I was inspired by the american clearwater foil guys and thought it would be pretty simple to print the shape of a foil with my 3d printer.
So I taught myself CAD and designed a front wing (in two pieces) and a middle segment that a rectangular aluminium tube (the fuselage) would slot into. I printed the first two pieces and am pleasantly surprised with the results. The plastic wing is a lot stronger than i expected, and i reckon one layer of glass over the top would be heaps (tbh i wouldn't be suprised if the plastic by itself could support a rider, although wouldn't last long).
Still early in this project, but a set of front wing, rear wing and fuselage (alu tube from bunnings) could probably be produced for about 20 bucks. Anyone want a set? I don't have enough time to design, print, glass, test and re-print. It'd be great to team up with someone with good glassing skills and go from there.
I have two of those alu masts from manta foils that they used to sell. I'm planning on using one of them, but I think a cheaper way might be to 3d print the profile of the mast and slot one or two alu tube spars down the mast to provide the stiffness.
There is lots more to do - refining design to save weight and increase efficiency, reduce warping at the corners of wings, re-design the middle segment to support a larger alu tube (I thought 2x1cm would be enough, but its absolutely tiny in real life).
The design of the wing was taken from a US uni webpage who publishes splines of hydrofoil profiles. I knocked up the rest in fusion360. the wings will be about 52 cm with a maximum 15.5 cm chord. they have a curve downward to the wingtip of 2 cm.
I'm just having fun with this, not looking to make a business or anything, so would love any help. I reckon we might be able to get to a produced foil for less than $200 (ex board) and share the foiling joy around.

the middle segment. As i said above that slot out the back is for an 2 x 1 cm alu tube which is way too small in hindsight. Beauty of CAD and 3d printing is that I'll just find a larger alu tube from bunnings and re-design and re-print this week.
Those little extrusions on the edges will slot into the wings. Hopefully that, plus a layer or two of glass will be strong enough.

Front view of the right wing segment showing the curve.

profile of the wing. also shows the slot that the middle segment will slot into.
From the top showing the arc of the wing.