Hi,
Do I need to varnish outside of my sectional shearwater bulkheads? The edges of the bulkheads are going to be exposed under sun light. If yes, do I need to fill the weaves and sand smooth before varnish? I'm about to put graphite epoxy on the bottom panels. Can I just use the graphite epoxy on the outside bulkheads for uv protection?
Chi
I've never built a sectional Shearwater so I can't give you a simple yes/no, but here's the info to help you make your decision:
Any epoxy exposed to sunlight needs UV protection.
A graphite-rich graphite/epoxy mix will provide that protection.
Graphite-rich graphite/epoxy mix is slippery. It leaves marks, like a pencil, when rubbed hard. Some adhesives may have trouble sticking to it. These are not problems when used as a scratch-resistant bottom paint, but should be kept in mind when deciding if it's OK for bulkheads.
Varnish is easier to properly apply to a smooth surface.
Epoxy-filled weave is more durable, more abrasion-resistant, than unfilled weave.
Painted, graphite/epoxied or hidden areas can have their weave filled with epoxy/phenolic microballoon mix. It's lighter, cheaper and easier to sand than epoxy. Adhesives also stick well to it and it provides a good degree of UV protection, though not as much as a graphite-rich graphite/epoxy layer.
Hope that helps,
Laszlo
Hi Chi,
here is how i apply Laszlo's formula in my kayak builds.
fill the weave on any glass on the outside of the boat including the outside of bulkheads on sectionals
fill the weave on any internal area that will be routinely used/exposed to water/dirt (e.g., inside the cockpit).
consider strongly an extra layer of epoxy (or even glass) under high abrasion areas. i put an extra layer of glass/fill in two rectangles where the balls of the feet will be resting on the inside of the hull becuase they will abraid that area quickly without good protection...particularly if you pull mud/sand into your cockpit.
the only place i routinely don't fill the weave is inside my forward and aft compartments becuase i am rarely using them.
varnish or paint everything outside (or the alternative mentioned by - graphite/epoxy)
varnish/paint the inside of the cockpit that is exposed to sunlight.
remember to varnish your toggles that hold your hatch covers in place.
h
Thanks, Laszlo and hspira. This is very useful.
The surface below the deck inside the cockpit is not exposed to direct sunlight, so there is no need to varnish, right?
Chi
   Where are you going to carry it?
I have seen them inside a car and dissembled on top of a small car. Everything its exposed on top of the car.
i usually varnish the cockpit floor/side not covered by the seat that will get sun - in front of the seat to under the cockpit forward most part of the coaming opening....and add about another foot...becuase the sun is not always direclt overhead.
i do not varnish the underside of the deck.
h
Thanks Hspira!
Grumpy, I'm planning to carry it inside my van.
Chi