Hi, I need some urgent advice please. I am making a mould for a bike heat shield. I am using the green Tooling Gel coat. When I demould the part I get lots of damage on the gelcoat surface. Especially at the edges bits break off very easily and around parts where I will need to drill in bolt holes. The damage does not appear repairable. I need your urgent advice as I need to finish this part this week. Thanks

Hi,

Firstly it should be perfectly possible to produce a mould without damaging the gelcoat surface, the damage will have been caused either by insufficient release agent application, gel coat that has gone past the 'tacky' stage (preventing the backing material from bonding properly) or by mechanical lock, you must ensure that the pattern suface is of good qualityand that the  mould can be withdrawn from the pattern without any areas with 'under-cuts' it some cases you may have to consider modifing the pattern or producing a split mould.

You will be pleased to hear that most damage is repairable; you can repair any chipped areas of gel by mixing up another small batch and apply it to the chips, you must first key the area with a course sand paper to ensure that the gel adheres properly. Build the coat slightly higher that the surrounding area and leave it to cure fully before flating it down with fine sandpaper and polishing it in, you should find that this will create a virtually invisable repair.

Paul Statham
Easy Composites / Carbon Mods - Technical