Replace glassed in chainplates

[medvinden]

I have a 37-footer where the chainplates are glassed in along the hull on the inside of the hull. The construction has been there since the boat was built in 1982 and has to my knowledge not caused any problems at all. But as a precaution I'm thinking about replacing the chainplates, since it would be considered impractical if they should fail in an inappropriate moment.

But how should I do this? I realise that it would be a good idea to extend the chainplate knees a bit. I don´t want to repeat the challenging construction, but if I would like to use the same position, how do I fasten the new chainplates without glassing them in again? Can I use stainless coach screws, reinforced by epoxy? (I don't like that idea.) Can i laminate some kind of bolts in the chainplate knee, that will fit the holes of the new chainplates? (I'm concerned whether it will be strong enough.)

[a64pilot]

Investigate having the new ones made from Titanium, it’s likely not nearly as expensive as you think. If Ti is used, there is no reason not to glass them in exactly as the original design, the Ti plates won’t need to be inspected or ever need replacing.
I shipped an old set to Allied Titanium and had them duplicate them.

Many things can be done and will work, but when you change the design of anything your now in unproven ground, and unless your Know and understand all the loads involved and can analyze them etc. you could end up with a problem. By staying with the original design and construction method, your staying with a proven system.

[medvinden]

The chainplates are 1 m long. It would make 1,3x6 kg = 10 kg of titanium. Do you have a good price for that?

[a64pilot]

Originally Posted by medvinden

The chainplates are 1 m long. It would make 1,3x6 kg = 10 kg of titanium. Do you have a good price for that?

I’m not a manufacturer, Allied Titanium is, call them.
You could likely drill through the installed ones and bolt on external chainplates, that should transfer the load to the current system, but you may not like the look.
Or you could do as many do, and hope for the best and do nothing.

If I were to go back with SS, I’d likely use duplex stainless and not 300 series.

[Chotu]

I’d do the external chain plates like a64 said in his last post.

It the most straightforward way to do it and will be as good as original.

[a64pilot]

In my opinion, and realize this is just my opinion, but other than bragging rights and possible marketing for resale, duplex stainless is every bit as good as Ti in a 1980’s boat, especially if external chainplates that can be inspected.

[Rick Williams]

We had the same thing on our 38' Downeaster ketch and decided to make them ourselves and bolt them to the outside: eliminates holes in the deck and allows for easy inspection. We got stainless strapping from the welder in the yard, got a $80 hydraulic bender from Harbor Freight and used the old ones as patterns.
The holes took a drill press and some patience and the buffing from mill finish to a high polish was time consuming but only took about a day.
Plus, come on, they look pretty good outside if you have any old school in you...

[Breaking Waves]

in theory, he would need slightly longer spreaders if he bolted to the outside hull - Right?

probably not a huge issue in practice, but might look a tiny bit odd the stays were slightly sloped and not vertical.

[Rick Williams]

For us the difference between new and old position was negligible.
We also used the old chain plates as the backers inside; win/win.

[Wulf]

Originally Posted by a64pilot

You could likely drill through the installed ones and bolt on external chainplates, that should transfer the load to the current system, but you may not like the look.

Just did that with a beautiful set made out of silicon bronze by Port Townsend Foundry. I fastened them through the existing stainless ones. Bulletproof and pretty easy to do. Just use sharp bits, slow speed and steady pressure (the more the merrier) when drilling stainless. And keep the bit cool. I just used a bowl of water for that. 1/4” pilot hole, then up to the finished size.

[roverhi]

Grinding out the old chain plates and have new ones made, fasten with carriage bolts from the outside if you want to keep the inboard setup. The only difference in topsides would be the 3-4 carriage bold heads.

Easiest would be to go external using the old ones as backing plates.

[jharding]

I had mine and three other boats chainplates x-rayed in place and all were fine, no reason to replace, just keep them sealed good on top

[Boatguy30]

So stainless has lasted since 1982, but now you need Titanium?

Just put some external tear drop style chainpates on. I can have this made-up to my designs if you wanted.

[Boatguy30]

Originally Posted by jharding

I had mine and three other boats chainplates x-rayed in place and all were fine, no reason to replace, just keep them sealed good on top

So it wasn't cracked the day of the x-ray, but what about today?

Crazy advice!

[medvinden]

I, and the boat, are situated in Sweden. Hence it is not the easiest thing to purchase products from the US. Nevertheless the Ti-alternative is way too expensive, just considering the pure metal price.

I got a quote from a local professional workshop on chainplates in duplex. The total price for 6 of dimension 50 mm x 10 mm, length 500 mm is 400 $. (Sorry for the metric system…) That is a good price to me, and I don’t think that somebody could match that with Ti. I think that duplex would be at least as good as the unknown version of stainless steel that’s been there for 38 years. The existing chainplates are 40x8 mm, so it would also add some additional strength to the system.

One alternative that I have is actually to replace the chainplates and glass in the new ones in the similar way as the ones that are there today. Choosing duplex would mean that they should last the coming 38 years, provided a good installation.

But I’m also considering the alternative to go external. The boat is a classic style long keel blue water cruiser. A lot of them have circumnavigated, or at least crossed the Atlantic to the Caribbean and back. It always rises interest with its classic lines and I don’t think that external chainplates would do any damage. But the problem is that the toe rail is quite high, around 10 cm. If the new chainplates would be external, then I would need a complete new setup of shorter stays. The distance sideways would only be 4-5 cm, which not would compensate for the higher 10 cm.

The boat is a Fantasi 37, built on a small yard in the heart of the Swedish boat building area on the west coast. The boat is by “experts” considered to be built with a quality that is higher than the neighbouring Hallberg Rassy yard. (But probably except the chain plate construction…) The yard is no longer producing yachts, but I have e-mailed them for their opinion as well, since they still do a lot of maintenance on the model and also know each boats (82 built) story by heart.