Steering the pontoon

Hi Guys,

The project is going along quite well and we went with a vw engine and a hurtz transmission. It is a direct shaft into the middle of the pontoon. I am working on the steering right now and need some advise.

My questions has to do with rudder surface in the water. This is a 20 foot light weight pontoon that weighs around 2000 lbs. loaded. the pontoons are very flat on the bottom and are not a typical round style pontoon.

The pontoons are 22 inches high and we are planing on having around 8 inches below the water line. I have built a dual rudder assembly that are 24 inches apart and on the same base plate.

Has anyone an idea how many square inches of rudder that would be needed to have below water line in order to be safe at around 20-25 kts of speed?

Also would is there a difference in having more rudder horizontal than verticle?

I would rather have more horizontal area and less verticle (depth) as for going in shallow water.

Also. I am using wood to start with as we can experment with different designs until we find the right shape. I am using oak right now that is 1/2 thick rounded. Any other ideas on the wood?

thanks
Mark