Almost every Tanzer 22 in existence has bent chainplates. The culprit is the boat's geometry. If the mast is lowered by hand, then all the shrouds must be disconnected, or they will bend the chainplates aft when the mast is almost down. Mine were both bent, which was the impetus to replace them.
Here you can see the difference in size of old vs. new. The new chainplates are 1/4" thick stainless steel, about 4" longer than the old ones. As well, the holes are drilled in an X pattern, to distribute the stress over a greater area of the bulkhead. If these chainplates look familiar, it's because they were provided by Owen Schneider (T22 #2043) who has a similar set on his boat. Many thanks to Owen's Dad Willi for doing the stainless work!
As compared to Owen's installation, mine are installed with aluminum bushings in the bulkhead. You can see these in the third photo, which shows the profile of the chainplate and backing plate. The logic is that six 1/4" SS bolts will have a shear strength in the neighbourhood of 11,000 pounds. However, they will tend to pull through the wood. To prevent that, aluminum bushings (1/4" ID, 1/2" OD) is inserted into the bulkhead to distribute the load of the bolt onto a much greater area.
I really should have used stainless bushings and backing plates, but corrosion is not a huge concern on Lake Ontario. Salt-water sailors may wish to go with an all-stainless option.
For those who think that this is way above their skills, consider:
Once the old chainplates have been removed, the first task is to widen the slot in the deck to accomodate the new chainplates. Here I'm using my new favourite boat tool, the Fein Multimaster. This is the best detail sander made, bar none. The head oscillates 21000 times per minute instead of rotating like a Dremel. The result is it cuts very quickly without jumping out of your hands. It's also able to cut in places that a Dremel can only dream of. Here I'm using a carbide abrasive disk to widen the slot. As there's no rotation of the cutting bit, there also isn't dust flying everywhere.
Before removing the old chainplates, I had made a template on deck of the correct position. Holding the template against the new chainplate, I was then able to have my Dad mark the holes for the new one below deck. After drilling one hole in the bulkhead, a bolt was inserted in the chainplate and the rest were drilled in situ. All holes were drilled from the main cabin, as the curvature of the hull makes this impossible from the v-berth.
The fourth photo shows the v-berth view of the port chainplate. This is just prior to fitting the backing plate.
To maximize the strength of my bulkheads, I decided to plug the old bolt holes. I used 1/4" fluted dowels (used for general woodworking, available from Home Depot) and glued them in with regular wood glue. As the bulkheads will be replaced next winter, there was no point to installing them with epoxy.
In the two right photos, you can see some water damage on the starboard bulkhead. Shortly after purchase in 2000, I removed the vinyl "veneer" from the v-berth side of both bulkheads to inspect for water damage. None was evident from there. Well, shame on me, as the cabin side of the starboard bulkhead has definitely seen water. However, I figure that with the new extended chainplate, and with eight bolts on starboard, it should be OK for one more season.
The difference between the middle and right photos is the hole size -- the right one has the holes drilled to 15/32", to make sure the 1/2" bushings are very snug.
With a difference in size of 1/32", there was no way I could knock in the bushings. The solution was to use the backing plate in the v-berth, insert a bolt from the v-berth, and then put the bushing and a nut on the cabin side of the bulkhead. As you tighten the nut, the bushing is slowly pressed into the bulkhead. The first photo shows a few of the bushings not fully installed yet; the other two show the completed port-side bushings.
This is test-fitting the port side chainplate just before final install. One of the holes didn't quite line up through the chainplate, bushing and backing plate, and needed to be reamed slightly with a 1/4" drill.
The existing chainplate covers were stainless steel, almost 1mm thick. I quickly decided that widening the slot from 1/8" to 1/4" was No Fun, and went looking for a better solution. The result is new covers made from white plastic. Much easier to work, and durable enough considering that they only need to protect the sealant from abrasion.
The second photo shows the starboard chainplate held up by one of the center bolts inserted in the wrong hole in the bulkhead. The three red dots mark the bottom of the deck when the chainplate is fully installed. This was done to make it easier to fill the gap with sealant. It's much easier to apply 3M 4200 to an open chainplate than to squeeze it into a 1mm wide gap! More sealant was added after the chainplate was lowered.
And the final result -- serious overkill, but something I won't ever have to worry about breaking!
© 2015 Melissa Goudeseune