Jay

: You have to remember, you're not doing a lay-up but a sheathing application.
: With the type of use we builders do, the wood is the weakest link in the
: bond. If you pull off the cloth wood would most likely come with it. The
: epoxy bond is thin and sometimes it will break from the cloth any you'll
: see the weave pattern in the epoxy.

I did two variations of the lay-ups, depending on the application: in all, there was plenty of epoxy put down, the glass pushed down when wet-out, or in the case of the tape, a thorough paint of the area, then the soaked tape was put on, and rolled or pushed down, then painted with more epoxy. Yanking the glass or tape, the epoxy coat on top came off, the glass did, too, the epoxy underneath stayed bonded to the wood. In all cases, the wood remained tough and was not in any manner the weak-link, but the epoxy and the apparent disconnect of the epoxy to the glass.

: That's why it's important to not sand too fine and to use an epoxy that's not
: too thick. And as I said before, epoxy takes weeks to gain full hardness.

well, 60 grain sandpaper to gouge the hell out of the area, then for second coat over glass or epoxy seal-coats, hot water and a scrubbing, lot's of rinsing, then after drying a wipe of alcohol if I remember to do so, mostly not done though.

: I remember Eric (Nick's brother) telling me how he stripped the glass skin
: from an old strip canoe done with polyester just by pulling the entire
: thing off.

Well, there you go...vinylester as the bond agent or two part epoxy? Do you think the polyester was the culprit or the bond agent???

: If you were trying for the absolute best bond, you would wet the wood good
: and do a wet layup into wet epoxy with cloth, insuring no starvation and
: full saturation. And you would fill the weave in the next 5 hrs. Filling
: the weave is like putting nail heads on all the epoxy that has come
: through the weave.

The general way I do it, and on all four yaks built, too, except that I always wait till the epoxy cures, then rough up with 60 grain, then srub with hot water and rinse very well...I categorically do not trust any "no-blush" claims.

: I say this once again to you. I believe you could pull off any epoxy
: sheathing in a few days with any epoxy on any substrate. And.. maybe you
: could pull it off in a year. If the weave is filled and real hard, it's
: enormously different. Sheathing is meant to protect, bond and stiffen - in
: that order. If your left over epoxy is hardening in the mixing cup and
: eventually you can sand it, Your OK.

I tested that staement this morning on to test cases done yesterday: the RAKA 127/polycon 22 mix, the 6 oz tape as a second layer did not pull off the 6 oz glass base layer. The Polycon 700/RAKA 610 did have partial failure of the tape and an area of the glass base layer off the wood. It also seems to not have really cured well. A word on curing, you're absolutely right, it takes weeks for a full cure to happen, and that statement of weeks would mean that say 95% (for the sake of a number as an example) of the epoxy full reacted and linked. It's really clear that the epoxy get's harder over time till the matrix is a friggin rock. My first career path I flew Tomcats. Big areas of the bird's surfaces were made up of a boron epoxy laminate, as was the radome of every bird I flew. The stuff is hard and ungiving, imagine hitting what I think was a sea bird while going approximately 300 knots off Pt. Mugu...a massive thump and blur of feathers, and on landing, just a smear over the radome and TCS housing. The energy released at impact must have been tremendous. Further, this same yak I'm doing the retrofit to was dropped sideways from 10-14 feet, the second time crunched into the bottom on 31 May 2002 and aside from all the deck fittings being ripped out and I being busted up pretty good, the yak fared well. That means the epoxy had years to cure fully: no stress delaminations or "printing," no seam cracks or failures, nothing. A store bought FG yak would have had the deck and hull seperate , if not been busted in pieces.

: In our normal usage of our vessels, the type of force you're testing with
: (un-sheathing by pulling it off) doesn't exist - that's why it works out
: so great for what we do. In other words, you're testing it in a way that
: it doesn't get used.

Well yes and no. What triggered the whole thing was the ease of this 3.2 oz glass just peeling off. Well, then I found that the 2 oz tape came off, too. Not a hard tug, but a casual pull, if not flicking the edge with the finger; it's that easy. The thing is I'm relying on the rear bulkhead to remain strong and true as well as the new cheek plates. Both will be bearing up to loads being placed upon them; they cannot fail. If a delamination happens, that means the whole process has failed, suggesting a fundamental component failure. The reason for this retrofit was the delamination of the plywood cheek plate and the desire to build a sloping rear bulkhead to reduce cockpit volumes and provide a back rest. The stuff never failed before.

It's clear now that some element of the mix failed, though I can't nail that down yet except...that the original hardener mix (hardner and accelerator)was the culprit. Here's the kicker...both elements in the original hardener were mixed with new 'other' component batches (old hardener and new batch accelerator, and vice versa). Tests with the new hardeners and the RAKA 127 still kicked! Now...that is sort of suggesting that the resin failed in some manner. The current thought as of 0815 this morning is that the dilutant is somehow causing some reaction to alter the chemistry in some manner. I'm still wondering if the polycon resin (Ciba-Geigy is the maker) is somehow responsible...however, for that batch of resin sold by Yale as Polycon 700 approximately 620 gallons have been sold and presumeably used and so far, no complaints.

As you can probably see, my last career path is deeply ingrained in my very nature; I have to find the cause(s), or process failure(s) that led to this. One thing is that my process has not altered, nor has the glass used. If comes back to the epoxy each time.

I truly appreciate your thoughts on this, clearly you've worked with epoxies and glasses for years and years and in all sorts of conditions. Hearing from the pros like you on this is terrific, and adds to the knowledge base...I'll keep the group up to date on results...since the batch/lot is potentially in other brands of epoxies, too.

Mike