Oiling the screw holes in Gunwales

In rgams thread on gunwale oil, it was suggested that the holes for the screws should be oiled as well as the exterior of the gunwales. This post requests suggestions on the best way to apply oil to the holes.

My only previous experience with wood gunwales was with gunwales that dry rotted from the screw holes. The gunwales looked solid on the outside, but when we took them off we discovered weak spots where the gunwale almost turned to powder in our hands. It wasn’t just the screw holes. The dry rot occurred at the few spots where the screw caused small splits in the grain, radiating out from the screw hole. There were only a couple such spots and I don’t think it was coincidence that that’s where the gunwale rotted.

Having written that, I can see a benefit from mounting the gunwales, then removing them to oil the holes. The benefit of that procedure is that any cracks that occurred will have a chance to soak up some oil. I think once the screw is removed, the crack will disappear, but it should still draw in oil. However, the removal and reinstallation are extra work, a nasty four letter word that I don’t mind saying but don’t like doing.

A one-step process is my preference. Drill the hole, squirt in some oil, fill the hole with a screw, and be done. I will appreciate somebody sharing a hole-oilin’ procedure (hmmm, that phrase…pls remove mind from gutter) for one-step gunwale mounting. Also, what kind of applicator is useful for hole-oilin’?

And even if this post produces no useful information, there is plenty of room for Freudian word-play, so maybe it will produce some entertaining reading. Screwing, protection, holes, oil…Who knows what associations will be made in the minds of p-netters?

~~Chip Walsh, Gambrills, MD

Heat Gun
I’ve been using a Linseed oil and Beeswax formula for my gunwales. I found that after brushing on this mixture that using a heat gun to follow behind the brush liquefies everything and the wood readily soaks it up. Oil is thinner when it is warmer, thus will penetrate into the wood farther. Of course obvious precautions should be used to not damage the hull by overheating.

dip the screws
in the oil before you drive them. Put oil in a shallow cup or upside down jar lid and simply dip the screw in the oil and drive before it has a chance to drip off.

If the wood is spliting out from the screw holes the pilot hole is too small, or the screws are poorly made and dull and the threads are not cutting into the wood, but pushing it aside like a wedge.

Production issues
In a custom made or home built boat, oiling the screws makes sense, but may not carry enough oil to seal. One also has the issues of dripping Watco on the enterior of the hull, which will mark it.

That’s why we Poly-urethane, sealing the screws in and the underside of the outwale to the hull gap.

Still testing rail sections w/ Watco/Armada/Poly on the boat rack. I’ll get some screws in those pieces.

screws from outside
I have always screwed gunwales on from the outside. Two reasons.

  1. The outside gunwale is mostly protection for the top of the hull and is not bearing the kind of stress that the inwale does if seats and portage yokes are hung from them. Therefore, I can save a bit of weight by making the outwale thinner, usually 1/2" or 3/8" instead of 3/4". The inwale bearing lots of stress is almost a full 3/4" thick and there are no holes that go all the way through the piece, just the threaded portion of the screw.
  2. Given a thinner outwale it makes better sense structurally to have the head and shank of the screw in the outwale and hull and the threaded portion in the inwale, the most substantial part of the three.

    All this to say it is easy, and I do this, to mask off the hull below the outwales so that I don’t drip oil on the hull.

The Fantasy had Factory Gunwales
My whole experience with gunwales was from one boat, the Mad River Fantasy. The gunwales were installed by Mad River while they were still in Vermont, so I think we can assume they had the proper size bit, the right screw for the job, and some people doing the work that were at least as competent as me. So I am wondering if a few holes with cracks are inevitable.

Most of the screws were fine, but a few had cracks running with the grain, away from the screw holes. And that is where the inside of the gunwale turned to powder. Had the owner of the boat ever taken the gunwales off and oiled them, the cracks would presumably have soaked up oil and all would have been fine. She didn’t. After ten or so years, when we finally were going to attend to the gunwales, they fell apart in our hands.


Linseed oil
I have seen many applications for Linseed oil but isn’t that the stuff that causes fires from spontaneous combustion if not properly handled? I always avoid it for that reason. I had not heard of the lso-wax gunwale treatment previously.

The gunwales already have a couple coats of Watco on 'em, so I will plan on sticking with that treatment.