Q Can I repair the damaged GRP rear bumper panel on my ’van?
After returning from a recent trip to Pembrokeshire, I noticed some damage to the passenger side rear of my 2019 Elddis Autoquest motorhome. It had either been hit when parked up or, more likely, I caught something when reversing.
The rear bumper has a right-angle split in it about 8cm high, and 5cm horizontal. There is nothing on the other side of the split, so there is no problem with water getting into the interior.
Rather than replace the whole bumper, I am wondering if it is possible to glue the split back together and, once done, filling any imperfections. If so, what is the best adhesive to use? Also, if it needs a small amount of filling to smooth any imperfections in the repaired area, what type of filler would you recommend?
Steve Wilshere
AI have carried out a lot of repairs to GRP (glass-reinforced plastic) and, when you have some access to the rear of the panel, this is very helpful indeed.
The first thing to do will be to get the surfaces to line up where you want them to be without any stress. This is probably the most difficult step because getting the two sides to mesh together again by pushing and pulling nearly never works because of the way that it splits and fragments. You need to be brave and cut the damaged edges away. Once you have removed enough that the surfaces will sit in the right place with only a little persuasion, it is time to turn your attention to the rear.
The rear has to be stabilised and braced to keep the front edges in shape and minimise the amount of remodelling that you will have to do. It must be reasonably clean, though, so give it a thorough wash and let it dry out.
I have normally used glass fibre matting and liquid to achieve this and have generally used Fastglas by Isopon. You cut the matting into the shape that you need and then mix the glass liquid. Hold the matting where you need it to be to bridge and reinforce the rear of the panel and paste the liquid onto it. I have also used strips of aluminium as a spine to provide the most rigidity and bridge the gap before applying the matting and liquid over it.
A little glue to hold the strip in place will make things easier, but the glue is only to hold it in place and should be nowhere near the repair edges. If the panel will not hold in the desired shape, you can use a longer piece of aluminium, bent to the correct shape and drill holes in the panel at the ends of the strip so you can bolt it in place.
Make sure not to get any fibreglass on the bolts because you will need to remove them and fill the holes later.
The fibreglass mix will get warm before it sets and this does not take more than a few minutes. Leave it for as long as it takes, so that it no longer feel tacky. This will be a few hours.
Now you can turn your attention to the outside. You should now have a fairly good restoration of the original shape of the panel with the broken edge being just a gap and this needs to be filled and smoothed. I use a plastic repair putty. I do not use fibreglass repair mixes because they set very hard and are prone to cracking. The mixes designed for plastic allow a little flexing and this is desirable.
All that is left now is to fill it, smooth it and prime/paint. Use a ‘high build’ primer to fill any imperfections before painting with a GRP or plastic paint; again to allow a little flexibility.
The scary part is having to trim things back so that they can sit flush. Other than that, if you take your time, it can be an enjoyable project. I always had to get this sort of thing done in a rush to get the vehicle back on the road, so it did get a little stressful at times!
Nick Fisher