Moisture damage

rukidn

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Apr 23, 2012
158
Catalina 310 258 Sandusky, OH
Last summer we discovered the cabin top panel covering the companionway slide was wet. We found a crack under the narrow sliding area oozing brown water. I traced the source to snaps added by the PO for a canvas cover. I bought an Eletrophysics CT33 moisture meter recommended by Maine Sail, and found much of the panel was soaked. After a full boat inspection, I also found couple small areas at the stanchions which am addressing. I can only reinforce Maine Sail’s recommendations to invest in a moisture meter. I conclude for boats our age, we should have already rebedded all deck penetrations.

Fortunately this area of the boat is removable. When we hauled out for the winter, I removed the panel, covered the boat for storage, and brought the panel home. As I began to cut the bottom out of the panel, I was getting splashed. The starboard narrow extension held free water but as I removed the 1/8” thick GRP panel coverer the bottom, I found much of the balsa, while dark and wet was surprisingly still bonded on both sides. I gutted this area with an oscillating multi-tool and prepped for new balsa. I found the forward-most section was also wet and began cutting into that area. I ended up all but a 1’ wide area exposed. I cut out the wettest and delaminated balsa, but left some that showed moist since it was tightly bonded to the panel top. With the bottom covering removed, I monitored with the moisture meter as it dried over the winter. With one side exposed, the balsa dried completely and I could track progress with the meter. Even with one side open to air, it took weeks to fully dry with the panel leaning over a heating vent. With the bottom panel and balsa removed the panel is quite flexible and would be easy to break if mishandled.

Once completely dry we started rebuild. The balsa is 3/8 from FiberGlast, which we found easy to cut with a utility knife. We used epoxy to attach the balsa to the panels and we cut away the balsa from all screw penetrations areas and filled those with thickened epoxy. The 1/8 covering removed was chopped strand mat construction and I chose to use the same. Epoxy doesn’t work well with CSM, and my recommendation would be to use polyester resin with CSM or use cloth. If I did this again, I’d use cloth and epoxy resin. We built up to 1/8 with 3 layers in most areas. I also faired the 4” wide slide cover undersides with thickened resin, since visible from below. I painted the bottom with TotalBoat barrier coat. The panel is now quite stiff and ready to reinstall after we launch as I don’t want to risk carrying the panel up the ladder while on the hard.

This was our first fiberglass repair project and we learned a lot on a part that was thankfully removable and has a repair area that is not readily visible. The primary lesson is check NOW and often for moisture, and to proactively rebed the obvious stanchions, chain plates and such, but to also address the smaller penetrations like simple snaps. /Ed
 

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Oct 22, 2014
16,146
CAL 35 Cruiser moored EVERETT WA
The primary lesson is check NOW and often for moisture, and to proactively rebed the obvious stanchions, chain plates and such, but to also address the smaller penetrations like simple snaps. /Ed
Great info Ed. Thank you for sharing.:beer:
 

JRT

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Feb 14, 2017
1,970
Catalina 310 211 Lake Guntersville, AL
Wow great info, I don't have any changes 8n this area but will keep and eye on it.
 

rukidn

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Apr 23, 2012
158
Catalina 310 258 Sandusky, OH
Project finally completed, albeit on our wounded boat. Pics below.

Because of the wide and varying gaps under the hood, Butyl Tape only worked well to bed the screw undersides on the slide extensions. I had to build up a tall "volcano" around the forward screw holes to bridge the gaps. The MOST critical area to seal is the forward corner screws as any water will puddle around the screw entries into the cabin top. Based on what I observed, if the caulking is compromised at all, count on water entry. Note the added snaps for a canvas cover. These were poorly bed with silicone and were the root of failure on the slide extensions.
 

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Mar 28, 2020
5
Catalina 310 Annapolis
Ours is soaked upon inspection and needs the exact same fix. Just wanted to say thanks for posting. Big savings for us
 
Dec 21, 2020
67
Catalina 310 Lake Hefner
Count us in with the same issue. I too inject caulk into all screw holes prior to bedding with burly tape. I pressure up as much as I can for as long as I can. My current go to caulk is flex seal. Thanks for detailing the fix. I'm going to make a plywood cover this winter so I can take the slide unit home to do it right.
 

rukidn

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Apr 23, 2012
158
Catalina 310 258 Sandusky, OH
Sorry you have the same problems. Regarding the temporary winter cover, you MUST seal the screw holes, especially those most forward. Water puddles quite deep around those screws.

3/8" balsa from FibreGlast worked well.
If I had do-overs:
-I didn't consistently mask the gelcoat edges and ended up with some resin messes to sand/buff. Be careful with the finished edges on the extensions at the companionway.
-I'd either use epoxy resin and cloth, or polyester and mat. Epoxy and mat is not a great match and won't wet out as well.
-Because I had all winter, I left the panel with some exposed wet but well bonded balsa to dry out. It took a LONG time. When is doubt, cut it out.

Good luck, and PM me if I can assist when you get started. /Ed