2 SEAT F-1 BOAT PORPOISING

[RANDALL TREDO]

I RECENTLY COMPLETED A 2 SEAT VERSION OF AN F-1 BOAT.THE BOAT IS EXTREMELY STABLE AT 90 MPH {THE FASTEST I DARE GO WITHOUT MORE SEAT TIME} AND STABLE UP TO 60 MPH.BETWEEN 60 AND 80 THE BOAT PORPOISES.I AM RUNNING A CLEAVER PROP. IS THERE A WAY TO STOP THE PORPOISING USING WEIGHT DISTRIBUTION OR MOTOR HEIGHT.

[Barney]

It's on a completely different boat, but by moving my front seats forward 3 inches, back seat back 3 inches, cured it completely for my Liberator.

I would think redistributing some weight would cure it. Just moving my ice chest from behind front seats to behind rear seat helps also.

[us1]

I race F1 boats and with our boats some porpoise alot and some less, but if your not in the power they will always porpoise more. I use a hydraulic up and down on my boats and with the motor down it porpoises less. I would love to see pictures of this two seater.

[RANDALL TREDO]

US1

I DON'T KNOW HOW TO SEND PICS THROUGH THE SCREAM AND FLY E MAIL. SEND ME YOUR E MAIL AND I WILL SEND SOME PICS. THANK YOU FOR THE INFORMATION.
RT

[Jimboat]

Porpoising is common on tunnels. It can most always be resolved by setup. Proper weight distribution will help minimize the problem. The tricky issue is that the "stability" of the hull is a function of all the hydrodynamic forces (sponson lift, motor drag, hull weight, driver and appendage weights, propeller lift; and all the aerodynamic (aero lift, aero drag) forces. The resolution of all these forces change at each different velocity. So the best you can do is setup the boat at this "transition phase" of accelerations, such that the "dynamic" CofG is as close to (or ahead of) the aerodynamic center as possible, and as close to static CofG as possible.

Static CofG (dead balance of boat) will remain in the same theoretical location for all operating velocities and conditions, and so by itself, does not provide a good indicator for determining hull performance.

Dynamic CofG, centre of balanced moment of all forces while hull is under specified running conditions. This will be different for each operating velocity or condition.

The location of Centre of Aerodynamic Pressure, for aerofoil (Tunnel wing)will change too, influenced by aerofoil shape (configuration) and Angle-of-Attack.

So, bottom line is...there's alot you can do to overcome the stability problems at the "transition" phase of acceleration. Easiest is to move weight around to proper dynamic balance locations.

p.s. - I'd love to see your pics!