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Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Body - Exterior> To replace or not to replace: roof skin on 77 Trans an
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Topic Review (Newest First)
05-14-2017 07:57 PM
idrivejunk I ain't gonna say nothing about "the guy who...". I've seen baaaad things, man. Guess I did kinda write a eulogy for a roof skin. Anyway, no on the ratchet strap and block of wood. Why would you need that? Clamps then screws where welds were should do for positioning the new panel.

I have never put a roof skin on a 2nd gen F-body, but have replaced a variety of roof skins in my time. Again, the last one I did was DC and wonderful. While you wait for delivery, I suggest a thorough search of the web for a detailed roof replacement article on a Firebird just like yours. Surely theres something out there
05-14-2017 02:54 PM
123pugsy I'll leave this to those with experience.
05-14-2017 01:44 PM
Schroeder Ok. Good to know.

Well, they say these reproduction roofs dont fit the best, so I'll ask now; how should I hold his down in place? I'm thinking sheet metal screws on the front and rear window flanges and maybe a ratchet strap around the center? I'll put a wood spacer or something between the inner roof structure and skin so I don't crush it and have more problems. I think I saw someone do that when I researched this months ago.

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05-14-2017 01:40 PM
123pugsy FYI: a reverse curve is the shape of a potato chip or saddle. It's created by stretching the edges of a sheet.
A bowl is created by shrinking the edges of a sheet and stretching the center.
05-14-2017 01:40 PM
123pugsy
Quote:
Originally Posted by Schroeder View Post
So if you had to bring the metal up did you not hammer and quench the metal after heating it?


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I tapped it on a dolly very lightly.
Can't remember if I quenched.

Don't read too much into this as a reverse curve is a whole different animal.

You cannot shrink a bowl shape and bring it up. It will only go down. This is only true in the middle of course. If you shrink the edge of a bowl shape, crown will be gained.

Just showing you a location torch heat is OK. Notice all the curves where I heated. It's not a big low crown panel like a hood, roof, deck lid, or door skin.
05-14-2017 12:18 PM
Schroeder So if you had to bring the metal up did you not hammer and quench the metal after heating it?


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05-14-2017 11:46 AM
123pugsy
Quote:
Originally Posted by Schroeder View Post
If I remember correctly, it was a small oil can when I started this. I heat shrunk with a torch and the areas still canned a bit, and that's when we started the shrinking disc business.

So where can a torch be used? I don't think I'll ever try it again anywhere, but I'm curious.


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Something with a high crown that the disc just won't give any more shrinkage.

I was having a heck of a time with a reverse curve on the rod and I took the torches to it. I actually had to bring the steel upwards.
05-14-2017 11:28 AM
Schroeder If I remember correctly, it was a small oil can when I started this. I heat shrunk with a torch and the areas still canned a bit, and that's when we started the shrinking disc business.

So where can a torch be used? I don't think I'll ever try it again anywhere, but I'm curious.


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05-14-2017 10:59 AM
123pugsy Do not fear the disc.

It got away because what you described was what I believed to be a simple small oil can.

When you posted the video, it was clear it wasn't a stretched oil can, it was a massive shrink.

Did I read earlier in the thread that you torch shrunk on the roof?

This is vital to know so you don't repeat mistakes. A large panel with low crown can never be hit with a torch w/o disastrous results.

The disc is fine. It did it's job perfectly.
What wasn't fine was my assumption that you had a basic oil can from stretched metal.

Next time some posts about a problem like this, I will request a video.
05-14-2017 10:29 AM
Schroeder Dynacorn roof ordered. Found it on ebay for $426 shipped. I csn live with that. Its a LOT better than any online store like classic industriess, NPD, or anyone else could do. As stated earlier, they were like $550.

Now time for the post-mortem report that IDJ has basically started....
So I definitely brought this miles closer to where it needs to be considering where it was, but it's still so far away. It's not time effective to keep doing this. I'm stalled on my project, and it's causing me to lose steam. I don't even wanna go out in the shop because of this. It's just so boring not making any progress. Bringing it back from the total disaster it was is all thanks to you guys, and I DEFINITELY learned a lot about slapping, shrinking, stretching, and general shaping- all stuff I'm gonna need as I flare my fenders, quarters, and keep "hot-rodding" this thing, BUT...I'm still not entirely sure why it went so wrong. And THAT is what scares me. I think things got WAY worse once I used the shrinking disc. I'm afraid of it now. Perhaps these oil cans that are now on the perimeter of the big black circle problem area were already there and I didn't notice them until I really got a feel for things, but I don't think so. I think all the work I did on this made them. It seems excessive shrinking can make oil canning just as easy as stretching. Maybe that's wrong, but it sure seems like it to me!!

As shown in the 1st video I posted, even the small oil cans on the PS side are around areas I shrunk. That's scary. Everywhere I shrunk got way worse just outside of the area. Perhaps I'm looking at it wrong and those areas appeared from the torch, and I just didn't notice it at first. IDJ, I think that's what you're eluding to when you mention that the application of heat was incorrect.

So, I guess we'll put this one to bed. I'll stop posting vids and bothering you guys as I chase my tail. I really appreciate the help. Just please help me with some of these last questions I have to help me with my fear of shrinking discs.

Ugh....now I've made myself an example and you guys will now post, "I once saw a guy ruin a whole roof by...." lol. Oh well.

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05-13-2017 08:48 PM
idrivejunk Pugsy hit the nail on the head when he said "To get metal to be the proper shape, the metal needs to be thinned or thickened pretty much an exact amount everywhere on the panel.". Your metal thickness is simply skewed too greatly and the original shape is long gone. But...

Again I see progress. Again however, we can't touch it. The difficulty level is too high for the individual at this time. Now its a mess that ought not to be hung on a car. Has been for a few pages. I am cynical by default but tried my best to be optimistic because the enthusiasm is so there. I support your suspicions about the method of application of heat being where it went wrong.

Stick a new roof on there and try not to let this experience negatively affect your thought process as you move forward on the project. There was a time when you needed about a cup of filler on that roof skin. At this point, even if a metal miracle were to occur, you'd still have bondo over the whole roof. That is the best lesson you can take from this, in my opinion.
05-13-2017 05:51 PM
123pugsy You mentioned you went further around the outside with the shrinking disc.
You cannot shrink good, unmolested metal to fix the issues.

W/O being there, it's impossible to tell which and where to planish. If I were there, I would just keep trying different things. Impossible to describe on line.
05-13-2017 03:15 PM
Schroeder Pugsy, what exactly am I working towards with stretching?

Ok, u have the whole area to a "normal" oil-canned. It is slightly above flush. When u press on it, it oil cans in and pops back up above flush. It isn't a massive 24" diameter inward dent anymore- unless you really push in on it, but again, if you do that, it'll pop back up.

Do I need to put guide coat on it now and slap the remaining lows or something?

I tried shrinking the raised center because I thought this is where I wanted to be to proceed, but as soon as I did that to just a couple spots it shrunk back in to an inward dent. I slapped it back up to being the normal, outward oil can

PS- I've drawn a line in the sand. If I don't have this fixed over the course of the rest of today and tomorrow I will be calling every vendor I can to see what they can do to make this cheap for me and reduce the shipping costs. At that point I'll be buying a new skin and taking the a-pillar skins off this one.

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05-13-2017 02:30 PM
123pugsy
Quote:
Originally Posted by Schroeder View Post
Ok. Well where should I proceed to stretch? Did you watch the latest vid in the post you quoted? The oil can area is a lot better, and I got there by shrinking an area further out than the over-shrunk, black circle area. Again though, whenever I make progress it seems like other problem areas appear. The oil can on the perimeter that I press in the video that makes the main oil can area pop back up is just one example.


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I edited my last post.
Should have watched the vid first.

First thing: Do not work any more areas that have never been affected by dents or torch shrinking. Do not go out bigger.
A guy feels like hitting these areas, but it's the wrong thing to do.
The only way steel comes back to the correct shape is by working any stretched or shrunken places. Shrinking perfectly good metal further away is really gonna screw things up.

Remember this for when you weld in a patch in the future. Only planish the heat affected zone (HAZ).

To get metal to be the proper shape, the metal needs to be thinned or thickened pretty much an exact amount everywhere on the panel. Thickening (shrinking) areas that don't need shrinking means they will need to be thinned, (planished, slapper on dolly)

I wouldn't blame you giving up now. It's really tough at this point.
05-13-2017 02:11 PM
Schroeder Ok. Well where should I proceed to stretch? Did you watch the latest vid in the post you quoted? The oil can area is a lot better, and I got there by shrinking an area further out than the over-shrunk, black circle area. Again though, whenever I make progress it seems like other problem areas appear. The oil can on the perimeter that I press in the video that makes the main oil can area pop back up is just one example.


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