by KCStudly » Wed Jun 22, 2016 10:28 pm
Epoxy is pretty impressive stuff. I recently had a minor chip on the back edge of one of my front lower teeth. Today the dentist repaired it with, you guessed it, UV cured epoxy. First he roughed the surface (imagine that whirring high speed die grinder tool noise that everyone winces at, but w/o the pain… no nerves exposed). Then he applied a primer/curing agent with a small syringe, removed excess and dried it. Then the resin, which I assume is premixed and filled with some sort of thickening media (it color matches teeth). Stuff cured in seconds with a little light beam tool. Then he shaped it a bit, faired the lap edges and gave it a buff… just like what I have been doing… only different.
In the real world of camper building I got the bottom edge of the curb side door all trimmed and cleaned up, thus completing the basic glass work on the door edges.
Looking ahead on my list for a little something more to do tonight, skipping past door hardware, and doing the door skin layups, I revisited the idea of cutting rabbets along the galley wall edges to form the hatch seal mating surface. The idea has always been to keep the inboard surfaces of the wall edges closer/tighter to the hatch lip, with the outboard surfaces stepped down allowing more of a gap so that the seal is not over compressed. My thought was that the step would also act as an extra barrier that moisture would have to climb over in order to get in.
Now, IIRC I have at least 1/8 inch clearance between the wall (uncut as it sits now) and the hatch, and in some places perhaps a bit more. (Between the hatch “bumper” and the rear edge of the floor I only have 1/16 inch.) The D-shaped ribbed bulb seal has a free height of about 3/8 inch and the rule of thumb is to try to compress the seal about 1/3 of its free height, not more than half (although the seal bulb doesn’t collapse on itself until it is about 1/8 thick… i.e. the section thickness of the bulb wall is about 1/16 inch… and the closed cell foam it is made from can be compressed even further… doing so reduces seal life and can reduce effectiveness due to permanent deformation).
So that means my target rabbet depth is only 1/8 inch or less (3/8 x 66% - 1/8 (fat) gap = 1/8 inch or less). So if I err on the side of caution and start with a 1/16 inch rabbet, is that even worth doing? See what I mean? (Tony’s prompting to get this thing done is ringing in my head.)
Now after confirming that the doors swing fine with the 1/4 inch gap all around, and that the gaps there could have been, and would have looked even better if they were tighter, I’m thinking maybe I don’t want the hatch seal to be that same width, and maybe I don’t want the seal to rest flush to the edge of the wall where it will catch more UV rays. So what if I err on the super conservative side and don’t rabbet the wall edges at all? I can place the seal a little further in, centering it on the wall, and if it crushes too much and degrades, I can always come back later, cut the rabbet, apply some fresh epoxy, touch up the paint and try again.
With the rabbet it would not be easy to reinforce the wood grain on the wall edge with the glass tape due to the sharp inside step. Sure I could complicate the hell out of it, laying tape on each surface and even floxing the edge along the step, but I had resigned myself to just using neat epoxy, then paint. If I go without the rabbet it would be pretty easy to lay up the tape along the full width of the wall edges, and that wouldn’t prevent me from adding the rabbet later.
One last thing, before he retired Grant Whipp said that I could easily crush this seal down to 1/16 inch and he wouldn’t expect much degradation. As mentioned previously, the seal was shipped loosely coiled, with the roll being somewhat flattened in order to fit into the mailing envelope. That would have been fine, the seal was soft and sprang right back when I took it out of the package initially, but then I put it back into the envelope and stored it that way. So the next time I looked it had creases where the bulb had been folded back on itself. So I rerolled the seal and stored it laid flat in a bigger box from then on. Tonight when I looked at it again it had more or less recovered with just a slight wrinkle wherever it had been folded previously. So, yes it recovers over time, but no, it is not fully resilient.
I will sleep on it, but I am leaning toward the simplification of no rabbet. Regardless, there are still a couple of divots (one minor and one much more significant prior router oops) on the street side wall edge that need filling before either the router bearing or glass can be laid there.
Creeping along here, but have next week off thru the 5th, so I plan to make good progress shortly.
KC
My Build:
The Poet Creek Express Hybrid Foamie
Poet Creek Or Bust
Engineering the TLAR way - "That Looks About Right"
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