Making the inner clamshell support

Last I checked-in I was contemplating gauges and getting ready to pull the transaxle and bring it to my transmission guy for a 3.44 R&P and a new 4th gear. Did that. Sent the 914 gauges to North Hollywood Speedometer for an estimate. Haven’t heard back yet, other than to acknowledge receipt. Fingers crossed it won’t be two grand…

clam detail1 0090

With the transaxle out I moved in to smooth the inside of the rear clam. This car was hand-laid and the glass looks mostly pretty good, but I want to paint the inside of the panels body color and I want them smooth, not a weave pattern. So, as with the front hood, I cleaned it with acetone, roughed with 80 grit, acetone again (glass wicks up a lot of wax that you don’t want to try to glass over), then Fibral. I skimmed it twice then moved on to their “Gripped” filler.


The contours make it hard to work with the palm sander so I had to do it mostly by hand. I made a few passes and got it down to 120 before I drew the line.IMG_9032.JPG

From my extensive research of “pictures on the internet,” that line is about the right spot for the edge of the inner clam support to end.

The inner clam support is that swiss cheesy thing pictured up top of this post. It was apparently there to stiffen the thin aluminum of the clamshell, which was put under some force at speed. Cool as fuck. And a detail that I have never seen replicated on a fiberglass Spyder.

I figured it was about time.

First I did the obvious thing: I folded in a cardboard template in order to get some idea of the shape and size of the material I’d need.

Next, using the cardboard as a template, I built a simple flanging press out of some plywood and lag bolts I had lying around the shop.

Then I unrolled a few feet of the aluminum flashing I bought to cover some of the fiberglass bits. I knew it would be too thin to make the actual part, but I wanted to test the press to see how the material behaved in it.IMG_9066.JPG



Just about as expected…

With the first test piece made in aluminum I could begin to contemplate attachment points, ways to bond the pieces together (could I braze? Maybe rivets and filler? What about epoxy?).IMG_9068.JPG

I could also better compare what I had to what i was shooting for.rear clam detail 3 0090.jpg

And I could use the piece to develop an effective home alloy swiss-cheeseifier.


This first attempt did not have the requisite flange. The solution? Drill a bigger hole in a piece of wood….IMG_9144.JPG

…and use a croquet ball…

IMG_9145.JPG…to force the metal partway through it.IMG_9146.JPG

Next (i.e., today) I moved up to some 22-or-so gauge aluminum sheet. This is the stuff you can get at Home Depot to make ductwork and stuff. It’s about twice as thick as the flashing.


Here’s the piece with the test flashing on top.



Marked it for holes before pressing, then:IMG_9155.JPG

Ugly! But it’s not that bad, really, because we cut off the part where it’s really wrinkly.

Now for the holes.


I decided to flange them to the inside, instead of out, in the interest of public safety. Those edges will be pretty sharp even after they’re wire-brushed down later, and anyway, I’ve seen both innies and outies among the Spyder pics.


Coming right along. Now for the side pieces:



A few more holes, for lightness…


IMG_9167.JPGAnd we’re getting pretty close to a viable piece.IMG_9168.JPG

I’m going to cover the inner fenders with flashing, add a couple holes there, and probably rivet all this together to make some final fits, before bonding a couple of tabs to the inside of the clam to rivet this whole thing to, and making a support piece to hold the (eventual) articulating prop rod.

I’m pretty happy with the progress I made today in the six hours or so I spent on it.


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