# Hydrofoils

Discussion in 'Boat Design' started by Chris Wood, Nov 11, 2008.

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### Chris WoodNew Member

Hi there, posted another question in the other forum about NVH but this is about hydrofoils...

We have the same boat - 10m long, 4.5m wide trimaran, we are in the process of designing hydrofoils but are having trouble with the dimensions of the profile. Are these dimensions in a ratio where boat length:hydrofoil length is a factor? Is it that simple or are there more things to work out?

many thanks again!

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### harlemrivermanSenior Member

its simple but the math is not in proportion to the size of the craft per se. look up bernoulli's principle on the web. you are designing a plane that produces lift at a specific speed needed to lift or raise the weight of the boat out of the water. at that specific speed the planes are pushed down from a retracted state, raising the boat and taking on new characteristics of planes in the water and boat in the air. the boats dimensions, left right up and down, are significant only in the sense of the weight and drag it produces.

the length of the top of the hydroplane in proportion to its bottom is a proportion that can be studied in context with the density of the water, sea versus lake, and relative speed of the craft needed to produce enough lift to raise the weight of the boat. nuances are the increased drag of the hull out of the water, and having enough power to maintain the plane.

hydroplanes are power-pigs, but hot as hell.

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### tspeerSenior Member

There are lots more things to work out. Go to the International Hydrofoil Society and purchase their AMV CDs. CD #1 has design manuals for hydrofoils and the CDs collectively give you a whole technical library on the subject.

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