1977 
TAYANA CT-37
CHAIN PLATE STUD REPLACEMENT

Here is how I replaced all twenty chain plate studs on my 1977 Tayana, hull number 63, 
model CT-37. First, I wanted to keep the chain plates in the original position, inboard, as I 
prefer them that way. Also, presently, my boat is on the hard while I carry out an extensive 
refit, restoration, and upgrade of all systems. 

I decided to replace the original chain plate studs for a few reasons the first of which was 
that the threads of some were damaged and in all likelihood stripped, as the nuts were hard 
to get off and on.  Second, there have been previous comments on the questionable strength 
of the original stainless studs. Third, I noticed small rust stains around some of the studs 
and on the back of the matching chain plates. Obviously, water had been getting into the 
chain plate housings over the years. Lastly, with the chain plates off some of the studs felt a 
little loose, that is, you could get them to wiggle a little if you applied some force directly 
to the stud. 

The chain plates were in very good condition with no corrosion or pitting on any of them 
and those small rust stains were easily removed. My Tayana has always been in fresh water 
and I have no corrosion on any of the metal parts. So, mainly for the above reasons I went 
ahead and replaced all twenty of the original studs with new 3/8 inch stainless steel studs 
which were in fact 3/8 inch, countersunk, Phillips head, 18-8 stainless steel machine screws 
with a "modified" head to act as an anchor point.  To make the anchor point I simply 
screwed on a wing nut, backwards, then slipped on a 3/8-inch flat washer, and followed up 
with a 3/8-inch hex nut and tightened the nut with a wrench. Once completely epoxied into 
position there is no way the new stud assembly can turn or work loose. 

Previously, when I first looked at the chain plate situation, I drilled a series of  3/8" holes 
into each of the four chain plate housings and examined the wood shavings which for the 
most part were only just slightly damp, if at all, in three out of four housings. The starboard 
aft one was unquestionably dry, as the wood shavings were much lighter in color than the 
other three, etc. I tried to dry each of the encapsulated wood backing blocks by using heat 
lamps trained on each of the housings for many days hoping that the heat would drive any 
moisture out through the holes. I think that it worked to a degree. After that, I injected 
CPES penetrating epoxy into all the holes and then epoxied them closed. I was now 
confident that all my chain plates assemblies were in good shape. At least, I hoped that they 
were. 

However, not long ago, after a few additional comments made by others doubting the 
strength of the original studs I decided to go ahead and replace all twenty studs while doing 
the refit. I did not want any problems with chain plate studs in the future and perhaps lose a 
chain plate while under sail, etc.

What I did was to use a 2.25" hole saw (without the centering drill bit), centered it over the 
old stud, and cut into the fiberglass chain plate housing as far as I could go until the hole 
saw hit the old stud and I couldn't go any further. Next, I used a chisel to remove the 
fiberglass plug and deteriorated wood surrounding the old stud. Then, I switched to a 
Forstner bit and removed all the remaining wood, the old stud, and cleaned out the entire 
cavity completely. That is, I removed all the wood from behind the fiberglass shell of the 
housing until all that remained was the fiberglass shell itself. Only one chain plate housing 
and backing block (starboard aft) was completely untouched by water and in perfect 
condition. In that case, I just undercut the wood backing block, back, to a point one inch in 
and around the hole cut into the fiberglass housing.  All the backing blocks were 
mahogany. The other three housing had deteriorating wood backing blocks. The wood was 
dark and showed signs of having been wet in the past although now dry or very slightly 
damp to the touch. Much of it sort of crumbled and fell apart as I removed it from the 
inside of the housing. In some instances, after just cutting through the fiberglass housing 
with the hole saw, I'd give a good tug on the old stud and it would come loose with little 
difficulty.  

I replaced all the studs by first removing only three studs from each housing and leaving in 
place two studs, untouched, so that I could use them and the chain plate as a guide when I 
epoxied in the three new studs. Then, I reversed the operation and I used the three newly 
epoxied in studs to hold the chain plate while it acted as a guide for the correct placement 
of the last two remaining studs. I used the hole saw and removed the two old studs and 
cleaned out the holes only when the first three new studs had all been completely epoxied 
in place and had cured. It worked out great and I had no difficulty in doing it in this 
manner. You must fill the holes up a little at a time while using thickened epoxy so that it 
cures properly. Putting in too much will cause the whole mass to heat up and go off. Then, 
you will have to grind it out and do it again. In discussing this repair procedure with a boat 
builder it was suggested I use wood flour, as a thickening agent for the epoxy as it would 
bond nicely with any good wood left in the cavity. I never used it before, just the regular 
silica, micro balloons, etc., and I really liked the way it combined with epoxy. It is very 
strong and the studs are now all set in and surrounded by solid epoxy. In fact, the entire 
fiberglass housing is solid epoxy and water can no longer get into the housings even if the 
chain plates leak. There is no way that the studs can come loose and the whole assembly is 
much stronger than the original. A shroud will break before the chain plate and five 3/8" 
studs shear or let go. 

Regards,

John Keefe
ODYSSEA CT-37
Youngstown, New York