How To: Osmosis treatment: how repairing and barrier coating with WEST SYSTEM epoxy will return your hull to almost new
By the time you notice blisters on the bottom of your hull, the process of osmosis is usually in an advanced stage, meaning you may be facing a large repair job. But fear not: by using the right products and techniques, you’ll save yourself time and hassle. Here, technical expert Richard Ross tells us about the osmosis treatment of Mirragio carried out by Reflex Yacht Painters at Monaco Marine in La Ciotat, France.
Whether it’s a big boat, like the 40m Mirragio, or a smaller one, the treatment for osmosis is much the same:
· First, make sure your hull is completely dried out
· Second, remove the blisters and repair the damage
· Third, add protection to seal out the surface and prevent moisture from re-entering
Patching up the hull
After the hull of the Mirragio was dried out and the blisters removed, the damaged surface was patched up with WEST SYSTEM 105 Epoxy Resin® and WEST SYSTEM 205 Fast Hardener® with WEST SYSTEM 406 Colloidal Silica®. The repair work was carried out in a tented-off area in order to create a warm, controlled and sheltered working environment. For this reason, 205 Fast Hardener was the perfect curing agent as it’s designed for use in lower temperatures, without the need for heating.
WEST SYSTEM 205 Fast Hardener was the perfect curing agent as it’s designed for use in lower temperatures, without the need for heating.
Once the repair work was completed, the hull was re-laminated with fibreglass and a mix of epoxy resin and hardener, with peel ply applied to create a lovely, textured and amine-free surface.
The barrier coat
The next job was to add barrier coats of 105 Epoxy Resin with 205 Fast Hardener and WEST SYSTEM 422 Barrier Coat Additive®. Using peel ply also means that no sanding is required before you add barrier coats, which is an important consideration. Sanding a laminated surface is time-consuming, messy and expensive, not to mention problematic, as you risk damaging the fibre of the fibreglass.
Applying a barrier coat is very important if you want to protect your hull from future damage because it helps to seal out moisture from the membrane. Once you’ve completed this task and the hull has been faired, you can apply antifouling paint. This will further protect against water penetration.
It may seem like a lot of effort, even for a smaller boat, but if you follow the right procedures and do a thorough job, then it will be that much longer before you need to carry out another repair on blisters – if at all.
Our thanks to Reflex Yacht Painters, who carried out this work in January 2014 and were supplied by West System International distributor, AGL Marine.
To find your local supplier of WEST SYSTEM and PRO-SET products, visit the WSI distributor page.
Read our article on fixing gelcoat blisters here.