Re:Developing windsurf boards (part2)

Sander van Essen

This is my reply on the message that I placed at the bottom:

This is exactly the subject of my thesis.

I am in the final year of my study Maritime Technology at Delft University of Technology in Holland, where I am graduating at the Ship Hydromechanics department.

Since I?m an enthusiastic windsurfer myself, I wanted to graduate on a project involving windsurfing. But I couldn?t find any literature or programs for windsurfboards. And I know most of the development in windsurfing is done by testing prototypes, like you mentioned in the first message. So I decided to develop my own program.

So I started (last September) with the development of a computer model to calculate the speed of a surfboard.

To do so I am first looking at the overall picture, like the equilibrium of sail, surfer and surfboard. I have almost completed the first version of my program. This will give me the possibility to calculate the speed of the surfboard given a certain wind speed and direction. But I have made a lot of simplifications to get this first version running. Like no waves and a constant wind speed.

I hope to complete this first version of y program in a couple of weeks.

Sander van Essen

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Previous message:

Developing windsurf boards (part2)

Posted By: Tiesda <<A HREF="mailto:tiesda@hotmail.com">tiesda@hotmail.co m</A>> Date: Thu, 7 Dec 2000, 1:40 a.m.

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.