Ocean Racing Catamaran Design

[oldsailor]

Does anyone know the the waterline L/B ratio of the hulls of big Cats like Orange 2 and Doha 2006.???

Cheers. Oldsailor.

[mmd]

The "cattlemarans" (day-passenger tour boat sailing catamarans) that I built for a couple of years in the southern Caribbean had a LWL/BWL ratio of 20:1, and they were definitely not racers. I would suspect that the big, fast boys are playing in the 24:1 range.

[oldsailor]

Thanks for that MMD.

I found in a back issue of the AYRS a whole set of test tank data which showed that at fineness ratios above 16 the trade off between wetted surface and L/B ratio starts to show diminishing returns.

Where the displacement can be kept down (ie: ULDB) a greater fineness ratio can be benificial.

I was just wondering what L/B those very big Ocean racers were using since they are ultra light, but still very strong. The French yard who builds them is not saying.!!!

Cheers. Oldsailor.

[oldsailor]

YES MMD.

I found a great shot of Playstation/Cheyenne and was able to approximate the LB ratio off the screen,and it looks like at least 20:1

There has been very little,if any, improvement since 1969 on the underbody hull shape of the Tornado, and it is 20:1.

The biggest drawback to the long and very skinny Cat hulls is the increase in wetted surface, compared to the lower L/B of a mono. However the Mono is badly penalised by Wave Drag, compared to the skinny wave cheating Cat hulls.

Cheers. Oldsailor.