And on we go.
OK, now I hate school.
Kidding, I still love school.
This last week we’ve been very productive despite going right up to the edge of screwing up and then recovering. Whew. 2 brains are much better than one. Of course, we’ve still made a few screw-ups, but they were relatively minor and easily fixed.
The word for the day: stopwater. A stopwater is a little pine dowel that we make ourselves and it goes in a joint that could potentially allow water to enter the boat. When it gets wet, it swells and forms a barrier to creeping water. We’re contemplating making a few stopwaters out of sodium. When the water hits them, they react with explosive force. We’d have to call them Gowaters. Of course, they’d sink the boat in an instant, but boy would it be exciting on launch day.
Here’s a stopwater.
Above, you’re looking at the stopwater that bridges the stem (mahogany, orange wood) and keel. You can see that it spans this joint. The pencil line above the stopwater marks the rabbet… this is where the top of the planks will rest when they join to the stem. When it’s finished, the stopwater will be cut flush with the rabbet and planking will hide it. However, if water ever creeps in along the joint, it’ll be stopped by the … stopwater.
Here’s another one, this time at the aft end of the boat.
See? Joints get stopwaters.
You may have been wondering what the heck the rabbet really does. Well, here’s the new stem with it’s new cool rabbet, and the old planking resting up against the stem. See how the planks curve into the rabbet? There you go.
We’ve attached the centerboard trunk to the keel now. It’s a little odd, between the trunk and the keel is a folded length of canvas that we soak in red oxide primer paint. It acts as a flexible gasket to keep water out of this huge long joint that could cause you all manner of problems if it leaked. I’m sure if we sealed it with 5200 (a boatbuilding sealer that stays flexible and holds like grim death) it would work perfectly well, but that wouldn’t be the Beetle Way. The Traditional Way. After all, this is a restoration.
Here you go, a trunk, stem, and keel all connected together. An almost complete backbone.
Here’s a closeup of that canvas gasket.
Have no fear, we trim all the excess so it’s all nice and tidy.
You can see the plugs that cover up the holes where the screws go in. We’ve since trimmed these plugs flush. The plugs are called bungs. The holes are called bung holes. Now you know where that term came from. Don’t you feel smarter? I certainly do.
Lookey lookey, we’ve got our transom temporarily set up at the back of the boat. We’re just moving along nicely here.
Once it’s attached, we’ll have a backbone. Until then, we’ve got a notochord at best.
October 26th, 2006 at 9:11 pm
Nice explanation of where you are in the process - and pictures are worth a thousand words.
But, a stopwater still seems strange to me. Why not just fill the joints with gunk instead - tar maybe? ;o) Are stopwaters more of a guide for fitting the planking pieces together? How many stopwaters does a boat usually contain, and does it depend on how many joints are below water? Then again, I do remember you taking off the tip of your kayak and rejoining it as part of the finishing process, so I suppose anything makes sense. ;o)
October 27th, 2006 at 7:29 am
Ah - 3M 5200 - the stuff everyone needs around the house, but doesn’t realize it until they hang around boats for awhile.
Agreed on the stopwater - seems, well, strange - like a sacrificial sponge for water that is hidden and therefore difficult to replace once the boat is put together. Is the point that the durability of the pine over time is better than any other classic material that would dry out and become brittle? Why not just fill the void with epoxy?
Or is it that the boat is dynamic in and out of water so whatever you put in there has to be fairly flexible over time? (i.e. the slight swelling of the wood moves things a fair amount over time)?
October 27th, 2006 at 6:22 pm
It’s a good question. Bedding compound (in the old days, tar or something like it) is slathered on the faying surfaces (the surfaces where 2 pieces of wood meet and are joined together) and its job is to maintain a flexible, watertight barrier. The problem is that over time, the wood does move a lot and bedding compounds get dry. It’s like having a rubber gasket to stop water, at some point, the rubber drys out, gets brittle, and stops acting as a sealant. So, what do you do? You let the very properties of wood that cause the problem, solve the problem. Wood swells and shrinks, particularly white oak (the stuff the keel’s made of). Pine does too, even more so. John had it right in that it acts spongy (soaks up water) and then it swells and seals up the joint. The wet-dry cycle of boats tends to not become a problem for a stopwater, as the stopwater does just what every other bit of wood in the boat does: it moves. For 3M’s 5200 and most other bedding compounds, that cycle eventually breaks the material down. You don’t use epoxy because the glue is stronger than the wood, so the wood movement leads to the eventual failure of the wood itself. For the stopwater, the only problem is the eventual rot of the woods involved as long as the stopwater is placed correctly.
It’s true, the stopwater is a pain to replace. It’s hidden just beneath the planking, so to replace it you have to remove a plank, which is a rather big deal.
A wooden boat needs a number of stopwaters. To figure how how many it needs, you look at how many joints connect the inside of the boat to the outside of the boat beneath the water line, or any place where there’s a lot of wate. This could be on deck then as well. Our boat uses 4, as there are joints at the stem/keel, centerboard trunk posts (2), and sternpost/keel.
It may be that modern adhesives and other nifty materials like 5200 will eventually make stopwaters obsolete. I don’t think many builders would really be sad to see them go. They’re tricky to fit and a pain to replace. Of course, replacing boards stuck together with 5200 is No Fun either.
October 30th, 2006 at 3:46 pm
I know the word of the day was supposed to be stopwater, but I’m pretty sure the one I will remember 50 years from now is bung hole.