Hey guys I built an RC airboat out of a full size boogie board years ago. It has a Super Tigre S3000 on it and I mix my own methanol and klotz castor for fuel. I have always had an issue with it spinning out while I'm trying to go straight. I just bought some wooden trim which is about a 1/4 inch thick and 3/4 in wide. I wanna cut to the length of the boogie board and epoxy it to the bottom. My question is how many strips do you think I need on the bottom to keep it straight but not restrict turning?

I decided to replace the boogie board too.

The strips on the bottom are bad news if you want to turn. At all. Your spinning out problem is due to your rudders bring WAY too small. They big of an engine needs a big set of rudders. At least half prop diameter for height and width at minimum. 2/3 to 3/4 prop diameter for width would be better.

I didn't wanna wait for an answer lastnight and this morning so I was doing my own research and I came up with what you just said. This is what I did. Went from 5 inches long to 8 1/2 inches and 2 inches higher than before.

This is a comparison. New VS old.

I would go deeper/wider yet. By another couple inches. At least. What size prop are you using?

18x10

I’d suggest the rudders be at least 9” tall with 10” being better, and 8-10” deep. Couple this with a 40-45° throw and you will have some impeccable steering and control. Having the boat properly balanced for center of gravity is important and shouldn’t be overlooked.

Nice project. To help it track straighter without losing too much turning ability, try adding 2 or 3 strips to the bottom. One along the centerline and the others about 3 to 4 inches in from each side should improve stability. Make sure they're straight and well-epoxied so they stay in place and guide the boat properly through the water. Looking forward to hearing how it performs after the change.

along with the larger rudders, proper keel strips, and getting the c/g of the rig down as close to the water as ya can,

a good gyro will help prevent the spinouts, rudder channel only.

this works excellent, allows slip/drift at medium speeds or forced turns at higher speeds. Surface rails are rounded and notice the inset on each side. the raised triangular shape toward the bow seems to have multi function.