New Rear Chainplate Mount

New attachment for rear stay

DISCOVERY

On our way from Colombia to Jamaica the chainplate holding the rear stay moved about ½ inch upward.  It is not supposed to move at all! The winds were about 30 knots in medium seas and I assumed the rear chainplate mount had weakened.

We fastened a spare halyard to a strong point near the stern of the boat to help if the stay slipped any further and continued.

Once in Jamaica, further inspection led to the inescapable conclusion that the mount needed replacement.

But after we return!

The boat stayed in Jamaica on the hard and we flew back to Portland for the summer.

For more information on Jamaica and Port Antoio please see the blog entry at:

 

OPTIONS

Chainplates are an ongoing problem for Tayana owners. Either the mounts weaken or the stainless steel corrodes; both require immediate attention.  Most of these problems are created because the holes in the deck where the chainplates  poke through -leak. These are very hard to fix because the chainplate is always flexing  under sail so calking generally won’t hold for long. The best I’ve found so far is the rubber used to mound windshields in cars – butyl rubber. But nothing is perfect and the best thing we can do is check all chainplates yearly.

To test you can try tightening each bolt (torque wrench recommended) and/or drilling holes in the fiberglass to see that water is not accumulating. It’s also a good idea to remove the stainless chainplates and have them inspected and polished on both sides since crevice corrosion is less likely on a polished surface.  Once polished they look nice too.

Tayana owners have created some very elegant solutions for these problems, including all bronze and externally mounted. But elegant solutions seemed less appealing to me when the boat is in a remote corner of the world with little marine researces. Given limited resources in Jamaica we elected to repair the chainplate rather than create a new architecture.

TIMING

We really didn’t have time to examine the full extent of the old mount before we left for our summer stay in Portland, Or.

I took some quick measurements and pictures to take back to the Sates that could be used to formulate more detailed plans and to create something to bring back to Jamaica.

Before summer break – the original

Another view as the chainplate exits the deck

 

 

 

 

 

 

 

THE PLAN

A page from the notebook with a sketch of the new wood block and the bolt assembly.

 

 

 

 

 

 

 

 

In Portland I purchased a six foot length  of Jatoba wood, also known as Brazilian Cherry. It’s a very   durable, very hard, very strong  and highly rot resistance tropical wood. Crosscut Hardwoods in Portland had a large ¾ inch by 5 inch by 6 foot piece at a reasonable cost. I had Creative Woodwork another Portland company, cut the piece into three and glue it together (with waterproof glue) to form a 15 inch by 4 inch wide  by 3 inch thick solid piece. They also cut a groove into the back to hold the new bolt assembly.

Tacoma Screw Company has 5/16 bolts made of 316 Stainless Steel, these are purchased 4 inches long. I bought 5 of these and also a piece of ¾ inch wide by 1/8 inch thick – 13 inches long  316 Stainless strap. A local welder with TIG capabilities welded the heads of the bolts to the strap. This assembly was necessary so when the bolts are tightened in place while embedded in fiberglass the bolt heads don’t turn.  I had brought the stainless chainplate back to Portland with me, so it was used as the template to weld the bolts to the plate.

None of the holes in the stainless chainplate are in the center or equally spaced, so it’s really important to  use the old chainplates as templates.

DEMOLITION

I  removed the old rotted wood after cutting the fiberglass that had entombed it for 30 years. To cut the fiberglass I had bought a battery operated vibrating cutting tool while in Portland.  You can buy lots of types of  blades for  these kinds of tools (made originally by Fein, now widely copied) . A ½ round blade made quick work of the most of the fiberglass removal. But the corners had to be cut with a small flat saw blade.

Next came the rotted wood removal. This took about a week, because I had to work on my back in a very confined space. I used the same battery operated vibrating tool with a blade to fit the space I was working. It helps to have lots of blades and of varous shapes and sizes.   Note: they dull pretty quickly.

Rotted Wood

Rotted Wood

To get at the rear chainplate mount is difficult on our Tayana layout.  But there could have been a few ways to get access. One would have been to remove, with a saw the cockpit lockers and work from the cockpit. I elected to work from below, but had to cut a wood platform from plywood first. The plywood went from the back of the quarter birth to the stern of the boat. I also mounted a handle to help me enter and exit the small access hole.

hollowed out cavity

 

 

 

The “cavity” after the old wood has been removed. Note the “knee” about ¾ the way to the top. It is a strong structure built into the hull that keeps the wood securely in place. 

CONSTRUCTION

I had the block notched to snuggly fit the knee, once it was opened up for measurement and fitting.

 

New parts carried from Portland.

 

 

 

 

 

 

 

The original wood was shaped for strength. It was wider at the base. Like a long trapezoid. The wider part makes it harder for the wood to move once in place.  I did the same, but it had to be smaller to fit in the cavity. So once fitted I had to cover the cavity then inject epoxy resin to fill any voids.

We fixed the new block in place with some temporary screws, put a single layer of fiberglass cloth over the assembly. Then I drilled some holes in the sides to inject resin.

 

A trial fitting without the chainplate

The resin was West System 105 with 206 slow hardener.  Judy and I worked as a team to mix and inject in small quantities to avoid batches hardening before use. It was 80-90 degrees in the boat. She worked in the lazerette mixing, adding filler for a mayonnaise consistency . I filled a syringe with the mixed epoxy and injected it into the cavity.  I had drilled injection holes at different heights as the  cavity filled.

FINAL STEPS

After the cavity was filled, five more layers of fiberglass cloth was layered over the cavity. If a new layer of cloth was to sit overnight I would put Vaseline on the bolts and the back of the chainplate (to keep the resin from sticking to those parts) , bolt the assembly in place to dry. This kept the buildup of resin to a minimum under the chainplate.

Almost done

Some cleanup needed then we are done

I added five more layers of cloth. Each layer is larger than the layer underneith. This creates more and more surface area for the resin and cloth to adhere to.  The last piece was about 20 inches wide.

The whole process took almost a month but it came out really well.

To read more about Port Antonio, Jamaica, here is a link to the blog entry.