Filip's Budget 3d Printed Hydrofoil

A few users have been interested in the 3d printed hydrofoil I made so I’m going to go through and explain how I did it and how it turned out. The newest version of the foil worked successfully and I’m still doing further testing to make the design better. The total cost of the foil is $32.

Designing the foil, I used the EPPLER 817 profile from airfoiltools. I designed it in Autodesk Inventor which is free for students.
My 3d printer has a 10" circular bed with a height of 12". This is larger than most printers and may be an issue for some people. I printed all of the foils in PLA at 0.25mm with 3 perimeters and 65% infill.

For the inside of the foils I bought some aluminium off amazon, which is used to keep the foils from bending and also makes an easy connection to the fuselage. I machined it into two pieces, one was 12" x 0.5" x 0.5" the other was 12" x 0.5" x 0.375". I had to sand these to make them properly press fit into the 3d printed foils.
I made the fuselage out of aluminum 1x1 extrusion and added 3d printed end caps to it, which I press fit in.

At first I printed the foils too small and I couldn’t get enough lift to get out of the water. I didn’t end up putting fiberglass on the new foil however I added some images of how I did it for the smaller one. The basic technique is to have a tiny overlap in the front and a larger overlap in the back and do one side at a time. Afterwards, use a lot of sanding to get everything smooth. I spray painted the foils red as well.
In the images, the red foils are the old kind with fiberglass and the white foil is the new version.

CAD Files

Washers can be added near the fuselage to mess with the angle of attack of the foil.

This image is just for a size comparison between the new white foil and the old red one. The new foil has an area of ~190in^2 total.

This is the best image I could find for the fiberglassing of the foils. I had to add some of the glue back where the fiberglass began to split.

Disclaimer: I’m still in high school and I barely know what I’m doing. The foils I designed aren’t necessarily optimized or stable they’re just a fun project I’m doing.


This is what it is all about! As far as I am concerned it doesn’t need to be the perfect solution, it needs to be the solution that will give you the most fun!


Hi @Filip. Congratulations for your design and thank you for willing to share the details!

U got any clue why it began to split? Is it bending forces, uneven glass layup?
No disclamers pls, we are all here to build and enjoy it! :slight_smile:

It began to split after it dried out; I suspect it just dried poorly.

One slight problem I had was the foils warped on the print bed. I put the fiberglass over the gap but didn’t bother finding a solution for the second foil.

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@Filip did you just 3d print the wings or the whole mast too?

I bought the mast off I emailed the guy and got an ebay listing for the mast, it was $50 with 20 shipping. A friend of mine cnc milled inserts however it turned out to be too weak and I ended up welding the mast to the plate.

Thats mine and plan one layer of fibreglass followed by carbon and a final fibreglass layer.

You think it’ll hold up?

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That seems a bit overkill mine worked with 1 layer of fiberglass, then 0 layers. I would go with the cheap option of 1 layer or 0 layers of fiberglass until you confirm that you have a foil shape and size that will work.

@Filip Ya was going to try same but afraid the 3d printed joint parts are brittle so wondering will one layer work. Could fibreglass the joints and then just do one layer over the lot and sand smooth then. Maybe best cheapest option!

this is the same as my first prototype, we got rid of the fusilage and swapped for a aluminium rod wit flat spots to mount the foils.

we used 4-5 layers of fiberglass and 2 layers of carbon on top for the mast and 2 layers of fiber and one carbon on foils.

best of luck, its really tedious with all the curves. alot of sanding . take your time .

also dont forget to reinforce the joint between mast and mast plate with carbon and fiberglass powder mixed with epoxy to make a curved join .

Slightly related, I made my board with a large piece of foamboard and added two pieces of wood, one on top and one on bottom, indented into the foamboard. I didn’t add more than the 1 layer of fiberglass I used elsewhere to it and it hasn’t broken yet.

I made my mast plate out of 1/8" aluminum which bent pretty fast. I’m in the process of getting a thicker piece welded on.

What speed did you get lift at?