Hello all,

I would like to build my own hydrofoil and attach it to windsurfboard. I found some designs with dimensions which the link is attached below, however it is related to kitefoiling. Is there any chance I can use foil below on windsurfing? If not, can you give any guideline or suggestions which includes dimensions of the hydrofoil in order to use on windsurfing?

Link for hydrofoil design: www.seabreeze.com.au/News/Kitesurfing/How-to-make-your-own-Hydrofoil_8649403.aspx

No. 1 by far is placing the front wing between your feet

A used windfoil will probably be as cheap or cheaper plus you'll get something that already works. You can usually find a pink NP alu for pretty cheap which are decent but not the earliest of fliers. A bunch of my friends scored Slingshots for about half of retail at year end closeouts.

As said above, wing placement is no. 1. Look at various windfoils and see what the common dimensions are for fuselage and mast lengths. Wings should be at least 800 cm2. Your biggest challenge will be getting the mast stiff enough and the whole thing strong enough. Kitefoils take most of their force vertically, not as much side load as windfoils. I've heard accounts of kitefoils simply bending under the load when adapted to windfoiling. Also, look up RobRock on youtube who has built a few of his own for ideas.

Unless there's a compelling reason why you want to build one, really consider a decent used one. Ask yourself if your time is much better spent learning rather than sanding. I fully get the DIY thing but if you're wanting to windfoil, get a windfoil. Only build it if you want to build one (and not spend that time on the water).

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Paducah said..
A used windfoil will probably be as cheap or cheaper plus you'll get something that already works. You can usually find a pink NP alu for pretty cheap which are decent but not the earliest of fliers. A bunch of my friends scored Slingshots for about half of retail at year end closeouts.

As said above, wing placement is no. 1. Look at various windfoils and see what the common dimensions are for fuselage and mast lengths. Wings should be at least 800 cm2. Your biggest challenge will be getting the mast stiff enough and the whole thing strong enough. Kitefoils take most of their force vertically, not as much side load as windfoils. I've heard accounts of kitefoils simply bending under the load when adapted to windfoiling. Also, look up RobRock on youtube who has built a few of his own for ideas.

Unless there's a compelling reason why you want to build one, really consider a decent used one. Ask yourself if your time is much better spent learning rather than sanding. I fully get the DIY thing but if you're wanting to windfoil, get a windfoil. Only build it if you want to build one (and not spend that time on the water).

I agree with Paducah above. Neil pryde aluminium foils are great to learn on as a entry level foil which you can get for quite cheap(<$800), I bought one( np AL 2018) worked well for me learning the first year, I would highly recommend if your not looking to spend much. DIY is a lot of work...I built just a front wing and thats just the easy part of Foil DIYs.

Thats some sale on the slingy Paduach...I guess year end sales are the way to go!

How much do you weigh omrdt?

Same as above, want to add. I don't like the pryde alu for beginners. It is one of the hardest foils I have ever used. I'd recommend a foil with a bigger front wing, the bigger the easier. Lets say about 1000sqcm.

if you want to keep on building your own, I'd recommend to measure some foils in a shop. Since you are going to use a regular slalomboard a lot of foils would be totally unfit (like the pryde alu, power way too far back). I'd recommend looking at the dimensions of the starboard 95 fuselage or mantafoils, or if you can get your hands on one a lok?foil or AFS, for they have their power situated reasonably well to work woth regular boards.

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CAN17 said..

Paducah said..
A used windfoil will probably be as cheap or cheaper plus you'll get something that already works. You can usually find a pink NP alu for pretty cheap which are decent but not the earliest of fliers. A bunch of my friends scored Slingshots for about half of retail at year end closeouts.

As said above, wing placement is no. 1. Look at various windfoils and see what the common dimensions are for fuselage and mast lengths. Wings should be at least 800 cm2. Your biggest challenge will be getting the mast stiff enough and the whole thing strong enough. Kitefoils take most of their force vertically, not as much side load as windfoils. I've heard accounts of kitefoils simply bending under the load when adapted to windfoiling. Also, look up RobRock on youtube who has built a few of his own for ideas.

Unless there's a compelling reason why you want to build one, really consider a decent used one. Ask yourself if your time is much better spent learning rather than sanding. I fully get the DIY thing but if you're wanting to windfoil, get a windfoil. Only build it if you want to build one (and not spend that time on the water).

I agree with Paducah above. Neil pryde aluminium foils are great to learn on as a entry level foil which you can get for quite cheap(<$800), I bought one( np AL 2018) worked well for me learning the first year, I would highly recommend if your not looking to spend much. DIY is a lot of work...I built just a front wing and thats just the easy part of Foil DIYs.

Thats some sale on the slingy Paduach...I guess year end sales are the way to go!

How much do you weigh omrdt?

So, I appreciate you all for inspiring answers. The reason I want to build one for myself is it is my final project on mechanical engineering. The thing is that I already have several designs however I want to minimize the risks in order to start manufacturing. The point which concerns me is placing the hydrofoil under the board, where should it be placed with respect to boards back side. I already have done several moment calculations, however it is theoric. Does the position of hydrofoil have huge effect of balance by very small distances or is it mostly related to skills of the surfer? @CAN17, I am 80 kg by the way, however the system should carry at least a person weighs 100 kg.

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omrdt9612 said..
So, I appreciate you all for inspiring answers. The reason I want to build one for myself is it is my final project on mechanical engineering. The thing is that I already have several designs however I want to minimize the risks in order to start manufacturing. The point which concerns me is placing the hydrofoil under the board, where should it be placed with respect to boards back side. I already have done several moment calculations, however it is theoric. Does the position of hydrofoil have huge effect of balance by very small distances or is it mostly related to skills of the surfer? @CAN17, I am 80 kg by the way, however the system should carry at least a person weighs 100 kg.

Literally, a project. Fair enough :)

The position is not hypercritical as the rider can subtly change position and bring everything in balance - even more so if the board is strapless. That's assuming the foil is generally in the proper position - if you have access to a decent windfoil, measure it. If not, perhaps someone here has already measured or cares to measure theirs.