Dinghy development: noisy foils

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noisy foils

Printed From: Yachts and Yachting Online
Category: Dinghy classes
Forum Name: Dinghy development
Forum Discription: The latest moves in the dinghy market
URL: http://www.yachtsandyachting.com/forum/forum_posts.asp?TID=13955
Printed Date: 09 Aug 25 at 2:38pm
Software Version: Web Wiz Forums 9.665y - http://www.webwizforums.com

Topic: noisy foils

Posted By: NickA
Subject: noisy foils
Date Posted: 30 Jun 22 at 10:54pm

My boat keeps screaming at me. Maybe it doesn't like planing or maybe it's yelling with joy; but the faster we go the louder it gets.

I think it's the rudder blade. I've faired the trailing edge, no chips or dints. It's a nice Wood and epoxy Milanes affair.

Doubt it's damaging the speed much, but people certainly know when I'm about to overtake.

Any ideas? Solutions?

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Javelin 558
Contender 2574

Replies:

Posted By: Paramedic
Date Posted: 01 Jul 22 at 6:38am

It'll be the trailing edge off the board or rudder (I think you'd feel it on the rudder). You have a slightly fat spot somewhere. Cut a couple of strips of insulation tape about 50mm long and place a piece either side of the foil in question and then go sailing. Move the tape up and down until the noise stops. You've then found the bit that needs work.

I don't think its performance detrimental.

Posted By: Rupert
Date Posted: 01 Jul 22 at 7:02am

I was always told to ensure the back edge of foils were chamfered slightly asymmetric, so one side would be 1/2 mm further aft than the other. This is supposed to change to stop the vibrations that cause the noise.

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Firefly 2324, Puffin 229, Minisail 3446 Mirror 70686

Posted By: E.J.
Date Posted: 02 Jul 22 at 8:16am

Is it your Contender? Quite a few get this. As other have said it is often solved by making the back edge imperceptibly asymmetric. If your OCD won’t allow that sort of clumsy engineering the noise doesn’t affect speed. There is something quite menacing about the gradual increase of a low hum overtaking. Very Jaws, and can put your competition right off their stroke.

Posted By: Guests
Date Posted: 02 Jul 22 at 9:10am

Nothing clumsy about Anti-Singing Trailing Edges - they are standard fit on the most advanced propellers. There must be some speed loss as kinetic energy is being converted to sound, but it will be minimal and it does sound good!

Posted By: NickA
Date Posted: 02 Jul 22 at 8:42pm

Yes the contender. So it's easy to access the back edge of the centre board with some insulting tape. Lifting rudder too.

On a related matter ..once the boat gets "humming" along, quite a lot of water comes up the front of the cb case and drains out the drain holes. Gasket seems good. Is this also normal? Wondering about slicing the gasket into two separate lengths, so the front bit can close with the board in "neutral" ie part up for planing conditions, but never heard of anyone doing that.

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Javelin 558
Contender 2574

Posted By: E.J.
Date Posted: 03 Jul 22 at 11:29am

No that is unusual, I’d immediately say it’s the gasket but if it it’s in good Nick a gap is being created forward if the CB somehow.

Posted By: 423zero
Date Posted: 03 Jul 22 at 11:43am

Is the board angled towards the bow? Rather than towards the stern,this could cause the water to drive up through the gasket. Failing that, glue a square of gasket material over the two strips, make sure it needs to be compressed when board is right down, could be a softer material than gasket.

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Robert

Posted By: NickA
Date Posted: 03 Jul 22 at 4:25pm

Contender board usually slanted back ( so the bottom edge is parallel with the hull). The leading edge is only vertical upwind in very light winds. hence a gap in front of the board that's filled by slot gasket ..or not if water pressure is forcing it open. Trying to peer down there whilst smacking along at 15knots is quite hard!

Might try the strip of rubber (physio exercise band stuff) at the gasket front. Or replace the gasket anyway, maybe gone soft.

NB. Not found any bumps on the foils and sticky tape made little difference. But the trailing edges are rounded, might file them flat & slanted.

Ta for the suggestions.

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Javelin 558
Contender 2574