How To: Repairing your fibreglass boat with epoxy
Once you’ve assessed the damage to your fibreglass boat and carefully prepared your surfaces, it’s time to laminate glass fabric with WEST SYSTEM® epoxy, as David Johnson explains.
In my earlier blog, Preparing for a fibreglass boat repair, I looked at the importance of working out the extent and type of damage you’re facing – and of bevelling the damaged area – before setting to work. Once you’ve taken those steps, what happens next depends on the size of hole you’re repairing.
The ultimate aim is to repair the skin of your boat to approximately its original thickness. Multiple layers of lightweight cloth will be as strong – or stronger – than a single layer of heavy cloth, so I would always suggest using WEST SYSTEM 739 450g/m2 Biaxial Fabric. Each layer is approximately 0.5mm thick, so if your laminate is 6mm thick, for instance, you’ll need around 12 layers of fabric.
Repairing in layers or using a single patch?
If you’re repairing an area of around 20cm diameter or smaller, it’s usually easier to bond your layers of fibreglass together away from the boat, wetting out and creating a complete single patch on a piece of clear plastic which you then bond to the craft. For larger repairs though, you’ll need to apply each layer to your boat individually, wetting out each one with epoxy.
The full process for both of these repairs is detailed in our publication, WEST SYSTEM Fibreglass Boat Repair and Maintenance. You can also find out more about creating a backing support, which is very useful if you have limited access to the panel that needs to be repaired, this type of repair is often referred to as a “letterbox repair”. But below I’ve outlined the key techniques I describe to people when I’m asked about fibreglass repairs at boat shows and other events.
Time to repair
Whether you’re creating a layered patch or applying layers individually, begin by taking a piece of clear plastic, drawing around the outside and inside of your bevelled area, and then use those drawings as cutting templates to create the required number of fabric layers.
In the 6mm example I mentioned earlier, that would mean you’d end up with a layer of fabric the size of the outside of your bevelled area, a layer the size of your tapered point, and ten layers of decreasing diameter in between. Biaxial glass fabrics are easy to cut with sharp scissors.
If you’re creating a single, layered patch outside the boat, cut a piece of plastic that’s larger than the repair area and allows you to carry the wet out patch to the repair, then wet-out each piece of biaxial fabric with epoxy and stack the pieces, smallest to largest, finishing with the larger piece of plastic. You could even replace this larger piece of plastic with peel ply to achieve a truly professional repair.
Next, apply thickened epoxy to the bevelled edge of your repair hole, apply the layered patch to the hole with the plastic or peel ply facing outwards, squeegee over the fabric to remove any excess epoxy and air, then allow the patch to cure and remove the release fabric.
If you’re repairing directly on the boat, make sure you start by using the largest layer of fabric, as this ensures you have the maximum possible contact with the repair surface. Apply a layer of thickened epoxy to the bevelled edge of the hole and to a piece of backing fabric. Then wet out the fabric and apply layer by layer, largest to smallest. (It’s a good idea to stop after you’ve laminated a maximum of 3mm of fabric due to the heat created. Applying peel ply means you can continue working once the first 3mm has cured.)
The finishing touches
Whichever process you use, after completing the repair you need to allow time for curing before removing the release fabric, fairing, finishing and then perhaps reaching for the paint or gelcoat.
It might seem like a complex process, but that complexity can easily be managed by careful planning. And don’t underestimate the role that the WEST SYSTEM 105-K Glass Fibre Boat Repair Kit can play in that process. It’s got everything you need to perfect your repair – from biaxial glass tape to epoxy resin and hardener, to peel ply and nitrile gloves.
Or, to put it another way, it’s your ideal preparation – in a box.
Find out more about how the WEST SYSTEM 105-K Glass Fibre Boat Repair Kit can help you create the most effective fixes to your fibreglass boat. And do contact us if you’ve got further questions about fibreglass boat repairs that you’d like to ask.