Advice on removing glassed-in chainplates

[knuterikt]

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

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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.