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Mast Head T Foil?

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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 Topic: Mast Head T Foil?
    Posted: 29 Oct 14 at 9:49am
So, I alluded to it in banter over on the kicker attachment thread, but it's been an idea I've been toying with, initially as a cure for turning turtle but with the secondary consideration of a power boost by converting tip turbulence to power generating flow at the head of the sail. Obviously it would only function with fathead sails, but what do the hive mind think?

Could such a thing be beneficial to the point main sail size reduction might even be possible?

How such a thing could be constructed, I'd suggest kite technology from kite surfing, so a bow leading edge secured with a central batten down the middle of the foil so it is two sided the central batten attaching to the top or top batten of the sail.

The result would be a wing tip foil closing the head. With the spin off of course of a mast head float.

Thoughts?

Edited by iGRF - 29 Oct 14 at 9:50am
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iiitick View Drop Down
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Post Options Post Options   Quote iiitick Quote  Post ReplyReply Direct Link To This Post Posted: 29 Oct 14 at 9:54am
I thought we discussed this topic a while back?

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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: 29 Oct 14 at 10:07am
Oh no did we already?

Nurse! I need some more of those memory tablets..
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Post Options Post Options   Quote iiitick Quote  Post ReplyReply Direct Link To This Post Posted: 29 Oct 14 at 10:13am
Originally posted by iGRF

Oh no did we already?

Nurse! I need some more of those memory tablets..

It was a long time ago when you and I were much younger....and Holman minor was still in short trousers.
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Chris 249 View Drop Down
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Post Options Post Options   Quote Chris 249 Quote  Post ReplyReply Direct Link To This Post Posted: 29 Oct 14 at 11:17am
It doesn't work; aerodynamics 101. You are better off using the same weight, area and complication to increase the mast height.

This has been pointed out repeatedly since the 1980s by big boat designers. It's also been repeatedly pointed out on Boat Design Forum by MIT aero professor Mark Drela (designer of world champion human powered boats and aircraft and AC winning multis) and Tom Speer (Boeing and Oracle AC designer).
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Post Options Post Options   Quote Medway Maniac Quote  Post ReplyReply Direct Link To This Post Posted: 29 Oct 14 at 12:11pm
Well, aircraft use winglets to recover some energy from the tip vortex instead of just adding span, and they are less concerned about the bending moment at the wing root than we are about the heeling moment, so I'm surprised that the great and good have ruled it out on sails.

I'd be interested to read their reasoning.  Do you have any useful links, Chris?
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Post Options Post Options   Quote MattHarris Quote  Post ReplyReply Direct Link To This Post Posted: 29 Oct 14 at 12:14pm
I thought it was used on aircraft as they are restricted by space in airports where the wings can only have a maximum width. 
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maxibuddah View Drop Down
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Post Options Post Options   Quote maxibuddah Quote  Post ReplyReply Direct Link To This Post Posted: 29 Oct 14 at 12:37pm
By stopping the airflow from falling off of the end of the wing because of the fin it increases the amount of lift for a given wing size. That enables the carriers to carry less fuel, saving money
Everything I say is my opinion, honest
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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: 29 Oct 14 at 12:40pm
Increasing the mast height as well as adding weight it adds leverage and heeling moment, so if the mast height could be reduced, or if a boat already has a given mast size, but the addition of a light foil up top which could tidy up the vortices up there and probably add area for downwind running and reaching due to the resulting upward swing as the boat heels, I'd like to see empirical evidence of it having been tried before writing it off.

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Post Options Post Options   Quote Rupert Quote  Post ReplyReply Direct Link To This Post Posted: 29 Oct 14 at 12:59pm
It could well work better than a float bouncing around at the top of the mast, a pad in the top of the sail or a flying saucer thing up there.
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