GLASSFIBRE REPAIR
A BEGINNER’S GUIDE
No need to fear GRP repairs with these helpful tips from Andy Pag
Repairing glassfibre can seem like a mystical art with so many products and techniques to know about. Get it wrong and it’ll need redoing within the year.
There are numerous ways to repair glassfibre so just because you’re not mimicking your boatyard neighbour doesn’t mean you’re doing it wrong. It’s helpful to understand the basics to avoid the pitfalls that lead to bad repairs. Any repair is going to follow these four steps:
Surface preparation
Application of resin
Gap filling
Finish
You can buy resin systems and product ranges which take the guesswork out of some aspects, and each comes with its own instructions, but a bit of knowhow will prevent you from getting sucked into the sales pitch and buying supplies you don’t need or aren’t compatible with your boat.
Stage 1: surface preparation
This is the dirty part. Sanding and grinding glassfibre is a horrible job. As it’s ground, minuscule shards of glass become airborne and land on your skin causing an itching that will drive you crazy. Wearing a forensic-style suit helps, and a respirator and goggles are a must, but no matter how careful you are it’s still going to itch and send dust everywhere.
Low pressure compressed air is the best way to get it off your skin, followed by running water, but don’t be tempted to rub it off, as this sends the glass powder into your pores and makes the itch worse.
Using a grinder with an 80-grit flap wheel is the fastest way to clean up an area ready for glassing, but it sends dust everywhere. Your boatyard neighbour will hate you and aside from itching, the microplastics you’re creating will end up in the watercourse. Asander with a connected vacuum cleaner reduces the dust and a well-run boatyard will insist you use one. Aplant hire shop will rent you one if you don’t want to spring for the cost of buying.
Arule of thumb is to sand back 12x the thickness of the material you’re repairing. So if the crack you’re repairing goes through a panel ¼in thick, sand back an area 3in around it. The aim is to do it with a gentle slope so you take hardly any material off at the outer edge, and are almost breaking through near the crack. Achieving an even gradient will help in the next stages.
