[MHml] engine power

[John Davis]

http://www.suzukimarine.com/boatbuilders/boattests/twinvee36.php

Hi Bill,

This link is for a different type of boat but has a weigh close to AB and
gives speeds at various rpm that might be of interest. The hull length is
shorter, so less wetted area and no sail rig but it is a cat with large
outboards. I think I recall seeing a Gold Coast Yacht with an outboard sled
but can't find the reference yet( with kortz handler nozzles)from memory. My
interest is in a motorsailer as Brian and others have promoted. It seems so
easy to mount an outboard on fishing boat but becomes very complex on a
sailing cat. I would like to see a simple sled arrangement(perhaps with
floatation extending past the motors), or mounting system for my turrissimo
9 to improve maneuverability and safety in windy conditions. This boat has
high windage for its shallow draft and is difficult to control in these
conditions, my main complaint of the boat. Have you talked to any prop shops
about the best propeller size,pitch and rpm for your setup and reverse
engineer from there for HP? Just a thought. Good luck.

John

-----------------------------------

Discourage?
Hardly.  I kind of plucked 20 knots out of the air as an "ideal".  If we
only got to 15 we'd be twice as fast, which is not trivial.

Of course the design challenges are non-trivial as well, and I do not have
one I am ready to spend money on, yet.  But I am learning
a lot about powerboat issues.  I'm not so concerned about the power
requirements of punching into big seas, as I am about trying to
visualize the thrust alignment of a hinged "pusher" as the couple goes over
big waves, or how to keep AB's bow loaded "down" into
head seas.  Here 6-7 knots is twice our current speed in these conditions.

Thanks for all the input and ideas.
Now back to the spreadsheets and CAD files.
Bill