Day: August 4, 2017

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Mixing epoxy

I’ve been mixing epoxy in the little plastic medicine cups using “craft sticks” (think Popsicle stick).  I thought I was doing a pretty good job of stirring, spending some time scraping the sides and swiping along the bottom corners of the cup to ensure everything was mixed up.

Last night I mixed up about 2 cc of epoxy, mostly just to try out my new syringe dispensers.  I let it sit in the cup with the stick propped up in the center.  Today I popped the slug of glue out of the cup.  Lo and behold, there are sticky spots around the edge!  Nearly all of the glue is perfectly hard and cured, but there is just a tiny little bit of uncured epoxy right around the bottom edge.  Apparently the stir stick is not a good tool for making sure ALL of the material gets mixed together.

In light of that discovery, today I did another 2 cc sample.  This time I did the mixing with an acid brush with the bristles trimmed down to about 1/4″ to 3/8″.  After mixing I cleaned the brush out with a little MEK, just to see if that would be worth doing or not.  We’ll see how that one turns out after the epoxy has had a chance to cure.  Acid brushes are pretty cheap, so even if the MEK cleanup doesn’t work out it’s not a big deal.  You can buy the brushes by the gross for around $0.12 to $0.15 each.  But what will I do with about 950 craft sticks?  Good thing I have grandkids.

 

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Prep work

I’ve been away from building for a while dealing with a remodeling project, the annual condition inspection on the RV-12, Oshkosh and few other odds & ends.  At Oshkosh I discovered that the wood shop guys had actually saved my miniature wing rib from last year (2016).  I brought it home with me, of course.  Last night I pulled the staples, cleaned it up and sanded it, and gave it a coat of clear polyurethane.  I figure it will make a nice wall decoration for my office.

Last night I also started cleaning up some of the enormous mess in the garage so I can get back to building.  I’m not quite there yet, but tools are slowly making their way back into drawers and onto pegs.  It may take a few more days, but it will be nice to get back out to a garage that’s not a complete disaster.  There are 14 wing ribs hanging on the wall, and the guy on the Biplane Forum is catching up with 11 finished.  He can work faster, since he can pull his ribs out of the jigs as soon as they are stapled.  I need to step up my game!

I did pick up a good idea from that discussion — using cut down acid brushes to mix & apply the epoxy.  They’re cheap, and it looks like I might be able to get more precise application of the glue where it’s needed, in the amount needed, with good penetration into the wood grain.  I’m anxious to try that, I have a handful of brushes here.  And, I got some of the epoxy  into 60 cc syringes so I can dispense exactly the same amount of each component.  I know it’s not terribly critical with T-88, but I still want to be as accurate as I can.