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Monday, July 01, 2013

Wet Core!

It was recently discovered that water had creeped into the laminate of the deck where the main mast is to be stepped. The culprit was a small tiny hole, less than 1/16th of an inch, where a plumb-bob was hung to spot the position of the main mast down below. Unbeknownst to me, a piece of tape covering the hole had taken a holiday before last winter. Its absence allowed water make its way into the laminate.

The discovery of this was somewhat abrupt. The admiral, one day, enjoying the view from the deck, stepped on this area, which caused a stream of water to squirt up and out of the hole. The fact that standing water was in there meant it was not absorbed by the plywood core (perhaps the core was already saturated), but there were some pockets inside the laminate where the water pooled. This in a place where you want the layup to be as solid as possible (bears the weight of the mast). This had me concerned, so last weekend I cut out the top laminate to assess the situation.

Top layer of laminate exposing plywood core.
This first picture is the exposed plywood core. The black bits are where water has been standing for some time. Once the fiberglass layer was cut, it came out with little effort. I pulled it up by hand. There was practically no adhesion between the glass and plywood. Still a mystery was how so much water got in there. Focusing on the removed bits of fiberglass reveal the story...

Underside of top laminate. Note the "rivers and bays".
Like a geologist examining the strata of rock and soil layers, I discovered how the deck was layed up by the factory (in this area at least). It must have went something like this:

  1. spray the gelcoat in the deck mold
  2. lay some glass at the mast step
  3. trowel in some mish-mash (asbestos thickened resin most likely) at the mast step
  4. place in a small rectangular piece of plywood core at the mast step
  5. lay some more glass, this time for the entire deck area
  6. place the plywood core for the whole deck
  7. lay the final glass laminate for the deck.

The factory mistake appears to be at step number 3. The factory did not use enough mish-mash, and this left large pockets of air between the glass and core. You can see it on the underside of the glass laminate in the picture. Notice how there are some flat surfaces, but otherwise there are gaps like "small rivers and bays" for the water to pool and sit. These areas appear brown in the picture. There were some areas of glass where there was no mish-mash at all.

The good news is that this is isolated to the step area. No water appears to have contaminated the main deck core. What to do from here is unclear. Cutting out the wet core will be difficult. The adhesion appears very good on the middle internal layer of glass. The plywood is pretty solid, not soft, as would be the case if there was significant rot. I am wondering how long it would take for the plywood to dry out over the warm summer months.

More on this later...




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