ABS Roofbox Repair

[Ham]

I'm going to repair my Thule roofbox, which is cracking on the curve just above where it rests on the bars.

I figger that a piece of abs, heat moulded to the curve, will work. Cemented with ABS solvent, with a pop rivet or two in to keep it in place. Now, here's the problem. Things like guttering will do a bonzer job of making a strong area of the repair, but being so thick and strong are likely to overstress the area around the repair. What is needed is light, strong ABS. I'm thinking paint roller tray. Anyone got better ideas or experience of repairing roof boxes?

[YahudaMoon]

I would not use a paint tray (cheese). Id go for guttering. OK there the same material though the guttering will be better quality as it has to be kite marked to British standard

Use an aluminum plate on the inside of your box though to stop the rivets coming out/loose

[Ham]

Guttering can be successfully moulded, but it is MUCH stiffer. given the amount of vibration and stress a roof box is under, I really don't think it would be ideal.  And yes, a paint tray is probably too low quality. Hence opening the question to the floor.

[YahudaMoon]

Yeah guttering would look like a butchers job'

You need to spend some time in your shed and fettle about. 

[Jurek]

... with a pop rivet or two in to keep it in place....

Test first.

The clinching pressure on a pop rivet could be sufficient to cause radial cracks in the ABS.

Putting washers either side of the rivet might reduce the risk of this happening.

[Jacomus]

I would be tempted to go with a DIY fiberglass kit, something like the one below - though I don't know if it would bond to ABS plastic.

Fibreglass KITS - Material and Tool Kits Fibreglass, polyester resin, fibreglass supplies, grp suppliers from Ariba

[Ham]

I considered fibreglass, but discounted it because of the harsh environment: vibration, cold, wet, dirt, etc added to the dubious adhesion to ABS, the cracks are on a bend with complex curves in tight radii

[Jacomus]

I considered fibreglass, but discounted it because of the harsh environment: vibration, cold, wet, dirt, etc added to the dubious adhesion to ABS, the cracks are on a bend with complex curves in tight radii

Hmm, I suggested it on the basis of it's use as fairings on motorbikes - harsh environmental / mechanical conditions and as you will be laying up yourself, it should conform very well to the complex shape.

I think that you are right to be concerned about it's adhesion though


Alternative suggestion - visit a few tips and try to get your hands on an old, broken roofbox and cut out the plate for the repair from that?

[Jacomus]

Perhaps some bumper repair stuff like

Repair Products - Repairing  Leather, Vinyl, Tile, Wood, Fabric & Cars - 12 Bumper Repair Kit

or

Repair Products - Repairing  Leather, Vinyl, Tile, Wood, Fabric & Cars - 74 Plastic Patch

might do the trick?

[rafletcher]

Use a heat gun to form the guttering - ABS deforms at higher temperatures.

[Ham]

As in my OP, I have worked that out. Trouble is, the guttering ABS is MUCH more solid than the surrounding, which, if it welds properly which I assume it will, is likely to create additional stress to what must be a weakened area.

[YahudaMoon]

Having worked as a commercial vehicle body builder for 20 years and working with all body materials I may be able to advise better with pics ?

[Ham]

Here it is.



There are cracks either side of the slidey bar connector, where the box bounces up and down on the bars.

More photos here https://picasaweb.google.com/londondailyphoto/RoofboxCracka#

[rafletcher]

Could be UV embrittlement too.

[Ham]

Tend to think not, on the basis that it has lived its life in the shade, and this is the underside. (it's about 12 ish years old)

[mrcharly-YHT]

Can you undo the bolts and slot an extra layer in?  I think that needs reinforcement.

[YahudaMoon]

Your only hope with that in my opinion is to use the method in the excellant drawing

Ive put 2" Inch /50mm in the drawing and 2 1/2 inch/75mm in the notes

I think 2"inch is to small, Id go for 3"inch + plate at least (I didnt see your other pics)

Then you need to cover the inside of the box where the ali is with fibre glass matting over lapping the ali by at least 2"inch either side

Making your fibre glass matting size at least 7" inch x 2"feet (or however long the damage is.

Then roll in your resin n hardner. I cant see it woking any other way


Theres no need for fibre glassing the outside

[Ham]

Well, Jacomus reminded me that I had seen those Repair Products but was trying to be too clever by half. I ordered the patch on Friday, arrived Saturday and I con confirm that it is the canine's cojones.

Job done.

[Valiant]

Bit of epoxy resin and jobs a good'un?

[Ham]

Patches are self adhesive with some kind of solvent cement. Really not going ANYWHERE.