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andy_cherub View Drop Down
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    Posted: 13 Jan 08 at 9:35am

Jim, firstly those papers refer to hydrofoils. The singing from a hydrofoil vs the hum from a daggerboard are quite different. It even shows the vorticies from the foil! & vorticies = drag  (ill run a hydro stats on different foils and get figures for a faired vs non faired board  )

Where are these papers from? I tent to ignore non RINA based findings as ive come across so many which are just so wrong its funny!
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JimC View Drop Down
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Posts: 6662 		Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 13 Jan 08 at 9:24am
This is a paper with some realworld research on singing foils. The speed ranges and construction materials are of course quite different.

http://docs.hydrofoils.org/hiper.pdf

Its interesting that they don't seem to mention drag being caused by foils singing.
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Chris Bridges View Drop Down
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Posts: 699 		Post Options Post Options   Quote Chris Bridges Quote  Post ReplyReply Direct Link To This Post Posted: 13 Jan 08 at 9:23am
Do oyu know when they are planning on replacing the wings and if they are going to phase them in like the rig? Its alright for some who have plenty of sponsors .
49er GBR735 (for sale) - Rutland SC
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Skiffman View Drop Down
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Posts: 291 		Post Options Post Options   Quote Skiffman Quote  Post ReplyReply Direct Link To This Post Posted: 13 Jan 08 at 8:43am

i meant upwind not downwind...

the carbon rig will be available to buy in the UK in September, remember the new moulds are not CNC. They are making a master plug that is CNC and then making the moulds off that. What makes everyone think that the new boats will be faster... the new foils are slower in most conditions to a faired set of old foils (which most people did). They will make it so in the first year you can use both rigs but if you use a new rig you have to carry correctors (3.5kg) and then in the second year and onwards you have to use the new rig in Gold fleet. The new wings are not carbon and are being changed because it costs so much to make the old wings.

I can not wait for the new rig especialy as our first worlds with them is going to be in Garda!

p.s ours do not hum and we do not make the back edge asymmetrical but they do in finns



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andy_cherub View Drop Down
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Posts: 768 		Post Options Post Options   Quote andy_cherub Quote  Post ReplyReply Direct Link To This Post Posted: 13 Jan 08 at 8:42am

If the dagger is asymmetrical then itll pull the boat sideways - like a gybing dagger board but with no control over it. The actual board itself "shouldnt" cause more drag than a turbulating board as the flows laminar. But dragging a 49er upwind sideways...................... thats where the drag may come in!

I just have my foils clean smooth and fair - does the job and we just get the wind as it 'whistles' through the rigging downwind, the higher the pitch the more apparent we are building!

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JimC View Drop Down
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Posts: 6662 		Post Options Post Options   Quote JimC Quote  Post ReplyReply Direct Link To This Post Posted: 13 Jan 08 at 12:51am
Originally posted by Skiffman

it should not happen, its the water turbulating off the back of your foils. You need to sand one side of the back edge to make the back edges asymmetrical.

I recently saw some research that suggested that will give you a bigger drag increase then the humming...
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Chris Bridges View Drop Down
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Posts: 699 		Post Options Post Options   Quote Chris Bridges Quote  Post ReplyReply Direct Link To This Post Posted: 12 Jan 08 at 11:01pm
I think it might be which is a shame
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andy_cherub View Drop Down
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Posts: 768 		Post Options Post Options   Quote andy_cherub Quote  Post ReplyReply Direct Link To This Post Posted: 12 Jan 08 at 10:52pm

I used to sail 49ers, then droped the campain for the 12. Still keep an eye on developments tho.

I hope the 49er doesnt go down the road some of the previous olympic boats went down, ie become just a sole olympic class as I think its a great boat for the "average joe" as its easy to go fast!

Oh well, time will tell!
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Merlinboy View Drop Down
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Posts: 3169 		Post Options Post Options   Quote Merlinboy Quote  Post ReplyReply Direct Link To This Post Posted: 12 Jan 08 at 9:40pm
I have to agree with you andy, i think it will be a different beast!  and not stuck in the misd 90's! 
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Chris Bridges View Drop Down
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Posts: 699 		Post Options Post Options   Quote Chris Bridges Quote  Post ReplyReply Direct Link To This Post Posted: 12 Jan 08 at 9:39pm
Originally posted by andy_cherub

I heard a rumour that the non CNC made boats wont be allowed to race with the new ones on the circuit in the future - I really hope this isnt true!

But Im all for the new 49er rig, think its a good thing - as long as its done properly and by what ive heard, over 4yrs and lead thats a good plan. Ultimatley the bigger rig and carbon mast will make it faster and more responsive - all of which is a big bonus!

 I hope not.. I thought it was just foils, to sail in Gold Class events you have to have the new CNC foils with the 49er ensignia on. I guess shouldn't matter too much because the people who campaign normally have new boats from their sponsor's anyway, just got to get the sponsors first!

I think its a great idea, as logn as they don't go on a psree and go for new carbon wings and everything they possibly can to make it more expensive for the little guys .

Not sure if it is 4 years, but its some time which i remember thinking yea some new rigs will tirckle down in that time.. 

Do you sail 49ers aswell?
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