Catamaran Rudder question

[chipgibbs]

I'm building a new Fightercat Cheetah single and am not sure how to size the rudder.

How much rudder should extend below the sponson?
I am using a skeg strut...should the rudder extend below the bottom of the skeg?

Thanks

ChipG

[srislash]

I would read the threads on them,I know Tony (properchopper)has one ongoing.See what size they used.Everything is here if you take the time to research.

[properchopper]

A generally accepted "rule of thumb" is 2.5 inches below the sponson surface. There's more to it, but that's where I start.

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[Chilli]

Chip, I like Tony's rule of Thumb. Dont worry about the skegs relationship to rudder length. The rudder should almost always be lower than the skeg. The rudder on a cat not only turns the boat but helps keep the rear planted in the turns. If you're too long, you loose a little speed. If you are too short, the stern can slide in the turns and the boat will spin out. So err toward the longer rudder. You could always trim it very easily. A couple years back when many of us were doing Mean Machine builds, we all had huge rudders (5+ inches) hanging off the transom. The boats turned great and they were still plenty fast.

What rudder did you use on the Cheetah Tony?

[chipgibbs]

Thanks guys, that's the same rudder I have tony.

Can't wait to get this pitch in the water.....might be able to run it around in my basement next week if the storm is as bad as they say.

ChipG

[properchopper]

Mike, I used this rudder http://www.offshoreelectrics.com/proddetail.php?prod=ros-rud-dualpu with the 1 5/8" setback ; I like SERIOUS hardware on the larger hulls. Same with the strut, which I modded from .250 to .187 and moved the strut foreward in the bracket (notice the extra hole) to line up the dog with the front of the blade. I'm building my Cheetah the same as a customer's I just built which does really nice on the water (see KBB forum)

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[properchopper]

Thanks guys, that's the same rudder I have tony.

Can't wait to get this pitch in the water.....might be able to run it around in my basement next week if the storm is as bad as they say.

ChipG

Chip, I hear you - I grew up in Long Beach N.Y. Had to bail/pump out the basement frequently during hurricane season

[Chilli]

Thanks Tony. Chip is one of our Capitol RC up and comers. I think we got the hook embedded in him good. LOL