Underwater surface finish
 

On Sat, 16 Aug 2008 12:38:29 +0700, Bruce in Bangkok
wrote:

...Should we be
attaching shark skin to our boats?

I have seen the dinghy sailors polishing the underwater surfaces of
their dinghys with 2,000 grit sandpaper and wonder whether this might
actually be the wrong thing to do.

Is there any empirical information regarding the application of this
technology to boats?

Bruce-in-Bangkok

Slime has been used successfully as a hull coat. It's a consumable
though.
There have been experimental hulls with clse spaced chines - getting
them right is quite a trick.
And finally, there have been air-blown hulls.....

Brian W

Underwater surface finish
 

Give it a few years. U. Florida has been studying shark and porpoise skin
for some time trying to produce a low friction non-depleting non-toxic
anti-fouling coating for the Navy. Last I heard they were in full scale
testing.

I was under the impression that anti fouling paint, or copper sheets
for that matter, work only because they are toxic.


It has something to do with the texture and flexibility. It is apparently a
thick coating that has a microscopic surface pattern that slime spores and
barnacles have a hard time binding to. It also flexes slightly under
varying water pressure so the barnacle cement pops off. A side benefit is
that those little bumps improve laminar flow reducing wetted surface drag.
Sort of like the dimples on a golf ball.
--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com

Underwater surface finish
 

"Glenn Ashmore" writes:

It has something to do with the texture and flexibility. It is apparently a
thick coating that has a microscopic surface pattern that slime spores and
barnacles have a hard time binding to. It also flexes slightly under
varying water pressure so the barnacle cement pops off. A side benefit is
that those little bumps improve laminar flow reducing wetted surface drag.
Sort of like the dimples on a golf ball.

It is the other way around actually. The dimples of golf balls are
there to trip the boundary layer to make sure you get rid of the
laminar boundary layer.

--
Martin Schöön "Problems worthy of attack
show their worth by hitting back."
Piet Hein

Underwater surface finish
 

I’ve been using this technique on my boats bottom for years. The
doubting Thomases in the boat yard assumed that it was because I was
just too bone idle to prepare the surface properly and that my
painting technique was lousy. But I knew better. Still haven’t got it
quite right though, a few more lumps this year and she should go like
greased lightning.

Mike.


I wonder whether this phenomena applies to boats? Should we be
attaching shark skin to our boats?

I have seen the dinghy sailors polishing the underwater surfaces of
their dinghys with 2,000 grit sandpaper and wonder whether this might
actually be the wrong thing to do.

Is there any empirical information regarding the application of this
technology to boats?

Bruce-in-Bangkok
(correct Address is bpaige125atgmaildotcom)

Underwater surface finish
 

On Sat, 16 Aug 2008 12:38:29 +0700, in message

Bruce in Bangkok wrote:

I wonder whether this phenomena applies to boats? Should we be
attaching shark skin to our boats?

I have seen the dinghy sailors polishing the underwater surfaces of
their dinghys with 2,000 grit sandpaper and wonder whether this might
actually be the wrong thing to do.

Is there any empirical information regarding the application of this
technology to boats?

The orientation of the surface is very important in determining
whether drag is reduced or increased, thus the effect is much easier
to manage on submerged bodies like sharks or aircraft, rather than
surface craft like sailboats that are subject to varying flow
directions due to wave action, heel angle, etc.

The effect is real. The major problem in application so far has been
that the surfaces are fragile and easily damaged by things like
slings, collision with minor debris, etc. It's not worth it outside
racing, and the RRS prohibit it.

Ryk

Underwater surface finish
 

I dunno bout all dat fancy schmancy stuff what youse guys is huffin' bout,
but its pretty common knowledge that in high speed stuff like the racing pad
on the bottom of a modern bass boat, an ultra smooth waxed finish is not as
fast as a scuffed finish. Of course us psychotic bass boat drivers don't
get much chance to compare around here. One run up the river, and you skip
two or three sandbars giving that pad a nicely scuffed finish. They always
seem to be faster coming back down river. LOL.

Bob La Londe
www.YumaBassMan.com