The Big Think

March 16, 2010


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!


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



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




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


Then I measured and made up the back spine.


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


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


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.




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.


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!).


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.


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.


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.


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.


This stuff really stinks. Literally.

Sanding, sanding, sanding. I sanded for hours.


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


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


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


And found a beautiful mermaid to model for me. 🙂


No so beautiful mer-man.


Watch out for him. He bites.


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.


  1. Remarkable!! Every Tri-Delt should read this post in its entirety.

    Comment by barrybrake — March 20, 2010 @ 2:58 am

  2. Thanks Barry! It was a really fun process, though at times I wasn’t sure if it was going to work. One of the most satisfying moments was getting the fleece on and thinking “yeah! It looks like a clam!”

    Comment by jasony — March 21, 2010 @ 6:46 am

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