Mudguards

Probably obvious to some, but here's something to bear in mind when installing steel mudguards (with homemade fittings). From the Gilles Berthoud team when I asked what went wrong with my cracked one above:

Probably one of the following problems, or a combination thereof:
Holes drilled too big and/or not deburred, creating a stress riser.
Holes in the fender not drilled in line with the holes in the bracket, which could mean the bolts apply stress to the fender.
Unadapted bracket with the wrong angle, applying stress on the fender. If the bracket is too flat or too round and stiff, it pulls the fender out of its radius and applies stress to it.
Fender installed with too much stress (from tweaking the radius too much)