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Tell me about T foil rudders. |
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davidyacht
Really should get out more Joined: 29 Mar 05 Online Status: Offline Posts: 1345 |
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Topic: Tell me about T foil rudders. Posted: 13 Feb 18 at 7:29pm |
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I think that I14’s were there before N12’s. Ref. Pressure Recovery, Frank Bethwaite talks about this with his Medium Dribbly NS14’s, by flattening the aft underwater sections the boat gets lift off the stern wave that builds up under the hull. I borrowed this idea for my Annie Apple N12 design. I also drew up a T-foil rudder using the I14 hub, but never had the courage of my conviction, though I did a study of the potential reduction in displacement due to lift, and there were marginal gains, I binned the idea because I calculated considerable drag at non optimal speeds.
I think Graham Camm and possibly Tom Eddom had a go at T-Foils around that time, and the results at the time did not appear to be ground breaking.
I think where the DCB gets it right is by using a low prismatic low drag hull form, and utilising the T foil to substitute for the hull’s planing surface. The adjustable pintle arrangement is also much neater than a pivoting hub that was the derigeur solution 15 years ago. |
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Happily living in the past
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iGRF
Really should get out more Joined: 07 Mar 11 Location: Hythe Online Status: Offline Posts: 6496 |
Post Options Quote Reply Posted: 13 Feb 18 at 8:18pm | |
Exactly ! Think I'll call it Pitch Perfect. |
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craiggo
Really should get out more Joined: 01 Apr 04 Location: United Kingdom Online Status: Offline Posts: 1810 |
Post Options Quote Reply Posted: 13 Feb 18 at 9:36pm | |
If you just want pitch stability you can go for much smaller foils and a fixed rudder as per the low rider moths.
If you want pressure recovery then vertical position of the foil is fairly critical. If you simply want to reduce displacement upwind then they need to be fairly sizeable as you will be looking to lift at least your weight off of the boat. Is the Farr a nosey boat? Doesn't look like it Will it go fast enough to benefit from pressure recovery? Not likely as it's a short high drag hull. Will the Farr benefit from displacement reduction? Probably |
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OK 2129
RS200 411 |
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Post Options Quote Reply Posted: 13 Feb 18 at 10:47pm | |
Very good! By the way, it's damping not dampening. |
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iGRF
Really should get out more Joined: 07 Mar 11 Location: Hythe Online Status: Offline Posts: 6496 |
Post Options Quote Reply Posted: 13 Feb 18 at 11:19pm | |
I've read stories of pitch poling on Burghfield and on the sea, so yes, it is capable of them and somewhere else I read about the further back you can get the less likely you are to go over the front. I've always wondered why nobody has fitted nose foils on the bow to help stop that. |
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Post Options Quote Reply Posted: 14 Feb 18 at 12:43am | |
Foils at the bow, like canards, are destabilising. if the bow lifts it will continue to lift, and if the bow goes down it will continue to go down.
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Do Different
Really should get out more Joined: 26 Jan 12 Location: North Online Status: Offline Posts: 1312 |
Post Options Quote Reply Posted: 14 Feb 18 at 1:04am | |
Firstly, hats off to you for committing to a new build boat.
Secondly, a genuine question, dagger board, gantry & t foil rudder vs shingle and shore dump? Has something changed your thinking?
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Daniel Holman
Really should get out more Joined: 17 Nov 08 Online Status: Offline Posts: 997 |
Post Options Quote Reply Posted: 14 Feb 18 at 8:25am | |
Yes you have to be chest deep and holding the boat singlehandedly into a big shore dump to slot the tfoil in from underneath.
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423zero
Really should get out more Joined: 08 Jan 15 Location: United Kingdom Online Status: Offline Posts: 3406 |
Post Options Quote Reply Posted: 14 Feb 18 at 8:54am | |
Thats the T-foil gone then, stick with the gantry, sods law T-foil is going to be a nightmare, you will always be conscious of it and it will spoil your fun.
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aardvark_issues
Really should get out more Joined: 24 Jul 05 Location: Weston-Super-Mare Online Status: Offline Posts: 505 |
Post Options Quote Reply Posted: 14 Feb 18 at 9:32am | |
They predate T foils in Moths and they were a bad idea then...
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