Monday, September 14, 2015

Daggerboard Hum (Loud!)

Sometimes when dinghies go fast they sing to you, as is the case in this video of a 14' Javelin class at speed on a long spinnaker reach. Originally designed by John Spencer of New Zealand as a follow-on to his 12' Cherub, the Javelin is a development skiff design, single trapeze with a moderate rig. The Javelin remains an Antipodean class, raced in Australia and New Zealand.

Yee-Ha!




9 comments:

Tillerman said...

Cool. Sounds like a whale!

my2fish said...

Too much orca. Did it sound a little orca-ish to you?

Tillerman said...

What's the physics of this? Is the hum a bad thing? Does it mean there is something wrong with your foils? Is it a sign that energy is being wasted on causing the vibration when it ought to be being used to make you go 0.001 of a knot faster?

my2fish said...

Wait, is it a cat boat?
Maybe it is purring, because it is happy.

my2fish said...

Or maybe they hum because they don't know the words.

George A said...

It would be a nice touch if the Go-Pro camera had a built-in GPS and displayed the speed in the upper right corner of the video.

Tweezerman said...

Tillerman,

I remember the Laser wood daggerboards would hum a lot at speed. Somebody at the time thought that was a bad thing and wrote that you should bevel one side of the trailing edge so that it would stop. I agree with you. In the grand scheme of things, daggerboard hum is a very tiny added component of drag.

doryman said...

The hum is caused by vibration, which is caused by the trailing edge being too sharp. There is a physical phenom that explains it mathematically but I forget it's name. (named for the gent who figured it out, of course).

Alden Smith said...

If you tuned the hums of the centerboards of 3 different yachts to the 1st, 3rd and 5th notes of an octave they could sail together and play a guitar chord.