Found this regarding windsurfer repair (old BIC? notice the ref. to 1981 price), however it's confusing, not sure whether he's referencing cross link repair or using cross link to repair linear?

HOT AIR WELDING/POLYETHYLENE

We use the hot air welding gun manufactured by Leister Co. and distributed in the United States by the Robert R. White Co. The gun costs $385.00(1981 price). Special tips are required; these cost approximately $80.00 each. The most often used tip is ______ . This tip uses 3/16" extruded high density polyethylene. Also needed are scrapers for cleaning the polyethylene.

The cross-linked polyethylene that we use is known as a thermo-set plastic. This means that once the plastic is heated and melted, it cannot be melted without burning it. You need to use a material that is the same as the skin. ( Therefore, the kind of weld a hot air gun produces is not a true fusion of the plastic (as in metal welding, brazing or aluminum helearcing).

Experience bond and controlling the three variables are needed to produce a successful bond. Three variables are:

1. Cleaning both the polyethylene board and rod with a scraping tool.

2. Controlling the temperature of the tip of the gun at 3OO°C.

3. Drawing the gun across the weld at a steady controlled rate.

DON'TS

1. Do not try and melt the extrusion into the board.

2. Do not hold the gun for too long in one spot. It may bubble and delaminate the hull.

3. Allow the weld to cool completely before testing the repair.

The repair can be finished by shaving the weld flush with the hull with a sure form or sanding.

The hot air welder can be used to repair daggerboard wells, mast-steps, skeg boxes, and replace large hull sections that have been damaged. When replacing hull sections, mast-steps, and daggerboard wells, it is best to cut out the sections with 2-3" deep of foam attached. Bond this to the hull with the epoxy and then seal the perimeter with the hot air welder