Older Catalina Chain Plates

Stu Jackson · Oct 21, 2008

Catalina Chain plates

Jim, both your C36 and our C34s have the same construction, and both the C36 and C34 websites have very, very good descriptions, with pictures, as to how to make them watertight. I "struggled" with mine until I just bit the bullet and did 'em right, and they've lasted a few more years than the "short cuts" I used to employ.

Building them up higher is a good idea, but it seems that the deck penetration is the point of failure, and unless standing water is sitting on top of the "hole" it should be waterproof anyway.

I agree, no one particularly likes them, but the guys who have written those website pages sure put a lot of effort into, first, figuring out how to do it right, and second, documenting their efforts for all of us to learn from.

The C34 website article on chain plates is in Projects at www.c34ia.org.

Could you please describe the "newer ones from Catalina?"

Maine Sail · Oct 21, 2008

The only thing I'd add to it is this of you really want don't want to do this again......

#1 Over bore the chain plate hole by another 1/8" on all sides where it is "close" to the deck edge. If a sealant will flex 400%, and the chain plate is right up tight against the hole giving you only 1/16" your chain plate can flex double, tipple or quadruple the amount if you go bigger. The thicker the sealant you have, within reason, the more flex will be allowed. Many times these holes are not lined up right from the factory and this leads to failure due to an insufficient flex gap..
In the photo below (Linked from the C-34 web site) the gap on the left side is sufficient but the gap on the right will fail earlier due to less allowable flex.

#2 After you're done potting the hole with epoxy and making an equal gap all the way around, use a laminate trimmer with a 45 degree bearing guided bevel bit, to chamfer the top of the hole slightly. This gives the stainless deck cap more of a o-ring effect and a thicker "gasket" at deck level around the chain plate.
45 Degree Bearing guided Bit:

Approx Depth of Bit:

A Beveled Fastener Hole:

#3 I advise against sealing anything on the inside of the boat. Why should you seal only from the top/deck side? If you develop a leak on the deck side you WANT to know about it asap. If you seal the backing plate side or below deck side of a fitting the water will be trapped in between if a leak develops at deck level. This trapped water can lead to either crevice corrosion of the chain plates or further deck damage if you did not pot the holes with epoxy. By not sealing the backing plate side of a fitting it will allow any leak to be seen and not forced into the deck or left trapped there starved of oxygen creating unseen and un-safe crevice corrosion..

Maine Sail · Oct 22, 2008

Jim said:
Would you consider looking into changing the Catalina 36 chain plates to the newer design that does not expose the caulk to weather?

I don't think I'd worry about it much. If you use 3M 4000UV or 3M 101 Polysulfide or Boatlife Life Caulk Polysulfide they should last a long time before the UV hits them.

As for changing chain plates, unless Catalina makes a direct fit replacement, it would be quite costly to do this upgrade. I believe the interiors and chain plate locations on the bulkheads are slightly different from the MK I model that I used to own vs. the MK II. I think you'd be best served to call Catalina or check with Tom Senator as he may know where to direct you. I have not owned a C-36 in a while so I'm a little out of the loop on matters C-36..