Dave
One final thought comes to my mind. Start out with plan to overdrill, epoxy fill redrill and seal method. Once you have drilled the oversized hole you will need to dig out the immediately surrounding balsa prior to the filling the area with thickened epoxy. It is during this digging out of surrounding balsa that you can determine if it is dry, wet, rotted or long gone. If wet then you follow the other peoples advice on what to do. If it comes out in brown gobs or chunks and is falling away then as others have said is rot. You need to open that area up and replace some core and definitely remove the rot. If it is missing then it is far past localized rot and again will need to open up. I suggest if this is a common case on your boat get a surveyor to map out the amounts and areas of moisture content. Also. To clarify the "overdrill" process. Where a bolt is ¼ inch I drill a ½ inch hole and then only dig out approx. a additional ½ inch all around. We are not talking a hole saw for this. Good luick with this. Nut Case is a 1987 model (and of course not a C&C) but is similar to the construction methods described. A thicker top layer of polyester and a lower layer with ½ inch end grain balsa in between. In areas where I found serious Rot (around a couple stanchion bases) the rot extended only 3 - 4 inches and the wet not a lot beyond that. The adhesion between the balsa and the fibreglass on the deck was pretty good. If you start digging and discover a previous repair and especially if that repair was done using some sort of plywood than the moisture would travel much farther than in end grain balsa. Have fun with your project. I have a cockpit seat to recore starting this week. Mike From: CnC-List [mailto:[email protected]] On Behalf Of Martin DeYoung Sent: Wednesday, April 23, 2014 1:09 AM To: [email protected] Subject: Re: Stus-List Scope of work... Dave, I had some additional thoughts. It is easy to pull one fastener of a piece of deck hardware and test the core. We peer down the hole with a bright light and use a dental pick to test the core integrity. Good core will look tan in color and be firm. The longer the core has been wet it will darken and soften. I suspect balsa core and polyester resin change chemistry during long term (10+ years) exposure to both fresh (rain water) and salt water. The change seems to be towards acidic. I have observed quick forming corrosion on tools and hole saws used on very wet and especially rotten core. It also smells bad, very bad of old resin and swamp. It will often corrode SS fasteners, sometimes severely. As Dennis or Bob mentioned, a little wet core is not a big deal. Rotten core that has totally failed, especially under/around high load deck hardware needs attention sooner than later. Larger failed areas can allow increased flexibility in the hull and deck structure. I found a large failed area under a white plastic cockpit opening port when I observed some stress cracks after a knockdown. (48 knot gust, boat knocked over far enough to have green water over the cockpit winches.) I expect most boats could use the deck hardware pulled, the deck core inspected and the hardware re-installed with new sealant every 10 years or so. I expect our work on Calypso will allow her to survive another 30 years or longer. Martin Calypso 1971 C&C 43 Seattle
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