Step 1 This is the fin before backing.

Step 2 Roughly cut a piece of Silkspan that will cover the entire back of the fin.

Step 3 Apply a moderate coat of Ultra-Seal to the backside of the fin.

Step 4 Press the pre-cut sheet of Silkspan on top of the Ultra-Seal. Groove the Silkspan between the fin rays.

Step 5 Apply one more coat of Ultra-Seal over the Silkspan and over the front of the fin.

Step 6 The finished fin.