Shrinking discs

[Cliff R]

I have welded up some major rust issues in the roof of the MY wagon caused by the 32 year old screw on parcel roof rack.
Unfortunately, 2 of the biggest issues were in the middle of the roof and I now have a problem with warping of the roof.
I see from looking on the net there are things called shrinking discs which attach to a grinder. Not sure how they work yet but the principle is the unit heats the area that is raised and when hot the area is cooled which shrinks things back down.
I guess I am lucky in that the areas in question are over one of the roof channels so I can adjust these a little with packing low points and running internal longitudinal struts down the roof to stop other areas popping back in or out, (ie, I can pop the panels back out so they look pretty straight but one push and they pop back in again) but it would be more practical to try to shrink the roof panel back in. I don't have access to oxy or the like. LPG maybe (I do have this) ?
Anyone had any experience with car metal warping and what did they do about it.
I have the roof liner out so have access to the underside of the roof but not directly under the warped area (downside I guess) where the roof channel runs.

[TOONGA]

this you tube video is a nice demonstration of using a shrinking disc, but I will say they editied a lot of the actual shrinking time out if the video to make it seem like it is a simple process. if you look at the side bar on the you tube page there are heaps of these videos.

TOONGA


https://www.youtube.com/watch?v=X8cruauERmI

[Bantum]

Ha - I was thinking of something else when first read the tittle ( my back is shrinking ) but yes that could work - the trick here is to get the 'high spots' as hot as possible ( ideally red hot, but without melting things ) & then rapidly cool with a damp / wet cloth. Repeat a necessary until its taught ... :0

Cheers, Bantum ...

[Cliff R]

Another issue has erupted with the removal of the roof luggage racks that I had forgotten about.
With the rack strips that run front to back of the cars roof removed the rigidity of the roof seems to now be weakened.
If any of the car doors are shut the roof makes a sound like someone hitting a drum.
It isn't as bad as it sounds (it isn't a big noise) but it is a sound/noise that isn't there with the luggage rails screwed on. It makes no difference if the roof lining is installed or not it is all dependant on the luggage rails being installed.
I will be, with much effort and time, able to sort out the warped roof with panel beating hammers, dollies, a jack and a lot of swearing but the drumming noise will take much more effort.
I think my options are to install something such as strips of steel up on the underside of the cars roof (inside the car) which would run between the roof cross channels, or maybe glue something like felt to the inside of the roof between then roof and the roof lining to insulate, stiffen and return some rigidity.
I had forgotten about the drumming sound but I had heard it before when some years ago I took the luggage rack off and was driving around with it off for a while. I thought of it odd back then but when I put the luggage rack rails back on everything became ridged and the noise went away.
Any other suggestions appreciated and yes I have actually thought of screwing the luggage rack rails only back on. This shows some logic and it would remove the noise, make the roof ridged again and protect the roof if I am carrying something (I will be installing ROLA racks later).
I cant think why there would be any differences between an MY wagon with or without the screw on luggage racks so I cant think what else could be causing this.
Any other thoughts.

[Bantum]

Having just gone to the trouble of fixing it, I wouldn't recommend putting screws back in - One easy fix would be to stick some quality sound matting on the underside, it will quieten down the cabin a bit & as a bonus reduce the flexing ...

Also check that the 'support bars' under are glued to the roof...

Cheers, Bantum ...

Add : I'd get the self sticking stuff like 'dynamat' etc ...

[Cliff R]

Bantum
As I hit the Send button on my earlier message I instantly thought "what the hell did I write that for".
I wont be screwing the rails back on as it defeats the whole purpose of what I have done so far.
Lets call it frustration talking. The car is at our old house where I have room to do the work so I cant just go out and do a bit of work on it, I have to walk down the road and around the corner or drive the same route to do anything.
I like the idea of the adhesive sound deadening, just have to sort out where to get it.
Depending on the insulation material I may also add some strips of 1/8" gal flat bar over the insulation. There is plenty of room up there between the roof lining and the roof so this is an option.
I do plan to ensure there is enough seam sealer between the roof channels and the roof but this was already there with the drumming sound so the deadener is probably the go.