On Sun, 27 Jun 2010 21:29:25 -0400, Dan Bracuk
wrote:

On Sun, 27 Jun 2010 15:52:02 -0700, Geoff
wrote:

:Most likely. Neoprene dates from the 1930's and is the most widely
:used synthetic rubber. Wetsuits and dry suits are made from
:nitrogen-foamed neoprene.

But these are not wetsuits or drysuits. These are fins. I just don't
see fins being made of neoprene.

Nearly all "rubber" today (and since 1940 or so) is neoprene. The fins
are hard molded neoprene made from "chips" of the stuff mixed with
"compounding" agents for color and elasticity or durability. There are
about a dozen different kinds of neoprene from DuPont. Pure neoprene
chips are a yellow-white or cream color powder, much like coffee
creamer.

Many composite airframes or structures use neoprene compounds in
addition to the carbon fiber laminations.