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Strip: A cautionary tale of two epoxies
By:Al Edie
Date: 6/12/2011, 11:49 am

Finally, after a long time, I had the deck and hull all tightly masking taped together, with the glass strips nicely hanging inside from dots of hot glue. All ready for the internal seam epoxy.

I had been using some West System epoxy for putting together various carbon bits and installing the Maroske fittings. I had been running lower than I expected on my Mas supply, so I used the West System stuff to conserve the Mas. Anyway, I reverted to the Mas for the hull/deck seam because I expected it to produce more transparent results, and I didn't want any color difference between the Mas and West System.

So, I mixed up my Mas, and used my spiffy 1 1/2" wide roller to apply it in both ends of the boat- you know, the areas where you have to stuff the loaded roller, one arm, your head (with respirator) through a hatch opening, all while executing a 90 degree rotation so as to vaguely see what the heck you are doing, and while attempting not to drool or smear epoxy anywhere other than where intended. I managed to get the seams nicely loaded with epoxy back to the hatch openings, and congratulated myself on getting the worst part done with relatively little pain, aggravation or mess. I then went back to the Mas supply and mixed up an new batch for remaining section of seam in the center of the boat. 30 mls part A, 6 mls part B, carefully measured.... Then it hit me. I had mixed the Mas at 5:1, the ratio I had been using for the West System stuff. The Mas, of course is a 2:1 mix. The shock of my stupid mistake spread over and through me like cold water. I could not believe what I had done. But there I was with faulty epoxy on the most difficult sections of the starboard seam. The hull and deck could not be separated without surgery because the bow and stern blocks, as well as the skeg box, were already epoxied and set. What to do.

To shorten the story, I ripped out the fiberglass tape with the bad epoxy on it, scrubbed the epoxy off the seam with rags, maneuvered a new tape in place (try this with a sticky seam surface - it is great fun, especially at the end of a four foot stick while you are stuffed through a hatch opening), and applied new epoxy. In retrospect, I might have been better advised to also scrub the seams with solvent, but I figured the tiny bit of epoxy left on the surface of the older glass would bond ok, and it did.

So, my advice to those who are tempted to have two types of epoxy involved in their project is this. On each and every container of epoxy to be used, put very large labels indicating the mix ratio to be used. Make it impossible to mix epoxy without an in-your-face reminder of the ratio to be mixed.

Humbled, but not yet defeated,

Allan Edie

Messages In This Thread

Strip: A cautionary tale of two epoxies
Al Edie -- 6/12/2011, 11:49 am
Re: Strip: A cautionary tale of two epoxies
Farback -- 6/12/2011, 12:42 pm
Re: Strip: A cautionary tale of two epoxies
jwuts -- 6/12/2011, 1:08 pm
Re: Strip: A cautionary tale of two epoxies
Bill Hamm -- 6/13/2011, 12:09 am
Re: Strip: A cautionary tale of two epoxies
Bill VerSteeg -- 6/20/2011, 2:03 pm
Re: Strip: A cautionary tale of two epoxies
Bill Hamm -- 6/20/2011, 2:38 pm