A Shipwright in Training

When I go to work, I go to work on hounds. Looking back at my first post about this back on Jan 27, I realize I’ve been working on these puppies a lot. I’ll get photos soon, but right now suffice it to say that I’m getting used to making hounds. 2 1/2 hounds are now complete, but I’m moving much faster than before. That feels good. Jim says that he expects hounds to take about 4-5 hours each, and it’ll take some time before I’m at that level. However, today I finished one off in about 6 hours!

Back at school the folks with the thin planks have generally put their shoulders to the wheel and are working along to get the boats ready to flip next week. While I was waiting for Kev to finish fairing his side of the boat, I built a little cradle that we’ll use to hold our boat when it’s flipped over.

When Kev finished fairing his side, we proceeded to scribe the waterline.

Now, doing the waterline is a pretty cool little process. There are low tech and high tech ways to do it, and naturally we’re going low tech. What’s the waterline? It’s a line that’s scribed onto the hull of your boat that describes the level that the water reaches on your hull when you’re afloat. If you dropped your nice white boat into a pond of ink, the waterline would be the top edge of the inked surface when you finally pulled your boat from that toxic dump. That’d teach ya to try to sail in ink ya scurvy lubber.

So, here’s the basic idea: you want to paint the part of your boat that sits below the water most of the time with bottom paint to minimize problems with little boring worms (insert your own joke here) and other marine pests. So, apart from sitting your finished boat in a very very calm pond and then carefully swimming up and making little marks where the water hits your boat, you’ve got to figure out where to draw your waterline. Luckily, the designers of most boats have already figured that out so you almost always have a place to start. On the Beetle cat, the waterline has one easily identified point: the place where the skeg goes into the hull. In the photo, the skeg is painted red. That back corner where the skeg dives into the hull? That’s where the water reaches too.

Really, when you think about it, the waterline is just a horizontal plane that cuts through the boat. To scribe a waterline you need a way of drawing a perfectly horizontal line across the curved surface of your hull. Boat builders are a clever lot, and a long time ago they figured out how to do just that.

You start by setting up two perfectly straight boards, one in front of the boat, one behind. You set them up so that the tops of these boards are level, and exactly the same height as your waterline. Easy, yes? No? Ok.

Get yourself a long length of clear plastic tubing. Put some water in it. Hold one end of the tube up to your boat right at a known waterline location (like that skeg / hull intersection). Now, you remember from school or real life experience that water seeks its own level. So, if you were to take the other end of the tube and lift it up, at some point the water at the boat end would come up to the level of the waterline. And, amazingly, the water in the section of tubing you’re lifting up would now be exactly at the level of the waterline. Hold that end of the hose up to your horizontal boards and raise them until they are exactly at the level of the water in your tube. Do that with each end of each board, and voila! You have now set up 2 boards that are exactly the same height as your waterline, and they’re level to boot.

That photo above shows our cool, low tech rig for mapping out the waterline. You can see the aft board (actually it looks like a bridge span) clamped to 2 vertical posts. You see the orange strings stretched out there in the foreground? We strung 2 strings on each side of the boat. One is right next to the boat, and the other is a foot or 2 away.

Are you figuring out what’s going to happen? Good for you! Gold star!

Since we know that these strings are right in the plane of the waterline, we can sight across 2 of them and see the points on the hull where the waterline intersects. Like this:

You can see both strings on this side of the boat. Now, we squat down until the 2 strings line up…

and there’s where you draw your waterline. Kev got on top of the boat with a pencil while I sighted along the strings and I directed him to make little marks on the hull.

After that, it was easy to make a thin batten, and nail it down along the hull so that it touched all the points we’d just marked. It looked like this from above:

After that, you take a saw and cut a shallow (1/16th inch deep) kerf into your hull along that batten. That kerf will make it easier to paint a crisp line. It will also make it easier for future painters and boat repair folks to know the exact location of your waterline.

Oh my god, did I say we nailed the batten down to the hull!! Yes, yes I did. Little nails. Shallowly driven. In fact, on my side, the batten kept snapping at the sharp curve at the aft end, so I battened 3 times! “But what about the holes?” you say. Well, think about what a little nail does: it pushes the wood fibers aside, like a drunk wedging into the beer line at a cocktail party, or an arrow shot into a straw bale. When the wood gets wet, it’ll swell closed again since no fibers were cut or drilled out. We can hasten that along with…

Steam.

It doesn’t completely close the holes, but it helps.

They don’t‘ go all the way through the hull anyway, and they’ll also be filled with paint.
I mentioned a low tech and high tech way to get the waterline before… the high tech way is to have a laser level set up to flash a level line across the boat. You then make pencil tic marks at that line just like we did by lining up the strings. The problems with this method are a) most places don’t have a laser level so you’d better have a back up plan, and b) the laser line tends to spread out across the surface of the hull if it’s hitting an area that’s close to horizontal. That makes it hard to choose where to put your pencil mark.

After the waterline was cut, I was finally able to putty my seams while Kev began to caulk his side. You use 2 different types of seam compound: one for above the waterline, and one below. The below type is red and tends to bleed through any paint you put over it, so it’s best to have red bottom paint below the waterline. The above waterline type is white and doesn’t bleed so much. We keep ours just a bit back from the waterline to minimize any chance it’ll bleed into the light hull paint.

I should have that finished by Monday. When Kev’s done, we’ll put on the first coats of primer (red below the waterline, white above) and it’ll really begin to look like a boat. In the meantime, this is where she stands to far.

This entry was posted on Saturday, March 10th, 2007 at 10:58 pm 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.