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fudheid View Drop Down
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Posts: 236 		Post Options Post Options   Quote fudheid Quote  Post ReplyReply Direct Link To This Post Posted: 19 Nov 19 at 5:15pm
That's too say, if this fence is creating any lift around it then it is a wing it contrivance under the definitions of the ERS/rule?
IF NOT.
then how much wider/ bigger can it get before the lift it generates is a wing or contrivance?
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fudheid View Drop Down
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Posts: 236 		Post Options Post Options   Quote fudheid Quote  Post ReplyReply Direct Link To This Post Posted: 19 Nov 19 at 5:11pm
Originally posted by 423zero

Can't see it clearly on phone, but it looks like it also as a reduced chord ?
If the manufacturer designed blade purely to reduce suction and you attempt to make it into a foil ! Speaks for itself.


Not attempting to make it a foil.
If it reduces suction is that no creating lift?
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423zero View Drop Down
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Posts: 2601 		Post Options Post Options   Quote 423zero Quote  Post ReplyReply Direct Link To This Post Posted: 19 Nov 19 at 5:06pm
Can't see it clearly on phone, but it looks like it also as a reduced chord ?
If the manufacturer designed blade purely to reduce suction and you attempt to make it into a foil ! Speaks for itself.
Robert
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fudheid View Drop Down
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Posts: 236 		Post Options Post Options   Quote fudheid Quote  Post ReplyReply Direct Link To This Post Posted: 19 Nov 19 at 4:48pm
So this fence isn't producing lift? It isn't shaped to change the flow of water around the foil? Canting / lifting the rudder doesn't increase our decrease the angle the fence makes?
Having a fence doesn't enhance the performance of the foil in certain conditions, i.e. it stops ventilation, stopping the stalling of the higher aspect foil?
If I make this fence larger when does it become a non allowable wing?
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423zero View Drop Down
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Posts: 2601 		Post Options Post Options   Quote 423zero Quote  Post ReplyReply Direct Link To This Post Posted: 19 Nov 19 at 4:22pm
Fence is not a performance enhancer, it is a fit and forget item, purely for maintaining steerage, much the same as a release cleat on rudder or a centre board that knocks back, plus a myriad of other boat damage limiting useful inventions.

Edited by 423zero - 19 Nov 19 at 4:25pm
Robert
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fudheid View Drop Down
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Posts: 236 		Post Options Post Options   Quote fudheid Quote  Post ReplyReply Direct Link To This Post Posted: 19 Nov 19 at 3:47pm
Originally posted by JimC

No, a fence has nothing to do with leeway or lift. Its purpose is to modify the boundary layer round the foil. The use on rudder blades is typically to attempt to reduce ventilation - sucking of air down from the surface - which causes the rudder foil to stall and the boat to lose control.

Ok so if it doesn't have anything to do with leeway or it isn't creating lift; what if the rudder is angled so the fence is at an angle to the flow of water does it creat lift then?
so it must be one of these as it is a contrivance of somesort? Fences are not  listed in the ERS so as a 'fence' it can be big as long as it is not producing lift (the national 12 rudder wing is not primarily about lift it is changing the flow of water off the stern - not lift?):
(d) FIN A fixed hull appendage primarily used to affect leeway or directional control. 
(k) TRIM TAB When a rudder(s) is used, a movable hull appendage, attached at the aft, or fore edge of another hull appendage.
(l) WING A hull appendage attached to a keel, bilge keel, canting keel, fin or bulb, primarily used to affect leeway and/or lift. (m) FOIL A hull appendage attached to a centreboard, daggerboard, bilgeboard or rudder, primarily used to affect leeway and/or produce vertical lift. 


Edited by fudheid - 19 Nov 19 at 3:53pm
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gbrspratt View Drop Down
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Posts: 169 		Post Options Post Options   Quote gbrspratt Quote  Post ReplyReply Direct Link To This Post Posted: 19 Nov 19 at 3:42pm
Originally posted by JimC

Originally posted by gbrspratt

   It originates from Merlin's and putting a halyard bag in between the kicker/boom/mast.


I see. Well that's easy enough and common enough. Attempted rule bending by logic chopping is nothing new: "if I can dream up a way to call extra [sail area|hull length|corrector weights|something else] a [something different] it must be legal".

Of course that's nonsense. If it quacks like a duck it counts as a duck. Just because its a halyard bag doesn't mean it isn't also sail area.



Is this not also true with a fence/wing/foil?

Definitely looks like a duck....
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JimC View Drop Down
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Posts: 6387 		Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 19 Nov 19 at 2:37pm
No, a fence has nothing to do with leeway or lift. Its purpose is to modify the boundary layer round the foil. The use on rudder blades is typically to attempt to reduce ventilation - sucking of air down from the surface - which causes the rudder foil to stall and the boat to lose control.
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fudheid View Drop Down
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Posts: 236 		Post Options Post Options   Quote fudheid Quote  Post ReplyReply Direct Link To This Post Posted: 19 Nov 19 at 1:28pm
Originally posted by 423zero

Taken from latest rule book

C.8.2 Daggerboards, bilgeboards, double rudders, winged rudders and similar contrivances are prohibited

is a fence not a similar contrivance? there's no mention of fences in the ERS. so a fence is a contrivance? as it primarily used to affect leeway and/or produce vertical lift?


Edited by fudheid - 19 Nov 19 at 1:31pm
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423zero View Drop Down
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Posts: 2601 		Post Options Post Options   Quote 423zero Quote  Post ReplyReply Direct Link To This Post Posted: 19 Nov 19 at 11:32am
Taken from latest rule book

C.8.2 Daggerboards, bilgeboards, double rudders, winged rudders and similar contrivances are prohibited
Robert
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