A disc wheel gives you about 1minute advantage over the bike course of an Olympic triathlon (40km). However, these wheels are very expensive. So I decided to cover the back wheel of my Felt bike with this homemade Depron + self adhesive vinyl film disc. You need for this instructable

a 1250/800/3mm sheet of Depron; you can use other foams too, but in my opinion Depron offers the best strength to weight ratio.
self adhesive vinyl film
thin cable ties

scissors, screw driver and a knife

Step 1: Cut the Foam Disc

Cut a disc out of the foam. The disc should be slightly larger than the bike's rim.Remember that you will need to cut a second disc out of the foam sheet.
Cut a hole in the middle of the foam disc.
Cut a straight line to the edge of the foam disc.
Pre-mount the disc on wheel.
Overlap the foam and mark the overlapping part.
Cut the overlapping part.

Step 2: Add Adhesive Vinyl Film

Pre-cut the self adhesive vinyl film. It should be slightly large than the disc foam.
Put the foam disc on the vinyl film. Apply the vinyl film by removing the paper release liner step by step.
Put the overhanging vinyl film over the edge of the foam disc and stick it to the back.
There might be air bubbles. Carefully cut them with a sharp knife to remove the air.

Step 3: Mount the Disc Cover on the Wheel

Put the cover on the wheel.
You will need to attach the cover with thin cable ties. Use a screwdriver to make holes in the cover. For each cable tie you will need 2 holes.
Put the cable tie through the first hole, then behind a spoke and finally through the second hole. I used 6 cable ties per disc.
Cut the overhanging part of the cable tie.