Siren's song?

Under certain speed and conditions my boat starts to whine or sing. I presume this to be caused by the asymmetric hulls or perhaps rudder vibration. Three questions: 1. What causes this noise? 2. Is it bad? 3. If so, should I try to fix it?

When I used to crew for guys back in the seventies they seemed to think singing hulls was a good thing... like they were sailing on the edge or something. I think the sport was so new back then that they really didn't know WTF.

Its the rudders...

From the support pages:

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Matt Miller
Former - Director of Parts and Accessory Sales
Warranty and Technical Support
Hobie Cat USA
(Retired 11/7/2022)

Actually I used to like to singing, it kind of added to the sensation of speed. I've never got my getaway to sing like that.

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06 getaway -- always remember, man with both feet in mouth have no leg to stand on.

Bummer. My rudders were badly yellowed so I just finished painting them. Thanks for the explanation. I'll just tell folks that I'm sailing on the edge!

Not all trailing edges are the same. The Tiger & Fox blades that I've worked on are way too thin, and can chip just like a potatoe chip. Others are way too wide which can cause severe humm & vibration. We're putting together another article for the HOTLINE which will cover these issues.

What's the HOTLINE? How do I get it?

On-line version is here: http://www.hobiecat.com/hobieclass/

To get a hard copy, you need to join the Hobie Class Assoc. of North America, here: https://www.hcanamembers.com/

I like the humming. Usually it happens when you are going at a pretty good pace or just about to lift a hull. Didn't somebody have a story about dolphins being attracted to the hum?

Not that i have seen but it sure makes my dog bark lol

_________________
06 getaway -- always remember, man with both feet in mouth have no leg to stand on.

Had to jump in here. I did the scissors thing and used a straight edge to check for hollows. Looked pretty good. Out on the water at about 10 knots they scream even louder. Back to the sanding board. This time I used a belt sander with 90 grit and carefully took the trailing edge down to 0.10 of and inch and squared off the back edge. Still screams. I've given up.

Don't give up...I've sent Matt the info for the HOTLINE article on rudder repair. Be patient.

After Matt's suggestion I went back and took a gun sight look at the trailing edges of my rudders. I couldn't see anything that looked like a flare, bulge or even the slightest distortion on either rudder. If that is what is causing my hum it is very subtle indeed. I'm more inclined to believe it is toe-in, vibration or some other adjustment. I am going to tighten my upper castings with additional shims and will probably try the cellophane, silicone caulk trick to the lower casting.

Some rudder materials seem to hummm more than others. I would bet you have Lexan blades. These do not have a smooth (shiny) surface. They have a glass fiber / swirl look. The harder material made it more difficult to remove the humm.

It is most definitely the foil shape causing the humm... not rake or toe in.

_________________
Matt Miller
Former - Director of Parts and Accessory Sales
Warranty and Technical Support
Hobie Cat USA
(Retired 11/7/2022)

Hey Sunvista, send me a private email address for you so I can send you some photos of rudder work. [email protected]

Rick...sent as requested. Thanks