Monday, April 06, 2009

First Day of Spring - Introductions

It's the beginning of the new quarter, but the project to which this blog is dedicated is already well underway. We began lofting the catboat, midway through last quarter, so we've been at it for about six weeks. We're making good progress, but most of the project is ahead of us.

There are primarily three of us working on the project, but we'll have a few guest appearances from time to time. By way of introduction, here's a shot of two thirds of our crew:

Tim is on the left, Jonas on the right, and my name is Martin. I'm not in the picture 'cause I'm the one taking it, but there'll be pictures of me to come. We are all students in the boatbuilding program at Seattle Central Community College's Wood Construction Center. Check out their website for information on the school. Now, on to the project at hand.

Our project is an 18' Fenwick Williams Catboat. This is the lines drawing from the building plans which shows the shape of the hull in all three dimensions. For anyone not familiar with boat plans, what you're looking at are the profile (top left), half-breadth (bottom left), and body plan (right) views of the boat. These drawings let you visualize what the finished hull will look like. And yes, she will be a beamy girl. The process of lofting is taking th
ese scaled down plans and drawing them out full size on the loft floor. This allows you to create patterns and ensure that the boat you build will be just as fair as the one the designer envisioned.

Here's another page from the building plans that lets you imagine what this little catboat will look like when she's plying the waters around the San Juan Islands:

Once the loft was complete, we started in on the patterns. All the pieces that will eventually come together on the building jig to form the structure of the boat are first patterned right off the loft floor including the sawn frames, stem, keel, stern post, deadwood, floor timbers, etc. By patterning the pieces off the loft which has already been proven fair, the lines of the boat in construction will also be fair. That's the theory at least.

The first pieces we patterned were the sawn frames. The sawn frames are spaced every two feet for the length of the boat and it is to these that the planks will be fastened. Oftentimes molds will be patterned off the loft, the planks fastened to these, and the frames steamed and bent in afterward
. In this case, the sawn frames take the place of the molds and rather than being discarded when the boat is removed from the building jig, they will remain part of the boat. Once the shape of the hull has been established by the planking, steamed frames will be installed between the sawn ones to supplement them and give the hull added strength.

Here's a look at the making of a sawn frame:

While there are many ways to spile (make a pattern) this is the way we found to be the most effective. First, we tacked a batten along the line that we wanted to pattern. In the photo above we're looking at the outside edge of the hull at station 14.

Next, we scribe the line onto our patterning stock using a scribing block. Note that the scribe block has two "fingers" separated by a gap that allows it to straddle the pattern stock which is rough cut to the shape desired but necessarily left proud. Also note that the finger on top is longer than the bottom one. This is because the lofted lines are drawn to the outside of the planking. This isn't always the case and depends on the designers preference. Since the pattern we're making is for the sawn frame which is at the inside of the planking, the longer finger compensates for the thickness of the planking, in our case, 3/4".

Once the frames were patterned, it was on to production. Since the shape of the frames is sawn into them it isn't feasible to cut frames out of a single piece of wood. The piece required would have to have an extraordinary natural bend to match the shape of our little catboat, so rather than scour the forests of South America for the perfect piece of purple heart, we opted to just make two part frames and join them together. As with everything in boatbuilding, there are many ways of joining these frame parts. The way we chose was the one described on the plans, which is to join the two pieces with a gusset on either side. Here we see Tim fitting just such a gusset, for station 12 I believe.

And it's not just the frames that we're making patterns for. All the parts that will eventually be assembled on the building jig are first patterned off the loft. Here's a shot of me patterning the keel timber using the scribe back method:

And the completed keel pattern in all it's glory. Note all the assembled frames in the upper right. While at times it seemed like progress was slow, the pile of parts was growing steadily.

With all the frames assembled, it was time to fasten them together. Since the two frames pairs don't actually touch each other, they are held together at their base by the floor timber. The floor timber also holds the frame to the keel. In the photo below of station 6, you can see that the floor timber (with the blue tape labels) is also notched to fit over the keel. You also see the cross spawl, which at this point is helping hold the whole thing together, but will also help line everything up when it comes time to put it all together on the building jig.

Since each frame pair has a cross spale at the same height, it is easy to make sure the frames are all level. And with the aid of a centerline drawn on each of the spawls lining them up is fairly straight forward.I have to say that a great deal of time was spent making sure that each station (frame pair) was symmetrical, and that the spawls were level and at a uniform height, but the thoroughness will no doubt pay off when we get to assembly.

By the end of the quarter we had all our frames completed. Here are the forward frames:

And the after ones:

If you look back at the lines drawing at the beginning of this posting, I hope you find more than a passing resemblance between these stations and the ones drawn in the body plan.

Before the end of the quarter, we also finished patterning, cutting out, and fitting all the pieces of the "backbone" (i.e. stem, stem knee, keel, deadwood, stern post). Here we see Jonas fitting the stem to the keel. Like the frames, these parts are fit right on the loft. This helps make sure everything ends up just the way Mr. Fenwick Williams intended. If you look closely you can also see the knee that will connect the stem and the keel drawn in the loft.

And here are the pieces of the stern fit and ready for assembly. The aft face of the stern post is notch to hold the transom when everything is assembled. Funny, we didn't get any pictures of the transom, but rest assured we've got that ready to go on the building jig too.

And with that we're pretty much up to date. Let spring begin.

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