Happiness... Second week of holiday. I've completed several moulds and ready for wind tomorrow to test a new stabiliser and a couple of Axis Black fuselage compatible front wings. Feel like I've come a long way since I started designing foils back around September 2019.
My process:
Design wing (openscad, I do it with formulae controlling the wing's surface)
Subtract a manufacturer's front mast connection at the angle I want the front wing to sit at.
Subtract shear planes to subdivide the part for 3D printing and dowel shapes for rejoining after printing.
Print- This works out around 3.5 days with PLA + and a 0.6mm nozzle, for an intermediate wing size around 1200 sq cm.
Clear my dowel holes with a drill to the precise dowel diameter(I oversize to D+0.3mm but they still needs cleaning).
Superglue the dowels and wing pieces together ansuring alignment of the trailing edges.
Use an orbit sander and around 260 grit to take the highs off the wing.
Bog up any print line cavities, sand and repeat.
Spray with high build primer, sand.
Use food sealing bag and machine to vacuum seal a membrane around the wing, keeping kinks and folds of the bag to a minimum.
Pack infusion mesh, budget glass fbre multiple layers around top and bottom of the wing inside a bigger vacuum storage bag. Set infusion spiral wrap and tube in place to vent into the infusion mesh.
Set resin brake with strip of peel ply on other side from infusion spiral.
Wrap my vacuum hose with paper towels, place at end of peel ply.
Seal resin intake hose.
Apply sealant tape around inlet and outlet, close vacuum bag around sealant, zip closed, test vacuum, fix any leaks.
Mix polyester resin with about 0.8% catalyst for a slow cure.
Place hose in polyester container, release clamp.
Monitor infusion until resin is past wing with a good allowance for the mould's flange.
Give the mould plenty of time to cure.
Debag infused composites.
Drill 2 x mould alignment holes at ends of composite mould.
Trim with a Dremmel to ends and sides of food vacuum bag.
Split the composites into the two wing sides, remove the bagged model.
Fill the food bag texture voids in the mould surface with budget filler or high build paint, allow to cure.
Sand smooth to 400 grit.(no polish).
Apply PVA mould release all over both inside faces of the mould halves.
Allow to dry, repeat if needed.
Use wing model for composites outline template and cut all the pieces out, allowing for tapering at the edges.
I use a lot of unidirectional and now I'm doing thin, high performance wings I use all carbon fibre. However unidirectional won't resist twisting and an exterior impact can split the fibres apart. So use a woven exterior skin and add double bias cloth to clad or space the unidirectional to boost it's robustness.
Epoxy the mould halves and allow to go tacky, trying to keep an even film.
Apply the woven outer skins to each side with overlap to the mould's mating surfaces.
Apply the unidirectional, unidirectional, double bias etc.
Epoxy in pieces of compressible core mat.
Mix up some glue filler with epoxy and ensure that there will be no air voids in the wing.
Close the two mould halves together, screw together with the two locating holes and clamp the rest of the mould's seams together ensuring evenness of the clamps.(I have spring clamps, lever clamps, I've got about 20.
Wait for the leaked out resin to go hard.
Clean off any resin bridges around the mould seams.
Drive in plastic wedges, putty knives to split the mould halves from the new wing.
I've done this for 3 different wing designs in the last week!
Note that the thinner the wing, the more unidirectional you will need. If you're on a budget, consider basalt. It's well priced and goes a dark brown when cured with epoxy. It's similar weight to glass fibre but more smash resistant than carbon or glass.
Also be careful around any mast attachment. When you do up the screws, you should not be squeezing sides together, between the screws ant the mast foot there should be only composite material, nothing compressible.