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Tell me about T foil rudders.

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davidyacht View Drop Down
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Post Options Post Options   Quote davidyacht Quote  Post ReplyReply Direct Link To This Post Posted: 13 Feb 18 at 7:29pm
I think that I14ís were there before N12ís.  Ref. Pressure Recovery, Frank Bethwaite talks about this with his Medium Dribbly NS14ís, 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 hullís 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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iGRF View Drop Down
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Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Posted: 13 Feb 18 at 8:18pm
Originally posted by Rupert

Originally posted by Sam.Spoons


What about t-foils and rudder gantries combined then, can we talk about those.......† Embarrassed


That'll feel 2 feet longer!


Exactly !

Think I'll call it Pitch Perfect.
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Post Options Post Options   Quote craiggo Quote  Post ReplyReply Direct Link To This Post 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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Peaky View Drop Down
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Post Options Post Options   Quote Peaky Quote  Post ReplyReply Direct Link To This Post Posted: 13 Feb 18 at 10:47pm
Originally posted by iGRF


Think I'll call it Pitch Perfect.

Very good! By the way, it's damping not dampening.
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iGRF View Drop Down
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Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Posted: 13 Feb 18 at 11:19pm
Originally posted by craiggo



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


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 Post Options   Quote Peaky Quote  Post ReplyReply Direct Link To This Post 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 View Drop Down
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Post Options Post Options   Quote Do Different Quote  Post ReplyReply Direct Link To This Post 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 View Drop Down
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Post Options Post Options   Quote Daniel Holman Quote  Post ReplyReply Direct Link To This Post 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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Post Options Post Options   Quote 423zero Quote  Post ReplyReply Direct Link To This Post 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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Post Options Post Options   Quote aardvark_issues Quote  Post ReplyReply Direct Link To This Post Posted: 14 Feb 18 at 9:32am
They predate T foils in Moths and they were a bad idea then...

Originally posted by iGRF

 


I've always wondered why nobody has fitted nose foils on the bow to help stop that.
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