DIY Miata Opera Coupe

Depending on how old you are, opera coupes reek of nostalgia or they just plain stink. Originally opera coupes were designed so that the rear-seat passengers could sit in the coach with their top hats on (presumably going to the opera). And so the canopies of these coupes were tall and elongated, and they put a tiny window in it so occupants could see out, but prying eyes couldn’t see in.

That’s how the story goes, and the styling endured for many years as the five-window coupe. Even into the ’50s the styling was classy, and despite the funky round porthole window, the Ford Thunderbird charmed.

Nice.

And then suddenly in the 1970s, American manufacturers embraced opera coupes en masse. To name names: Buick Riviera, Chevy Monte Carlo, Chrysler Cordoba and New Yorker, Dodge Charger, Ford Granada and Thunderbird, Mercury Cougar, and Plymouth Gran Fury, among many others (Wikipedia lists about 80 cars with opera windows).

Opera coupes.

The styling and details varied from different manufacturers, but they all shared an unmistakeable “she’s my sister and my daughter” resemblance. This collection of recessive genes resulted in cars with flat, elongated roofs covered wholly or partially in plush pleather-vinyl, even though they weren’t convertibles. Inset into the C-pillar of that fakery was a window too small to be useful, often with some kind of meaningless symbol.

Mercury Cougar typified the style. See more opera coupes here.

European manufacturers didn’t jump on the bandwagon, but you can see some of the influence in various cars from that era. By the 1980s, the nostalgia had worn off, and a more futuristic angular styling took over. Consumers were like deer stuck in front of headlights… as long as they were pop-up headlights. And the opera coupes died out.

No opera window, no pleather, but similar shape.

Against this obvious trend, and the fact that everyone else had stopped making opera coupes, the dubious team of Chrysler and Maserati brought back stupid and begat the T/C in 1986. They consummated this mistake atop the most soulless milquetoast chassis of any era, the Chrysler K-car. To be fair, the T/C was a convertible, so it wasn’t entirely a styling exercise.

Chrysler T/C by Maserati, with round port light and Maserati logo. You can read more in Worst Car Wednesday.

At the time, they probably argued who’s name would go first. 600 million dollars later, I’d wager both manufacturers would like to disassociate their names entirely. I wonder who was responsible for the spoiler?

The T/C was the last of the breed, and thankfully opera coupes haven’t made another comeback. But if you squint, you can kinda see the opera coupe shape in a C5 Z06 (ducking). If you put a tiny window in it (ducking and covering), it’s there.

Opera coupe hardtop, convertible, and fastback.

The C5 Z06 roof came about about because Chevrolet wanted something lighter and more rigid than the fastback, and so they made a fixed-roof coupe (FRC) version of the C5 using the convertible body. The C5 FRC Z06 then became their high performance model, and it’s equal to just about any sports car today. And while the opera coupe hard top has more drag than the slippery C5 fastback, the hardtop has less lift, and with a powerful car like this, reducing lift is more important than reducing drag.

To bring this back to Miatas, my friend Cameron built a custom hard top for his NA race car, and it shares some of the FRC genes. I rather like it, and it gave me some ideas.

Cameron’s Miata top is made from a Mustang roof, facing backwards.

Miata Opera Coupe?

I don’t race with NASA, but I find their rules intriguing. The ST/TT rules allow you to change the shape of a convertible top, as long as the top doesn’t extend past the forward edge of the trunk lid. Ergo a fastback convertible would not be legal in this series. However, there’s still plenty of room for improvement and rules bending.

The first thing I’d do is elongate the roof, using the shape of the aerodynamic template. I’d boat-tail the sides, but leave the top rather broad and flat at the trailing edge. Miatas have rounded rooflines and this creates lift and also makes air passing over the roof hit the wing at different angles along the entire length of the wing. A flatter wider trailing edge should feed the wing air at a more consistent angle, and with less turbulence.

The longer roofline would result in a nearly vertical rear window. It’s not intuitive, but the worst angle for a rear window is 30 degrees, and the Miata’s is about that. I’d recess the window to create a box cavity, because that should reduce drag as well.

Finally, just like my fastback, I’d make the B-pillar region narrower in the hips than a standard hard top. This would come with a compromise, because in the rain with the windows up, I’m sure a reverse eddy would suck water into the gap behind the window. But I consider damp shoulders a fair tradeoff for a canopy that’s less of a parachute.

As I put those design considerations from my head onto pencil and paper, a shape emerged. Oh shit, here I go bringing back stupid.

Construction

I’ve built several tops, and for all of them I’d say construction isn’t difficult, but it is time consuming. I can make a functional version in a weekend. To make one that also looks good takes fucking forever. It reminds me of something I heard on a boat building forum: “I’m 90% done with the sanding; I’m half way there.”

I started by using the front bow of the soft top frame, so that I can quickly attach it to any NA/NB Miata. I then took a piece of thin luaun plywood and cut slits in the back half of it, and then shoved this under the soft top frame.

Plywood with slits allows it to conform to shape.

Then I made some forms that would allow the plywood to take shape over the roof, and tacked everything in place with brads. I covered the slits underneath with blue tape, then filled the gaps with thickened epoxy.

Ready to fill the gaps with thickened epoxy.

With that done, the roof would hold its shape enough to sand down the high spots. I did that, then covered the entire roof with a layer of fiberglass cloth. I wasn’t originally going to fiberglass the inside, but then I decided I was going to make it bomber strong, and glassed it. So it’s essentially a surfboard construction, with a lightweight core and fiberglass all around.

I originally swept the sides of the top all the way to the rear of the trunk, as in the pictures above. However, after closely reading the NASA rules, I cut the sides shorter so that no part of the top was further rearward than the forward part of the trunk lid.

Design Elements

The roof is so strong that I started thinking about it as a stressed member, and it occurred to me that I could bolt the roof into the usual spots (windshield frame, behind the doors, and Frankebolts), but I could also attach it to the Hard Dog rollbar. I sourced some rollbar clamps online, put big T-nuts into the roof, and now the roof bolts down in eight locations. This should provide some rigidity to the chassis, and the reassurance that this top is not coming off unless God wills it.

For all of that strength, it’s about the same weight as an OEM top. A lot of the weight in an OEM top is the greenhouse, which provides amazing visibility. This one does not. The rear-view mirror gives a fairly unobstructed view straight back, but if I turn my head, it’s a big ole blind spot. I may have to fix this with, you guessed it, an opera window.

It could use an opera window to complete the look. Or landau bars?

In the end, I feel like I succeed on all counts, but she ain’t much of a looker. Part of that is it looks like an opera coupe! The other part is I suck. I like making aero, but I hate doing the final stages of bodywork. I have no patience for it. My body has decided it doesn’t either, and developed a sympathetic allergy to Bondo. I always wear a respirator, but if I sand Bondo without covering my skin, I break out in hives wherever it’s exposed.

That’s inconvenient, because at this point I’m 90% finished with this top, and I only have a little Bondo and sanding to do before I have it painted. But now I’m like, someone else please finish this for me!

Custom wing and opera coupe top, like peanut butter and jelly.

And then it occurred to me… you know what would be even easier than painting it? I wouldn’t even have to finish sanding! That’s right, vinyl. Cover it with fake leather, just like they did in the ’70s. Fuggin opera coupe.

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