planing catamaran hulls/sailboat

[Guest625101138]

You are not quite getting my point.

It takes a lot of force to make a boat plane. It does not matter much about the shape. It depends mostly on the weight.

The forces generated by the wind to overcome the drag produces large moments that need to be countered. By the time your "bottle" is immersed enough to counter the moment it is the only hull that matters as it will carry the entire displacement when you have enough force to plane. The only time this is not the case is when going directly down wind and then the moment will be driving the bow deeper.

Do some diagrams of the forces acting on the boat and you will get some idea of what I am talking about. A good planing hull will have drag roughly equivalent to 10% of its weight. The sail force to produce this will be applied high up on the sail and there will be a large heeling force that is a function of the apparent angle of the wind.

To go fast in moderate wind the apparent angle will be quite small so heeling force much larger than drag force. Do the apparent wind vector for a boat doing 20kts in 20kts of wind beating upwind.

Rick W

[tugboat]

great Rick...ill do that..im not a designer...im a sailor first a designer second. But its great to learn...i guess i always figured there was away to intuitively know certain things since the polynesians had planing craft and they never really used math or engineering..but i wouldnt want to build a boat and have it be slow..i think in the end ill opt out for stock plans...