I let the epoxy cure for about 6 hours before returning to put the plywood webbing on.
Plywood cut roughly to size (I will route the edges afterwards), I applied T88 to the upper surfaces of the spar and then layed the ply webbing on top to make an impression of where I would have to apply epoxy to it. Lifted it off and worked on an even coat of T88. Both mating surfaces needing an even coverage.
Plywood layed down again and weighted with whatever I had at hand. Hardwood timber, water, paint tins and mitre saw.
Left over night and I now have the foundations of a wing spar.
