How to plug redundant bolt holes?

[KenMcCulloch]

I am in the process of renewing a skin fitting (head inlet). The old skin fitting had a flange on the inside and three csk machnine screws (M5 or thereabouts) with nuts on the inside keeping it fastened to the hull. I intend to replace it with a simple threaded skin fitting, the type with a large nut on the inside and a flange on the outside. That leaves me with three redundant 5mm holes about 10mm from the skin fitting hole itself.

My plan at the moment is to make three pegs, very slightly oversize, and drive them into the holes with a little sikaflex to ensure a good seal. I have some handy offcuts of mahogany similar to the planking to use for the plugs. A sharp chisel will come into play to trim the excess length, a wee dod of primer and i hope only a close examination will give away the fact that there were ever holes there. Can anyone suggest a better plan or any refinements??

 

[oldfrank]

The only problem with pegs is that you'll inevitably end up with 10mm plugs with a cross grain. The cross grain will absorb water and therefore expand at a different rate. You don't say if the hull is varnished or whether the fitting is below the waterline. If varnish is involved, I'd borrow or buy a plug cutter of appropriate size, drill out your 10mm holes to a clean edge and glue in mahogany plugs - you can then line up the grain on the plug with the grain on the planking - and then they'll really be difficult to spot. You should consider fitting a backing piece inside the hull to take the fitting and also cover the inside of the existing bolt holes. It's good practice anyway but if they're below the waterline and your plugs somehow become dislodged, you'll get a sinking feeling. OF

 

[Peterduck]

I have to disagree with Frank on this one. I certainly wouldn't open the hole out from 5 to 10 mm. 6mm maybe, to get a fresh surface, but any more and the holes are going to break through to the main hole in the centre. Although water does move more freely along the grain than across it, the expansion of a 5 or 6mm dowel isn't going to be all that much, and a coating of red lead over it should minimise that. On the other hand, if it is in highly visible brightwork, then a proper plug is the way to go. I would epoxy the dowel in place, but that's just my preference.
Peter.

 

[KenMcCulloch]

Thanks guys. It's a heads inlet below the waterline so appearance isn't critical, and opening the holes out to 10mm would weaken the area unacceptably. I think I will go with my original plan (which does include a backing piece inside the hulll, thanks Frank).

 

[oldfrank]

Peter, You're right.I misread the original posting and understood the exiting holes were 10mm. Anything wrong with Imperial? OF