Hi guys,

I put this post in here, as I have 3 different questions to help me create a CNC'd Hydrofoil for kitesurfing.

Background: I made 2 masts and 4 hydrofoils using different techniques including 3D PLA printing, vacuum bagging, pine and plastic cores and composite filament winding for some pieces. I have had limited success in that they all work and have been ridden, but due to flex it's time to aim at the higher performance end of the spectrum now.

The plan is to use a sheet of G10 ( prototype #2), or Marine ply ( prototype #1), and CNC cut out a long, thin 3D symmetrical foil shape. 1 meter long / 1 cm thick / 10cm Chord ( width ) and it must be 3D profiled to be finished to the correct shape, down to less than 50 microns.

Question 1, Because the part is so long and thin, I have ruled out using a 4th axis to rotate and machine the part due to flex + vibration. I was planning on cutting 1/2 way through the part to the centerline, flipping over , placing in a female mould half with only the ends of the part ( off the end of what I need ) bolted down, and then cutting the ends off after. Alternatively I could make a channel in the female mould, connect my kracher vac and try to vacuum hold the male piece in the female mould for final cut. ( with some guide lugs off the end to position accurately ). Any more tips or other methods that may work to get the basic shape done.

Question 2, The part thickness is only 10-11mm maximum and G10 stock 12mm thick, reducing down to probably 1mm or 0.5mm part thicknessat the trailing edge. If I am using plywood or G10, what sort of minimum thickness could I machine without part bits breaking off, and does anyone have any guides regarding stepdown to get a thin plywood trailing edge ( I am guessing G10 won't matter as it will not chip away ). Take into account, that after machining the part, I will be cabon fiber compositing over the part with the carbon wrapping the front, and trailing off the rear edge to achieve a fine trailing edge sandable finish.

Question 3, I don't have a lot of stock to remove, and I have some 2 flute Bull / round nose that I was going to use on the plywood, but can anyone recommend a tool for the G10 - taking into account there is not much stock removal to achieve - and I'm pretty much at the 3D profiling level with a max single cut height of 5mm to get to the centerline of the part, and minimum of 1mm?

Quesition 4, I have a 750Watt draper woodchip extractor, with the clear bag under. I replaced the 20 micron stock filter bag, with a 1 micron bag. Should this be sufficient to filter the air of the G10 particles?

Nick