tunnel and cat sponson

[vanduzer]

Why is it that a inboard cat. sponsons are flat on the bottom and an outboard tunnel are angled. I would imagine that it has to do with the cat motor being more forward then the tunnel. My 8 year old son asked and I have no real answer. I sure that one of you guys know the answer.

Dave

 

[Mark Poole ModVP]

The weight being forward has a lot to do with it yes. Outboard tunnels are tail heavy with the weight of the engine and the boat is steered by swinging the entire engine and prop back and forth. Many years ago there were some tunnels built with pads on the sponsons but that was back when the fastest tunnel was 35 mph. At todays speeds the boat has to set and lock into the turn and can only do that with angled sponsons.