Here's an article by Edwin Thomas I found online:
How to Repair Rubber Dive Fins
The majority of dive fins on the market today are mostly plastic, but all fins have rubber parts and some high-end fins are still made using all-rubber construction. Rubber fins are more flexible than their plastic counterparts, but they are also less durable and more prone to tearing and other forms of damage. To get the most out of your rubber fins, a little knowledge of how to patch up tears and holes in the rubber is necessary.
Instructions
Difficulty: Easy
Tears and Splits
Things You’ll Need:
- Pocket knife
- Waterproof glue
- Duct tape
- Sandpaper
- Tape measure or ruler
- Bicycle inner tube
Step 1
Cut away any loose or hanging bits of rubber with a pocket knife. Prepare the tear or split in the fin by scratching the surface of the rubber on both sides with your pocket knife. Do not gouge the rubber, but make sure it has a rough surface, as it's better for the application of adhesives.
Step 2. Apply a bead of waterproof adhesive to one side of the split or tear in the fin, and then force the two sides together. Wetsuit glue is a suitable choice, since it is commonly found in dive shops, but another waterproof glue will do in a pinch.
Step 3
Lay down a strip of tape down the top and bottom of the split. This both helps to hold the tear together and helps create a better finish when the repair is done. Allow the adhesive to dry for six to eight hours, then carefully pull up the duct tape.
Holes
Step 1
Shape the hole in the rubber fin by sanding it into a bowl-like shape with medium-grit sandpaper. This inevitably widens one end of the hole, but that is necessary for the repair. Sanding also roughens the surface for a good adhesive bond.
Step 2
Measure the top and bottom of the bowl-like hole you widened in your rubber fin with a tape measure or ruler.
Step 3
Cut out pieces from an old bicycle inner tube, making the first piece the same size as the wide end of the hole in your rubber dive fin. Then cut successive pieces of rubber, each one smaller than the one before, and stack these pieces up. When you have a stack as thick as your fin, stop cutting.
Step 4
Glue the inner tube pieces together using a waterproof glue, one stacked on top of another--from smallest to largest--so they form a conical plug.
Step 5
Apply a dab of waterproof glue into the hole in your rubber fin, and push the plug you made in Step 4 into the hole. Allow the waterproof glue to dry for six to eight hours before you attempt to use the fin.
How to Repair Rubber Dive Fins | Trails.com
