[PSUBS-MAILIST] gel-coat

[Tim Curtis <navark@yahoo.com>]

Hey there,

Don't go sand-papering up your hull just yet....

Micro-turbulence stimulators have been around for
quite some time, and are proven to decrease drag
fairly substantially - we have done some tests and
have found reductions of up to 20%.  Having said that,
the surface has to be very very high precision, and
any degree of fouling on the surface will counter all
the good effects.  If you were to carefully design a
micro-groove skin for each section of your sub, then
you might get somewhere - you need to Reynolds match
the geometry of the stimulators.  Applying the same
geometry over a whole vehicle will result in increased
drag, as will applying a random geometry.  Some of the
America's Cup yachts have tried using these
stimulators and have not had success - mainly because
the flow fields and velocities are not very consistent
at all with sailboats, but the same reasons apply for
subs.  Your best (and easiest) bet is still to make
your sub as smooth and streamlined as possible, unless
you are willing to invest years of study and machining
for a one-off application.  Your choice!

    -Tim

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