Sitting in the rib jigs right now are the last aileron rib (#16 of 16), and the sixth false rib. After the glue cures on these, I’ll modify the second jig to fit as many false ribs as possible. I think I can fit three on it for sure, possibly four – but that’s doubtful. I’d like to start cranking out four false ribs at a time.
So I guess it’s time to go start shopping for the best plank or two of white pine I can find to get started on the laminations for the tail surfaces. Pretty sure Menard’s will be my source for those; the stuff I find at the other big box stores is more suited for a dog house or the pulp mill than anything else.
Yesterday I glued up the last full rib (#26) and the first aileron rib. I’m going to call this a milestone. 🙂 I now have 15 more aileron ribs to go, then 34 false ribs. I suppose I should pull out the plans sheet for the spars and see exactly what I need to order for them. I have the BOM, but it doesn’t really tell me what I need to know without looking at the plans too.
I had to look at the plans a few times. It looked like the plan sheet was calling out just one geodetic brace to omit for the aileron ribs, but the locations to mark for eventual cutting didn’t make sense. I finally realized that the text read, “Omit this X-brace for aileron ribs”… as in, BOTH braces, not just the one. Great! That’s two less pieces to cut and glue.
This morning I pulled the first rib out of the jig to check it out. I was a little apprehensive about it, to be honest. I had tried to use a little digital scale to weigh out the epoxy, and that didn’t work well. The scale didn’t see tiny increases in weight as “activity” and would power itself off every few seconds. I ended up “eyeballing” the mix by volume, and hoped I got it right. With a little less than 15cc of glue I was hoping it was right, and last night it was still feeling a little “tacky”. Well, this morning that epoxy is perfect, nice and hard, glossy surface and zero tack. My test piece with a couple of scraps of geodetic brace glued with no clamping broke apart in pieces, with no failure at the glue joint. The wood failed and the glue didn’t. Success all around.
The only deficiency I can see is, there’s maybe a little more glue than needed. Glue had run down under several of the joint areas and I have some cleanup to do on the “bottom” side of the rib, the side that was against the jig surface. I’ll need to figure out how to get the right amount of glue in there when I pre-glue the groove. Other than that, it looks really good and I’m thrilled with it. It looks like about 10cc is what is needed to glue up a complete rib. That means when I get the second jig built, I can mix up 20cc and glue two ribs at a time. The more glue gets mixed at one time, the easier it is to get the mix ratio perfect so that will be good.
And, I’ll have to put this rib somewhere in the middle of a wing where it can’t be seen by the Oshkosh judges. That way it won’t screw up my chance at that gold Lindy. 🙂
After a couple hours of cutting and sanding geodetic pieces, I finally mixed up a little T-88 epoxy and glued up the first rib. Kind of a milestone — the first full size wooden rib I’ve ever built. Can’t wait for tomorrow when the glue is hard enough to pop it out of the jig. Then we’ll see whether this one gets used on the airplane, or used for destructive testing.
Cutting those geodetic pieces is a lot of tedium. Even more so since I didn’t send the strips before cutting, so i then had to sand each piece individually. next time I’ll clean up the capstrip prior to cutting. I was cutting two pieces at a time, with the capstrip stock taped together. I may go for 4 or 6 pieces at a time as I get better at it. And, I need a better solution for holding the pieces. I knocked three of those cups off the bench at various times while assembling it. Things will be a lot easier if and when Pete’s R/C Cub gets off my workbench.