The construction system was an aspect that drew us to CM. It uses top end materials, not generally available from production brands.
Epoxy resin, carbon and e-glass, PVC cored laminate is infused and post cured. The resin is the glue that bonds all the hull materials together so it has to be best to use the strongest glue. Epoxy resins have up to four times the bond strength of polyesters (used by most builders) and vinylester (a modified polyester) falls between the two.
From my experience, epoxy is essential if you want to build a light and strong boat. Race-boats wouldn’t use anything else (unless restricted by class rules, to limit cost).
Carbon fibre adds stiffness for a given weight but also adds cost. CM offer a couple of options regarding the amount of carbon used and we’ve opted for bulkheads, bridge deck and cabin top. They create a carbon “box” in the middle of the boat where the hulls are joined, the rig sits and shrouds attach, which should contribute max stiffness per precious £.
The forward cross-beam and longeron will also be carbon wrapped.
As a yacht engineer pointed out, stiffness is important in cats because their structure is fundamentally flawed! The mast sits on a bridge – the forestay is attached to another bridge – and the shrouds are attached to separate hulls, which could be on different waves. Monohulls and trimarans do have upsides…
Stiffness maintains headstay tension (upwind rig efficiency), translates drive from the rig into boatspeed and reduces fatigue from flexing, to make the boat last longer.
The hull and cabin top shapes are designed to keep the weight down, with simple curves in most areas allowing the use of un-scored foam. Complex curves require scored foam to bend to shape and these scores open up, fill with resin and add hundreds of kilos for no structural benefit.
Furniture The furniture in the CM is foam cored and laminated to the hull shell so it’s light, it contributes to the overall structure and it can’t creak.
Finish Like Gunboat and HH cats, the CM’s hull is finished by fairing and spraying. Awlgrip paint saves several hundred kilos over gelcoat. There are many colours to choose from and, after five years in the sun, painted epoxy boats tend to look much smarter than polyester gelcoated boats. AND… polishing is not needed! Now we’re talking!!
Construction summary
Coming from a composite boat production background, I’m impressed by the build system. Race-boat level lightness, stiffness and strength, with added benefits.
