Iota Refit | Tuesday, April 1, 2008

Determining the condition of, and replacing as necessary, the two fiberglass-encapsulated wooden knees used for securing the mast's lower shrouds was the final part of the project for me to address.  Tapping the outsides of the knees with a hammer seemed to indicate that the starboard side was sound, but the port side was ominously hollow-sounding. 

To confirm, I drilled some test holes through the fiberglass and into the wooden cores.  To starboard, both test holes revealed clean, dry, solid wood within, confirming the sounding results.  To port, my sounding results were similarly confirmed:  the wood inside was terribly wet and deteriorated, with no structural integrity remaining whatsoever.

Below:  port side (left); starboard (right)


To rebuild the port knee, I first removed the two shelves inside the locker behind the head.  I was able to avoid removing the main exterior panel.  Then, I used a grinder and a cutoff wheel to cut the fiberglass next to the hull, releasing the knee; once cut, the remaining wood inside simply crumbled away into an unrecognizable soggy mass.  Water poured out of the slot as I continued cutting.


I cleaned out the mess and then ground what remained on the hull to remove paint, old filler, and rough edges.  Then, I cut a new knee, using the old one as a pattern, from a lamination of plywood, epoxy, and fiberglass that I'd build previously:  two layers of 12mm marine Meranti plywood, epoxied together and with two layers of 1708 biaxial cloth on each side.  Despite being thinner (by 1/2") than the original wooden knee, the new structure would be substantially stronger.  I rounded the outer edges and sanded the new knee smooth.

With the bonding areas cleaned and otherwise prepared, I epoxied the new knee in place and formed gentle fillets between it and the hull; I also filleted and epoxied the knee to the underside of the deck.  The old knee had not been covered or secured to the deck, and it was this small gap, with its exposed wood, that eventually allowed water into the knee and led to its demise.  The connection to the deck wasn't required from a structural standpoint.

To hold the knee in place while the epoxy cured sufficiently, I grabbed the only thing at hand--a hammer, which happened to fit perfectly between the base of the knee and the cabinet.  I put a small lamp in place to help the cure along, since I wanted to install the fiberglass right after lunch.


Before installing the knee, I used it to pattern three layers of 1708 biaxial fiberglass, which I'd use to secure the knee permanently in place and encapsulate it fully, similar to the way the original had been installed.  Once the fillets cured sufficiently to allow me to remove the bracing, I installed the three layers over the top and out onto the hull about 6".  To further waterproof the top, I added small pieces of tabbing between the deck and the knee; again, these weren't required from a structural standpoint.


In other work, I removed the cockpit coamings so that I could apply the final coats of varnish, a process I hoped to have complete within a few days.

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