FT86 as a 2-seat sports car

[Dadhawk]

Originally Posted by Irace86.2.0

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.

I am not an engineer so I could be completely off base, I admit that. But, if you look at the structure of the 86, is is not the middle bar that's an issue but having to cut the frame at the windows that would weaken it. The middle roof frame could stay the same with t-tops, obviously not with a Targa.

In fact you could probably strengthen the middle bar a bit in a t-top design.

There was a lot of talk early on that the 86 was originally designed to be a convertible (as an option) and of course Subaru/Toyota even had a prototype running around for a while. Supposedly the thresholds and some of the crosspieces are "heavier than the need to be" for a coupe, whatever that means.

Since I don't track my car, and couldn't give a flip about 100lbs here or there, I should probably just shut up. I would absolutely love a Targa version of the car, but no chance of that happening (at least from the factory!)

[Irace86.2.0]

Originally Posted by Dadhawk

I am not an engineer so I could be completely off base, I admit that. But, if you look at the structure of the 86, is is not the middle bar that's an issue but having to cut the frame at the windows that would weaken it. The middle roof frame could stay the same with t-tops, obviously not with a Targa.

In fact you could probably strengthen the middle bar a bit in a t-top design.

There was a lot of talk early on that the 86 was originally designed to be a convertible (as an option) and of course Subaru/Toyota even had a prototype running around for a while. Supposedly the thresholds and some of the crosspieces are "heavier than the need to be" for a coupe, whatever that means.

Since I don't track my car, and couldn't give a flip about 100lbs here or there, I should probably just shut up. I would absolutely love a Targa version of the car, but no chance of that happening (at least from the factory!)

I’m not entirely sure if you are now agreeing with me that a targa and t-tops are virtually identical in structural integrity. Obviously the T-tops are slightly better, but they aren’t really designed for chassis loading and would buckle if it wasn’t for secondary reinforcements. Regardless, these types of chassis compromises and luxury items add weight and are not for me. I just want a plain coupe, so it is strong and light, and it is too bad most coupes integrate targas or t-tops into the design. The C8 for instance is a targa or a hardtop convertible. There is no dedicated coupe option. The 300ZX only offered the slick-top in the base NA model; all turbo models had the targa or convertible. It is a GT car, but check the history, and it seems odd that few sporty cars were dedicated to being a bare coupe, and all the modern sports cars in the last 20 years have been compromised by being a convertible or being a targa/t-top. Unless the car has a carbon fiber monocoque, I don’t want a heavier, leaky targa or puny cross-bar. Just give me a sports coupe and take my money.

[ZDan]

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.

Originally Posted by Irace86.2.0

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.

Ah, Lotus... Elise/Exige is plenty stiff for its weight. It has a novel frame design of bonded aluminum, with two deep large cross-section closed rectangular beams running along either side of the cockpit. Which doesn't help with ingress/egress! Also the frame design makes it all but impossible to repair if damaged. Still it's pretty cool to a structures guy like me.

Quick search says 10,000 N-m/deg for Elise, 10,500 for Exige. Stiffer for its weight than a current C8 Corvette or 992 convertible. Considering the Elise originally came out in 1997 with that frame design, that is saying something that it is *still* up there with serious modern machinery as far as stiffness/weight. I mean, a '97 Corvette was *less* stiff than the Elise at 9100 N-m/deg, despite weighing more than 50% more! 993 coupe was 13,900 according to one source. A much later 997 Targa was reportedly 11,000, pretty much no stiffer than the WAY lighter-weight Elise of the same era. I'm sure a 993 convertible or targa are *really* low...

For sure, for most "normal" cars with normal door openings and repairable structures, a targa roof is either gonna lose a buncha stiffness or add a buncha weight, or both. Elise/Exige did it right, but again there are drawbacks that most people who buy Corvettes or 911s wouldn't want to live with!

[ZDan]

Originally Posted by Dadhawk

I am not an engineer so I could be completely off base, I admit that. But, if you look at the structure of the 86, is is not the middle bar that's an issue but having to cut the frame at the windows that would weaken it. The middle roof frame could stay the same with t-tops, obviously not with a Targa.

In fact you could probably strengthen the middle bar a bit in a t-top design.

Middle bar shown just looks to be a local doubler/stiffener for the roof to keep it from having a "drum" mode, it's not anything that would work for a T-top roof. You would *have* to strengthen and stiffen that middle bar, by a LOT. Basically replace it with something that has some cross-section to it. And you'd also have to stiffen the bejeezus out of the windshield frame, and the aft targa hoop structure. And still you'd have to add a lot of stiffness to the lower part of the chassis to make up for the lost structure up high.

Since I don't track my car, and couldn't give a flip about 100lbs here or there, I should probably just shut up. I would absolutely love a Targa version of the car, but no chance of that happening (at least from the factory!)

Yeah, I think they'd have to add too much additional structure, it would be a P.I.T.A. for sure, and the end result would be significantly heavier and with a significant loss of stiffness. Great illustration of the unibody, honestly it doesn't look to me like it was designed to accommodate a convertible, t-top, or targa version without a *lot* of modification in a lot of areas.
IMO this would be a much less feasible project than making the short-wheelbase 2-seater!

[Irace86.2.0]

Not quite a dedicated hardtop, but this is lovely. Ticks many boxes and the price isn’t bad.

[ZDan]

Originally Posted by Irace86.2.0

Not quite a dedicated hardtop, but this is lovely. Ticks many boxes and the price isn’t bad.

I love this thing!
The crazy thing is, though it looks like an extremely cab-rearward front-engine rear-drive car, it's mid-engine! There's actually room for its transverse V6 behind the passenger compartment!

As with the Elise/Exige, it gets its frame stiffness from having very deep and wide sills. This frame is heavily triangulated space frame of square-section steel tubing with some sheet panels. It looks to have very efficient load paths between suspension mounts. As with the Lotus, it doesn't have "normal" door openings and driver and passenger are tight against each other as they are between the wide/deep sill areas occupied by the frame structure.
Don't have figures but I'm sure it's plenty stiff for 950kg/2100 lb.

[Irace86.2.0]

It is great, but it doesn’t have the reliability, amenities or build like a major OEM. I bet it will feel slightly more kit-car from a Lotus, but like a Lotus, it’ll have that boutique, racecar quality that sets it apart from other cars on the road. It is a catch 22 where its most endearing qualities are also its shortcomings.

[Dadhawk]

Originally Posted by Irace86.2.0

There is no dedicated coupe option.

All of this is to say, that giving the choice, their marketing research tells them that more people buying these cars than not, prefer some type of opening in the roof so that's what the manufacturers build into them.

Even if they built a "coupe only" version of a car that has a sunroof, moonroof, glassroof, t-top, targa, etc in it it is likely the hardtop has the structure for the other underneath so it's unlikely to be a dedicated coupe anyway.

That's one of the things I like about the 86 platform, no options, which is what I think you are looking for, just with two less seats.

Personally, I had sunroofs and t-tops from a longevity prospective, I've never owned one that didn't leak at some point. The problem is they get tied into "premium features" in the cars.

I also don't want glass roofs, but every manufacturer (particularly in EVs) seems enamored with them now.

I do like Targa tops because, in my experience, they are less problematic and don't ruin the lines of the car like a convertible top does. That's one of the reasons I always like the Fiat X1/9 although I couldn't afford it at the time it was new.

[ZDan]

Originally Posted by Dadhawk

All of this is to say, that giving the choice, their marketing research tells them that more people buying these cars than not, prefer some type of opening in the roof so that's what the manufacturers build into them.

Not so much "marketing research" for the Elise/Exige and the Jannarelly. Rather if you are building a car not for the masses, you can have very efficient load paths with an open roof, but it cuts into both interior space and forces high/wide sills. It can be easier and less expensive to build a dedicated sports car this way while maintaining light weight. But usable interior space and ergonomics of ingress/egress are out the window. Also the manufacturing techniques are not as translatable to mass production with cost as a factor.

Even if they built a "coupe only" version of a car that has a sunroof, moonroof, glassroof, t-top, targa, etc in it it is likely the hardtop has the structure for the other underneath so it's unlikely to be a dedicated coupe anyway.

Yeah, they design all the required stiffness into the built-up lower frame of the car. Hence the Exige only sees a modest increase in stiffness from bolting in the removable top.

That's one of the things I like about the 86 platform, no options, which is what I think you are looking for, just with two less seats.

Basically, a modern 240Z is what I want. S2000 came close, but as a dedicated roadster like the Miata, it throws away a lot of utility and you have to live with wind noise. BRZ/86 also come close, but now the compromise is longer wheelbase with the rear wheels relatively far aft for an FR car which kills weight distribution.

I do like Targa tops because, in my experience, they are less problematic and don't ruin the lines of the car like a convertible top does. That's one of the reasons I always like the Fiat X1/9 although I couldn't afford it at the time it was new.

If the car is small and lightweight enough, and they build in structure in the sills (and the tunnel in the middle of the car if it has a tunnel) to efficiently get the desired/required stiffness, then you can have a removable roof without killing stiffness or adding too too much weight. But you have to design it that way from the get-go. The masses want big doors and they want as much interior space as possible, they don't want high and wide sills and a bulky central tunnel taking up space. For "normal" cars the targa is a big compromise. Reportedly the C4 Corvette development team were furious that they were forced to have a removable targa roof because they wanted more stiffness and less weight! For the c5, the main reason they went to the rear mounted transmission was for stiffness in the face of the still-mandated removable roof (on most models), *not* for weight distribution (which was unchanged).

[Irace86.2.0]

Originally Posted by Dadhawk

All of this is to say, that giving the choice, their marketing research tells them that more people buying these cars than not, prefer some type of opening in the roof so that's what the manufacturers build into them.

Even if they built a "coupe only" version of a car that has a sunroof, moonroof, glassroof, t-top, targa, etc in it it is likely the hardtop has the structure for the other underneath so it's unlikely to be a dedicated coupe anyway.

That's one of the things I like about the 86 platform, no options, which is what I think you are looking for, just with two less seats.

Personally, I had sunroofs and t-tops from a longevity prospective, I've never owned one that didn't leak at some point. The problem is they get tied into "premium features" in the cars.

I also don't want glass roofs, but every manufacturer (particularly in EVs) seems enamored with them now.

I do like Targa tops because, in my experience, they are less problematic and don't ruin the lines of the car like a convertible top does. That's one of the reasons I always like the Fiat X1/9 although I couldn't afford it at the time it was new.

If that were always true then the coupes would be almost the same weight as the targas, but that isn’t the case. Besides stiffness being down on the MKIV, the targa is about 80lbs heavier, as an example. In some cases it may be best to leave bracing in or to develop a car to be strong as a convertible and then add a roof, but material, time and labor costs can really add up, so it is often the case that unnecessary bracing is removed.

I do agree that a targa is better than a hardtop convertible like the Miata RF. If it had that I probably would get a Miata and do a K24 swap.

[ZDan]

I lowered it a little. Perfection...

[sato]

Yesterday, I drove off with 3 coworkers for a quick lunch, which made me thankful the GT86 has 4 seats (forgot we fit smaller adults in the back). However, two of them girls started bickering incessantly halfway thru lunch, so it made me wish I could only accommodate the hot one...

Ate cafeteria food today.

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[ZDan]

Originally Posted by sato

Yesterday, I drove off with 3 coworkers for a quick lunch, which made me thankful the GT86 has 4 seats (forgot we fit smaller adults in the back). However, two of them girls started bickering incessantly halfway thru lunch, so it made me wish I could only accommodate the hot one...

Ate cafeteria food today.

Over three years I don't think I've ever had anyone in the backseat. Have used the space, just never for humans...

[sato]

Originally Posted by ZDan

Over three years I don't think I've ever had anyone in the backseat. Have used the space, just never for humans...

Yeah, it's only my second time... Desperate measures. Still, you could be right. Damnit, they could have been sexy aliens. Had me fooled!

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