That is exactly how you bed fasteners in wood-core fiberglass boats. You over-drill the hole, fill it with epoxy, then drill the fastener hole in the epoxy. This prevents moisture from rotting the wood core.
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I removed the door, flipped upside down, sanded the bottom, taped around the edge (a little proud) and poured west system epoxy. After sanding it down a bit it's about 3/32" thick. Drilled holes and then filled with epoxy for the door shoe/sweep screws. Also injected a bit more epoxy into a few other spots that seemed the surface had opened up a bit but when I looked that the door (top/bottom) the glue joints were tight. Added 3 more coats of exterior finish. Put on new door sweep and seals. Looks good IMO after 9 years so far.
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Nice work, Mreza. The fact that the crack goes diagonally through one of the staves makes me wonder if sunlight play a role in those cracks forming. Also, your tenon must be lower than the top of the cracks, and on the center mullion the tenon must be right where that crack occurred. With the mullion crack, in particular, I don't see how water played a role in the failure. I'm thinking sun was the prime contributor. The winter sun must hit that door at the bottom, yes?
John
Thanks John. I think the crack may be very close to the tenon (here is the picture I have for the bottom rail mortises).
I don't think water has been an issue at all. The most likely cause must have been: 1) I couldn't get proper seal/coat at the bottom of the door as I finished coated the door after hanging it, and 2) sun. This door gets a lot of sun all winter/summer and it gets hot (hot to touch!). It is quite noticeable the fading of color of the door vs the 1/2" or so part around the edge that lays on the weather seal (those area's color hasn't changed much).
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Oh yeah, I see how it's faded down near the bottom, now that you pointed it out. The tenons should help prevent the stave core from splitting with its cross-grain glue surfaces. I wouldn't be surprised if the cracks in the stiles end near the bottom edge of the lower tenon. In any case, you've done a nice job with the repair work. Hopefully, it will be clear sailing from here on out with nothing more than routine maintenance.
John