Filling hole in exterior of wooden hull

[MikeBz]

I need to fill a ~1.5" diamter hole covering a bolt head (engine mount fixing) in the exterior (below waterline) of an iroko hull. Does the panel have any advice?

Mike

 

[JesseLoynes]

How deep is the hole?

Did the bolt go in bedded on mastic type stuff or caulking cotton? So is the fastening waterproof before you fill the hole over the bolthead?

 

[MikeBz]

I haven't measured the depth (I'm guessing it's around an inch). The fastening doesn't appear to be totally waterproof although the previous owner thinks this is due to the boat having been out of the water for 7+ months and that it will take up on relaunch. I'd rather assume that it's not waterproof and ensure that whatever I fill the hole with will waterproof it - not least because the endgrain will be exposed (albeit painted) to moisture otherwise.

Mike

 

[LittleShip]

Epoxy a wood plug in the hole , it can always be removed at a later date if required.
Tom

 

[Scarboroughsloop]

Would the epoxy not crack as the wood moved?

In a similar vein I have just had a frame refastened under the waterline. Would red lead putty be ok for stopping this type of hole?

 

[Peterduck]

If it's an inch thick, I'd assume that it has gone all the way through the planking and if you don't do something about it you might as well hang out a sign, " water enter here". Make up a graving piece in the shape of a diamond, with edges that taper toward one side. A matching hole needs to be carved so that the sides taper toward the centreline. The water pressure will then tighten the plug up. The long axis of the diamond should be parallel to the planking grain. Glue the graving piece in place with epoxy, keeping a light pressure on it with a prop from outside. Too much glue is better than not enough! If you can match the species of the planking, so much the better, but if the timber is oily, don't forget to clean off the loi from the paying surfaces before applying the epoxy.
Peter.

 

[Peterduck]

If you're not too slow about the repair, there should be minimal movement of the wood. I should also add that here are epoxy resins which are quite happy to be applied to wet timber, and obviously these would be preferable. Red lead putty should be OK for stopping a fastening, especially if you prime the cavity with red lead paint first.
Peter.

 

[Ferretmn17]

I would go with the epoxy, if the boat has been out of the water that long the wood should be dry enough to get a solid joint. I know someone who removed the stopcocks from their hull and filled the holes with epoxy, since re-launch (5 years+) the holes have remained watertight.

 

[andrewbodenham]

Mike,
I'd cut a plug from piece of iroko, maybe using a hole saw in a drill stand or bench drill with the pilot drill removed. Ideally this would be lightly oversize - you can then taper it a bit by sanding or paring. The sides of your hole need to be cleaned back to fresh wood to ensure a good bond. I'd use a thixotropic polyurethane like Balcotan to glue the plug in, degreasing the surfaces with acetone first. If the plug is a snug fit it should stay put when you've hammered it in until the glue cures. Then clean off.

 

[Sniper]

I'm with PeterDuck on this one, having just done exactly the same job (albeit above the waterline) The graving piece was bedded on thickened epoxy and, once cured, planed flush. A bit of wood filler and sanding and its impossible to tell where it was.

 

[kenneth1964]

I would go with the epoxy and plug, but make your epoxy up with marine filler. Get a large container as this will give you more working time. Put filler in first then add your epoxy and mix to thickness you require. The boat will fall apart before the bung and epoxy come away from surrounding wood.

 

[MikeBz]

Thankyou for all the responses & advice. Having cleaned the goo out of the hole things have become both clearer and more complicated... The end of the bolt is almost flush with the hull surface, so anything it's filled over with will be extremely thin at that point. The bolt is an engine mount, so it's likely to suffer some vibration, hence the thin layer of whatever is put over it is likely to fall off pretty quickly.

At this point I can see 2 options:

1. Do it properly - cockpit floor up, remove engine mounts etc. whatever is required to get at the other end of the bolt (can't see it at the moment), shorten bolt, put it all back together and then plug or fill as per all the advice above.

2. Watertight 'bodge' - epoxy the bare wood edges of the recess, fill with red lead putty, then glue/epoxy a faired piece of wood onto the exterior of the hull to completely cover the hole. It doesn't sound nice but it will be safely watertight and less ugly/draggy than the transducer mounting.

Mike

 

[mikefleetwood]

Surely your "option 2" is the way to go in this case. You don't really want to seal in the end of the engine mount bolt with anything too permanent - you never know when you might need to undo it! Just fill flush with the surface with red-lead putty, don't both to glue anything over the top. I would assume the bolt head has a washer, or somesuch, under it to spread the load. Probably red lead or other goo to seal it too, when done up tight (I hope!) it won't leak, so filling to surface is largely cosmetic and keeping the end grain sealed. Certainly don't bother undoing, shorten bolt, etc. - life's too short and you will probably make more problems than you solve.