[PCW] Sailability of powercat hulls - was Hybrid Powercats

[Malcolm Tennant]

Dear Mark,

Your informant was quite correct as far as he goes. However our experience
with the CS hull as applied to motor sailers shows that  it is possible to
apply a power boat hull form to a sailing catamaran to produce a boat with
superior sailing and powering characteristics. We first used an early CS hull
in 1983. This was on the Cordova.[see our web site under motor sailers] This
boat motored at 18 knots and sailed on a reach at better than 20 knots [I had
a photo of the sum log reading 24 knots!]  It is the logitudinal rocker that
the sail boat requires to enable it to tack and minimise transom drag that
restricts its speed and leads to "squatting". The CS hull removes this rocker
and results in a much less"displacement" of the water flow. Straighter water
flow equals less resistance.

The simplest way to counteract the diagonal downward thrust of the rig that
your informant talks about is to move the rig further aft. The CS hull does
have a fine half entry angle and would be prone to be effected by the height
of the thrust of the rig[CE] so the hulls are made longer and the rigs moved
further aft.

The CS hulled motor sailer motors well and sails well. The only compromise is
that they do not tack well, due to the straight keel line. This might be a
problem on a round the buoys racer but is not too much of a problem on a long
range ocean cruiser.

Regards,

Malcolm Tennant.

MALCOLM TENNANT MULTIHULL DESIGN LTD
PO Box 60513, Titirangi.
Waitakere 0642
NEW ZEALAND
Ph: +64 9 817 1988
e-mail: malcolm at tennantdesign.co.nz
www.tennantdesign.co.nz
www.catdesigners.com