1) Are hulls same shape in a Cat 2) hull spacing

[Will]

I'm thinking about building a catamaran... either power or sail.

My question is... are the two hull's identical in shape?

This would allow me to build only one mold.

ALSO - is distance apart important? I'm guessing that the eddies and currents from the bow cutting thru the water would make it important to have some minimum distance between hulls for best performance.

Thanks for any help.

Will

[sorenfdk]

The two hulls are not necessarily the same shape, but most are.

The distance between the hulls is important, especially for a sailing cat. Larger distance = more stability, smaller distance = more resistance. But the distance can also be too large and make tacking difficult.

Anyway - before you can begin building, you'll of course need a design. If you buy one, these problems have probably been solved by the designer. If you want to do the design yourself, there are a LOT more things to consider, so I would suggest you find all the relevant litterature you can, and start reading.

[Tim Bard]

Look at Compu-Craft for plans >>> ccplans.com

Col Clifford has a lot of designs and ~50 years experience.

He is a very clever designer

Tim

[sorenfdk]

Oops - I forgot something!

Most sailing cats have symmetrical hulls, BUT most powercats have asymmetrical hulls!

[Will]

Gee, I wonder why powercats have asymmetrical hulls and Sailing Cat's don't ?

I thought many of the Sailing Cats were also being sold as Power Cats... just by leaving the mast off... but what do I know

thanks for any additional comments - Will

[SailDesign]

Distance between the hulls also affects drag - bigger distance, less drag. However, bigger distance also = more structure needed for cross-beams, etc. You pays your money and takes your choice

Steve

No one mentioned, the seperation distance of a sailing cat is the big factor for speed. THe cat can take huge sail area because the cg when loading a hull is way outboard. A hobie 16 has asymetric hulls, and I've heard it allows the boat to perform without a centerboard, a lead I have not investigated. Most hulls separation distances are limited by the 8 or 8.5 foot max trailering width mandated by the DOT.

also, wrt some power cats, I have heard that assymetric shape has been used to lift water to a raised engine, like a tunnel hull allows a raised engine on flats boats. One usage.