A Shipwright in Training

That’s a Bruce Cockburn line by the way. Lately it’s been ringing true as I spent the better part of a day refining the garboard clamping system. I had previously made swinging blocks that clamped the plank in, and they worked fine for holding the plank on the boat while it cooled.

However, these couldn’t really exert much force against the plank, and it became apparent pretty quick that I needed something more sturdy to really hold the plank solidily against the frames while I was fastening.

I like the idea of having something that swings down over the face of the plank. You can swing it out of the way when you’re putting the plank on, and you can also insert wedges between it and the plank to exert some good force on the plank.

So, solution #2 was to put in an angled block below the garboard and attach a longer stick to the bolt that the previous swing arm was attached to.

The stick would have a cut out on the end to go over the block and lock into the angle.  The idea was that the angle would lock the stick in and keep it from pulling away from the plank. It was a good idea, but the angle was exactly the angle that the stick swung out from the boat. It would have locked in just fine if the stick was being pulled up, but it would have simply slid away from the block if there was any force pushing the stick away from the plank.  Hmmm. 

Attempt #3 was a modified block with an angle and shelf cut into it that would lock the stick in place and keep it from being pulled out.

Fan Cee!  The problem was that this solution required an elaborate cut in the end of the stick to fit the block.

To make matters worse, this thing is extremely weak. That would have snapped along the short grain the first time I put any pressure on it at all.

Ok, Attempt #4. This time I cut out some scrap metal to make a little tab that will slip over a screw head. I’ve seen picture hanging systems like this.

So, bolt it onto the end of a stick, and make a cut out to accept the screw head.

The cut out is right here…

Put a screw extending out from one of the old angled blocks, and the arm swings over it and engages the head positively.

Now I’ve got an arm extending over the plank that’s fastened securely on both ends and that can easily swing out of the way if I need to remove the plank.

This allows me to put wedges between the arm and the plank to hold it tightly in place.

And that worked well. Phew. When it comes time to remove the wedges, just tap the bottom of the arm to the left and it’ll slide off of the screw head, releasing the wedges.  You can also see a couple of blocks with wedges along the top edge of the plank.  Those are there to help add some force downward on the plank… it needed some edge setting.

Where the angle is right, I can forego all this fancy stuff and simply wedge in a cedar post to hold the plank in place.

Now, you could also simply screw an arm onto 2 blocks above and below the plank to get the exact same result, but you wouldn’t have the convenience of swinging it out of the way when you’re putting the plank in. If you were working with another person, and didn’t have to take the plank off and on to fine tune the fit, that simpler solution might be the best way to go. Now I’ve got the little tabs all made up and can use them on a longer arm for clamping the first broad.

Trial and error. Now I know at least 2 approaches that I’ll never have to waste time on again.

You see all the blue tape along the edges of the plank in the photos above?  That’s how I make note of things to pay attention to when I fasten the plank.

In this case, I’ve marked out lines to indicate the frame and floor edges, the location of a metal strap that has to be drilled through before fastening the plank, the location of a transverse bolt that I don’t want to hit with a fastener, and a reminder that the bottom edge of the floor is 2″ above the rabbet. I’ll then pencil all this info onto the plank once it’s clamped in place and use it to lay out my screw pattern.

Good layout on the front end prevents many angry tool tossings.

But, wait I’ve gotten a little ahead of myself here.  What’s that I was saying about proper prep?  Here’s the plank all nicely attached, but what about prepping the rabbet before installing the plank?

Oh, yeah, guess I should do that.  Dang beginner mistake.

Unscrew everything, take the plank off and get everything prepped correctly.

We want to put bedding compound along the back rabbet and roofing tar on the frame ends.  Why?

Let’s start with the frame ends.  The ends have exposed end grain, meaning that water just loves to wick up into the frames from this point, so you have to seal them very well.  One way to do that is to bed them in roofing tar. Another way is to soak them in pentachlorophenol regularly, and that’s how the previous owners kept these frames in such nice condition.  We’re not going that route, and we’re not going to take the frames out of their sockets to get the tar deep in there, so we compromised by injecting tar into any tiny gaps we could find around the frame ends and otherwise slathering them with goo.

We put bedding compound along the back rabbet to protect the plank and rabbet from water infiltration from the INSIDE of the boat.  Yes indeed, condensation rolling down the inner planking faces collects in the bilge and that’s very bad for wood.  Why?

Because condensation is fresh water.  Mold likes fresh water.  Salt water is a natural preservative (think pickles), so it’s nowhere near the problem that fresh water is.  It used to be common practice in big ships to shovel salt into the bilges for this exact reason.

But, before doing all this sealing, we should paint the back rabbet and frame faces with red oxide primer.  Why?

We’re going to put bedding compound along the back rabbet and bedding compound is oil-based.  If we didn’t seal the wood first, the oil from the compound would absorb into the wood, leaving only the dry components of the compound in the joint.  Chalky residue does not a good seal make.  And Yoda, talking in phrases oddly, does not good grammer make.  We use the red oxide primer because we’re not allowed to use red lead.  We paint the frame faces, even though we don’t bed them, because it’s always a good idea to seal up wood surfaces now that we won’t ever be able to reach again.

Ok, NOW can we put the plank on?  Yes, yes we can.

Here’s the forward garboard installed.  I got the aft section installed yesterday but for some reason didn’t take a photo.  Just as well.  A photo of a plank installed on a boat tends to be exciting only to the person who put it there!

Next up, do it all over again with the plank above it, the first broad.  I’m thinking it’ll go much much faster.

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This entry was posted on Sunday, March 2nd, 2008 at 11:03 am and is filed under Classes. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.