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post #18 of Old 07-24-2007
Lead is for slow pokes
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Smile Yeah but....

Originally Posted by sailingdog View Post
No catamarans that I know of plane.
Mine does...

Think about it! Anything doing that speed must build up pressure under the hull and generate lift. Cats are light, high powered (well some are ) and their hulls are narrow, the combination means that you are planing more easy (no noticable "speed hump")... so much so that its hard to notice the transition (some sports boats are that good U hardly know it). When I look off my transom's at 15 knts+ it looks just like looking off the back of any other high speed planing vessel. You might not be generating similar lift to a mono hull at that speed but then you have not got the drag either.

My old Paper Tiger (hard chine cat) planed more noticeable than the round bottom boats I sailed against but at some point they generated lift. We had a big cat (60'? Plywood? ) locally called "Big Bandicoot" that actually had V type planing hulls like the Paper Tiger (more power boat style)...

I suppose the question is what do you call planing? How much lift is planing? Sitting right on top of the water? or merely exceeding the hulls displacement speed capacity.

Just like all hulls displace water there is a speed at which all hulls will generate enough lift to rise up out of the water. Physics demands it! The only questions are things like...

At what speed?
How much force does it take?
Can the hull take it?
How stable is the hull form at that speed?

A multihull's speed comes from several factors. Multihulls plane on the water rather than plowing through it like most monohulled sailboats. Multihulls also use the wind in their sails more efficiently because the extra hulls keep the boat from heeling over excessively. Multihulls are lighter than comparable monohulls, so their lighter weight also increases their overall speed.
Chris White, excellent multihull designer

2c MBz
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