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Old Yesterday, 05:55 PM   #1
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Default Foiling Boards..a way forward or a dead end ???

Current foilers use an inverted T foil..at high speeds its impossible to reduce their SA and hence will not compete with non foiling boards ...

Come up with an idea so boards can use reducing area/contant lift foils...
If an orthodox fin (albeit a large one) was allowed to pivot on a longitudinal axis parrallell to base of board. (ie along its root) then that fin would deflect to windawrd under influence of leeway... This would be correct orientation to give lift (against gravity)...if stopped at 45 degrees..half fins lift would work against leeway...half against gravity.. (If fin pointed leeward it would give negative lift...Google Bruce foils)
If a number of these pivoting fins were distrubuted under hull to provide balance (ie in some sort of triangle ??? two towards rear ,one under mast foot) then at some speed board would lift clear of water...and foil... Centre of lift as it did so would creep windward but that might not be an issue for windsurfing (CoG is outside hull any way)

As board increased speed it would rise further out..reducing area in contact with water..maintaining constant lift automatically, reducing drag and hence allow much higher speeds...

Any thoughts...
Anyone... (Tried patenting idea...but pivoting fin not new (amazingly)...applying to a board is ???
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Old Yesterday, 08:03 PM   #2
Join Date: Aug 2006
Posts: 67

You don't need any T-foil to sail on the fin, just ask any Formula sailor...

If you do want a foil then the classical V-shape should do the trick of reducing the lift when the board rides higher.
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Old Yesterday, 08:29 PM   #3
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Sorry Krister think you are missing point...boards for a while ...long before Formula... have been riding foil...but only to reduce underhull friction..not to eliminate it completely(was a technique in real old days to do it with dagger board but in any conventional type of board..contact with water has to be maintained somewhere...for a number of reasons..fin never provides sufficient lift to lift entire load..and if it ever did both pitch and roll stability would be almost impossible to control...idea mentioned above is to lift board completely free of water;reducing drag from initially the board and as board rises further from foils themselves..(Current foilers T foil has to remain completely submerged..my idea is more akin to foiling as in foiling cats/Hydroptere..except with both those windward fin is used to oppose healing forces..postive lift(against gravity) is only obtained from leeward foil...since a board does not transfer any heeling forces to hull such a system would not work (ie it would sink windward rail..) In idea decribed all fins would produce positive lift on both tacks.(and would adjust automatically..under action of leeway)
But thanks for comment...
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Old Yesterday, 08:34 PM   #4
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Planing hulls no matter what the shape can compete with a submerged foil in a drag /to lift competition... a foil giving same lift as a board would produce far less drag and hence with same power give a higher top speed..(only in theory at moment...but look at efficiency of Hydroptere..it can achieve 50 knots in 23 kts of wind...that is purely down to efficiency of foil.. (Yes I know Formula at lower speeds are as efficient but not at speeds of 50 kts..)
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