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Tell me about T foil rudders.

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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: 13 Feb 18 at 2:57pm
Graeme,
First rule of tfoils, you donít talk about tfoils.
Second rule of tfoils, itís always much, much cheaper and easier to achieve a similar end by making your boat a foot longer :-)
Fab. Ha aha ah
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Sam.Spoons View Drop Down
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Post Options Post Options   Quote Sam.Spoons Quote  Post ReplyReply Direct Link To This Post Posted: 13 Feb 18 at 3:06pm
What about t-foils and rudder gantries combined then, can we talk about those.......  Embarrassed

Edited by Sam.Spoons - 13 Feb 18 at 3:07pm
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Jack Sparrow View Drop Down
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Post Options Post Options   Quote Jack Sparrow Quote  Post ReplyReply Direct Link To This Post Posted: 13 Feb 18 at 3:27pm
Basically - Energy recovery. You are effectively surfing your own stern wave as well as reducing the weight of the crew / crew displacement by placing your weight over the foil.

BTW... to the forumite - thanks for the YouTube link. Shame the YouTube bar stewards have stopped paying advertising revenue for YouTubers with under 100k views!
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Post Options Post Options   Quote Daniel Holman Quote  Post ReplyReply Direct Link To This Post Posted: 13 Feb 18 at 4:07pm
Pressure recovery is a very minor part of the gain, applicable to heavily rockered hulls at lower speeds.
Itís all about getting displacement out of the hull (typical dinghy resistance to weight ratio 1:10 at 10 kts) and onto the foil (l/d ratio ~ 30:1) at semi displacement speeds (so 6-12kts for dinghies)
Above that speed generally the bow down moment of the rig means you canít run the foil in positive so itís just wasted area. Some pitch damping though.
At high speeds or when beating Away, running in negative keeps the bow up on short boats with big rigs downwind, meaning you donít compromise the hull design the rest of the time to make it surviveable in bear aways and hairy downwind stuff.
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Post Options Post Options   Quote turnturtle Quote  Post ReplyReply Direct Link To This Post Posted: 13 Feb 18 at 4:35pm
Itís good to know that with all these customisations the new boat will be so FARR out of class, that even you will accept there is no conspiracy around your own personal handicap...

Back to dinghy development, not PYAG bashing... hurrah!


Edited by turnturtle - 13 Feb 18 at 4:35pm
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Jack Sparrow View Drop Down
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Post Options Post Options   Quote Jack Sparrow Quote  Post ReplyReply Direct Link To This Post Posted: 13 Feb 18 at 4:59pm
Originally posted by Daniel Holman

Pressure recovery is a very minor part of the gain, applicable to heavily rockered hulls at lower speeds.
Itís all about getting displacement out of the hull (typical dinghy resistance to weight ratio 1:10 at 10 kts) and onto the foil (l/d ratio ~ 30:1) at semi displacement speeds (so 6-12kts for dinghies)
Above that speed generally the bow down moment of the rig means you canít run the foil in positive so itís just wasted area. Some pitch damping though.
At high speeds or when beating Away, running in negative keeps the bow up on short boats with big rigs downwind, meaning you donít compromise the hull design the rest of the time to make it surviveable in bear aways and hairy downwind stuff.

I thought my post would drag you out of your tower. Now iGRF doesn't need to come to your stand. LOL.
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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 6:12pm
Energy recovery I don't buy, nor can I see them doing much about keeping the nose up, but pitching dampening I can see, so could keeping the nose down on upwind legs into the sea. I also think the additional length offwind in marginal planing could help, especially if mounted back a bit on a gantry, but I'm not sure how class regs would view that.
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Jack Sparrow View Drop Down
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Post Options Post Options   Quote Jack Sparrow Quote  Post ReplyReply Direct Link To This Post Posted: 13 Feb 18 at 6:34pm
It's fine in the class rules iGRF. But getting the right section / size for the foil will take some maths / experimentation. As will the adjustment system. Although Moths / N12's have done most of that work for you.

Yes there is energy recovery. Yes there is reduced displacement. Yes there is pitch dampening. It depends which way you pull the strings.

FYI... I was in N12's when this idea was first conceived. Conceived by an incredibly bright but back of the fleet sailor. Who's name escapes me. Who was widely ridiculed at the time by top of the fleeter's for his badly built experimentally rudder stock and therefor it's lack of ability to show it's performance gains. 
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Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Posted: 13 Feb 18 at 7:10pm
Originally posted by Jack Sparrow

It's fine in the class rules iGRF.


Eh? Did I read that right? Have I died and gone to heaven?

Bring it on, I can't wait..
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Post Options Post Options   Quote Rupert Quote  Post ReplyReply Direct Link To This Post Posted: 13 Feb 18 at 7:25pm
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!
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