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Old 04-01-2018, 03:48 PM
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Dynacorn roof skin on 77 Firebird Trans Am

Hey guys, it's been awhile since Ive posted. Over the winter I got a new phone, rooted it, got into techy stuff and have been wasting time with home automation. Now I'm getting back into my car right when I'm not going to have any time because we'll be in the fields soon! :-( oh well, I'll work it in on the side like always. Just like everyone else.

Anyway, if you remember I purchased a whole car to cut the roof off and put it right on my car. Well I screwed the skin up, so I had to buy a new dynacorn unit. I'm still not ready to say it's a bad piece. It is THICKER than stock by several thousandandths and measures spot on to the original (with a tape measure), but I MAY have a couple issues. It seems like it may be a bit short. Some internet searches for "dynacorn roof skin replacement on 2nd gen fbody" will promptly return results of people having similar problems when doing this same project.

I've started locating the roof skin off the stock quarter panels. I'm working forward in a sense. It seems the front may be short by 4-7mm depending on where I measure (.146"-.276"). See pics. I measure off spot weld centers in the donor car skin to the inside edge of the donor roof skin window flange right where it 90s up to the skin roof surface. I then compare this by locating the tip of my steel rule in the new skin 90 and then measuring to the center of the correspondening spot weld on the inner roof structure. Its an approximation, but I think it's telling. The inner roof structure is welded to the car. I did this measurement for one weld on the PS and one on the DS. DS (2 spot eelds right near each other) was ~7mm and the PS (3 spot eelds right near each other) was ~4mm.

I will NOT be installing the factory window trim on the finished car. I want a flush glass-look. I'm not actually buying flush glass and will just be installing some of that push-in foam/rubber glass perimeter beading around the windows like on the 4th gens and most modern cars. I've seen this on a couple cars at good guys and you'd never know the difference. It looks great and is a fraction of the price of these flush-mount front and rear windows. Even on close inspection it looks like a pricey flush-mount install.

That being said, IF I am off too far, won't the push in seal give me some room for error? If the channel between the front edge of the roof skin and top edge of the windhshield is too wide I think I could get buy by welding in a filler rod contoured to the skin to narrow the gap. Then I'd just push the rubber channel in and its flanges would go onto the windshield a bit and a bit onto the roof skin as they should, and you'd never know the channel was actually a little too wide.

As with all things, I know this is probably easier said than done. I'm probably missing something. Please take a look at the pics and tell me what you think. The side to side ratchet straps definitely help the positioning. The skin was WAY further back before putting them on- maybe by like 3/8". I MAY be able to crank them down a click or two more without worrying about popping the roof skin in. The ratchet strap that runs the length of the car in the center isn't really cranked down or doing anything. When I tried to crank that one the roof structure just bowed and if any of the straps were gonna cause damage it was gonna be that one.

How should I proceed?

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Old 04-01-2018, 04:35 PM
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Welcome to the world of aftermarket panels.. What i would do is temporarily set the windows in place at this point to see how they fit. That will tell the tale. Then you will see how much to adjust and where..

You may need to do a bit of slicing and dicing to get to where you want to be.

Sam
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Old 04-01-2018, 04:49 PM
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Quote:
Originally Posted by OneMoreTime View Post
Welcome to the world of aftermarket panels.. What i would do is temporarily set the windows in place at this point to see how they fit. That will tell the tale. Then you will see how much to adjust and where..

You may need to do a bit of slicing and dicing to get to where you want to be.

Sam
So do you think it looks way off? I can't make em my mind. I figured I'll have to put the windows in. I'll have to tack some panels on to make that happen. The cowl is currently off. I'll get er done though!

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Old 04-01-2018, 04:53 PM
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I do not think it is way off.. just not perfect is all.. Quite common for a replacement panel to need some adjustment in actual practice..

Sam
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Old 04-01-2018, 06:10 PM
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Originally Posted by OneMoreTime View Post
I do not think it is way off.. just not perfect is all.. Quite common for a replacement panel to need some adjustment in actual practice..

Sam
Hmm...I'll see what the stock window pieces look like. I'll be a week or more on that. I'll post back when I get them mocked up.

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Old 04-01-2018, 06:39 PM
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Honest reproduction part description in catalog:

"Similar, can be used if nothing else is available"

Brian
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Old 04-01-2018, 06:44 PM
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Originally Posted by MARTINSR View Post
Honest reproduction part description in catalog:

"Similar, can be used if nothing else is available"

Brian
Thanks for sharing. I'm guessing that came from Ames? I'd say it's more than similar. As I get further into it I may find out why they put this note in the description though... In my case, i have nothing else available. I tried the donor car route and found some rust on the underbelly of the skin between the roof structure that needed addressed. That's why I split them and ended up with the mess I did. I'm gonna have to make this work. Any cutting I may have to end up doing simply will not occur on the outside surface of the skin. I'll only be able to keep modifications on the flanges. It's all my skills will allow.

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Old 04-01-2018, 07:37 PM
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Quote:
Originally Posted by Schroeder View Post
Thanks for sharing. I'm guessing that came from Ames? I'd say it's more than similar. As I get further into it I may find out why they put this note in the description though... In my case, i have nothing else available. I tried the donor car route and found some rust on the underbelly of the skin between the roof structure that needed addressed. That's why I split them and ended up with the mess I did. I'm gonna have to make this work. Any cutting I may have to end up doing simply will not occur on the outside surface of the skin. I'll only be able to keep modifications on the flanges. It's all my skills will allow.

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It's from an old friend of mine, he said it as he pulled a part out of a box that came in the mail for his 65 Vette.

You just have to accept it unfortunately. If you plan on it being perfect, you will be disappointed. If you accept it will be "similar" then you make it fit with some passion and skills and it's done.

Brian
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Old 04-02-2018, 07:09 AM
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Glad to see a new skin. Put the ratchet straps away please. I would like to see how it fits without them. It does not look terrible but glass should be fit before you weld.

What you are dealing with are the bends. The angles may not be perfect and that is not unusual even with OE parts.

In your situation, I proceed thusly:

Clamp the front where it fits best, look at the back. Remove clamps. Clamp at rear where it fits best, look at the front. One of these ways will be better than the other usually.

Clamp the worst fitting end as close as you can get it (ignoring other end), then drill 1/8" holes through both layers out near the corners. Unclamp that, reposition, and clamp the good end. Go back to the poor fitting end and use an awl through the holes to align them best you can then clamp or run screws. With it thoroughly clamped or screwed this way, now you can gently persuade the edges of the roof to relax in this position. The new panel should lay right in place with little gap left to clamp when welding. Warpage occurs when welding metal under tension, so you want as little force needed as possible to hold it in place after final fitting.

Good tips so far, and my position on glass fitment hasn't changed... Skip that at your own risk. Sounds like the molding you're using could be more forgiving than the stock type.
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Old 04-02-2018, 08:08 AM
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Quote:
Originally Posted by idrivejunk View Post
Glad to see a new skin. Put the ratchet straps away please. I would like to see how it fits without them. It does not look terrible but glass should be fit before you weld.

What you are dealing with are the bends. The angles may not be perfect and that is not unusual even with OE parts.

In your situation, I proceed thusly:

Clamp the front where it fits best, look at the back. Remove clamps. Clamp at rear where it fits best, look at the front. One of these ways will be better than the other usually.

Clamp the worst fitting end as close as you can get it (ignoring other end), then drill 1/8" holes through both layers out near the corners. Unclamp that, reposition, and clamp the good end. Go back to the poor fitting end and use an awl through the holes to align them best you can then clamp or run screws. With it thoroughly clamped or screwed this way, now you can gently persuade the edges of the roof to relax in this position. The new panel should lay right in place with little gap left to clamp when welding. Warpage occurs when welding metal under tension, so you want as little force needed as possible to hold it in place after final fitting.

Good tips so far, and my position on glass fitment hasn't changed... Skip that at your own risk. Sounds like the molding you're using could be more forgiving than the stock type.
Original poster, THIS is some good advice that idrivejunk just gave you! Fitting parts like this is sort of like a country western line dance, every person isn't perfect, but it all fits pretty well.

Brian
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Old 04-04-2018, 06:09 AM
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Yup, I noticed the skin was clamped perfect on one end, resulting in a 1/4" gap at the other. By moving the skin 1/8th" you effectively divide the shortage and end up with 1/8" on both ends. Perfectly normal for a repro and, most likely, an original as well. By doing what IDJ suggested, you can cut the shortage by another 1/16" on each end.
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Old 04-04-2018, 06:25 AM
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I've been trying to remember if we had to add to the one we used. I'll ask. If splitting differences won't do, that may be required in this case.
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Old 04-04-2018, 08:00 AM
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To quote a friend of mine who's done more than a few roof skins:
"Sometimes a vinyl top makes sense after awhile"

Its going to take a lot of fiddling; don't force it, don't get mad. Just walk away and come back tomorrow.
Thats actually a very nice trial fit to be honest, and better than I expected. I'd be pretty happy with that piece, as long as you inspect it close for handling damage or an uneven crown.

I've been redoing the interior in my streetrod all winter. Nothings square, nothing lines up and sometimes you do the driver side and it looks so much better than the passenger side that you just did - you feel compelled to redo it. Just relax and take it in stride.

Thanks for documenting all this
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Old 04-04-2018, 11:31 AM
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Originally Posted by idrivejunk View Post
I've been trying to remember if we had to add to the one we used. I'll ask. If splitting differences won't do, that may be required in this case.
I asked the guys who did the '73 at work and they said they did not have to cut anything but the roof did come up short like yours, Schroeder. They said there was trouble with the distance between the rear window bed and the back edge of the side window / roof rail. Like the windshield part and the part over the doors is good, but the rear window flange is too far forward. But it is not so bad that it doesn't work, with the stock molding arrangement.

On any window bed, one flange's edge may not match the other so don't sweat that too much. Matching the glass contour is what matters. So if you pry like crazy to get the rear bed just barely far back enough to work... which is what others are doing, then clamp the skin to the inner, chances are it will match the glass OK. Fortunately the body design allows a bit of inprecision, and also the stretch can be made without causing big trouble on the face of the panel. Just always stop short of bending it beyond the edge flange.
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Old 04-05-2018, 06:18 AM
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Quote:
Originally Posted by Too Many Projects View Post
Yup, I noticed the skin was clamped perfect on one end, resulting in a 1/4" gap at the other. By moving the skin 1/8th" you effectively divide the shortage and end up with 1/8" on both ends. Perfectly normal for a repro and, most likely, an original as well. By doing what IDJ suggested, you can cut the shortage by another 1/16" on each end.
Exactly.. Spilt the difference, I used to say that every day when guys complained they cant get a good gap. if you split the difference and its still not acceptable then you take it to the next level. Usually that just means getting a bigger hammer. then comes the port a power etc..
On the front, the angle is off about a 1/4". all you need to do is bend it forward a bit if you hold a piece of the original next to it you'll see what I mean. It a simple fix to tweek it forward I have a big pair of channel lock pliers that I use for doing this you just bend it forward a little at a time until they line up.
Its hard to explain without showing you and being right there but I'll try: The Lets say old skins lip is a 90 degree angle and the new skins lip is about 75 degrees, bending it forward until its a 90 is whats needed. Now, the exact angles degree is not important I just used those numbers to explain. but just bend it until the edges line up and screw it down. then get your old trim pieces and and install them to see how they fit. THATS the important part. in reality what your worried about isnt even that important so dont sweat it and dont ruin the skin trying to get those edges to line up with a micrometer. because in reality you can weld it in as is and never know once the trim is on. screw it down like it is then install the clips and moldings or just tape the moldings on and see if Im wrong. No Sweat.

Last edited by deadbodyman; 04-05-2018 at 06:30 AM.
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