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Old Dec 06, 2012, 12:22 AM
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Como - Italy
Joined Mar 2009
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Originally Posted by pompebled View Post
Hi Matrix,

The boat you chose is a fast electric, which steers very good when running at speed, hence the small rudder surface.

Making narrow turns with a catamaran at low speed needs a much larger rudder, which will have way too much authority when you run the boat on the plane. The rudder throw must(!) be reduced than, or you'll risk flipping the boat.

A simple way to acheive this would be to mix the throttle and the rudder channel in such a way that the rudder throw is decreased, as the throttle signal is increased.

As a side note; a catamaran is very reluctant to make narrow turns while crawling, due to the hull design.
A monohull will do a much better job at that.

Regards, Jan.
Hi Jan,
Thanks for the reply.

I know that Surge Crusher is not designed for low speed, but it has other characteristic that are good for my experiment, for example the CAT hull allow me to install the echosunder on the flat part of the bottom and also it tend to turn "flat" that is perfect for the echo transducer readings.

There is no problem if rudder will be oversized because that boat will never go at hi speed , I will limit the throttle at 10/20 % as in the second video to prevent flipping and also for safety reason as it it is autonomous....

For your experience, what size of rudder could be good for narrow turns ?
I plan to build a new rudder based on a standard one, same depth and shape but with double or more lenght to double the active surface. Could be good ?


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