Small Homemade Hydrofoil Boat 

10kmh normal vs. 23kmh hydrofoil

I will comment on that when I have gone through some waves.

@@bjofuruh have you gone through some waves?

I use the good old versatile Clark Y airfoil for the hydrofoils. It works great at these low Reynolds number. Angle of attack is between zero and one degree positive measured along the underside of the hydrofoil. They must be adjustable so you can find the exact angle for your speed and weight.

And can I ask for at least the approximate width and length of the wings? Thank you@@bjofuruh

@@MrBrumla The area of the rear foils are: 0.090 m², The front foil is 0.035 m². That gives a total hydrofoil area of: 0.215 m² Rear foils: 0.90 x 0.10 m Front foil: 0.50 x 0.07 m The all up gross weight is: 136 kg.

@@bjofuruh If I calculate my weight, the weight of the engine and the fuel, then in these items alone I will reach about 120 kg. My engine is a 6hp Yamaha 6DM 2 stroke, 2 cylinder. If I am very handy, I will manage to make the boat up to approx. 80 kg in weight. So the total weight will be approx. 200-220 kg. I am wondering if the dimensions of the underwater wings as you wrote to me will be enough, or if it would be better to increase the dimensions in percentage terms.

@@MrBrumla I previously had a heavier boat with a 5 HP engine and the same hydrofoils. It had an all-up weight of 167 kg. The top speed was 32 km/h. I think you can size up the hydrofoils to get the same wing loading as I had with this heavier boat. It worked great, and with 6 HP it may be fast.

I made a spreadsheet with all variable parameters for the boat, so I could calculate weight, weight distribution, lift, drag, engine power and so on. If you are interested in designing your own, you should purchase Ray Vellingas book on hydrofoil design.

@@bjofuruh Ray's book is the key!

Yes! It can turn at full speed. Not shown here because the aileron mechanism was not yet fully adjusted, so it was still a bit unstable in roll.