8 replies to this topic

[minusman]

Hi,

I am about to start restoring my MK1. The numpty who had it before me cut stripped all the paint off the roof and forgot to reapply any paint - so it is nice and flakey, and then cut a sunroof in it for good measure!

Has anybody replaced a roof skin? Did the roof skin change on MK2 and onwards or are they all the same? I know the inside is different as the headlining comes only as far as the rail.

Where is the best place to cut - say an inch from the gutter or grind out the spot welds?

Any help would be greatly apreiciated.

Kind regards

Minusman

[taffy1967]

I'm not 100% sure, but I know the MK3 Minis were the last to get the rain gutter drip rail down the side.

So if the MK1 & MK2 Minis were the same, then you'll be looking for a pre-1976 Mini.

[Cooperman]

One of the only pressings which remained unchanged from 1959 to 2000 was the roof panel.
When my Cooper 'S' got rolled it needed a new roof panel.
First of all I removed the head lining. Then I drilled a 3/4" hole in one corner of the old roof and with an air chisel (you could use an electric saw) I cut the old roof off leaving about 2" of old roof. Then, with a 1.5 mm thick cutting disc I cut that last bit off right up to the inner edge of the gutter. Thus, the gutter now had an extra thickness of metal. The gutter was then cleaned back with a grinding disc to bare metal. The new roof had 5 mm holes drilled all around the gutter flange approximately every 30 mm.
It was necessary to bend the vertical flange above the rear window backwards a bit to allow the new roof to be positioned for welding. The welding was done a few holes at a time using a large number of body clamps until, finally, it was welded all the way around. The rear flange was tapped back into place & the welds ground back with a grinding disc. To get the 'roll-welded' appearance, I got some fibreglass resin and a little hardener, mixed it and lightly brushed it into the gutter all the way around. With the brush marks still there after it hardened, it looks just like a roll-welded original. The inside of the repair was seam sealed.
It was primed and painted, including the inside where the joint is, then the head lining re-fitted and it won a rally 2 weeks after it 'fell over' in a Welsh forest.
However, I have recently been thinking about the possibility of using a structural adhesive to just bond the roof panel on. Maybe 'Tiger Seal' or something similar would work. I guess a call to the 'Loctite' Technical support department might give an answer.
Personally I think i would stay with welding.

[midridge2]

as above but maybe prime and paint the underside before you fit it.

[Cooperman]

as above but maybe prime and paint the underside before you fit it.

I didn't because I still wanted to paint around the edge where the weld line is inside, which was seam sealed, so I painted the entire roof after fitting. The car had to be masked inside anyway. Yes, you could paint the inside first, but you would have to mask the flanges to ensure the weld would take properly before painting, then mask inside for final painting of the seam.

[minusman]

Thank you all very much - that has given me clear direction. I think personally I would stay with the welding too - if you think about it the roof does a major job as part of a monocoque adding to the overall stiffness - and glue of any description won't cut it in my book if my family are travelling in the car! Imagine you had a side impact. I bet any glue manufacturer won't put their name to the likely hood of the roof popping off and as a result the side of the car folding in on top of you, with the other vehicle on top likely as not!

Has anybody actually done a bonded roof or is it myth anyway?

[midridge2]

cooprman remember the cant rails have changed on minis with headlining rods, you cannot get in to paint around the flanges or seam seal it.
sorry, just reread the posting and its a mk1.

Edited by midridge2, 10 September 2009 - 12:01 PM.

[Cooperman]

cooprman remember the cant rails have changed on minis with headlining rods, you cannot get in to paint around the flanges or seam seal it.
sorry, just reread the posting and its a mk1.

Yes, you're quite right. However, the roof panel is identical as is the method for fitting it.
I guess with the later cars, after fitting it's just necessary to get some sort of anti-rust treatment over the back of the cant rails.
With regard to bonding a panel in place, I think that some of the current bonding materials are very strong. After all, some aircraft structure is now bonded. But, in Aerospace engineering, the actual bonding processes are very strictly controlled and, to some extent, tooling costs are not an issue. I also would 'stick' (Doh!) with welding.

[Trog]

There are quite a few cars out there with bonded body structures... Lotus and Aston Martin both use bonded ally bodies. Modern adhesives are very good but both these are assembled in very clean enviroments and use "thermoset" adhesives.

Other point to note about bonding is that the joints are very good in shear but poor in peel. On the Lotus they reinforce the joints with structural rivets at the ends of the joint to stop peel.

My feeling is with a structural part like the roof don't bond unless you realy know what you are doing as a bad joint will fail...