After working out the method on the port exhaust flange, making the second one was much quicker on the starboard side.
I’m using four layers of 1810 biaxial for the flange. Since the Centek exhaust components appear to be no thicker than one or two wetted out layers, the exterior flange should be the toughest part of the assembled piece.
These scissors make a world of difference when it comes to cutting tough fabrics. They look like they’ve been through a big boat refit, but they’re still cutting well…even after chewing through that Kevlar we used to make the bullet proof cabin top.
Once the fiberglass is fully wetted out, I lift it into place on the hull. I’ve already put the blue tape around the hull opening and applied mold release wax carefully to it so the finished part will pop off easily.
I wrapped the flange layer inside the pipe on the bottom. On the top, where the pipe sticks out a bit, I applied another strip of wetted out 1810 on the inside that extends out and joins with the outer layer. The finished part should be quite robust.
The fairing compound is the same US Composites 635 thin resin thickened with a 1:3 ratio of cabosil and microballoons that we used elsewhere on the boat.
Initially I liked US Composites epoxy, but the more I use the stuff the less I’m impressed. While their 4:1 fast hardener will smoke in the pot in no time on a hot day, it takes way too long to set and a whole lot longer to cure than West System. With US Composites, you can sand the fairing compound the next day IF it’s warm enough overnight. With West in identical conditions, you can start sanding in two hours. If I had to do it all over again, I would have saved a ton of time and money and just bought a barrel of West resin from the start.
The one plus point for US Composites is that if you’re wetting out plywood edges or otherwise trying to seal up a piece of wood, the fact that it takes forever to set and cure seems to allow it to wick in further than West. That’s just a guess though.
Anyway, the following day I popped out the two flanges and continued fitting them.
Before popping the parts off the hull, I drilled the holes so the flanges would bolt up exactly as they were molded. Even without bolts holding the parts in place, they fit right up to the hull.
I used a 5 gallon bucket to trace out the circle…the same bucket I used to outline the 1810 fiberglass fabric. Then I hit it with a grinder and sanded back to the line.
I need to weld up some 6061 angle and make a platform for the muffler, but otherwise the exhaust system is ready for the paint shop.