# Foil selection & Build efficiency, range

Hello guys,

I am a mechanical engineer, also doing my graduate on hydrofoils and cavitation.
I will be analyzing the flow characteristics of cavitation in turbulent multiphase flows if anyone is interested. The aim is to create a system that self-optimizes the hydrofoil according to needs and less cavitation, which would also go a long way with the propellers.

Right now my aim is quite huge, but we will figure at as we go.

Is there any guide or any calculation on build creating? As far as I can see most of the people are using the hydrofoils they pick only considering the lift and drag coefficients, is there a guide that people follow?

As much as I had browsed through the forum, made a dozen of searches, I wasn’t able to find a satisfying guide for beginners.

I am also a happy windsurfer who is almost getting above 25 knots winds most of the time, however I would like to expand my wind range, therefore I am interested in the details of the business.

** The question is: Is there any guide for beginners on this purpose? **

All answers are appreciated, sorry if this is a repeating question over & over. If yes, the topic can be locked immediately.

My apologies for the grammar if it is eating you up inside.

In addition, I am planning to make one beginners guide, an all included with the design and the optimization of the hydrofoil, if one doesn’t exist.

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Is a post regarding board sizing

This an efficiency calculator

I’m looking forward to seeing your guide. Let us know what else you are looking for.

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The board is quite easy in my opinion, the idea should be more based on where the foil is going to be placed at. I find it quite meaningless to place the foil at the end of the board, In my opinion, it must be placed at the center of weight for the ease of usage.

The more the weight is around the foil more of the efficiency of the lifting force.

The hydrofoil design tool:
It is more of an efficiency & power calculator for the wing design, not the hydrofoil profile. For what I am interested in, which is the profile of the hydrofoil, it doesn’t reflect quite an idea.

I am spending some time on it.

I am not trying to be a smartass for the stuff that is already done, it is quite helpful and gives an idea about what has to be done. What I am imagining what would be good for the optimization of the profile.

The chosen profile can make the efficiency go up to 25% if used well. There are cases in autoclaves I have encountered that they were using *1.5 sized motors due to badly chosen propellers, which creates a huge price difference.

The ultimate design I am imagining is the wings changing the angle of attack after take off for less drag & best result.

I would gladly inspect some other links as well, if it helped you out.

I remember I had seen a link on this forum about the takeoff and maximum speed of some commercial hydrofoils, however, I wasn’t able to remember where I had seen it. It would help me big time if anybody would help, so that I would get an idea about the velocity range

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Thank you a lot by the way, for the useful links.

Just my 2 cents:

center of gravity of the board on top of the front wing…
but my foil was attached to my board already, so i was able to play with the electronic/battery case position. The weight of the case is so important that it position influence greatly CG of the board…
first try, i had the case just above the front wing… didn’t work at all… everything was just shooting up flying out of the water…
second try was with the battery case as much toward the front of the board as possible… muuuuch better, and i could take my regular stance on the board.

My gut feel for now:
the motor pushes at the bottom of the mast, the mast itself creates drag that has its resultant higher than the motor. so this couple result in a momentum rotating the board backward. To achieve equilibrium, you need the CG of the board forward. (yes i’m voluntarily excluding the wings… i guess they then to rotate the whole in the same direction as the motor…)

that’s why in effect, for the working solutions, you see the mast quite at the back of the board, the batteries forward of the mast, …

Well, I have been kind of playing around with windsurfing for a while, I am fairly more comfortable on a board.

To be more specific, the paddleboards can be considered as the example, On the carrying point of these, the batteries can be used.

The reason that you were having trouble with the board flying around is because you were waaaay back at the board, which results as the board flying around.

If you consider the center of gravity with the board, without the person, the batteries should be at right that point for the ease of usage.

However, this depends on where you are fairly more comfortable on the board. If you have a board where the center of gravity is defined, that would be better for you.

I will do some sketches anytime I got my hands on any wacom tablet, I hate drawing on the computer with 2D sketches.

Of course the best case scenario would be diving the weight 50/50. that would give you out the pleasure of driving a BMW.