Crazy idea or possible future hydrofoil hover board design?

[cglazier]

The degree to which each surface contributes to lift in any axis is directly related to its perpendicular area. The strut is a pretty big chunk of area that you most definitely control from the board.

I understand what you are saying and the strut (mast) is certainly a big part of our hydrofoils. But... For example, when a racer is aggressively headed upwind he is riding at perhaps 45 degrees and there may be as much mast surface in the water as wings surface. So you might think the mast is equally important..

But most of the force is striaght down the mast and onto the wings and so the mast has much less effect than the wings. The mast only has effect when you push sideways on it. The mast is mostly just drag much of the time (except when you are turning).

In a perfect world the mast would be tiny and then hydrofoil designers could choose a small foil (like a fin) for yaw stability. A small fin near the rear wing would be more effective for this than a big deep chord mast.

CG

[Starsky]

Yeah I agree. I get that when heading upwind hard with strut at 45 degrees, the bigger force vector is down the length of the mast, but the strut at 45 degrees can't not influence lift in the purely vertical. At 45 degrees, half the lifting force of the wings is driving upwind, and yaw of the strut helps to control depth.

I think its simple enough to say that all surfaces below the waterline on a KBHF are control surfaces and their influence relates directly to size. I don't doubt that a smaller strut could be better, but it will always have chord and always be a control surface.

[jakemoore]

This guy has some cool maglev videos

[Mossy 757]

Yeah I agree. I get that when heading upwind hard with strut at 45 degrees, the bigger force vector is down the length of the mast, but the strut at 45 degrees can't not influence lift in the purely vertical. At 45 degrees, half the lifting force of the wings is driving upwind, and yaw of the strut helps to control depth.

I think its simple enough to say that all surfaces below the waterline on a KBHF are control surfaces and their influence relates directly to size. I don't doubt that a smaller strut could be better, but it will always have chord and always be a control surface.

You're making my point better than I can. I'll add this: I'm sure almost every designer is trying to get away with as little mast length/chord/camber as possible because the drag is likely a much larger factor than any supporting lift that creates board speed upwind.

That being said, the drag the mast does create almost certainly adds directional stability, which is a factor to be considered when it comes to ease of riding. You need to be really physical to ride at the front of the fleet upwind, and every little design aspect that changes stability profile makes a difference.

I think the question with mast design is how to maximize stability while minimizing drag, with some combination of compromises revolving around the material science of composite lifting foils that need to be both efficient and strong/stiff.

[Starsky]

Actually it was C Johnson's point. We just keep repeating it!