Quite a lot of interest has evolved around the possibility of developing windsurf boards from a CAD/CFD approach, hence this second post on the same subject.

Following the original post (13/11/00), I would like to clear up some points and summarize:

The concept is to be applied specifically to windsurf boards, NOT surfboards. The diference is that the former consists of sailing, and the other uses the motion of waves and gravity for propulsion.

Even more specifically, the CFD approach is most interesting in the area of development of race boards.

The greatest concern expressed is how to evaluate and quantify the sailor and his 'feelings' when testing boards. Many have referred to the requirement of an 'expert sailor', who will be able to input data and interprete output data. The 'expert sailor' is myself, therefore finding one would therefore not be too much of a problem...

Starting simply, given a board shape mesh in an appropriate CAD format, is there anyone out there that can plot the pressure distribution accurately on the underhull of the board given a specified angle of attack, and loads on the board (1. forces due to the rider's two feet, 2. mastfoot pressure, 3. mass of the board and 4. lift from the fin).

The relation between the group of forces described above can be measured empirically and the relationship between those values and variables such as sail size and sailor size can be determined also empirically.

The pressure distribution on the board will already help significantly in terms of development efficiency (assuming that various hull forms can be 'tested' by importing hull meshes) , and given that modelling is done on flat water, analysis should be quite straightforward.

The second stage would be to then also determine the angle of attack of the board according to the speed at which the board is travelling w.r.t. water. This is when things get really interesting.

The third stage would be to take into account the fact that the board does not travel straight under the hull but diagonally considering lateral drift of the board.

The fourth stage would be bank the board on its side (known as carving the board round in windsurf-jargon), by changing the load distribution on the board.

The action of waves would be too complex to include, but the output data from flat water modelling is sufficient for the board's behaviour in rough water to be predicted.

If there are any further questions or comments, or if there are any volunteers to get something started, please get in contact via the post are via email.

Tiesda.

(1). It looks like that we (the reader) need to get familiar with the windsurfing in the first place. (2). What about the effect of the wind? I mean is windsurfing done on the calm and flat surface of water only? (3). If you are an expert on windsurfing, then can you teach a newcomer to do windsurfing without getting wet? When I was a kid, I learned how to ride a bicycle by trying. And in the process, I had a few collisions with my brother in the open field. (4). Assuming that I am a newcomer to windsurfing, or a computer which is trying to model the windsurfing, then how do you instruct me or the computer keep from getting wet? Maybe getting wet is all right in the windsurfing? (5). I think, you need to tell us the rules involve in the sport of windsurfing first. (6). Back to the technical part, I think, if you assume: the water is flat, (this can be done by assuming that the far field is flat) the wind is constant, the sailor's position on the surfboard is right and balanced, then I think, with today's technology, one can compute the flow over the surfboard with the free surface. (similar to flow over a ship or a submarine) I think, this should answer your technical question. (7). But, I still don't know how to teach a newcomer or a computer to ride a bicycle. (without falling to the ground ) (8). So, I would say that, designing the windsurf board under the artificial conditions is possible and can be done. But most people would not consider it as the windsurf board design or optimization, unless you can link it to the sport of windsurfing.