Power / Sail catamaran

[vectorges]

A Yahoo group had an interesting thread about using a catamaran as both a power boat and a sail boat. The design was to split an existing fiberglass powerboat down the keel. Build a hull tunnel from plywood and fiberglass (ala the current trend in big horsepower catamarans).

Does anyone have any experience, or at least thoughts on this topic?

I think this approach shows a total lack of appreciation of what a sailing catamaran is all about.

Multihulls in general use slender light displacement hulls to move efficiently with low drag. They don't need a lot of power to propel their slender light displacment hulls. By using two widely spaced hulls, they can get maximum stability out of the small waterplane area from each of their light, slender hulls, so each hull need have no form stability of its own and can therefore use round sections for minimum wetted area.

Did I mention the hulls need to be slender and light?

Splitting a power boat will give you two short fat hulls with lots of wetted area and a heavy structure that's got its strength in the wrong places. The length will be too short to provide adequate diagonalor pitchpole stability. The drag will be so high that it will be an absolute dog under sail, and won't go well to windward.

A far better approach would be to start with a sailing catamaran and add the power and fuel tanks needed to get the desired speed and range under power.

Originally Posted by vectorges

A Yahoo group had an interesting thread about using a catamaran as both a power boat and a sail boat. The design was to split an existing fiberglass powerboat down the keel. Build a hull tunnel from plywood and fiberglass (ala the current trend in big horsepower catamarans).

Does anyone have any experience, or at least thoughts on this topic?

I built catamaran sail and speed boats for 5 years