Tub Aluminum, Part 1

With the frunk area well in hand I turned my attention to the cockpit. These Beck-design (and the Vintage Spyder variant) replicas are a bit more than three and a half inches longer than the real deal, and most of the extra real estate is in the body tub, mainly to accommodate taller drivers. Making the cockpit look authentic is a challenge just because of the added length. The curve of the inside rocker panels is another giveaway: the original cars had a crease between two straight panels.

So I kinda sorta made my own:


Covering the interior with aluminum is a matter of pride. Most of the inside is going to be painted body color anyway, and the glass was already smooth, so some of this exercise was kind of pointless. I realized later.

The original plan was to remove the floor, wrap it in metal, and replace, but after I got most of the rivets out I realized it was never going to come out without a lot more work, because it’s bonded to the frame tubes with what looks like Liquid Nails Mondo Strength.

That stuff melts with a heat gun, and you can then slice through it with music wire, and I pondered doing that for a day or two. Then I wondered: where am I going to stand while slicing the floor off the car? It’d be a bit like cutting off the branch you’re sitting on. The only way would be to work from underneath with a blade. I finally decided just to cut the alloy panels snug to the tubes and glue them in (mostly) with the same stuff Thunder Ranch used. To begin then…IMG_9833


The under-dash sections of the floor are simple, made of flashing, sanded on one side with 80 grit, cleaned with acetone and glued-in with construction adhesive which I raked with a fine-toothed trowel to get flat consistency. When the panels were laid down over the glue I rolled them hard with a trim paint roller. These slide under the center steel plate and the tubes to hide the edges, and they will be left unpainted, but covered by a “floating floor” made of wood. Remove the floating floor and you’ll see the raw aluminum.

Next I moved to the rocker boxes. These are complicated by the (incorrect) curve molded into the replica tub, and by the extra length of the tub. I worked-out the holes and spacing to be as close as possible to the originals while accommodating the additional three inches or so. As always, exactingly blueprinted:


Transferred carefully to the tub, and…IMG_9844

…Oh shit…that ain’t right:

OK, that’s better:IMG_9848

Now to make our flange press/buck:IMG_9849IMG_9850IMG_9851

And cut the holes in the car…


Here’s the look we’re going for (this is from a Spyder Factory replica of 0090):

tub side ovals.JPG

Obviously not gonna get that flange just right with our primitive wood buck-and-plug method. But most people never notice that double lip flange. Also: this whole section is normally hidden under upholstery anyway.

Next we make the body holes just a little bigger than the ones we plan for the metal.



Now for the fun! This is 20 gauge or so. IMG_9859.JPG



Confession: I wish I’d cut these holes smaller to make a deeper flange. The 3 1/2-inch hole saw would have been about right.



Chocolate pretzels for holiday giving:


And back to work. These floor bits could have been skipped: the area will be painted and then covered by upholstery; the thin aluminum is just kind of a thing that will get dinged-up meantime. But, I’m married to the bit: everything aluminum! All aluminum!


Now for the wheel wells. These are hard because they’re big, and the curve is long, and of course everything is under the dash, where you can’t really reach without folding yourself into a fetal position. I worked it out with butcher paper and transferred to the flashing.


Then cut the under-seat bits out of the 20-gauge.


There’s a point to this one. Some have complained about the perceived strength of the fiberglass floors in these cars, and some guys just bolt the seat directly to the floor, both for simplicity and to save height (tall people tend to be looking at the top of the windshield if the seat is up off the floor much).

So this relatively thick alloy will be epoxyied to the ‘glass to make more of a composite structure and add a bit of strength. It’s almost moot, as I plan to weld low C-channel steel rails across and mount the seat adjusters to those (seat bottoms should end up no more than  two inches off the floor), but if the next owner is over 6-2 he or she might have to cut those steel reinforcements out, and then they’ll appreciate the extra floor strength.

Also: this won’t be painted, so: ALLOY!

Moving on then, we haveIMG_9871.JPG

More CAD. Remember, the rocker boxes originally extended to the fender wells to add strength to the tub and body. The absence of the boxes in front of the tub bulkhead is a dead-givaway the car is a replica. So.IMG_9872.JPG

This time I went with the smaller hole saw and got a much better flange, which is good since this hole will be exposed out in the open for anyone to see.IMG_9874.JPG

A little bending.


A little trimming. Some more trimming. A bit more bending. Additional trimming, andIMG_9877.JPG

Sort-of fits!

Tried next to get the insides of the doors done with a single sheet, right-angled to the door floor. Turns out that was a mistake.



Again, these’ll be unpainted, but covered with upholstery. But I plan to put the upholstery panels in with velcro, so this wrinkled bit will be taken out and re-done.

Of course, we can’t forget to put alloy behind the rocker box holes!


And the driver’s side box. This one gets no oval hole because the fuel pumps will be mounted on it.


Dry fit again. Looks like it’ll basically work out.


“Blueprints?” “Brownprints?”


Sheet metal bits, cut and ready to bond.


Now for the firewall. There’s a caveat here: replica firewalls are usually very simplified versions of the originals. You can actually buy a “correctly shaped” fiberglass firewall and glass it in, but once that’s done, it’s almost impossible to line it convincingly with sheet aluminum. Too many compound curves. So this car will get an aluminized firewall with rivets, which will look cool as shit, even if the Porsche specialist concourse judge will be able to spot it.

Butcher paper-aided design.



Now for the adhesives.


Saving a few rivets by folding the top of the rocker box over the weatherstripping lip.


I left the front few inches up to give something to attach the little curvy piece that later cars had near the front of the door. Bent up a test piece from the thin stuff.


I can always fold it over or cut it off later….

Next, marking the rocker panels for rivets. Pretty much using all the ones I saved on the top, on the bottom.


Laid up the inside firewall with adhesive.


By the way: all of this takes way more time than I thought. Hours and hours of snipping, bending, reaching, cutting, sanding, riveting, drilling. I mean, I’m jazzed for it, don’t get me wrong. But there’s a real disconnect between what one envisions the procedure feeling like and how one actually feels after doing it. Advil helps.

Here’s the edge of the rocker box glued up.




The back of the firewall was set with JB Weld, mainly for heat tolerance. To finish the edges of the firewall, I cut small strips of aluminum and formed each one into the curves, then glued them in and riveted.



They match side to side, and most of the rivets go through front to back. IMG_9927.JPG

I have some quarter-inch solid round head rivets to finish off the top of the firewall with some drama, but the ones I bought, at 3/8 of an inch, are too shallow to reach through.

I ordered some 3/4-inch ones from McMaster-Carr, and will make a dolly to shape them in with the hammer. I think it will clean up nice, but I guess we’ll see.





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