I'm building the Annapolis Wherry. Has anyone pre-coated (before stitching) the panels with epoxy. I talked to WEST system tech support, and they found this would not add significantly to the stiffness of the panels for bending.
My first few boat kits I'd epoxied the side hull mainly after the boat had been constructed. Lately though I apply a couple of epoxy coats to side hull panels before the build, as it helps avoid drip lines falling down a vertical surface. For any parts of those hull panels that have to be epoxy-stitch-glued to other pieces, I'll just give those parts a light sanding before applying the glue, so that the epoxy glue can adhere better.
By making judicious decisions on what parts to pre-coat, you can achieve some finish quality improvements and time savings by pre-coating/sanding some panels/pieces with epoxy prior to assembly. There is a small increase in stiffness, so some high-stress bends might be more difficult to achieve. Just choose wisely on what to pre-coat - most bends will be achievable. However, as you said, you can often achieve a nicer finish (no drips, etc.), and achieve it more quickly (much easier to sand flat panels with no corners, filets, seams, etc. to worry about) by pre-coating.
Pre-coating over stained panels (if you choose to stain anything) is almost a requirement prior to assembly. You don't want epoxy anywhere near the wood until you've got it stained and then the stain is protected by an epoxy overcoat prior to assembly (even the first panel puzzle joint step). You might even use stain-colored epoxy for the assembly to make things look better. The trick is to try to never sand back into bare wood after staining - a tough thing to accomplish. I've stained several things on several boats now, and am beginning to shy away staining due to all the extra work involved. I just had to do a major repair on my (stained interior hull top 3 lapstrakes) NE Dory. A tree fell on it and I had to replace about a 2 ft length of the gunwale and the top two lapstrakes in that area. Trying to do stain matching was a PITA.
Don't forget that you can pre-coat many parts other than hull panels prior to assembly. One other thing to watch for if doing this is clearances for assembly fit-up. If you've got the "tab A goes into slot B" type thing going on, you have to consider how you'll handle that during pre-coating. Options include not coating the mating area, sanding back to bare wood in that area after coating, or slighlty altering dimesions of slot or tab (or whatever) to make things fit. I've selected many pieces for pre-coating that weren't called out for that treatment in build manuals and had success. This was especially true on the Road Runner (but then again there isn't really a detailed manual for that boat, anyway).
A trick I use to speed up pre-coating the bits-and-pieces parts is to make up a bunch of supports using scrap wood with 3 nails sticking up through them - sized for different parts. You can coat one side on the part while laying on your plastic covered table, then flip the part over with the wet side supported only on the 3 nail points. Then you can coat the other side and edges. You get a whole part pre-coated in one cure-time. The 3 little nail pinpoint marks become inconsequential as further sanding and finishing steps take place.
You'll often be doing some final, over-all epoxy coats after all assembly is said and done- to make sure all sanded areas are re-coated, to cover filets, etc., but it is nice to start with nicely pre-coated parts even as you finish up these final coats. - Bubblehead
Adding another tip: Waste epoxy and used brushes/rollers is a major expense on these boats. The fewer start-stop events you have with epoxy the better. So I've learned to try to prepare many things for coating at one time, many pre-fit-up joints ready for assembly, etc., then keep mixing and working quickly to apply to all the parts/joints at one time. Even had the clamping needs figured out and layed out in advance. This does take some large work surface area. I've had three six-foot tables full of parts going all at the same time at some points on some builds. And even then, I put tape or whatever on the partially completed boat to ID where I need to add some filet fill, dents, repairs or whatever, and will use the last of the stiffening-up epoxy in the cup to address these areas by adding a spoonfull of cellofill or wood flour to the remnants in the cup and doing the fill job. Of course this is all easier to do at 65 degrees than 95 degrees.
So, if you can forego the satisfaction of doing a start-to-finish coat/sand/coat/assemble/coat/sand process to see one part or step completed at one time you can save yourself a lot of epoxy, rollers and brushes. This technique does require lots of forethought and thinking things through, but actually speeds up the build process and saves materials at the same time. It also requires the self-discipline of not trying to see one thing at a time getting done piece by piece, step by step.
I'm just started building the Kaholo, so obviously there's no concern about the finish on the inside, but I'll brush on some epoxy on the edges of he frames and maybe where the frames go on panels, just to have some extra protection, in case water gets behind the fillets.
I guess I wouldn't coat the whole panels, since it would require sanding, once it's thoroughly dry, before applying another coat of epoxy
Dagi, I advise against pre-coating the bottom, side panels and frames with epoxy prior to stitching. If you do, it will block all of the pre-drilled stitch holes with with epoxy. Once the bottom and sides are together and glued, it is easy enough to coat everything well. The bottom of the top deck will be coated with epoxy prior to mounting it. JUST FOLLOW THE DIRECTIONS!!
