The Big Think

March 16, 2010

Clam

Filed under: Woodworking — jasony @ 9:19 am

I build props for Sing every year. Sometimes they’re fairly straightforward projects (I built a 4’x4’x4′ box a few years ago.. yawn). Sometimes, though, I’m asked to build something that I have no idea at first how I’m going to go about it. This was one of them. I was asked to make a giant functional clamshell that a person could hide inside.

The group gave me about four months of lead-time until I had to deliver it, and I spent three months just thinking about it and trying not to sweat at what I’d gotten myself into. How does a woodworker whos primary medium consists of mostly right-angled material create the compound organic curves of a clamshell? I had no idea, but after several dead ends I hit upon the idea of using fiberglass. I’d never used fiberglass before, but every year I decide which new “Maker Skill” I’m going to learn and this year just so happened to include “figure out fiberglass”. Happy coincidence.

Here are some pictures I took during construction. It was a very fun (though at times messy and smelly) process. It also gave me a very useful skill if I have to make curvy shapes in the future. Overall not nearly as difficult as I had feared.

First, I made a model in Sketchup and sized it to fit a person. It was just large enough to hold a person but not so big that it cost a fortune. Fiberglass is relatively expensive!

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Next I measured out the plan template from my Sketchup drawing.

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Once I got it all onto a single sheet of paper I transferred the measurements to the plywood and marked up the sheet.

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Drew the “rib lines” to connect the back to the lip

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Then I measured and made up the back spine.

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I then cut the whole thing out and tried the spine in place

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Cut out the hole (what I called the “toilet seat”) and glued on the spine.

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Next I cut out and glued on the ribs. This was a big pain as I had to reinforce each joint on both sides. It took hours! I don’t have a picture of measuring and cutting the ribs, but it was an adventure. I made one central “reference rib”, then made four successively smaller ribs for one side. I then copied and made mirror image ribs for the other side.

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When installing the ribs I had to notch out the back spine to fit them. This was a laborious process since most of the work had to be done with a chisel and hammer.

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Next, I covered it with stretched fleece and stapled it into place. This was the “aha!” step. Until now I hadn’t figured out how to make a 3d skeleton of an object into a smooth surface. The fleece trick was neat, easy, cheap, and fast (four good things!).

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Next I soaked the felt in fiberglass resin to harden it up. This took much more resin than I thought it would since the fleece was so porous. It basically soaked it in and I had to keep reapplying it. After it was dry I sanded the whole thing, then applied another coat of resin. While the resin was still wet I pushed fiberglass matt into it and covered with a third coat of resin. The blue lines you see below were reference lines for the fiberglass fabric. I had to fit the rectangular fiberglass cloth on to the curvy clam shape like a puzzle, and this arrangement gave me the best use of my available cloth.

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Next I traced the shell onto another piece of plywood and cut out the bottom part. I made up angled pieces of wood to hold the front of the bottom lip off of the base to give the singer a little more room inside. The base is on wheels so it can be wheeled on and offstage quickly.

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On to sanding! It was amazing how strong and light it was. The microscopic dust from the fiberglass is very bad news (can give you silicosis), so I had to be very well protected. I have several layers of shirts on to keep the glass fibers from getting to my skin. They’re horribly itchy if they do.

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Next, I sanded the resin again and then I applied two coats of Rage Gold body putty to smooth the whole thing out. Rage Gold is a little expensive (about $50/gallon) but TOTALLY worth it compared to cheaper brand putty. It goes on easily, dries fast, and sands like a dream. I’ll never go back. The cheap stuff is harder than rock and impossible to sand when dry. No comparison. When the Rage was dried I sanded it down, then reapplied it in spots where there were small holes or places that needed patching.

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This stuff really stinks. Literally.

Sanding, sanding, sanding. I sanded for hours.

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Next, I bought three hinges and measured them out for location, then screwed them into the base.

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Then I stapled some more fleece onto the bottom lip before attaching it onto the base.

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Gave the shell a coat of gray spray primer that I had lying around.

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And found a beautiful mermaid to model for me. 🙂

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No so beautiful mer-man.

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Watch out for him. He bites.

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All told it probably took me around 40 hours of work from start to finish, but I had a ton of fun. I definitely never thought I’d be able to build a clamshell of all things. It was a challenge, but I’m proud of how it looks! It’s given me the ability to build with fiberglass and given me a lot of confidence in making curvy shapes.

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