berny Posted April 25, 2004 Report Share Posted April 25, 2004 Ok, does anyone know why my foils hum? One rudder and one d/board get a real sing song going as soon as the boat reaches a certain speed. It can't be fast and I'd like to eliminate it because it's annoying but I'm at loose end having checked the alignment and I've also tried fairing but no result. I have a suspicion it might be that the gelcoat isn't bonded to the glass laminate in some places. That's about all I can think of as being the culprit. Any other ideas? Bern Link to comment Share on other sites More sharing options...
catsailor.net Posted April 26, 2004 Report Share Posted April 26, 2004 Very easy problem to fix. Grab a smooth flat file and file the trailing edges of the rudders and boards to remove the hum. Basically get the trailing edges sharp and the hum will go away. This has been a feature with every rudder/board I have had. Link to comment Share on other sites More sharing options...
mal gray Posted April 26, 2004 Report Share Posted April 26, 2004 Other things that cause hum: rough foil surface uneven foil from side to side nicks, dings Modern foils tend to be more susceptable due to their stiffness. Link to comment Share on other sites More sharing options...
Greg W Posted April 26, 2004 Report Share Posted April 26, 2004 Bloke I get to do any repairs reckons that a flat trailing edge is the go if a sharp edge can't be filed - that is file it flat at the back. Whaddya reckon? Cheers Greg Link to comment Share on other sites More sharing options...
berny Posted April 26, 2004 Author Report Share Posted April 26, 2004 My foils are taken from moulds that I had built from plugs I made. They are vac. bagged carbon/foam laminates, very straight and very strong. The sections are NACA sections and are 'squared off' at the trailing edge as the NACA designs dictate. To shape them to a point would be a counter productive and unnecessary because one rudder and one d/board are noiseless so it's not the square trailing edge causing the problem. They are also finish blocked with 1200 wet&dry so their surfaces are fair and smooth. Bern Link to comment Share on other sites More sharing options...
REV YUKKA II Posted April 27, 2004 Report Share Posted April 27, 2004 make the trialing edge as sharpe as a knife and the hum will go. Link to comment Share on other sites More sharing options...
Greg W Posted April 27, 2004 Report Share Posted April 27, 2004 Filing mine as we speak and will try them out on da weekend. Will let you know how they go! Cheers Greg Link to comment Share on other sites More sharing options...
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