Exhaust accident bodywork repair

[JonB]

Hello

Last night while driving spiritedly I went over a hump and the car bottomed out after catching "big air". The rear exhaust clamp (mid pipe to silencer) caught something and the joint came apart. This morning I was refitting the exhaust and spotted cracks under the rear bumper around the exhaust box. Seems to be quite a bit of hidden damage as the floor between the cracks move with the box.

So to the question. I need to reinforce the boot floor. I'm not planning on respraying under the boot because the cracks are not immediately visible (being under the car). Never worked with fibreglass mat before so I need a dummy's guide. Any advice? How to prep the boot floor so the new mat sticks to it properly? Should I tape the cracks together? Etc, really..

Thanks
JonB

[Concrete-crusher]

I did a similar repair , I used carbon fabric and pure epoxy , I can sell you some if you want , I will dig out some pictures of the work

Steve

[types26/36]

Keep a look out for the miles wilkins book.
https://www.amazon.co.uk/Restore-Fibreg ... s+Bodywork

[dougal9887]

Preparation is key to a good repair. Inside the boot, the glass fibre should be ground back in a taper of 3" or 4" either side of the crack to leave a shallow valley. Outside the boot the join can be held in place, if necessary, using temporary strips of plywood or aluminium sheet screwed in position. The valley is then built up using progressively wider strips of mat, aiming for a level finish the same thickness as the original panel. Once set, the temporary strips can be removed and the surface made good with body filler. On completion, the repair will be very strong and almost invisible.

[alan.barker]

This is only how i do it.
If you don't want the cracks to come back or see where it was repaired only use Resin and Matt. On out side finish with Resin and Tissue. NO FILLER or it will shrink after maybe a Year and you will see where it was repaired.
In 45 Years of working on Lotus and grp been there done it and i've learned how to do correctly
It takes longer using only Resin and Matt + Tissue but it's the only way for a 100% repair.
The first thing Option 1 does is to Tissue so cracks and repairs don't come back to haunt you. finish on outside Resin and Tissue ONLY.
Alan

[69S4]

Dougal's explanation is how I've done it and from the sound of things it shouldn't be that difficult a repair. If you've not worked with glass fibre before though you'll find it's messy stuff to play with. Arm yourself with a load of plastic gloves from the local diesel pump and more small paint brushes than you think you need as they're both one shot items.

[Pastapesto]

Hi John

Sorry to hear about the damage.......very common thing.......one small tip for the future, change the clamps to the type that are a "band" of metal (bit like a large/wide hose clamp) and turn the tightening bolt sideways when tightening. Then there is less to catch if there is a next time. "U" bolt clamps are not a good idea for our cars unless they sit away from the lowest point of ground clearance. If you already have the band type then good.

I always use these people for fibreglass stuff....https://www.ecfibreglasssupplies.co.uk/
Very helpful, good price and will answer all your questions.


In my own experience, old yogurt pots are good for mixing resin in & as others have said, you will need lots of brushes & gloves & cheap enough to chuck away. Also, always remember to put the mixing container somewhere safe as when it's going off, it gets very hot & so may be a smallish fire risk. For some strange reason I always enjoy doing this type of job......I must be a little strange.....

Miles Wilkins book is a must if you own an Elan.

Good luck

A

[dougal9887]

I agree with the tissue and resin on the surface, however the OP didn't appear to be too worried about the underside of the car appearance.
If it was on the upper body I would add that once the temporary supports are removed, the surface should also be ground back to form a shallow recess surrounding any damage, screwholes etc. Then apply a single layer of resin/tissue within the recess and finally finish with body filler.
I have no evidence of repairs by this method 7 years on.

[Barney]

I believe there is a relatively new fabric called Peel Ply that could be spreadout on the underside and once the resin has gone off can be removed. Details can be found on http://www.ecfibreglasssupplies.co.uk/category/peel-ply

I have no experience of using it but have been following a yacht makeover where the results for a smooth finish after lay up seem to be very good
https://www.youtube.com/watch?v=GgL86Pc99M4 about 8m:30s for removal of peel ply.

[JonB]

Interesting, thanks!

I've been looking for a copy of Miles's book for ages. They are unnecessarily expensive when found - cannot think of a reason why.

I would like to have the cracks closed up for the repair as I think this will make them harder to spot. They're under the bumper but as this area is painted I would like to try and avoid the necessity to respray as that is beyond my ken!

Only thing that concerns me is whether or not a repair to one side of the cracks will still flex and open the cracks. I see the reasoning behind grinding the inner panel back to make a bowl or valley - how wide should it be?

I guess I'm lucky that it's the boot floor I'm repairing. About as invisible a place to repair as is possible, bar the wheel arches, and easy to get at. I was thinking of laying a thick mat to include the exhaust mount bracket bolts so that the repair will be stronger than original.

As to exhaust clamps - I had a thin clamp such as has been suggested that itself got ground away, so I replaced it with a U clamp, upside down to keep the long threaded parts away from the floor. Despite this the clamp was half ground away and dug into the silencer's input pipe, deforming it quite badly. I'm pretty annoyed at that because it was a NOS silencer. But... oh well. Life goes on. As the front clamp also came loose I was able to reset the centre pipe somewhat and get it, and the rear clamp, closer to the chassis. Now the rear clamp is fouling, so I'll be buying another low profile clamp.

[Barney]

From that same YouTube series (some good fibreglass info in the series), I hear him explain the magic ratio of 12:1 for the slope required either side of the crack or hole. So lets say its 5mm thick then grade back each side by at least 60mm.
The decision to brace across the crack is one that I cant really comment on - I guess that depends on how much flex is possible between the two parts of the fibreglass.

Good luck with whatever route you take.

[Foxie]

In 2004, returning from the MSA Euroclassic to Florence in my Plus 2, my wife and I called by to visit my brother in Milan. Going in to the underground car park I caught the exhaust of the Plus 2 on the lip of the ramp. The complete exhaust (all welded in one piece) from the manifold back, including a large lump of fibreglass with the rear mounting, was ripped off the car. I got a fibreglass kit and repaired the fibreglass damage. ( I had to repair 4 cracked wheel arches and more when I originally got the car ) The main pipe had been bent. We found a garage in the Golden Pages which agreed to repair the pipe. It was about 3 miles away, across the north side of Milan.

My brother and my wife, with the exhaust pipe/silencer sticking out the back of his little Fiat hatchback, and me in the Lotus headed off across Milan, with the deafening rasp from the open manifold echoing through the narrow streets. We had not gone half a mile when I noticed that I had a large POLIZIA car on my tail. Expecting sirens and flashing blue lights every second , I drove on in mounting terror. They must have followed me for over two miles. Then as suddenly as they appeared, they were gone ! Whew !

We arrived at the garage,(see pic) where the pair of (non-english speaking ! ) mechanics did a very nice job repair on the pipe and refitted it to the car. They charged me what I thought was a very reasonable ?100 for the while -u-wait service. ( cash ! )

The repair survived the return journey to Ireland, (over the top of the Little St Bernard Pass, and the Col de L'Iseran), and for a long time more, until I eventually fitted a substantial skidded clamp to the gearbox. I haven't lost an exhaust since, and the original emergency fibreglass repair is as sound as ever.

[wotsisname]

There is a tool that can be inserted into pipes to make them round again. Stainless Steel might be too tough, but it may work Ok for mild steel...not used one myself though.
https://www.carbuildersolutions.com/uk/ ... htener-set

[nmauduit]

There is a tool that can be inserted into pipes to make them round again. Stainless Steel might be too tough, but it may work Ok for mild steel...not used one myself though.
https://www.carbuildersolutions.com/uk/ ... htener-set

I've used it on different race cars where low bodies don't get along well with speed bumps or track vibrator : it works quite well, even deep with an extension (the trick is to do a little at a time, and come back to do some more if need be). Using heat to further improve results would not be recommended since the tool relies on rubber O'rings for initial grab inside the pipe.