Whilst working abroad in Greece as a sailing instructor, I was lucky enough to get to try a wind foil (a windsurf hydrofoil). By the end of the summer I was competent sailing the foil and when I returned to the UK I was eager to continue using it. However, I was horrified by the price of hydrofoils and soon realized that there was no chance of me being able to buy one. Most hydrofoils also require a specific reinforced fin-box to deal with the increased loads. I decided to circumvent both problems by designing and making my own foil that will fit in my existing boards without breaking them.
I decided to base the design on an existing foil to maximize the chances of mine working properly. I chose the Neilpryde Glide Wind because it is optimised to work in power boxes (the fin box on my board). However, I did decide to make a number of changes to the design, most significantly the material choice for a lot of the parts (from aluminium to carbon).
I used the sketch picture tool along with various pictures of the glide windfoil to get the design in solidworks, tracing round the shapes in the pictures. At this stage I decided to scale up the size of the front wing by 20%. I decided to do this because the larger area will give the foil more lift and therefore mean that I will take off in lighter winds. I also simplified the shape of the fuselage (top part in photo) so that it will be easier to bandsaw out of aluminium.
- The Wings
I used this CAD file of the individual parts to design two molds to get the shape for the wings. Both wings need a shape to them to stabilize the foil when its moving through the water. According to Neilpryde, the shape of the front wing is designed to make rolling turns and carving easy and the rear wing, being more angular, wants to sail in a straight line. Together they enable easy carving and straight line cruising.
I cut a piece of 2mm MDF using the band saw to the width of the mold. I then soaked the ends in warm water to make them more flexible. This enabled me to bend the MDF over the form so the carbon will have a smooth surface to be molded on.
I then used CA glue to attach the MDF layer to the mold. Both molds were then covered in Polyethylene (PE) So that the Epoxy Resin (Used later) wont Stick to the mold.
The front wind needs a foam core to give it the correct shape. I quickly realised the foam was very rigid and wouldnt bend round my mold. Therefore, I decided to split the sheet into 50mm wide sections and then glue them back together. Before everything was glued back together, I used the hot wire cutter to cut the wing profile in each of the pieces. This gave the rough shape of the wing.
I glued the pieces together using PVA and used matchsticks in the foam to get the alignment and strength I wanted. The pieces were held down to the mold and together by pieces of tape.
Once the PVA had set, I removed the tape and then mixed more PVA with some foam dust to use as a filler. I used this to fill all the gaps on the top of the wing.
2. The Mast
3. The Fuselage
4. Fitting & Assembly
