Rodrigo Alvarez

Tinkering as a way of life

Kite Foil – Design & Lamination

We’ve been busy the last few weeks working on the kite Hydrofoil. While I was working on the rest of the design, to allow independent work, my colleague has worked on the mast. The design will be composed of 6 main parts shown below in different colours. The wing box (not shown), the mast (turquoise), back wing (pink), fuselage (red), front wing (purple) and AOA adaptor (green)

Mostly finished hydrofoil design

To allow Gonzalo to start shaping the mast, we chose a classic symmetric foil shape which due to its drop-shape provides the least amount of drag. As our main material was 15mm thick laminated plywood, we chose to maximize the foil thickness to that amount. The ends are slot shaped, so both, the base and the fuselage can be milled to fit.

Here we had to take an executive decision, most kite foils we saw online were completely disassembleable. Being carbon, we suspect they a are also much sturdier than ours. As due to the mast length, the bending moment will me maximum at the base, we want to minimize the chance of creating weak spots where two parts meet. Therefore, we have decided to laminate together the base, the mast and the fuselage. Although this will make it harder to fit in cars and to handle in general, we believe it really decreases our chances of failure.

Fuselage, mast and base assembled together prior to lamination

We used a manual milling machine to cut the slots in both the fuselage and the base. As the fuselage was already set up in the machine, we also drilled the holes for the front and rear wings. We have used wood T-nuts for all unions, even for those that are not intended to be disassembled, just in case in the future we need to separate the parts

Render of the finished hydrofoil

Mast lamination

As this part is the first we have ever laminated using glass fiber, we have chosen what looked like the easiest. We chose a 3 direction lay-up as shown below. Our main concern is the bending moment in the roll axis, this is why we have emphasised the red direction over the green and blue, and we have totally skipped a direction 90 degrees of the red.

To give us a fighting chance Gonzalo asked me to provide supports to set up the mast as shown in the image above. Him, having the role of manufacture engineer knew what he wanted, and after a few back and forth Whatsapps we converged on a solution.

The result achieved looks promising! Our next steps are the manufacturing of the back wing, and the lamination of the rest of the parts