Potting and Rebedding the Upper Shroud Chainplates on a New Style C22:
Before I reinstalled the Bulkheads I needed to "pot" the holes where the chainplates go through the deck.
Chainplate Deck Slots
The chainplates are not welded to the flange/plate that screws to the deck.
they simply slide into the slot in the deck plate and the deck.
The whole configuration relies JUST on the the sealant used, to prevent water from getting down into the deck and further down to the bulkheads.
The problem is, like anything else on a sailboat, the chainplates will move, and eventually the sealant will fail.
If you don't regularly inspect the chainplates for leaking, the deck has an unprotected wood core which can rot, and your bulkheads will also get water damaged.
To help reduce the risk of serious damage I "potted" the chainplate slot in the deck, with epoxy. That way, if the sealant ever leaks, the water won't get into the deck core.
The basic idea, is you want to line the holes in the deck with epoxy, so that the wood core is sealed up.
There are 2 ways to do this:
You can either make the slot and holes oversized so you can fill them with epoxy, and redrill the holes to toe correct smaller size.
Or you can use a rotary tool or drill to cut away some of the deck core, leaving the outer fibreglass untouched, and then fill the hole with epoxy and redrill it.
For these chainplates I used both methods. One for the screw holes, the other for the chainplate slot itself.
The first thing I did was to put duct tape on the bottom of the chainplate slot inside the hull.
This way I can fill the slot with epoxy without it simply draining into the cabin.
Next task, was to drill the screw holes larger than they are originally.
Since the screw holes don't go all the way through the deck, I measured the depth of the hole, and put some tape on the drill bit at that length, so would only drill that deep.
There are adjustable depth stops made for drill bits. I lost mine and haven't replaced it because the tape method works well enough for the few times I need it.
Drill bit with tape used as a depth gauge.
Once the screw holes were drilled larger in diameter, I had used a Dremel #654 bit, to remove the deck core around the chainplate slot.
Some people do this with a bent nail or other means. I have a no-name dremel style rotary tool with a flex shaft so I use that.
The slot itself was a bit smaller than the dremel bit, but the ends of the slot were big enough for the bit to fit.
I simply inserted the bit into the hole, deep enough so that I was cutting only the core, and not the outer fibreglass layers.
Buy using the thin, smooth, shaft section of the router bit, against the outer fibreglass layer, as a guide, I cut away a layer of wood core from around the hole.
Once I had finished cutting the small layer of core away, I used an air gun to blow all the debris out of the hole.
Next I:
a) put tape over/around the holes to protect the deck from excess epoxy.
b) cut away the tape from the holes
c) mixed up some west system epoxy from a repair kit I had (a single packet of epoxy will do more then both chainplates)
d) used a syringe to fill the holes with epoxy
e) waited a few minutes
f) sucked all the epoxy out
g) added west system adhesive filler to thicken the mixture
h) used the syringe to fill the holes with the now thickened epoxy
I) waited 24hrs for the epoxy to fully cure. (in warmer weather the epoxy would have cured faster)
Chainplate holes filled with epoxy.
Once the epoxy had fully cured, I used the a drill bit to drill the screw holes to the ORIGINAL, SMALLER SIZE.
As before, I used tape as a depth gauge on the drill bit, so that I didn't accidentally drill all the way through the deck.
I then temporarily screwed the chainplate cover plates in place.
This way I could use the plates as as a guide to re-cut the chainplate slots.
Cover Plate Ready to Be Used As A Guide To Re-cut The Slot.
To drill the slot, I used a drill bit that was the same size as the chainplate thickness.
First I drilled a series of holes side by side...
Multiple Holes Drilled Where The Slot Should Be
Once I had a series of holes drilled in the slot, I took the same drill bit and pulled it sideways to cut between each hole and make the finished slot. The plate worked as a guide.
The drill bit is fairly thin so your need to do this fairly gently so you don't brake the drill bit. By doing it gently, you can cut the epoxy without damaging the hard stainless steel plate.
The original slots were larger than the slot on the plate. Since I was using the slot as a guide, the gap around the chainplate was smaller with less chance of a leak. There was just enough of a gap to allow good adhesion for butyl tape or sealant.
I should note here... I was using safety glasses the whole project, so I didn't get bits of debris in my eyes. Trust me... USE THEM... I've been to the hospital twice over the years, getting debris removed. The second time I had even been using safety glasses and still got stuff embedded near my cornea ! Go blind and your sailing days are over.
Chainplate Slot Complete
Test Fitting The Chainplate Before Bulkhead Re-installation
Once the bulkheads were fully re-installed and the chainplates bolted in, I used Butyl Tape to bed the chainplate deck plate so that water couldn't get in. Before I bedded them, I used a countersink bit to slighty countersink the top of the screw holes. That way the sealant or butyl tape had something more to adhere to.