Attaching to Foam Sandwich

It is tricky to keep the allan key under control to avoid damaging the skins, especially if they are thin moth ones.

For anything with any load as jim says a screw is a bad idea.

My favorite option for medium load fittings is to make up a 2mm thick carbon plate 15-20mm bigger than the fitting and bond nuts to the back. The plate is then bonded to the deck and can optionaly be covered in a couple of layers of carbon.

If you want you can make the plate fit closer by drilling a cavity in the top skin and foam so the nut will sit below the deck level and if you trim the bolts to the correct length you can do it without putting a hole in the inner skin to help avoid leaks.

The key thing with foam sandwich is to spread the load, anything that will do that is OK

 

I need to attach a fitting to a foam sandwich hull, I've got an old book by Rodney Pattison that recommends drilling the hole, inserting an allen key attached to the drill, spinning the key to destroy the foam around that area and then injecting epoxy to create a solid area to screw into. Is this still best practise or have any other (maybe less brutal?) methods come about since then?