Clench nail removal?

[stromborg]

Recently I was eyeballing a lovely 12' lapstrake boat found on the side of the road the other day. Nicely built little thing, I remember seeing it at a local fundraising auction several years ago, I don't think it has been in the water since and it is now back on the block for another fundraising effort. There is a through-and through crack in the first plank below the waterline that might or might not take up after putting the boat back in the water. I gently explained to the other old codger looking at the boat why simply spooging epoxy in the crack probably wasn't the best way to fix it and went on my way. But then I started thinking about how to best fix that plank if it didn't take up or got worse.

Looking closely I can see the builder used clench nails to fasten the laps, how does one go about removing those nails to fit a new plank? Screws back out, rivets you grind the peen off and drive out, but those bent-over nails look like they would be a serious PITA to remove and could easily cause a fair bit of damage to the good planks on either side. There's got to be a way, right?

[Stiletto]

Not having done it, I think that taking the heads off with a dremel, and then carefully punching the shank might cause the least amount of damage.
I'm interested to see what others think.

[Peerie Maa]

I think that the only way without doing too much damage to the inside is to drill off the head on the outside. Start with a fine drill for a pilot hole then go bigger. Then punch it through.
Alternatively, I was advised by a colleague who learned his trade by an old school apprenticeship. Get hold of a stainless table knife with a thin straight bade, with a solid stainless handle, rather than a bone or plastic one, and grind off the rounded end. Then sharpen the square tip. Then you slip the blade into the lap and cut the nail as if with a cold chisel.
Third alternative, Fein multi tool saw blades are quite fine, cut the nail with one of those between the laps.

[Chris Woodward]

You can lift the clinch with a tack remover. Or a fine sharpened screwdriver. Back the tool with a piece of sheet brass shim stock against the plank. Force the tool under the clinch carefully and pry up just enough to get a small pair of sharp pointed dykes around the nail.Nip off the clinch and pull the tack out from the head side. You will get some gouging and denting of the planking but it should be minimal. The plank that you are replacing should get the worst of it. Practice on that lap first. Easy, easy now, don't go hogging into it. Be carful and slow.

[Peerie Maa]

You can lift the clinch with a tack remover. Or a fine sharpened screwdriver. Back the tool with a piece of sheet brass shim stock against the plank. Force the tool under the clinch carefully and pry up just enough to get a small pair of sharp pointed dykes around the nail.Nip off the clinch and pull the tack out from the head side. You will get some gouging and denting of the planking but it should be minimal. The plank that you are replacing should get the worst of it. Practice on that lap first. Easy, easy now, don't go hogging into it. Be carful and slow.

If you do dent the wood, pour boiling water on the dent, that will lift it, or most of it out.
Don't forget to re-nail with the next larger gauge nail.

[stromborg]

Thanks for the ideas. Grinding the heads off the nails gave me a flashback to ruining an aluminum intake manifold trying the drill out a snapped thermostat bolt. Prying up the clench is equally fraught. I hope whoever bought the boat finds a good solution.

[holzbt]

I'm assuming they are copper nails and fairly small diameter. I've ground the bottom of a pair of diagonal cutting pliers (dikes) on a belt sander to make them thinner. I just force them through the wood and cut off the clenched part or the head depending on which lap. I don't worry about damaging the plank that's being removed as I'm only using it as a pattern. Minimal damage to the planks above and below the plank being removed. It goes fairly quickly but I've mostly done this with cedar planking and only once with mahogany.

[heimlaga]

The normal way of removing clench nails is to use a chisel and chop around the nail in the plank to be removed.
At the upper land of the plank you chop around the clenched end of the nail. Only deep enough to be able to pry up and straighten the nail and cut it off with a pincer. Then the nail can be driven out.
At the lower land you chop around the head only deep enough to allow you to drive in the nail a bit further. Then the inner end can be straightened and cut off with a pincer and the nail can be driven out.

[Yeadon]

A couple thoughts to consider.

Heat the outside head of the clench nail with the tip of a soldering iron. Send the heat all the way through the nail. The nail will soften and pull out without a lot of trouble. I've also used dikes to slip under the head of the heated nail, which can then be worked out slowly. You may have to reach inside the boat and ease the clenched part of the nail loose a bit too. Do what ya gotta do.

To fix the crack, if it's cedar you may be able clean out the crack with a dental pick, chisel or sandpaper or whatever works, then mush it all back together with thickened epoxy. Also known as ye old drag and fill. Cedar is really forgiving like this. Be sure to drill a small hole a touch wider than the crack into each end of the crack first to keep it from running even further while you're messing with it. Other option for a larger crack might be to route it out and install a spline with the cedar proud of the plank. Once epoxied in, you can just smooth down the spline with a block plane.

You could also dunk the boat, soak it up, and then fix the crack once it's moved back closer together. The boat would have to dry for the epoxy to take but you'd have a better idea of what you're dealing with. I'm not totally sure I'd bother but it would still be interesting to see what happened.

[skuthorp]

Farriers nail pullers. Designed to straighten the clnch and then pull out without damaging the hoof further.

[Fitz]

The majority of the time I use a tack puller. With a little practice it results in minimal damage. I have also used an angle grinder to remove the clench. This takes a bit of concentration .