Another year draws quickly to a close, with what feels like not a lot of progress on this project. I have a tall stack of ribs, but really nothing else. I had hoped to have a good start on the tail surfaces by now, but haven’t even started on them. We’ll need the basement for a family Christmas party, so no laying a 4×8 sheet of MDF over the island down there to start laminating pine. No worries, though. I have located some nice clear pine boards at Menard’s that will rip down nicely into 10′ long lamination strips. I have an order of Finnish birch ply queued up on Aircraft Spruce’s web site, ready to place the order once I’m sure I have all the stuff on there that’s going to be expensive to ship. As soon as we’re finished with the post-party cleanup, I’ll have the basement available to work in through the rest of the winter since the garage will just be a bit too cold for epoxy.
I also got a great idea from one of the guys on the Biplane Forum. I’ve been pondering how to store the wing ribs. I think I’ll build short pieces of main and rear spars out of pine and non-certified plywood, just to assemble all the ribs and clamp them together. That way I can surface sand them all together, and maybe if I’m lucky use that assembly to run them through the table saw for trimming as well. Maybe.
Nothing new, but last night I gathered up all 47 full ribs and stacked them up, carefully aligning the cross pieces for the main spar, aft spar, and nose spar. I was a little concerned about the amount of variation I might find, considering the ribs came out of two jigs over a period of 20 months. I was very happy to see that there’s no more variation than could be attributed to wood thickness. Less than 1/64″, probably under .025″ anywhere along any of the ribs. Then I stacked up the dozen false ribs I have done so far, same story.
Wait – 47 full ribs? Yes, it seems somewhere along the line I must have lost count and built one extra aileron rib. I’ll either keep it around as a wall hanger/test piece, or maybe stick it under the wing walk for a little extra support. I’m not sweating it.
This exercise has also reinforced my idea to build a sled for the table saw to lop off the ends of the ribs for the leading and trailing edge pieces. They are very highly consistent, as they should be, so I think that will save time and make subsequent assembly steps easier.
The bad news is — my T88 epoxy is junk. I refilled the dispensing syringes and the resin looked a little “off”, not perfectly smooth and clear as it usually is. Maybe a little cloudy and with a different texture. I mixed up a small amount and glued up some test pieces. Where I glued the flat sides two sticks of capstrip together, the joint held well and pulled apart well into the wood. However, where I had glued a couple pieces of geodetic brace into the slots, the glue joints failed allowing the braces to pop out without breaking. The glue also was not clear and hard, as it should be, but had an almost grainy or mealy texture to it. I don’t have any trust in the remaining glue in those bottles. I’m certainly not going to risk using substandard adhesive to save about $20 worth of epoxy! Into the trash it goes. I have two new bottles here, and half a dozen new 60cc syringes on the way from Amazon.
Well, I set up the second jig for three false ribs. I’m only making two at a time on that one, though, plus one on the first jig, so three at a time. One of the three setups on #2 is just not quite “there” enough to suit me. To be honest, I don’t really know how much difference it makes if there’s a 1 to 2 mm variance in the shape of the lower or upper surface of the airfoil. I’m getting the ribs all as close to identical as I possibly can, but I know I’ll need to do some minor true-up work once they are all ready for assembly to the wing spars. What I think I’ll do is stack them all together on some scrap wood cut to match the size and shape of the spars, then use a long sanding block to true everything up. That’s a while of, still.
In the mean time, I’ve got around a dozen or so of the false ribs done, and am cranking out 3 per day on the days I get any work done. Now, however, I’ll have to take a day off to hot-soak and bend some more capstrip. I’m out of the pre-bent pieces.
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.
I got two false ribs glued up last night and pulled them from the forms today. The new razor saw arrived yesterday afternoon, so that was nice to have. I’m leaving all of the ends of the top and bottom capstrips a little long. I am planning to just build a sled for the table saw out of MDF, with dowel pins or wood blocks to locate the ribs for the four cuts I’ll need, referenced to the main spar and rear spar. That’s one cut for the nose, one for the trailing edge, and two for the tail ends of the false ribs. That can wait until all of the ribs are finished, maybe later depending on how cold & crowded it is in the garage. They really don’t NEED to be trimmed until I’m ready to assemble the wings, so that may be a while yet.
I figure I’ll get two, maybe three false ribs out of a pair of capstrips that would make one regular rib, so I’ll have plenty of opportunity to use whatever method I do finally end up using to pre-bend the wood. Over the past couple of nights I’ve tried a couple of methods of bending capstrip. The other night I ran a bucket of the hottest water I could get from the tap. It was probably 140 F or so, coming from a bar sink just a few feet from the water heater. I put half a dozen capstrip pieces in there, let them soak a couple of hours, and put them on the bending forms. That seemed to work well, with no broken pieces.
Last night I added a gallon or so of hot water to the bucket, just to top it off some more. The water would have been lukewarm at best. I soaked another half dozen strips for 12 hours or so. Of the six, one snapped as I was bending it in the form. That’s about what happened the last time I tried soaking in cold water, so obviously that’s a waste of time and good spruce. Won’t make that mistake again.
Well, the work bench is cleared off — well, at least enough to get both jigs on it. I’ve got a couple dozen sticks of geodetic brace stock shaved down. The epoxy syringes are filled. All I need now is a razor saw and a steam setup.
Yes, I have a razor saw. Somewhere. I pulled it out during the kitchen remodel, and I remember seeing it in a box of tools we were using, but now I can’t find it. It’s a Zona, good quality but inexpensive. A new one is on the way. Two, in fact; one medium and one fine tooth. I also have a steam box that I built for the capstrips, but I’m unsure whether I’ll use it in the basement. It takes bench space (which I now don’t have down there), and drips water out the end by design. I’m thinking about ways I can use it vertically. I had looked at rigging up a piece of pipe or something with a heating element for hot water, but it looked like an awful lot of extra work considering I’m over halfway through the ribs. I’ll probably need it for the tail and wingtip bows as well, but I’m not entirely sure yet how I’m going to steam 6 to 9 foot long strips of wood. Tonight I tried soaking half a dozen capstrips in a bucket of hot water for an hour — we’ll see how well tat worked.
Well, I thought it had been a lot longer since I did any construction, but I see it was only back in February. I really wouldn’t have been surprised to find that I’d gone an entire year without building anything. But, I’m getting ready for winter and more building. To be honest, I’d had second thoughts recently about even continuing with this project. Sometimes it seems like such a massive undertaking, especially when I see pictures of guys attaching the wings and getting flying wires made and rigging done… only to tear it all apart again and then start covering. Covering!! How the hell an I ever going to cover this beast? But then I decide that maybe I’ll keep at it after all. Hey, it’s relatively cheap… so far… as hobbies go. It keeps me occupied for as long as I care to work on it, and nothing bad happens if I let it sit idle for a while. Even a long while.
Over the past few days I’ve been working on getting my absolute pit of a basement workshop cleaned up at least enough to be able to move around and use the workbench. A new water softener installation, a kitchen remodel and a few other household projects meant there was a lot of mess left over, and a whole lot lot of crap got just piled everywhere. Most of it’s cleaned up. Not enough, really, but at least enough for me to be able to take stock of where I am. In hindsight, I suppose I could have, you know, looked at my blog posts, but where’s the fun in that?
I need 26 normal wing ribs, and they are all done. I need 16 aileron ribs — the same as the normal ribs, but just missing a couple of cross pieces. Of those, I have built ten, so there are six left to build. Then there are 34 false ribs — just stubs from teh leading edge back to just behind the main spar. I’ve built one of them, so 33 left to build. Those should be quicker to build, since there are only about a quarter of the geodetic braces to cut and glue. Unfortunately, each will still occupy a full rib jig — so two at a time is still the limit. Unless… maybe after the aileron ribs are done, I can tear down one of the rib jigs and rebuild it to do several false ribs at a time. I think keeping one rib jig intact would be good, just in case I should ever need to build more ribs for a repair or whatever.
I’ve got a bunch of geodetic brace stock sanded down to the correct thickness. Enough for sure to do the rest of the aileron ribs and get a good start on the false ribs. I’ll probably do half a dozen more, then put the oscillating sander away and maybe knock out a few ribs. I’m starting to get a little fired up again.
I’ve knocked out a few more aileron ribs, two at a time. I’m about halfway through them and trying to speed things up a little, so I don’t die of old age with a half finished airplane.
Yesterday I decided to use up a piece of obviously bad capstrip Aircraft Spruce saw fit to ship me. This piece has a large chunk missing out of one edge, part of a knothole or pitch pocket or something. Part of it is in no way suitable for aircraft use or much else for that matter. But – there’s enough good wood there to use it for false ribs, so I made one of those. That went OK, but it’s apparent that I will need to soak the top capstrip in HOT water for the false ribs.
I’m looking forward to starting work on the tail surfaces. I’m planning to get out to the garage and clear off the workbench this week, lay out the plans and see exactly what I will need to get started. The wood called out is white pine, so I’ll start checking the local places for suitable pieces of white pine or Douglas fir… a little heavier, but I know Menard’s sells some good boards from which I can cut suitable pieces for the laminations.
Five down, eleven to go. Cutting the geodetic braces individually is really not as much of a chore as I thought it would be. I am finding that I’m going through the 6′ lengths of stock quickly, though — I figure I have enough shaved down for the next 3 ribs, maybe 4, then I’ll have to fire up the drum sander again and make some more. Not that it’s stupidly tedious work or anything, mind you.
In hindsight, it would have been a whole lot less work and actually less expensive to have bought 3/8″ thick spruce spar stock and just ripped it down to 3/32 strips, losing half the board to saw kerf. I am at a loss to explain why that little bit of math didn’t make itself obvious. Of course, I thought at the time that shaving 1/32″ off those strips would be quick and easy. Not so much. So… if you’re building a Celebrity from plans, you’d be better off doing that.