It's amazing how much rot there was throughout this boat at and below the waterline. It had essentially been held together by the planking. I think I will now be replacing EVERY frame from the transom almost to the stem. Those nearest the stem (2-3 frames) may just get new tails scarfed in. Almost all of the rest are rotten/cracked/missing/compromised from the turn of the bilge to the keelson. Most of the frames that land on the stem are okay. Photos (coming soon) will tell all.
Looking at the keelson lying across a couple of sawhorses now, it has a huge "S" curve to it. From earlier discussions both here and on the phone, I'm pretty sure the keelson should be dead flat on the bottom side from the tip of the stem all the way back to the transom. That puts the taper (reduction in height) on the top face of the keelson, right? Otherwise, if the top of the keelson is supposed to be flat, then I need to take the taper from the underside. I can measure the old one to determine the original height at various stations along its length; I just don't know where the reference line should lie!
Also, what about the sister keelsons, AKA stringers? They have quite a crown, running fore & aft. The center portion is fairly flat, but the rear 2' or so drops about 1/2", starting where the aluminum transom brackets attached, and the forward 3' or so drops something like 1.5"! I think I posted photos of this earlier. The rear I understand due to the weight of the outboard pulling up on the stringers via the brackets. What I'm not sure of is whether the taper on the front end of the sister keelsons occurs only on the bottom of those members, with the top (supposed to be) flat, or if the top face was shaped such that it curved downward toward the front. This is really the same question that I had for the keelson, but with the opposite assumption.
Putting a long straightedge on the underside of the floors (cross-members between the sister keelsons), the rear three are very much inline. The front one is lower by about 3/8 - 1/2". This pretty much follows the serpentine flow of the bowed keelson/hogged keel. I just want to know what it SHOULD be as I replace all these longitudinals.
Any advice is welcome! Measurements and/or comparisons to your own boats is even more welcome.
-wte
PS - I'm thinking of gluing/epoxying my new keelson into one monolithic timber with screw reinforcement. Three reasons: (1) there's so much rot from water that has gotten between the boards that I'd like to eliminate those cracks, even if they're bedded together, (2) if anyone ever takes this boat apart again to this extent (in 2059?) to replace part of the keelson, I don't think it's going to be too much more work for them to replace the entire thing, and (3) if any one part of it's rotten, it probably all needs to be replaced again anyway. Your thoughts? (I know I've heard of oak/epoxy issues, esp. in salt water...)
