Describing a graph

[sobo]

Hi

this is a graph of total bare-hull resistance coefficient vs speed that I obtain using Hullspeed software for a 8 meters catamaran boat.

Can someone help me on how can I describe this graph?
This boat's service speed would be 9 knots.

It shows that the resistance is high during start-up which is normal. But, why would the resistance become fluctuate during 1-6 knots?

hope that someone expert can help me understand the graph.

Thanks

[sobo]

here is the picture

[DCockey]

The fluctuations are due to changes in the wave lengths of the waves generated by the boat as speed changes and the effect of the waves on the hull. Should be described in any book with a section on resistance due to wave making.

Does Design 1 have around a 8.7 m waterline length, Design 2 around 9.6 m and Designs 3 and 4 around 10.8 m?

[sobo]

thanks for the answer

for your information,all design have the same LOA, Breadth and Volume Displaced.

LOA=8 m
LWL=7.5 ~ 8 m
Breadth= 2 m

can I get your opinion on the service speed?. I got it from my calculation. Is it look normal for a cruise boat?