Getting the CW35 aileron nose ribs located perfectly in the aileron is critical to making sure the aileron is straight and consistent with the other wing. Today I slid the torque tube into place and checked the fit of all the pieces that I can at this point. After making some adjustments to the holes in the CW36 end plates, I glued the three CW35s in place in the middle of the aileron. The next step will require cutting the trailing edge to install the aileron end caps, so I want to make sure the torque tube location is easily and consistently reproducible.
I think at this point I may just bolt the torque tube bearings in place (I have a set of 3D printed temporary pieces) and cut the last piece of AL tubing in half. This will let me work with a much shorter and easier to handle piece of tubing while setting up the ailerons.
I’ve seen all kinds of methods people use to mix up their T-88 epoxy. The manufacturer says to mix the resin and hardener (Part A and Part B) 1:1 by volume, or 100:83 by weight – which are the same thing. Plenty of videos on YouTube and EAA Hints for Homebuilders show various methods, and I’ve read some pretty involved threads on various homebuilding message boards. Some squeeze out equal lines of the two parts. Some cut the bottle tips to different sizes and squeeze out for a measured amount of time. Some have built scales to measure out by weight. Some do it in graduated mixing cups, like the little medicine cups that are easy to find. Some just use “TLAR” – or, “That looks about right”. You can buy T-88 in twin dispensing cartridges that automatically dispense and mix the glue — but it’s something like six times the cost of buying it in bottles, and of course you’re going to waste some each time when you throw out the mixing tube.
I have a bit of an aversion to not measuring epoxy accurately, and estimating and hoping for the best didn’t seem to me like a good plan when building an airplane. I know the precise ratio isn’t super critical; even System Three says that. Still, though, why guesstimate or get “close enough” when it’s so easy to get an exact amount?
I bought some 60cc catheter tip syringes through Amazon. They’re cheap and disposable, though I’ve reused mine a number of times. I fill one with Part A and one with Part B, and usually use a permanent marker to mark the cap for the Part B (darker) syringe, just so I don’t accidentally mix the caps up and ruin some epoxy. I’ll fill them just past the 60CC mark, then stand them tips-up overnight to let all the trapped air bubble up to the top, then squeeze a little back into the bottle or jug until the plunger is exactly on the 60cc mark. Pull the plunger back just a bit to get a little air in the tip, and cap it.
By doing this you can very accurately measure both parts to mix up any desired quantity of glue, from 2 cc up to 120 cc. Gluing plywood spar webs to spar caps? I’ll mix up 20 cc at a time, 10cc from each syringe. Building ribs? About 8 or 10 cc of glue will do two wing ribs, so 4 or 5 cc from each syringe. When the syringes are empty, you can either be a cheapskate like me and refill them, or just toss them in the trash if they’re too grungy to re-use or if you’re Daddy Warbucks and don’t care about the cost. I’ve got two pair of syringes that I use, and each has been refilled probably six or eight times. I just ordered some more syringes, since these are getting a little sticky and I want to keep fresh ones on hand. I use them for other things as well, so it’s never a bad idea to have some around. You also don’t want to run out of glue before you’re done building for the day, so I try to always have at least two sets filled.
Note: Pay attention to the quality of the syringes you buy. The first few I bought were made by B-D (Beckton-Dickinson) or Brandzig, are nice heavy duty plastic, are marked with 1 cc graduations, have good caps, and are generally high quality. The next batch I bought are thin, lightweight, shorter, marked with 2 cc lines, and are generally cheap Chinese crap. I’ll toss these after the first use and chalk it up to a lesson learned. As is almost always the case, it’s better to spend a little extra for good quality.
