Dynamics - A Simple Vector Model

General Discussion
21

Wow, that’s nice stuff.

Thanks,

Kevin

(Edit, 10/01/06. Post was incorrectly directed to janklow, it was meant for MTB and his posted data.)

22

I have no doubt in the experience and insight you’ve acquired from your research.

If anyone is looking around for a tested model with some research to back it up, it would make sense if they pursued yours.

No arguments.

And, once again, thanks for posting the data. It was very generous of you.

Thanks,

Kevin

23

Regarding your edit.

Once again its a framework, no equations of motion yet. The whole point was just to get the vectors in place, so they can be used later.

Thanks,

Kevin

24
Quote:
If you don't understand it how do you know I 'flung' a 'rant'. If you understand it and disagree with it, please share your insight.

Thanks,

Kevin

I think it started when you assumed fluid lift/drag for a wing would apply to a low aspect ratio (0.3-0.5) planing body, whereas in reality the equations fall apart for any aspect ratio less than 5, and completely fall apart for planing bodies instead of “flying” wings.

This is far from the first critical logic error you’ve made in posts over the past few months. Surfboards generate lift through displacement of water, and from planing forces. Planing forces can be resolved by their own equations, and you need to resolve displacement through an assumption as to how much water the board displaces - it is not a trivial amount by any means, and shifts in lift between displacement and planing have pronounced impacts on surfboard performance.

The other, major, error, is that your treatment doesnt’ seem intent on discovering anything useful about surfboards. Of course, maybe I’ve just not seen where that is coming yet.

Carry on.

25

Actually I’ve assumed nothing other than that flow, the normal to the surfboard, and the vector normal to the board length (tail-to-nose) are knowable. So far, all I’ve done in this thread is attempt to layout a framework of vectors that could be used to describe a surfboard in three dimensional space. I applied a classical Lift/Drag treatment using the vector model as an exercise - aside from that, it’s not an arguement for the approach.

In fact, if you’ve read some of my prior posts/threads, and there is no reason why you should have, there’s a chance you may have encountered a comment or two regarding my disagreement with prior (published or otherwise) applications of both planing and Lift/Drag, and how my approach differs. Nevertheless, that’s not what I’ve addressed in this thread (so far.) So far, it has simply been a description of a surfboard, possibly surfing, using vectors.

Perhaps you were thinking about another thread.

Thanks,

Kevin