FT86 as a 2-seat sports car

[ZDan]

Originally Posted by Tcoat

What Hawk said.
We are back to compromises. They of course could make it but it would either be heavier or considerably more expensive.

It would be lighter-weight, and should be *less* expensive to produce. Less material used, fewer parts. Of course they could probably charge *more* for it though!

[Dadhawk]

Originally Posted by Irace86.2.0

...Even the MR2 was a targa....

Was it? Mine wasn't, although it had a sunroof. I think the later models AW10 had t-tops, but not a full targa, as an option but you could get a coupe. The same was true of the AW11 I believe.

The AW30 is a different story of course.

[Irace86.2.0]

Originally Posted by Dadhawk

Was it? Mine wasn't, although it had a sunroof. I think the later models AW10 had t-tops, but not a full targa, as an option but you could get a coupe. The same was true of the AW11 I believe.

The AW30 is a different story of course.

Same difference.



Odd that the only car I can think of is a Cayman or Elise for a “modern” (last 20 years) sub-3000lb sports coupe. All the others have been classic sports cars aka roadsters. The closest thing has been hardtop convertibles. I guess this is historical too. Most coupes were bumped up to GT size.

[Ohio Enthusiast]

Originally Posted by Irace86.2.0

Elise... sports coupe.

An Elise is a targa, comes with a soft and a hard tops (and even a gull wing top!). An Evora is a little too porky for your sub-3000 criteria, but then again some Cayman variants/years are also heavier.

It does makes one wonder why sports cars are lumped with convertibles? A convertible is detrimental to a sports car (being less rigid), while plenty of convertible buyers don't care about sportiness.

[Dadhawk]

Originally Posted by Irace86.2.0

Same difference.

Not really because if you wanted it without it, you could order it that way. Not to mention the T-Top retains most (if not all) the rigidity provided by a roof panel.

[ZDan]

Originally Posted by Dadhawk

Not really because if you wanted it without it, you could order it that way. Not to mention the T-Top retains most (if not all) the rigidity provided by a roof panel.

I don't think this is true... You lose a *hugely* effective shear panel that weighs very little yet contributes a LOT to stiffness. T-tops will generally be both heavier and less stiff. It would be close to impossible to get the same stiffness contribution from the thin longitudinal stiffener going fore/aft, and would require significant stiffening of the windshield frame and aft "targa" hoop frame as well. T-tops are a great way to add cost, add weight, reduce stiffness and add potential leaks all at the same time!

[Dadhawk]

Originally Posted by ZDan

I don't think this is true... You lose a *hugely* effective shear panel that weighs very little yet contributes a LOT to stiffness.

I was thinking more of with the panels in, not with them out, but you are probably correct unless the car is designed around i, like say a C7/C8 Corvette.

[Cephas]

I'd still rock an 86 with a T-top though, because nostalgia...

[ZDan]

Originally Posted by Dadhawk

I was thinking more of with the panels in, not with them out, but you are probably correct unless the car is designed around i, like say a C7/C8 Corvette.

Unless they are literally bolted in place, the tops themselves aren't contributing anything significant to stiffness. And if they are bolted in place (C4 Corvette?) there's still a weight penalty as "hard points" are needed where the top(s) bolt in and it still requires much stiffer windshield frame and targa hoop structures. And unless these structures and the removable panel(s) themselves are made *massively* beefier, there'll still be an overall hit on stiffness.

C5 and C6 Z06 Corvettes were fixed-roof coupes and weighed 100 to 150 lb. less vs. non-Z06. They cared about weight on those! For C7 they decided adding a supercharger was more important than reducing weight, so the C7 Z06 kept the removable roof and gained ~300 lb. vs. the C6 Z06

Corvette is designed as a convertible with all the necessary rigidity built in. Not the most structurally efficient way... The 911 is apparently designed this way as well. The convertible is pretty stiff at ~15,000 N-m/degree, but the fixed-roof coupe version is 40,000 N-m/degree, more than twice as stiff! They claim 27 Hz natural frequency for the coupe, so convertible should be ~16.5 Hz. My "rule of thumb" was for body/chassis natural frequency to be at least 10x suspension frequency (which I think should be conservative), so they're not likely to offer a super-stiffly sprung track-oriented version of the convertible...

[ZDan]

Originally Posted by Cephas

I'd still rock an 86 with a T-top though, because nostalgia...

I would own an early-70s vintage C3 Corvette by now if not for the T-tops! They, annoy me... C3 gained a good 200-250 pounds over the C2 on the same basic chassis/suspension design. C3 was originally going to have a 1-piece removable roof but they lost so much stiffness they had to "invent" T-tops to get barely-acceptable stiffness by 1960s standards!

[Irace86.2.0]

Originally Posted by Ohio Enthusiast

An Elise is a targa, comes with a soft and a hard tops (and even a gull wing top!). An Evora is a little too porky for your sub-3000 criteria, but then again some Cayman variants/years are also heavier.

It does makes one wonder why sports cars are lumped with convertibles? A convertible is detrimental to a sports car (being less rigid), while plenty of convertible buyers don't care about sportiness.

I think it comes as a hardtop. The last gen MR2 was convertible. The one before I thought was primarily targa/t-top with some limited hardtops. Targas n t-tops are always heavier and have more chassis flex. I owned a MKIV hardtop and targa and the weight was less and stiffer with the dedicated coupe. Of course the chassis flex was terrible with the roof off, but even on it wasn’t the same.

I think it has to do with the classic/history definition of a sports car as a small, light, good handling, two seater roadster. Sports coupes or coupes were their hardtop counterparts. Not all convertibles are sporty cars. They make them for larger sedans and economy cars too, but it is definitely more common with small sporty cars. Seems like something that small is made to be a convertible because it’s claustrophobic to people...? I don’t get it.

[Irace86.2.0]

Originally Posted by Dadhawk

Not really because if you wanted it without it, you could order it that way. Not to mention the T-Top retains most (if not all) the rigidity provided by a roof panel.

See above. Maybe your experience is different, but the roof on targa isn’t great. Better with it on than off of course. That little bar in the T-tops is better than nothing, but still far from ideal.

[Ohio Enthusiast]

Originally Posted by Irace86.2.0

I think it [Elise] comes as a hardtop.

Probably thinking of the Exige (the more coupe track-aero version of the Elise)? It's still a targa, with the roof panel being more permanently attached (i.e. bolts requiring tools vs. snap brackets), but it's still not structural and can be removed (and actually can be interchanged with an Elise with some work). I'm deep into Lotus as a potential purchase in a year or two to supplement the BRZ.

[Irace86.2.0]

Originally Posted by Ohio Enthusiast

Probably thinking of the Exige (the more coupe track-aero version of the Elise)? It's still a targa, with the roof panel being more permanently attached (i.e. bolts requiring tools vs. snap brackets), but it's still not structural and can be removed (and actually can be interchanged with an Elise with some work). I'm deep into Lotus as a potential purchase in a year or two to supplement the BRZ.

Well if that is the case then we have the Cayman and old Porsches and kit cars and more expensive stuff. The landscape is that much more bare. Damn.