New Chain Plate Design– Removing old chain plates and readying the deck

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We recently posted our ideas for redesigning the leaky chain plates on the C34 and C36 (1990-2003) models on this main message board on Apr 8 and the final design on Apr 12.  In speaking to some fellow sailors it appears as if the problematic chain plate design goes back even further.  They are currently being installed on Tony's C34.  Here we describe removing the old chain plates and readying the deck for the new ones.

Removing the old chain plates

Our experience is with the C34 however the C36 is the same in this regard except for the center chain plate on the C36 which is a long bar with several bolts through the bulkhead (rather than the tie rods connecting the other chain plates to the hull).  Access to and removing the tie rods is straight forward.  Remove the nut from the "L" beam attachment end of the tie rod and then unscrew it from the chain plate itself.  

To remove the actual chain plate: 1) Remove the small cover plate on the deck.  Get under it with a putty knife to break the seal or else you risk lifting away some of the gel coat (esp if they have been rebedded with 3M 5200 in the past as was found with one of them.) 2) Remove the nuts and the through bolts holding the chain plate to the deck. 3) Break the seal between the bottom plate of the chain plate and the underside of the deck (putty knife again).  (Note that the bottom plate should never have been sealed but it was in this case by the previous owner). 4) Work the chain plate loose from inside the cabin.  

You will be left with a rectangular hole ("slot") which requires cleaning.   Note the black (i.e. mildew) staining we found on the removed chain plate (Image 1) and on the underside of the deck (i.e ceiling of the salon) (Image 2).  Mildew = leaking.
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Readying the deck
Next steps are:
1)   Remove old sealant
The slot was cleaned using a rotary tool with a cleaning bit. (Image 3)  Luckily we didn't notice any rot in the wood core but look for this and remove what you can.  If it turns out there is rot beyond reach, then you have a bigger job to do than just worrying about the chain plate.
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2)   Mask slot hole from inside the cabin then coat the inner core with thickened epoxy.  (This is the part that should have been done in the Catalina factory during production).   When it is cured, remove the masking tape and use a rotary tool to remove the epoxy that pooled and cured around masking tape.

3)   Next use a rotary tool to create a chamfer around the slot hole on the topside of deck. (Image 4)
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4)   Since the deck through bolts often also leak, drill out these bolt holes using a 5/8" bit, use a 1" counter sink to create a chamfer (Image 5) then fill the hole with epoxy, allow it to and redrill with a 3/8" bit to fit the through bolts.   
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Clean with acetone. This will result in the deck being ready to receive the new chain plates.  Note this process can be followed even if you are simply going to re-install your original chain plates.

Our next posting will discuss the chain plate re-installation process we followed.

Tony Germin          
1997 C34 #1331      

Rick Verbeek
1999 C36 #1763

Lakeshore Yacht Club
Toronto, Ontario