transom hung rudders

I am building a 1 m catamaran 10 to 1 scale to an original design (slightly modified) i wanted to keep the look of the transom hung rudders. anyone have any ideas on how to make them work ?

“Usually” transom mounted rudders are done on a vertical transom. By rounding over the deck/transom, you’ve added additional engineering.

I am not sure of the method of build, or the degree you want to modify - and if you intend for the rudders to be fixed in down position on a permanent basis, or if you want them to “kick up” like a beach cat does?

Depending on your final desire - there are a couple of ways to accomplish this…

  1. Cut off and add on a section of stern with vertical transom. Easiest way to attach transom rudders, but a bit of hull modification required.

  2. You could cut/hinge current transom and mount a fixed rudder under the stern - but the entire stern would swing up. Not sure if this is practical, and a bit of thought/design needed to accomplish the hinge concept. This would require a double bulkhead where you want the stern to “kick up”.

  3. Easiest and least work would have rudders mounted under the stern. (This also reduces air turbulence on the rudders with possible cavitation if you “crank” them over to fast at speed). You can still install a rudder arm (DuBro steering arm) to top of each rudder post, and connect by cross arm of carbon tube. Steering one would steer the other at same time. If you go this way - look up “Ackerman Steering” as it is like a car steering - each wheel (rudder) travels a different radius arc.

As you have sterns now, there is no place to hang the top gudgeon for a rudder to hang on to.

Please provide a bit more thought on what you want for final outcome, and I’ll help you as best I can.


thanks. I have got the attachment on the back of the boat sorted but the way to get the tillers to move together from a centeral point in the middle of the boat is making me scratch my head. I have the tillers on with a carbon cross beam so they turn at the same time but i need to know what kind of servo to use and how to attach it to the cross beam.

kind regards :slight_smile: