Tuesday, May 15, 2018

Whale bumps...

How 1500 becomes a worrisome number, regarding a recent "accomplishment", and some stuff you really need to know...

I've been spending a lot of time pondering over better ways to build a better auxiliary rudder self-steering gear and I keep thinking whales and rudder shapes.

Why whales you might ask.

Take a look at a humpback whale fin...

Note the bits on the leading edge?

Now check out this rudder from rudder wizards Betts Boats who always seem to be just a step ahead of the cutting edge (pun intended) where foils are concerned.

Notice a similarity?

The word for today is T-U-B-E-R-C-L-E though some folks just call them whale bumps and what those bumps do is affect the flow coming off the bumps forms pairs of counter rotating swirls or eddies coming off each side of the bumps. The bumps act as vortex generators that keep the general flow attached to the suction side of the fin when there is an angle of attack that normally would cause the flow to separate from the leading edge. Which, where rudders are concerned is very much a goodly thing.

There has been a lot of research and application in the aviation world, foils for wind generators but pretty much bugger all in sailing circles. Though, I expect that's about to change quite a bit in the not-too-distant future.

They even use them on surfboards!

So why are we not using them on self-steering foils?

Listening to a whole lotta Springsteen

So it goes...