Remaking old screw holes

[richardabeattie]

I am refitting the engine hatch in the cockpit sole. It is held down by 16 self tapping screws but the holes are now worn and the screws don't hold well. I propose using 2 part gellcoat filler to fill them prior to redrilling with a small bit to get the self tappers started. But is gellcoat filler good enough- not too hard/brittle - or have I got to buy something cleverer?

 

[Wooden Boat Fittings]

The principle's right, but I'd use thickened epoxy as the filler, not gelcoat. Depending on the colour you want, you could use microballoons or wood flour as the filler (it doesn't matter which if you'll be painting it). If the material surrounding the hole is at all suspect, ream (drill) it our further first. Fill the holes right up, let the epoxy set, then drill pilot holes for the self-tappers.

Mike

 

[Norman_E]

Gellcoat filler is pretty brittle. If you are screwing in to GRP, and the hatch needs to come off more than very occasionally, then you should consider a different approach. Consider whether you could fit stainless nutserts into the GRP and hold the hatch down with machine screws.

P.S. If you are going to drill out and fill as suggested above you could even expand the nutserts then just set them in the wet epoxy.

 

[ronsurf]

I would use epoxy, but cut some glassfibre into it (tiny pieces cut with sharp scissors) to make a paste. Then stuff it into the hole, wait for it to set and drill a new pilot hole and refit the self tappers. The glassfibres ensure the whole lot won't pull out as a plug, or crack like filler may. Stainless inserts are a good idea, but seat those with the glassfibre paste stuff. It works really well for filling holes and maintaining some GRP strength.

 

[David2452]

Just had a similar issue with a large inspection hatch on a GRP potable tank, I attacked it differently, just opened the holes out a little, countersunk a little more and went up from 5mm to 6mm sheet metal screws.

 

[pmagowan]

You can use thickened epoxy and then coat the screws with a bit of oil/grease and put them in while it is still wet. They shouldn't then stick to the epoxy but should have perfectly moulded threads. If you get it wrong and they stick a bit you can heat the screw up by putting a blow torch to a heavy duty screwdriver whilst engaged with the screw. It heats the screw and then frees it.

 

[Ruffles]

I find it only works if you widen the hole. Otherwise the new epoxy is too thin...

 

[MM5AHO]

I didn't catch if the holes are in ply of fibreglass.
In doing similar hole refurbishment, I've found a few tiny sawcuts along the radius into the rest of the material help. They get filled like the hole, but increase the surface area between the new and old. A round plug of new stuff in a round hole can sometimes come unplugged.

 

[lw395]

Gellcoat filler is pretty brittle. If you are screwing in to GRP, and the hatch needs to come off more than very occasionally, then you should consider a different approach. Consider whether you could fit stainless nutserts into the GRP and hold the hatch down with machine screws.

P.S. If you are going to drill out and fill as suggested above you could even expand the nutserts then just set them in the wet epoxy.

+1.

 

[duncan99210]

Just had a similar issue with a large inspection hatch on a GRP potable tank, I attacked it differently, just opened the holes out a little, countersunk a little more and went up from 5mm to 6mm sheet metal screws.

+1 Simple, quick and no mess.

 

[David2452]

+1 Simple, quick and no mess.

Indeed, and if one uses decent EJOT sheet metal screws they fare much better in GRP as they have a higher root to major diamiter ratio and self drill.