Core Values

Last summer we peeled up all the teak decking and filled about a thousand screw holes in the fiberglass skin with epoxy.  We knew we had some serious moisture issues in the core material and would eventually need to address the problem. “Eventually” finally came last week.

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The new bowsprit is nearly finished (more on that later) but before I can install that and the new Samson posts I still need to tear up that last little bit of teak deck hiding underneath (and deal with the wet core on the foredeck).  The task is messy but the concept is simple, and many others who’ve replaced deck core on their “leaky teaky yachts” have gone through a similar procedure.  First, support the ceiling from the inside so you don’t deflect the inner skin while you’re working above.  Next cut through the top skin of fiberglass and pry it away from the core material.  Finally, dig out all the bad core, epoxy in the new core, and re-laminate the top skin.  Simple, eh?  Well, almost.

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Jeni’s been working out of town the past couple weeks and this presented the ideal opportunity to tackle this looming must-do project. I needed to take apart the v-berth where we sleep in order to support the ceiling from inside.  The inner and outer glass skins are each about 1/4″ thick and the coring is 1/2″ thick.  Laminated together in a sandwich construction they make for a very stable structure, but individually they’re quite flexible.  Once the skin is cut loose simply standing on deck while working can cause the crown to deflect inward, potentially causing permanent deformation as the resin cures.  Cutting fiberglass is a messy ordeal, but running the Shop Vac just ahead of the Skill Saw blade (set to cut about 1/2″ deep) made pretty quick work of the task.  Since the bowsprit is still on the boat I only cut up to the Samson posts.  I’ll do the rest of the foredeck once I get the sprit removed.  The chain locker bulkhead wall is a good support structure for the rest of the deck and the remaining area isn’t really large enough to require additional interior bracing.

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Once the skin was cut loose, next came the chore of popping up the individual blocks of wood coring.  The Ta Yang shipyard used a hodgepodge of some sort of  end-grain soft wood and rectangular pieces of plywood in their deck construction.  The upper deck skin on these boats are glassed upside down in the mold.  Workers then hand place the individual blocks of core material and the spaces between the blocks are flooded with resin before laying up the inner skin.  Taiwanese Tetris, if you will.

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After all the core was removed, the insides of both skins received a rough sanding to remove any additional lumps of resin and give the surfaces some “tooth” for the new epoxy to grab onto.  I ordered the new end-grain balsa core from Merton’s Fiberglass Supply and they were about the cheapest place I could find at $27 per 2′ X 4′ sheet, plus shipping.  Using the top skin for the pattern I simply laid it out and cut the core to size using a utility knife.

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Each sheet of balsa, as well as the inner surface of glass skin was thoroughly wetted out with neat West 105/206 resin and slow cure.  Balsa soaks up the thin resin pretty good, and the initial wetting-out helps it stick better than if only thickened resin was used.  After that, thickened resin was spread using a notched trowel and the balsa sheets were weighted down until the epoxy cured.  The same wetting-out and thickened epoxy process was applied to the top side of the balsa core as well, and the fiberglass deck skin laid in place and weighted down.  With the large quantity of resin needed and the fact that daytime temperatures were approaching the mid-90s, I wouldn’t have been able to get it done without a helper.  Jeni was mixing up pots of epoxy as quick as I could get it spread, and working as a team we managed to get it all down without loosing a batch.

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All in all the job wasn’t too difficult, just a bit messy.  Coming in at over a half gallon of epoxy (not to mention all the thickening agent) to finish around 26 square feet of deck, this definitely isn’t one of those low-buck projects.  And, there’s still the side decks and under the bowsprit to finish…

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