Advice on removing glassed-in chainplates

[Kcoplan]

Hi all -- I am new to this forum, but have really benefited from perusing the threads here. I have a 1983 Wauquiez Hood 38 (38', 21,0000 lbs) which we routinely sail offshore. This winter, I have the mast down and am performing appropriate maintenance and upgrade. One major project is to replace the 30 year stainless steel shroud chainplates. I looked into getting them inspected and decided it wouldnt be that much more trouble or expense to replace them, and I want to replace them with titanium so that I will never lose sleep about crevice corrosion in dark places.

The chainplates are glassed in to massive fiberglass knees that bolt on to the main bulkheads. The good news is that you can remove the knee-chainplate assemblies, so I can work on this is my partly heated cellar rather than on the cold boat.

I am grinding out the knees from the inside to expose the chainplates, and am most of the way there on the port chainplate. The chainplate has a glassed-in stainless steel "root" (I dont know what the rigging term is for it). The root, which is welded to to through-deck chainplate, consists of a series of plates of different sizes that are overlapped and welded to each other -- presumably to give the glassed in chainplate some bite in the fiberglass.

Looking ahead, once I get the entire face of the chainplate and root exposed, I am going to have to pop it out of the knee. While the polyester-stainless bond cant be that strong, from my grinding and chiseling so far on the exposed face, I'd say its strong enough.

Any thoughts on the best way to pop the steel out without destroying the gelcoat side of the knee? I was wonder whether running a torch up and down the steel might break the bond, at least by making the steel expand compared to the glass.

Advice from someone who has already done this would be greatly appreciated! I saw the link for the "China Doll" chainplate project, so I see some people have been bold enough to grind chainplates out of the hull proper -- removing them from removable knees has got to be an easier task!

Thanks in advance,

Karl
S/V Mabel Rose

[knuterikt]

Any pictures? It's not easy to visualize this.

If you upload pictures to one of the free picture hosting sites (www.photobucket.com is the one I'm using)
To share here you copy the [IMG] link and paste into your post.



This is what the post looks like while editing


The result is like this

[Kcoplan]

This is the interior of the knee showing the surface of the chainplate AFTER grinding out most of the interior layer of the fiberglass (about 1/2" thick fiberglass). The knee is a sandwich -- fiberglass-stainless chainplate root-- stainless. I have ground out one of the layers of the fiberglass "bread" and need to release the stainless chainplate root from the remaining slice of fiberglass "bread."

https://plus.google.com/photos/10015...41200786?hl=en

Hope this works!

---Karl

[Brion Toss]

Hi all,
I'm preparing an actual consultation for this question, but in general one can either duplicate what is there, improve on the current glassed-in configuration, or install a rational alternative. I recommend the latter, which would involve removing the old chainplate, fairing the channel in which it sat, and lagging in a new chainplate. Well, not just lagging, but putting machine screws into epoxy-potted holes. If these are of sufficient depth, they will be as strong as throughbolts, removable if need be, and easily inspected.
There will be no loss in chainplate strength, as only the material outboard of the chainplate has been bearing any load; the bolts will simply apply their effort there by different means. For appearance's sake, you can fashion a cap, to replace the inboard glass that has been removed.
Fair leads,
Brion Toss

[Kcoplan]

The knees attach to the main bulkhead. The inside of the knee faces forward and is bolted to the main bulkead. The outside, gelcoated side of the knee faces aft, away from the bulkhead. Reglassing the inside of the knee is not an appearance issue, since no-one ever sees it unless they unbolt the entire knee and remove it.

But I am convinced the glass on the inside of the knee is structural. There is only 3/8" of glass on the outside, aft facing, gelcoated face of the knee. I can't believe that would be enough bury for potted screws to give any sort of hold. And I don't think the loads are purely transverse, since the chainplate root is at an angle, it looks to me like the vector of the chainplate loading will be pulling the root up and "out" from the inside of the knee. ("Out" in this case means away from the inside face of the knee, even though the pull is towards the interior of the knee itself).

There is absolutely no evidence of water intrusion into the buried part of the chainplate - this is purely a preventative maintenance and improvement project.

I am thinking that maybe the best solution is a series of through bolts into the aft, outside, gelcoated face of the knees, with ends of the bolts poking into the new layers of glass. I still plan to rebuild into the inside of the knee, just to maintain the "belt and suspenders" build philosophy of Henri WAUQUIEZ. I want to use titanium so that I will never have to inspect the plates again as long as I own the boat.

[robhenders]

Hi,

This is Rob from the China Doll... In answering one of your QST: the anchor for the chain plates did indeed pop out of the bonding, once the encapsulation 'cap' of about five layers of fabric were cut along the outlines of all 6 anchors embedded in the hull, cutting into the hull at just about the thickness of the plates. What was really interesting is the fact the chromium in the SS at the surface of the plates remain bonded to the polyester inside the hull. This left a 'blue tint' on the hull's inside surface in the glued in the resin. Just a slight bit of pressure using a small crowbar pried against the hull and the anchor sides did the trick.

Note that when ordering the grade 5 Ti plates, the anchor part that will be bonded to the inside of the hull, using West System epoxy thicken with silica, the most tenacious grip can be achieved by having the anchors sand blasted and not polished, as one would have for the outside 'show' portions of the plates. There's no need to have G5 Ti passivated as it has only one spot on the galvanic scale... At the very top, almost totally inert (G5 that is... Not CP Ti...).

With the sand blasted anchors I was able to bond into the hull the anchor using the same method as the original manufacture did, except I used epoxy silica and epoxied biaxial stitched cloth, in six overlap layers, to have a totally tie-in of the plate to the hull.

One original design aspect that I did change from the manufacture was to go with a two-part chain plate system; originally the anchor and thru-hull were one-piece. The new two-piece system totally seals the hull so no intrusion of water / moisture can enter the hull at the anchors. Before, the system could leak at the deck and being a common compartment straight up and out on the deck, if the chain plate covers leaked (which they did on and off over 25 years), that intrusion of water would fill the anchor cavity.

The whole design of the new system is available for review online in the Allied Titanium Catalog. Just look under boat type of Passport 51. And say hi to Chris for me...

-Rob.