I'm sure most of you are aware of my build in progress, A Wee Dram.
https://www.rocketryforum.com/threads/care-for-some-scotch.157850/
Well, I had a bit of cross-pollination of information and observation between my projects last night that applies to my journey with learning the ways of epoxy. Since this rocket is made with tubes that are wrapped with a paper label, I had to make slots in the label that would allow glue to contact the fin root as well as the actual tube. Additionally, I cut notches in these slots to accommodate four tabs on each fin so that I had more surface area for glue to contact both the fin and tube. (Although this is technically a through-the-wall fin design, the tabs do not extend all the way to the motor mount because this is a four-motor cluster with three fins and I didn't fee like doing THAT much math)
So, what does all this have to do with my epoxy/denim experiments? Well, I had the opportunity to finally combine epoxy with acetone and get a feel for how well it works. After the initial silicone based glue cured on the fins, I was left with a bunch of little gaps between the body and fin roots due to minor imperfections and inconsistencies in the slots I made (this was expected). So, to fill those gaps and to act as fillets, I wanted to use some epoxy, but I wanted to use only a TINY (about 1/16" wide) amount to keep from messing up the appearance of the body or fins. To do that, I decided to use a syringe with a thin applicator tip to apply the epoxy with pinpoint precision, but the epoxy was too thick to work in the tip. So, I added a splash of acetone (I didn't weigh the parts exactly, but I would guess a rough 1:1:0.5 ratio of the halves of the epoxy plus acetone by weight) and loaded up a second syringe. This time, the mix came out easily with a runny consistency like cheap pancake syrup, and flowed easily into millimeter-wide gaps.
But here's the real kicker: I used Loctite 5 minute epoxy for this, and that time estimate is pretty accurate. However, adding the acetone almost DOUBLED the working time! After five or so minutes, the epoxy was about the consistency of freshly mixed epoxy and still could be easily spread around. After a good ten minutes or more, it was starting to stiffen up. By the time I had cleaned up my supplies and put the rocket up to cure overnight, it had been close to 45 minutes and the fins still had a bit of a wiggle to them. I was worried that I had made a mix that wouldn't truly harden, but as of this morning, the wiggle was gone.
SO.
I was initially hesitant to try the Loctite 5 minute epoxy for the denim composite experiments because I didn't think I would have enough time to saturate each piece before It began to cure, but by thinning it with acetone, it not only becomes more liquidy, but allows for more working time! I still need to get some non-absorbent paper plates (although now i am contemplating metal pie plates since I mixed last night's epoxy for the fins in a metal cap from another scotch tube) in order to prevent the acetone from being absorbed before it can properly mix with the epoxy, but aside from that, these results are very interesting and encouraging! I might even try the same thing with the JB Weld since I first read about the acetone trick from their website. More fun to follow!