[Public-List] Chain Plates and water intrusion around them.

crufone at comcast.net crufone at comcast.net
Tue Mar 24 08:36:10 PDT 2009

Hello all, 

Something else to consider when replacing or upgrading your chain plates, fastener bolts and repaining structural wood damage. 

This has been covered in many DIY boat repair mags and I believe that it is worth doing to help prevent water intrusion through the chain plate holes to the structure down below. 

Around each chain plate slot through the deck one builds up a 'curb' or 'collar' which stands proud above the deck let's say 1" to 1-1/2".  This 'curb' can be mfg from epoxy or polyester resin.  It will have a water tight bond to the upper deck surface.  It is intended for the chain plate to be able to move/flex slightly around in the slot through the deck and this new 'curb'.  The 'curb' height provides more surface area for the bedding compound to fill the gap between the metal of the chain plate and the surrounding fibreglass structure. 

Water washing over the deck must be at least as high as the curb to attempt to enter the bedding area and thus infiltrate into the structure down below causing the wood structure to rot over time. 

Yes, yes, yes, this is a foolish logic while at sea.  My thought is that most of the time our boats are not at sea but resting in a wet slip, on a mooring or on the hard outside in the RAIN.  I believe that it is mostly the rain water which causes the damage we find at our chain plate fastening structure.  If our boats are at sea only 5% of their life over a 40 year period of time, then one can appreciate the damage rain water can cause. 

The 'curb' effect does a GREAT deal to prevent this type of water intrusion and damage to our boats.  In addition the bedding compound should be more effective for a longer period of time because of the increase in volume used to caulk/bed in the slot. 

If one takes the care to finish off these 'curbs' nicely, they don't detract too much from the good looks of the boat. 

Michael #133 

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