Repairing a bad planking butt-seam

[James McMullen]

This 1940's built Bill Garden designed sloop had a problem with a bad plank joint. This boat was iron fastened using yellow cedar planking, and the ends of both planks at this particular seam had deteriorated as the fasteners went south to the point where refastening through a new butt-block wasn't an option. The rest of each plank was in great condition, so we didn't want to chop out any more than we had to for this fix.

The solution was to remove the bad ends and scarph in a new short piece to fill in the area. The scarphs were cut so as to leave the feather edge ending where it could be backed up by a frame, and new butt-blocks were placed behind the scarphs so that the whole assembly could be bolted through and through.

http://inlinethumb45.webshots.com/43756/2334045710105767272S600x600Q85.jpg (http://home-and-garden.webshots.com/photo/2334045710105767272yVfPTp)

Here we see the scarphs after cutting and planing to shape and after pre-drilling the new fastener holes, but before plugging the old fastener holes through the frame with trunnels. The patch was bedded in 5200, and then the seams caulked up with a strand or two of cotton and seam compound. I'd show you a picture of "after", but there's no point since you can't even tell where it was under the bottom paint. :D

http://inlinethumb60.webshots.com/44027/2031731270105767272S600x600Q85.jpg (http://home-and-garden.webshots.com/photo/2031731270105767272sDUPeU)

[Dan McCosh]

I've done that repair maybe 20 times over 25 years or so, but just glue the scarf with epoxy. It works fine. The backing block is just creating another potential rot pocket.

[nedL]

Very nice. I am a bit surprised that the original planking isn't more discolored/darkened after 60+years. Must speak of good original construction & proper continuous maintainance.

[James McMullen]

. . .just glue the scarf with epoxy.

Below the waterline. . . .completely water-saturated 1 1/2" thick planks. . .repair done outside in the PNW winter. . . .No way just gluing with epoxy is the way to go here, amigo! This repair was done correctly. I would use an epoxy glued scarph on topside planks or on a trailerable boat without hesitating, but that's not the right solution for a heavily built, carvel 40-footer downstairs.

Backing blocks must be shaped and bedded properly, yes. Properly made, they last for over 60 years, as most of the other butt-blocks in this boat have done.

I'm by no means anti-epoxy--we buy it by the 10 gallon pail--but there's a time and a place for it.

[Yeadon]

Was the fear that the epoxy wouldn't saturate both surfaces and bond, so that's why you went with the 5200? If everything was dry and warm, would epoxy have been preferred?

[James McMullen]

With the thicknesses of the wood under consideration and the fact that it was a repair to a thoroughly soaked, underwater portion of a large boat, a non-flexible adhesive like epoxy is less likely to stay truly stuck together than the traditional through-bolts and bedding approach. This is a part of the boat where a less than 100% sucess rate would be life threateningly unacceptable.

If you were building a small boat like a peapod, new, then epoxy would be an excellent choice for glue-scarphing your joints. For a 40' carvel-planked displacement sailboat, glued scarphs are more troublesome, expensive and time consuming to make than the tried and true butt-block method. Remember, this boat had a problem not due to the original construction method, but because of localised metal deterioration over the last 60 something years.

[Dan McCosh]

Below the waterline. . . .completely water-saturated 1 1/2" thick planks. . .repair done outside in the PNW winter. . . .No way just gluing with epoxy is the way to go here, amigo! This repair was done correctly. I would use an epoxy glued scarph on topside planks or on a trailerable boat without hesitating, but that's not the right solution for a heavily built, carvel 40-footer downstairs.

Backing blocks must be shaped and bedded properly, yes. Properly made, they last for over 60 years, as most of the other butt-blocks in this boat have done.

I'm by no means anti-epoxy--we buy it by the 10 gallon pail--but there's a time and a place for it.

A 10-1 scarf joint is considerably stronger than a traditional butt block--which acts mainly as a barrier to an open seam. Working in bad weather may be an issue, but a glued joint is basically stronger and less prone to leaking. The backing blocks certainly don't do any harm, but my experience is that butt blocks are a prime source of rot as the drain channels plug and they collect debris. The first scarfed plank I put in was about 25 years ago, well below the water line, and has been fine through drying out, freezing, etc. I've used the technique to replace butt blocks and to install new planks, with no sign of failure. This is in 5/4 planking stock.

[lincolns1st]

Very nioce! How long did it take?

[James McMullen]

What kind of boats, Dan? What kind of fasteners? If you're not backing up your glue-line with fasteners, this doesn't sound like correct standards and practices for the size boat we're talking about here. Certainly not for a boat that's going out and then back into the water in the same week like this one did.

[Dan McCosh]

I have to admit I missed the point about using 5200 as a caulk. I don't know anything about the capabilities of 5200 as a glue, let alone below the waterline.
I have done epoxy-glued scarfs in planking for decades, without backing blocks. The joints are reinforced by the fastenings in the adjacent ribs, however. The planking is 5/4 stock, with #14 silicon bronze screw fastenings. Old butt blocks have been a chronic problem, and eliminating them was one reason to use the scarfs to begin with. Fastening through the glue line isn't going to add much to a glue joint, as half the joint will be too thin to hold a fastening anyway. The 5200 probably will act like a glue, but I don't know too much about it. If weather is an issue, that's another matter--temperature canl affect the strength of many polymers as they cure. I don't do structural gluing below 50 degrees F. or so. I don't really see any problem with your technique structurally, only the issue with adding an unnecessary water trap.

[boattruck]

JM, I also have quite a few of these repairs out working well over the years on boats similar to yours( including my own), we use epoxy and a 12/1 scarf( 10/1 is minimum, 12/1 must be better?) we are able to get the stock dryed and glued in a week long haulout, if we cut our scarfs early and let em start drying (we use a router and a jig). I use temporary screws and blocks to get the feather edges down, cotton caulk the seams while the glue is still wet so you don't have a messy clean-up. Pull the blocks, plug the temporary screw holes, run in any fastenings you might need. Fair, prime and paint. I only say all of this, because most likely this pretty girl could likely need a few more of the same, if we are all lucky enough to live so long, Cheers, BT