I have two 380 motors with a weird speed controller( It will only let me turn by using one motor and turning the other one off, I think its called vector steering,)and radio gear. I am planning to use this stuff in a rescue boat

Basically everything needed to run but I have no Ideas on what the design for the hull & frame should be and what material should be used. I am on a budget and would really like to not spend more than $50
I am planning to use this rescuse boat on is a 40" long 9" wide Shockwave 36, But I would probably make it big enough to pull up to a 60" long catameran just in case I decide to buy one.