rain, rain go away.

Took this week off to rest and work on repairing our forward scuttle hatch on Shamrock, naturally, last week was dry and sunny, now its raining cats and dogs.
The jointery in the hatch frame is excellent, 1" thick x 6" tall, flawless construction. The problem comes in when they attach the substructure for laying teak. They used 1/8" teak plywood tack into place with mild steel nails (corrosion) while the resorcinol glue dried, over this they glued 1/4" marine ply and bedded/glued 1/2" teak, screwed through the teak and ply directly into the frame. 
All held well, unfortunately failure by previous owner to recaulk the teak allowed moisture to penetrate around the edges and get under and delaminate the teak plywood. Of course attaching 1" trim around the top put screws right at the joint line of the 1/8" teak plywood and frame, gave the water a direct route to the teak laminate core. Trim (eyebrows) while not keeping with the remainder of the boat, should have been 1-1/2" tall allowing screws to be placed 1/2" from the bottom of the eyebrow and directly into the frame, would have been a better alternative construction method. Untimately, don't think this would have made a difference as the plywood was not saturated with epoxy to prevent water migration.
All said and done, despite the delamination, the hatch still held my 200 pound weight without flexing. I removed all the bungs in the teak decking and eyebrows (trim); I was unable to work a pudy knife under the eybrows to pull them free, we placed a fir 2x4 against the hatch side butted up against the underside of each eyebrow and gave it a wack as we walked the full length of the eyebrow, all poped off without damage to eyebrow or frame. Not sure, but I think they used brown polysulfide or 5200 to bed the eyebrows. I useed a Japanese saws to cut down through the joint line between planks and into the 1/4" plywood; once the cut was carefuly made, we were able to wedge a 5 in 1 puddy knife between the marine plywood and teak plywood above each frame section and gently pry off the teak plank. Careful cutting and gentle prying  allowed us to remove one plank at a time, gradually weaken the structure and allow removal of the teak and ply without damage to the frame. The last layer of teak plywood glued to the frame with resorcinol glue was removed with  with a carbide scraper and block sanded to original wood, tough stuff, held good as any epoxy.
We learned an important lesson about Sunbrella, to delay repair of the hatches (re-caulking), the previous owner had new covers made for all the hatches in 01/2004, at that time there was only a small water stain in the teak ply of the scuttle hatch in one corner; by November, both forward corners had  6" moist delaminations. Sunbrella is a breathable fabric, as such, allows moisture to penetrate and traps it under the cover, with the covers laying directly on the hatches, there is no air space to allow moisture to escape. It's like camping in a tent, during a rain the roof is dry until you touch it with your finger and it will start to leak.
About 5 years back and two owners, they sanded all the teak and applied Cetol, last owner used Armada (acrylic), both painted over teak and caulking, as most caulking manufacturers warn of chemical damage to caulking. Teak and caulking expand and contract at differing rates, Cetol and Armada both cracked at the caulking/teak joint on all hatches, directing water into the joint. Either material makes the greatest non-skid material (bare teak) slipery and dangerous underway.
In retrospect, the original construction is as good as your going to get in the business. As always, there are a few things I would have done differently in building the hatches, epoxy saturated all the plywood and added more heigth to the eyebrows and placed the screws into the frame rather than into the plywood/frame joint line.
If we had know of the construction and owned the boat years ago, we could have prevented the present damage, I would have stripped all the Cetol/Armada off, removed all the caulking, epoxy saturated the plywood ends, recaulked all the hatches leaving the teak bare and omited the Sunbrella cover to let the teak breath.
As weather warms up, it looks to be a busy spring as we be removing the turtle and companionway hatch to inspect for similar water damage. Such is the nature of boats.
Best wishes,
Marty Chin, BCC Shamrock

Do you Yahoo!?
All your favorites on one personal page – Try My Yahoo!