Encapsulation/bonding Ti-6Al-4V internal chainplates

[robhenders]

Installing new chainplate anchors on a Passport 51 with internal chainplates that are encapsulated into the hull. The originals were bonded in the hull with primary bonding as the hull was built out on layup. The hull is from 1983 so it was a polyester mat/roving integration of the original SS304 anchors into the hull.

I noted that the builder (Wagner Stevens Passport Yachts) mentioned using a vinyl ester buildup of mat/roving --as vinyl esters are less prone to moisture intrusion--, but I do not believe this is the best thing to do because I am relying on a secondary bonding more so than the primary bonding.

In the case of secondary bonding, wouldn't an epoxy resin with bi-axial stitched cloth be the better solution --as an epoxy rein is more tenacious than a vinyl ester-- and a stitched glass is best for strength?

The new anchors are sandblasted grade 5 titanium plates, and the new chainplate system uses a two-part chainplate, with the anchor and 'top' getting attached using special 'clevis' (shoulder) bolts. Google 'China Doll Chainplate Project' to find links to project pictures on Picasa.

Feliz Navidad!

-Rob.

[Brion Toss]

Hi,
It looks like no one else wants to step up to this, so I'll offer an utterly unqualified opinion. While you might find that some mix of materials would indeed prove strongest in this application, it is very likely that just about anything remotely appropriate would work; given sufficient surface area to distribute load, and adequate adhesion to the original material, it would seem easy to create a structure that would be much stronger than the standing rigging.
I am delighted to hear that you are using titanium, since, as I'm sure you know, it is not vulnerable to the crevice corrosion that probably ate your original chainplates. One thing to consider doing would be to leave drainage, so that any moisture, whether intruding from above, or from condensation, wouldn't hang out in the "pocket," not because I'm worried about the metal, but because the 'glass won't discolor, and you'll still be able to see if anything is leaking, before it gets serious.
Fair leads,
Brion Toss

[robhenders]

Thanks for the post reply. Google "china doll Chainplate project" to see pics of the plates encapsulated. The epoxy with 403 high density was used with bi-axial cloth in three laminates. Note that the titanium plate did not need passivation and was sandblasted in finish. This greatly improved adhesion to the metal and the hull polyester was activated with acetone after being grit sanded. When pulling the old plate off the hull, the chromium oxide left a blue hue and the plates were easily pried from the hull, with some pressure and a good "pop." A test to attempt to remove a newly epoxied on plate was unsucessful at significantly greater pressures.