Listers:
FYI, while trying to determine what caused water infiltration into the balsa core above the water line up forward (the last place that hasn’t been repaired), a few days ago we identified the fittings securing the forestay chainplate as the likely culprit. Although I’m sure there are more accurate names, the two fittings work together to make a stemhead fitting. One fitting runs vertically on the uppermost portion of the bow, just below the deck, and has the forestay chainplate (looks like a large tang) welded on it. The forestay chainplate/tang comes through a slot cut into the deck. The second fitting is bolted onto the deck and has a slot for the chainplate/tang at the forward end and some hardware to connect jib tacks at the aft end. We believe there are two issues at work that caused water infiltration: 1) the lower set of bolts holding the chainplate/tang fitting were drilled through the uppermost area of balsa core, thereby providing a pathway to the core if not properly sealed (which they were not); and 2) the deck fitting that fits around the chainplate/tang was allowing water in (probably a lot over the years). When we removed the deck fitting, we discovered that it was originally installed about ¾” aft of where it should have been. This was immediately obvious because the originally drilled holes and the aft portion of the slot where the chainplate/tang comes through the deck had been re-glassed. We then realized that the forward portion of this fitting had been modified to fit the more forward location (the forward rectangular corners had been cut off so the fitting/plate would fit). We also noted that the slot for the chainplate/tang was not centered, with the tang pushing against the deck opening on the port side while leaving a 3/16” or so gap on the starboard side. We widened the slot on the port side to accommodate sealant. We will be putting everything back together when it warms up a few degrees. We are debating what sealant to use for the deck fitting, particularly in the slot around the chainplate/tang. My expert is thinking Sikaflex 295. What say you? Matt C&C 42 Custom From: Dennis C. via CnC-List <cnc-list@cnc-list.com> Sent: Tuesday, March 22, 2022 2:50 PM To: Stus-List <CnC-List@cnc-list.com> Cc: Dennis C. <capt...@gmail.com> Subject: Stus-List Re: Chainplate Sealing - now sealants in general Some thoughts on sealants. Sealants are primarily silicone, polysulfide, polyurethane and blends of them. Add to that butyl rubber. First, as a rule, I like butyl for any hardware that has the potential to flex or move. Chainplates fit that criteria. My default sealant for most everything else except plastic is LifeSeal. For plastic I generally use silicone. Here's a reference for where to use sealants: https://drive.google.com/file/d/12WmFxRiqzUw2xiqLaEtfBpS1pYocZID-/view?usp=sharing Note that Life Calk is a polysulfide. Do not use polysulfide for plastic. LifeSeal is a blend of silicone and polyurethane. 4200 is polyurethane. I don't use 4200. Got too many partially cured tubes. Look at the expiration date before you buy. 5200 is NOT a sealant. It's an adhesive. From the 3M website: "3M™ Marine Adhesive Sealant 5200 is a one-component, high-strength, moisture-curing, gap-filling polyurethane for permanent bonding of wood, gelcoat and fiberglass." Note the word "permanent"! A bit off the subject, but Flexpaste seems to fix gouges in rubber rub rails fairly well. Who'd a thunk it? An "as seen on TV product" that actually works on a boat! -- Dennis C. Touche' 35-1 #83 Mandeville, LA
