I have seen a few videos of proas moving fast and they are making a humming or buzzing sound.  What is vibrating?  My guess is the rudder.  Is this detrimental to sailing speed and/or component longevity?

Here is an example: https://www.youtube.com/watch?feature=endscreen&v=EAyDS1NuK_A&NR=1

I think I heard this on Jzerro vids as well.

Thanks,
-jak

At very high speeds you can get vibrations and oscillations in the rudder(s), the rig and even the hulls themselfs. The plywood in the vaka can start to oscillate out and in between frames and stringers. When enough energy is absoberbed by any kind of structure you allways get vibrations and oscillations somewhere. This is a big problem when designing airplanes. the skin on the main body and the wings can start to flutter and very soon develop local areas of material fatigue. I don’t think it is very common in sailboats, but when you start pushing it with very light structures it becomes a problem.

I guess the sound in the video of Jzerro sailing at 17,5 knots is the wires in the rig.

Cheers,
Johannes

Is the link right?

Apologies for the bad link.

Try:

https://www.youtube.com/watch?v=ddKOFVAtPDw&list=PLB52B5A88A4DC39FA&index=16

Many years ago I bought a book by George Dyson on building Baidarkas using aluminum tube frames and modern cloth and coatings.  He maintained that the flexible nature of the skin actually helped reduce friction, and was potentially another reason for the blubber layer on whales and dolphins.  Apparently he took his skin on frame boat to some sea kayak races and embarrassed a few Kevlar and graphite “rigid” pure racing boats.

Ive ruminated on using this contruction method for a proa.  I should be closing on my big shop with small house attached in the next couple of weeks, and finally have room to build.  Wonder if I’ll ever catch up with Johannes?  😊