Does anyone know how much drag a normal catamaran creates when being towed through the water at say 7 and 15 knots?

I am now ready to begin testing my design and want to try to find out how draggy the hulls are, therefore I am going to tow it behind another boat and measure the drag at various speeds, I will be using a spring balance but don't know what weight range balance to hire/purchase.

I also intend to set up a tug of war type test to compare my hull design against some existing boats, i.e. tie one end of the rope to my new boat run it through a pulley on the tow boat and then tie the other end to the comparison boat. Whichever boat wins the tug of war will have the most hull drag. I am happy to publish the results if people are interested.

Gareth
www.fourhulls.com