Australian boatbuilder Roger Mutimer is developing an alternative to a high-performance stepped hull: a completely aerated hull. Roger has been experimenting with a somewhat radical hull surface. A welder by trade, Roger Mutimer says he has been designing and building aluminum boats for many years; they range in size from 13′ to 75′. Here’s the latest:
Rogers passion is designing and building aluminum boats. The latest project is a new hull design for powerboat racing. This aluminum hull is fully aerated and can be used on any powerboat design. The concept is not to try to get the hull out of the water, where you have no control, but to keep the hull on the water and use its movement over the water to draw air in so as to create a completely aerated hull. A problem found with many of the stepped-chine racing hull is that everything stops at the step. So when it comes down and hits the water, the water hydraulics up into the step, forcing the hull to go in the opposite direction. This theory is to have a lot of small steps over the hull to overcome that problem. All trailing edges plus planning strakes are sharp enough to cut your finger on.
Recent tests show the hull with a Mercury 300XS racing outboard on the back; with 35 gal of fuel and she came in at 2,646 lbs. On the water it managed to get 70.1 mph, but it could only get 5,700 rpm out of the motor. The run reached 70.1 mph and then the throttle was released, and the boat stopped as though he had put his foot on the brake.
The drawings explain how they did the test. As you can see, 3,516.48 lbs vacuum is a fair bit of drag on the hull.