How can I mount a foil on an old directional board?

[Herman]

For holes through the board do not drill oversized holes. Drill correct size holes then with bent wire or cut down small Allen key or similar ream out required amount of foam. Fill with resin and ré-dril correct size holes. Don’t ream out too much foam or it will end up heavy imho. Also consider using glass balls in the resin.

[fluidity]

I put aluminium for the plate which would make it pretty strong but sandwiching unidirectional and woven thick enough would also work for the bottom plate.

[longwhitecloud]

you simply need one of these, a router, epoxy and some glass

https://shapers.com.au/foil-fin-track-insert-boxes/

[MCN]

For holes through the board do not drill oversized holes. Drill correct size holes then with bent wire or cut down small Allen key or similar ream out required amount of foam. Fill with resin and ré-dril correct size holes. Don’t ream out too much foam or it will end up heavy imho. Also consider using glass balls in the resin.

Have done the same. Fast and cheap solution.
I also did one board with long holes (poor mans track) with a router so that you can move the position of the foil.
To much epoxi in the holes at the same time can melt the foam and laminate. do it little by little and with some cellulose filler

[fluidity]

My one is actually in progress. Pretty rough except for being CNCed. 2 layers of unidirectional 600 gsm, 2 layers of biaxial 400gsm?, 2 layers of 200gsm twill glass. All vacuumed with a foil base plate with the 6mm groves to line things up, one the glass is at green stage I'll clean out the slots with a knife. and assess the rest of the surfaces. Feel like I'm overdoing it with the top plate, except in a hard hit it's the area on top that distributes the load from the weaker board.

Longwhite cloud- Both thread author and myself have the commercial foil boxes already on order. I ordered mine a couple of weeks ago.