Coroplast would have been smart if I had read your post in time. And there's a member of (Canadian) parliament in the family, so we have a whole stack of lawn signs just sitting in the back yard! oh well.

Here's what my DIY fender thinks about all you naysayers:





Made using the plastic from a discarded tub of icecream, then made rigid with a coathanger spine that continues up part of the original fender, attached by drilling 2 holes into ends of both fenders and ziptieing together (probably should have used 4 holes and 2 zipties, but oh well).

The black duct tape covering it is because the way the plastic was curved, the ice cream label was showing on the outside. And I live in the type of neighbourhood where you don't want to have the words "red cherry" next to your ass, if you're male.

Went for a 20km ride today, and it had just rained this morning so the roads were all wet and dirty and full of puddles. I went over the puddles at full speed (something I would always avoid before), and the back of my shirt is COMPLETELY DRY AND CLEAN!!!! (well except for the sweat) Not once during the 20k did it even touch my wheel, despite the fact that it bounces around like crazy and should probably be attached to the rear wheel hub.

So it cost nothing, took 10 minutes to make, worked perfectly, and I got to say "TOLD YA IT WOULD WORK!" to everyone who doubted me. What a project