When faced with similar decision regarding how to replace wet plywood I went with solid epoxy/glass cloth in the high load areas. The area immediately around the mast is also full of fasteners (halyard blocks, cleats, etc.) so replacing a ply or balsa core with epoxy/glass should reduce the chance that a future owner will be faced with failed core even if a bolt hole leaks. In less loaded areas I matched the original balsa but paid close attention to wetting the kerfs and edges with epoxy. All the fastener holes will be over drilled and filled with epoxy.
Calypso’s designers and builders (Bruckmann’s custom shop) called for plywood around the mast collar. When I opened up that area the 44 year old plywood was very wet but only rotten in a few areas. Owing to the high halyard and rig loads in the area I chose to replace the plywood with a lay-up of epoxy, bi-ax + mat, cloth, and epoxy board. I tapered the solid epoxy/glass into the balsa cored area (also new balsa) outward until all the wet/failed core was replaced. As I have access to a supply of thin epoxy board I made up a pattern of the repair area and laid up two “U” shaped inserts that worked much like purchasing 3/8” thick epoxy board. (For a visual, think a thinish toilet seat cut in half long ways.) I custom shaped the inner and outer edges to the repair area (much like a dentist shapes a tooth for a crown). The full repair lay-up session took at least ½ gallon resin, 2 people, and 5 hours. I used vacuum bag and mechanical means to hold the layers in place. To gain the full replacement thickness it took 8 to 10 layers of 25+OZ bi-ax + mat along with my pre-fabbed insert. I do expect to hear some interesting pops and cracks the first time we fully power Calypso up under sail as the new epoxy/glass takes its first full load. I also expect the hull/deck will feel stiffer than it has been in years. Martin DeYoung Calypso 1971 C&C 43 Seattle [Description: Description: cid:D1BF9853-22F7-47FB-86F2-4115CE0BAF2F] From: CnC-List [mailto:cnc-list-boun...@cnc-list.com] On Behalf Of Petar Horvatic via CnC-List Sent: Monday, February 08, 2016 6:41 AM To: cnc-list@cnc-list.com Cc: Petar Horvatic Subject: Re: Stus-List repairing large wet deck core areas So I did some digging over the weekend and I can say few things regarding deck and core along the genoa tracks for C&C38 mk2 from 1976. Top laminate is 3/16” thick. Balsa is ½”. In my case, wet areas are pretty extensive. Tapping and sounding the top got me to mark out a big rectangular area. It extends from about 2” inboard of the genoa track and its about 12” wide. It runs the length of the track. There is a 4” wide section of marine ply (also 1/2” thick) under the track itself. I wonder if I do the same or just keep balsa. I posted some horrifying photos on cruisers forum. Warning, pics are pretty disturbing. http://www.cruisersforum.com/forums/showthread.php?p=2039627#post2039627 Haven’t done the bevel yet, and still have about an hour to get all the rot out. As I said on CF, I’ll do epoxy repairs and use the double bias stitch mat and toss out the top laminate. I’ve had enough of polyester. Its porous nowhere near as strong, and if you go to trouble of doing this much work, might as well not skimp out on material. The big question is how to transition to gelcoat again? The cutout is the length of the track so I am not worried about genoa cars getting stuck on the track due to deck transitions. Petar Horvatic Sundowner 76 C&C 38MkII On the hard at Stanley’s in Barrington
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