Replacing Tayana 37 chainplates

Chainplates:

There are essaintaly 3 ways to go about dealing with the shortcomings of the tayana 37 knee design. First bronze chainplatesyou could remove the plates, check for water intrusion into the knee and inspect the bolts. The problem with this is you can’t actually see where the bolt enters the knee. This is where the corrosion will happen. The only way to be sure is to dig them out and check them. If the wood in the knee is dry, its unlikely the all the bolts are heavily corroded.

The second way to fix the chainplate issue is to remove the old knee and build a new one in its place, using an external backing plate and stainless carriage bolts to hold the chainplate to the knee. This will result in an assembly that can be removed and checked, which was the main fault of the original design.

However the other main drawback to the original tayana design is it creates 7 holes in the deck where materials of different expansion coeficants are close to one another. Theres also a ton of stess and fex acting on this small joint. All of this serves to make sealing the chainplates where they pass through the decks quite a chore. This is the reason the chainplates corrod in the first place.

Inorder to avoid sending the chainplates through the deck at all, they must be moved outboard. This fixes all the shortcomings of the original design and actually adds about 4” to each side deck. Gone are the days of swinging around the shrouds on the way to the bow.

This approach can and has been done with all stainless and all bronze. I will be talking about bronze as that is the matineral that i employed on Satori.

Pete at porttownsend foundry is who manufactured the chainplates. The cost per chainplate was about $170 each. These arrive beautifully finished and ready to mount. The customer can specify the bolt pattern.

bronze chainplateEach chainplate is attached with 3/8” bronze carriage bolts, washers and nuts. The bolts ranged from 5” to 6.5” in length. A 1/4” piece of G4 Plastic makes the backing plate.

The external plates hit the caprail, which protrudes about an inch outboard. I guess i could have cut the cap rail but that would look kinda hacked up. To avoid this I made 6 teak shims that hold the plates off the hull and caprail. They all get the shrouds even farther outboard, allowing more room on the side decks.

Widening the shroud attachment points: 

Whenever I’m messing with the design of a major component of the boat I like to have confirmation that what I’m doing is not weakening the rig. Here’s an exchange I found on the TOG site regarding concerns about widening the chainplate attachment points.

“Mike,

I asked the same question about spreader length of a respected

professor of naval architecture. He said that the wider shroud base

will reduce rigging loads and enhance rig stability with no down

sides.

Tim Mize

Windhorse #229

Boston, MA”

 

This email confirms my own logic that widening the chainplates will benefit the rig and not detract from it.

 

Rebuilding the chainplates:

Even though I elected to keep the original yard design, I think this exchange with perry is important enough to include:

 

“Here is an email exchange with Bob Perry regarding chainplate

replacement on the Tayana 37. My text is cut down a little for brevity

but Mr. Perry’s responses are in full.

 

Q: When the (chainplate) knees get replaced, as the designer of this

boat, after all these years, would you reconstruct the knees in a different

way than originally done by Tayana?

 

BP: Yes, most probably. I would go for plywood knees perpendicular

to the hull, as knees are normally, and covered with several layers of

glass bonded onto the hull and deck. This is the typical way I do knees. 

Bob P.

 

Q: Would this entail turning the chain plates 90 degrees from the

existing position?

May I share your response with the TOG association on Google Groups?

 

BP: Yes. My normal system of attaching chainplates has them 90 degrees to

the centerline.

 The birth process of the TY 37 was a bit unusual and many of the

details that became standard were developed by the builder prior to my

involvement with the structure.

Sure you can share this information. Half the stuff you read as “Bob

Perry says” is not what I said anyway.

Bob P.

 

Thanks Mr. Perry for the exchange.

 

JD

Vic BC

#375″

IMG_1331 IMG_1330 IMG_1166 IMG_1254 IMG_1718 Look at all that stainless!

3 comments for “Replacing Tayana 37 chainplates

  1. June 28, 2015 at 11:59 am

    Looking really good. I got new 316 stainless chainplates but haven’t put them on the boat yet.

    I like the look of your chainplates.

  2. Mike
    July 5, 2015 at 6:07 am

    Young Man. You are living my dream. We are in he process of selling our Hunter Vision 36 and I am looking at Tayana 37s. Do they have enough sleeping sleeping quarters for a Queen and her crew?

    • sailorlee15
      July 17, 2015 at 2:15 am

      I think the 37 is a great value. I also think they are the ideal size for a cruising couple. Depending on the layout they provide ample sleeping for up to 6. Let me know if you would like more information! Good luck in your search!

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