is slower rather than faster.

Phillip Lee
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Re: T-foil rudder?

Post by Phillip Lee » Tue Mar 08, 2011 10:51 am

Interesting stuff, I'm a former Mothie from the days of T foil rudders and have sailed a 14 with the large T foil rudder. On the Moth the biggest benefit was that it added pitch inertia to the boat and stopped it hobby horsing upwind. The short Solent chop is just the right wavelength to get an 11' hull pitching and stuffing into each wave upwind. The T foil transformed this motion into gentle bodily rise and fall and made a big speed difference. I snapped my T foil off when launching once and carried on out into the chop, what a huge difference. In addition it almost banished nosedives downwind. On the 14 the foil is large and does a similar thing with the crew moving weight aft to counter the nose down trimming effect going upwind. Downwind in the 14 the kite does most of the bow up trim plus the dynamic lift from the hull of course.
On a canoe being so much longer the pitching effect is not so marked in the chop at Lymington, plus we can't move weight aft so much to balance the trim effect a foil would give. Like all foils it would add drag, which may outweigh any benefit. I'm not trying one either.

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