Eddy currents in stators

[TDC]

1.  Would conductive materials be ok around the outside of a stator if they are 6mm or so from the coils?

2.  I'm thinking of winding four in hand so they can be connected series, parallel or series parallel for 12, 24 or 48v, is that ok and should diodes be used to prevent eddies between the parallel windings?

[Flux]

Depend what you mean by conductive material. 6mm outside the coils will still be in a reasonable magnetic field. You need to avoid significant metal  in this region, conductive but high resistance material such as carbon fibre probably would be ok.

With a 4 in hand winding the 4 sections ought to be near enough to connect in parallel but at 12v the current will be such that you need multiple diodes so you may end up with diodes per string for convenience. Although diodes will block circulating current below cut in, it will come back beyond cut in. Blocking them may get you to cut in earlier by keeping the prop from stall in the run up but try to keep the sections as close as possible or the loss will be there at cut in.

Series paralleling individual coils would likely give you trouble but with 4 in hand spread over all the coils it should work ok.

Flux