Chainplate Can-o-Worms

[barnakiel]

Yep. I have re-read what people say and your responses.


I think you may, all other roads explored, REMOVE the lowest portion of the wedge - below the lowest bolt. This portion brings marginal if any structural support to the whole.


At this point you would see the lowest bolt exposed and entering the skin, from which you may get some idea of how it is fitted (welded, countersunk, etc.) into any, if, existing backing plates in, or outside the wood skins.


b.

[JPA Cate]

Oh, let's wait till Mr. Departing2017 hears back from the builder! I'm thinking removing some of those ceilings to get a little look at that backing "wedge" block. Fortunately, the screws are exposed. Please take more pics as you begin to uncover (reversing the build process).

I'd suggest small, conservative steps, till we have a better idea what's happening. The boat itself is atypical, and we want to be like good doctors, do no harm.

Good luck with it, Departing 2017, must be quite fraught thinking about it. Sorry, but I'm thinking of you as Mr. Can of Worms for the moment, will try to learn your proper name.

Ann

[Departing2017]

Originally Posted by JPA Cate

Oh, let's wait till Mr. Departing2017 hears back from the builder! I'm thinking removing some of those ceilings to get a little look at that backing "wedge" block. Fortunately, the screws are exposed. Please take more pics as you begin to uncover (reversing the build process).

I'd suggest small, conservative steps, till we have a better idea what's happening. The boat itself is atypical, and we want to be like good doctors, do no harm.

Good luck with it, Departing 2017, must be quite fraught thinking about it. Sorry, but I'm thinking of you as Mr. Can of Worms for the moment, will try to learn your proper name.

Ann

Thanks, everyone, for all the great suggestions. I'm in the process of tracking down the thermal imaging camera as we speak.

I will definitely post lots of pictures here as we dig in.

[Departing2017]

Quick update:

I've been in contact with the builder. To the best of his recollection (most of the drawings and other documentation for the build have been lost), the embedded backing plates were routed into the outer mahogany ply of the hull and then glassed over. The plates were drilled and tapped and the studs threaded in with red Loctite.

I've attempted to remove one of the seemingly healthier studs. I was unsuccessful. First, I heated the stud with a small torch and attempted to turn it with a stud extractor. No luck. Then, I used a long 1/8" drill bit to hug the shaft of the stud until I hit the metal backing plate. Next, I inserted the straw for the can of penetrating oil and shot the back of the hole several times throughout the day. I let the mess sit overnight and then heated the stud again (very carefully) with the torch. Finally, I applied the stud extractor and a bit more muscle and snap. Another broken stud. See photos.

I wouldn't go as far as to say the original design is flawed. I mean it did last for 44 years, and we've put more than a few thousand miles safely under the keel over the several years we've owned the boat, but I don't think salvaging the original design is reasonable. So the current plan is to drill all the way through to the outside of the hull and through-bolt to external backing plates. Another variation would be to reverse the setup and move the chainplates to the exterior, adjusting shroud length with toggles. I'm still contemplating.

I've also attached a photo of one of the chainplates that was hidden behind some joinery (no ceiling or cover boards) so you can see how they're fastened through each stringer. I'm guessing, based on the weeping rust that the studs on this one aren't going to be in any better shape.

[barnakiel]

Now there is the question of "how", eh?


This is one of the most interesting and educative threads at CF I have seen for a time. I will love to see how you tackle this and what challenges are solved with which solutions.


Our knees are nearly identical. However, ours are not solid, only L shaped, so we access nuts easily.


I imagine drilling for the new bolts will now be done from the inside? I say this as I know that from the outside it could be hard to to match the holes in the new plates.


Except that drilling from the inside will call for plenty of planning and testing if you can fit the drill machine and yourself, into the right position ...



I can also imagine you will need a loooong drill bit ... ( I needed to order extra long bits not too long ago working on our wood project here - standard shops seem to only stock standard (short-ish) bits.


My other comment is the humidity in this knee - now, and then again later when the bolts pass the backing plates and end up on the outside. This humidity is part of what has killed the original bolts over time.



On the outside, you will have some choices too. You will likely remove the skin in the bolt head area, so that the head rests on the metal plate directly. And then sealing and painting over. Alternatively, you can countersink and thread the hole BUT this would again be a challenge to align. But would allow for a flat finish.



Overall, it seems fitting the new plates to the outside may be the easier way?


Very best regards,
barnakiel

[glenn.225]

Originally Posted by Dsanduril

Beg, borrow, or rent an IR camera. Wait for a reasonably warm day. Fill a sock or stocking with ice, then place that in some plastic to catch drips. Use tape or other means to hold the ice-filled sock against the chainplate, trying to get the best contact at the stud locations. Pile some more ice on deck around the head of the chainplate. Wait 5-10 minutes.

Take the IR camera outside the boat and image the chainplate area. Set it up for only a few degree range around the hull temperature to give you the most contrast for small temperature differences. If you see distinct spots at the stud locations, with the area between close to hull temperature then you probably have individual bolts embedded. OTOH, if you see indistinct blobs that blend toward each other then the studs are likely welded to or installed in a carrier. You should be able to estimate its width from the temperature blobs.

I’ve never done this with chainplates, but we use similar techniques in the field all the time to delimit embedded metals in many substrates. It will all depend on the amount of “cover” the metal has from the outside. Lots of cover and you may not be able to see what you want. Little cover and your hidden metal should stick out like a sore thumb.

+1 to this, we use them on residential structures before ripping out doors/windows. You can see exactly what is there. Only I was going suggest a heat lamp on the inside.

[JPA Cate]

The guys here on CF seem pretty united that [sorry for the gross name] "weasel piss" (1:1 atf and acetone) is the best loosener of stuck metals. Jim mixes up his own, paints it on with a tiny watercolor brush, and watch it seep in; and we have used it successfuly on many items that might have broken, otherwise. He used to use Kroil. To me, weasel piss definitely works better than the Kroil.

Maybe, just maybe, it will work on your studs. We try to let it sit overnight, but sometimes impatience has overwhelmed us.

Imho, you'll want to put the boat back together with its original rigging geometry, if at all possible, and you will benefit from the narrower sheeting angle if you can do so.

Ann

[mlydon]

Here’s my suggestion for an easy fix......

Get the chainplates off (grind the heads if you have to)
Grind the studs flush with the wood wedges (slightly further, so not to interfere with your new plates.

Drill a new set of undersized holes between the existing studs down to the backing plate. In other words, relocate the holes on the new plates into the gaps between the current holes. Carefully drill an appropriate tap drill JUST through (past) the backing plate without going through the hull.

Tap the new holes and backing plate with the appropriate tap, and epoxy new studs into the holes.

Should be as strong as the originals, as all the load is shear anyway, and your original studs are still there hanging onto the wedges in shear.

Matt

[kev_rm]

heat is by far the best method for stuck fasteners...

[Departing2017]

After taking some time off to further research and prepare for this project, and to install a composting head (they really are pretty great), I just made a bit of progress and answered one giant, looming question.

There are no embedded backing plates. The "studs" actually are hex head bolts with fender washers counter sunk into the outer wood ply of the hull (As a reminder, we're three-ply cold molded mahogany with a glass/epoxy skin.). The builder used fairing compound to fill in around the bolt heads and then covered with the outer glass layer.

I located one of the bolt heads with a borrowed FLIR camera (Thank you Dsanduril for that bit of advice). I vise gripped a soldering iron to the threaded end of the bolt inside the boat. Then I rubbed down the outside of the hull with ice and watched for the hot spot through the camera. It showed up clear as day. I marked the spot and then drilled with a small bit. I almost perfectly bullseyed the bolt head and then carefully carved it out with a Dremel (I did get a little squirrely with the drill at first, so the first hole isn't perfect. I expect to get better though). From there we were able to easily drive the bolt out of the hull with a hammer and punch.

Check out the photos. Now I only have to do this about 53 more times 😬.

[barnakiel]

Awesome! If you had asked me, I would have guessed such a 'light' design could not hold the quite some tension from a shroud. And yet.


Glad to see you found a way!


Thank you for posting this. Very educative.



barnakiel

[Manateeman]

This is kind of an old school suggestion. Exterior silicon bronze chain plates with button head bolts. Broach the exterior chainplates holes to square for the bolts which you can thread to perfect length. Polish up the interior plates using extra heavy nuts. Did a custom Bruce King I built...black hull with silicon bronze which turned a beautiful green patina.
You can TIG weld the bronze easily and add thickness close to the deck. Silicon bronze bends well and will last longer than me.
Happy trails to you.
Mark and his old school Manatees

[Departing2017]

I finally have an update.

The new chainplates are here! As strong as stainless. Half the weight. And no corrosion. Ever.

I [emoji3590] titanium

[Departing2017]

I just noticed I started this thread in August. This has been a long, sometimes frustrating, yet rewarding journey, and we are almost done and ready to cross some more oceans.

Here's the summary. Most of the holdup has been caused by delays in fabrication of the new titanium chainplates. The running joke around the marina has been some variation of the following exchange: "Hey Departing, any news on the chainplates?" "Next week," I reply. That's been going on for over four months.

Here's where we are today. Six out of a total of nine titanium forever chainplates are in. Three had be be sent back because of some errors in fabrication.

I was lucky to find an absolute magician with fiberglass who doesn't mind coaching me along the way to improve my own meager skills with the messy stuff. We have most of the holes filled, glassed over, faired, and ready for paint. As you'll recall, we rubbed down the exterior of the hull with ice and used a FLIR camera to pinpoint the old bolt heads, so the damage to the hull from removing the old plates was minimal. This is a lot of the reason we've been able to pull this whole project off without hauling the boat.

The bolts we are re-embedding in the hull are also titanium. Expensive? Yes, but we won't ever have to worry about the fact that we cut off the oxygen supply to another set of stainless bolts. The bolts that fasten the chainplates to the bulkheads are accessible (and replaceable) from the interior, so we went with 316 stainless to cut costs.

Here are a few photos of the the project in various stages.

Cheers.