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-   -   C4 design question (https://www.corvetteforum.com/forums/c4-general-discussion/3646450-c4-design-question.html)

kg4fku 05-03-2015 06:41 AM

C4 design question
 
So this is a question for all of you that know the in's and out's of the design of the C4.

Why does the Targa Top not have the the front release handles that were designed for the Convertible Top?

I know the Convertible C4 came a few years behind in the C4 era but the design probably was there already.

I have only been in a C4 Targa once with the top off and I remember it being quite the process of undoing the allen bolts, lifting and then storing the top.

I had a demonstration of the new C7 and was surprised the top came out so easily. No tools required. Three latched and out it comes.

I love the look of the Targa Corvette and would love to add one to my garage alongside my convertible. I think it is the best of both worlds with almost none of the compromises.

crowz 05-03-2015 07:01 AM

Because if I release my convertible top at 55 mph its not likely to actually come off the car but even if it does its not likely to kill anyone.

You pop the top on a targa at 55 mph and it gets wind under it somebody behind you is getting a killer frisbee in the face.

kg4fku 05-03-2015 07:04 AM


Originally Posted by crowz (Post 1589550942)
Because if I release my convertible top at 55 mph its not likely to actually come off the car but even if it does its not likely to kill anyone.

You pop the top on a targa at 55 mph and it gets wind under it somebody behind you is getting a killer frisbee in the face.

Someone's been watching fast and furious too much.....

Still... the new C7's have latches similar the convertibles so that alone cannot be the answer.

crowz 05-03-2015 07:24 AM

Never watched fast and furious actually. They launch a targa top in it?

The bolt down design was part of gm's safety worries. There is so much flex on a coupe with the targa top out that with it in and the lock design the convertible uses it would never hold.

Without an x brace like the convertible has the coupe flexes a bunch with the top out.

All the car companies during that time were using the threaded bolts too.

kg4fku 05-03-2015 08:02 AM


Originally Posted by crowz (Post 1589550991)
Never watched fast and furious actually. They launch a targa top in it?

The bolt down design was part of gm's safety worries. There is so much flex on a coupe with the targa top out that with it in and the lock design the convertible uses it would never hold.

Without an x brace like the convertible has the coupe flexes a bunch with the top out.

All the car companies during that time were using the threaded bolts too.

Yup, they launched one from a Toyota Supra. :rock: I can only imagine that is what it would be like in a C6 Z06 or ZR1 when the roof delaminates and blows off.

Who else used a bolt on Targa? The C4 is my only real experience with a Targa and it's removal. I have seen the early Porsche 911's but never saw one while the targa was being removed. If I recall correctly, the those were folding canvas style tops.

I get the C4 top is part of the upper structure and needed for rigidity of the frame and the car was initially designed to have a T roof vice Targa. However, I just think a better design could have been made by the end of the C4 life span. Seems that the Targa design was really never revisited during the C4 lifespan.

I have no idea how the C5 or C6 Targa latches so I have no idea wen the bolts and "special tool" process were abandoned in favor of latches.

3JsVette 05-03-2015 08:11 AM

With an additional 30 years of development and structural improvement the C7 should be easier to remove and have less of a body rigidity compromise when it's removed.
The C4 chassis is nowhere near as rigid as the C7 design. If you can catch the "How It's Made" C7 Corvette episode on Velocity I think you'll be impressed with how far the assembly line process has progressed.

ricasso 05-03-2015 08:16 AM

What kind of jackass would even think about loosening or trying to remove a targa while on the move??? :crazy2:

kg4fku 05-03-2015 08:17 AM


Originally Posted by 3JsVette (Post 1589551143)
With an additional 30 years of development and structural improvement the C7 should be easier to remove and have less of a body rigidity compromise when it's removed.
The C4 chassis is nowhere near as rigid as the C7 design. If you can catch the "How It's Made" C7 Corvette episode on Velocity I think you'll be impressed with how far the assembly line process has progressed.

I would like to watch that show. I never saw the C4 production so wouldn't have a baseline to compare it to. Do you know what the episode number was?

kg4fku 05-03-2015 08:18 AM


Originally Posted by ricasso (Post 1589551168)
What kind of jackass would even think about loosening or trying to remove a targa while on the move??? :crazy2:

Someone trying to rescue their buddy off the side of an eighteen wheeler of course...... Come on, what kind of question is that? :rofl: :hide:

wfd1739 05-03-2015 08:27 AM


Originally Posted by kg4fku (Post 1589551183)
Someone trying to rescue their buddy off the side of an eighteen wheeler of course...... Come on, what kind of question is that? :rofl: :hide:

:funnypost: :rofl::rofl::rofl:

kg4fku 05-03-2015 08:27 AM

I will say that the C4 targa is way easier to remove than this one. :eek:


kg4fku 05-03-2015 08:30 AM

C4 targa is easier than to remove than this one...

try number two




kg4fku 05-03-2015 08:35 AM

for your viewing "pleasure"



starrman62 05-03-2015 09:50 AM


Originally Posted by ricasso (Post 1589551168)
What kind of jackass would even think about loosening or trying to remove a targa while on the move??? :crazy2:

The same jackass that they have to put warnings on preparation H that says don't take orally.

c4cruiser 05-03-2015 09:57 AM


Originally Posted by kg4fku (Post 1589551107)
I have no idea how the C5 or C6 Targa latches so I have no idea wen the bolts and "special tool" process were abandoned in favor of latches.

The C5 and C6 targa tops use latches; one at each front corner and a single latch at the rear center. But the C5 and C6 frame is much stiffer than the C4. In fact, the C5 frame was designed with the convertible in mind. The C6 frame is basically the same but with some added stiffness.

The targa tops in the C3 generation also used pairs of latches. Two latches at the outer front and rear and two tabs that slid into slots on the "T" portion of the roof. These latches were very small compared to the C5 latches. They didn't provide any structural support so all the latches had to do was to keep the tops in place and keep rain out.

kg4fku 05-03-2015 10:09 AM


Originally Posted by c4cruiser (Post 1589551622)
The C5 and C6 targa tops use latches; one at each front corner and a single latch at the rear center. But the C5 and C6 frame is much stiffer than the C4. In fact, the C5 frame was designed with the convertible in mind. The C6 frame is basically the same but with some added stiffness.

The targa tops in the C3 generation also used pairs of latches. Two latches at the outer front and rear and two tabs that slid into slots on the "T" portion of the roof. These latches were very small compared to the C5 latches. They didn't provide any structural support so all the latches had to do was to keep the tops in place and keep rain out.

Very familiar with the C3 T-Top roof. :thumbs:

crowz 05-03-2015 04:03 PM


Originally Posted by kg4fku (Post 1589551107)
Yup, they launched one from a Toyota Supra. :rock: I can only imagine that is what it would be like in a C6 Z06 or ZR1 when the roof delaminates and blows off.

Who else used a bolt on Targa? The C4 is my only real experience with a Targa and it's removal. I have seen the early Porsche 911's but never saw one while the targa was being removed. If I recall correctly, the those were folding canvas style tops.

I get the C4 top is part of the upper structure and needed for rigidity of the frame and the car was initially designed to have a T roof vice Targa. However, I just think a better design could have been made by the end of the C4 life span. Seems that the Targa design was really never revisited during the C4 lifespan.

I have no idea how the C5 or C6 Targa latches so I have no idea wen the bolts and "special tool" process were abandoned in favor of latches.

Toyota used bolts too on the targas but they put a knob on the bolts where the c4 has a bolt head.

Jon Hekking 05-03-2015 05:24 PM


Originally Posted by crowz (Post 1589550991)
The bolt down design was part of gm's safety worries. There is so much flex on a coupe with the targa top out that with it in and the lock design the convertible uses it would never hold.

Without an x brace like the convertible has the coupe flexes a bunch with the top out.

All the car companies during that time were using the threaded bolts too.

True, my car has considerably more flex with the top out. It's a big difference.

Tom400CFI 05-03-2015 05:33 PM


Originally Posted by crowz (Post 1589550942)
Because if I release my convertible top at 55 mph its not likely to actually come off the car but even if it does its not likely to kill anyone.

You pop the top on a targa at 55 mph and it gets wind under it somebody behind you is getting a killer frisbee in the face.

No. That is not why.

The reason is that the top is a structural part of the car. Latches aren't strong enough to perform that task.

EDIT, I see this was covered already.

Tom400CFI 05-03-2015 05:53 PM


Originally Posted by kg4fku (Post 1589551107)
I get the C4 top is part of the upper structure and needed for rigidity of the frame and the car was initially designed to have a T roof vice Targa. However, I just think a better design could have been made by the end of the C4 life span. Seems that the Targa design was really never revisited during the C4 lifespan.

From "Corvette from A - Z51", they started w/latches in the prototype C4's, and...
"The latches weren't able to transmit as much load into the hatch as the car wanted; they'd actually pop open.
So we had to go from the quick release latches to the bolt on roof. We measured the maximum load going through the latches and found it to be about half a ton
."

^That is a lot of force...too much for a simple latch.


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