It’s only late August, but I’m trying to get started on cleaning up the garage / workshop for the winter. I can’t build in its current state. Too many other projects, too much clutter. I’ve got to get stuff put away, thrown away, stowed, etc. Then I want to get the rest of the geodetic strips shaved down for assembly, so I’m not out there all winter miserable as I run them through the sander.
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.
Bending more capstrip, and glue efficiency
Last night I tested out the upgraded steam box door with an hour of steam. While that was going on I grabbed a chunk of scrap 2×4 and cut a second bending form. I wasn’t happy with only being about to bend three lengths per run of the steam box. I really need a better blade for that band saw… this one is cheap, and while it will claw its way through a 2×4 it’s not something I would want to do regularly.
But — I have two bending forms, which means I can now do six lengths of capstrip at a time, so I won’t run out as often. The steamer seems to work pretty well. It’s not quite as perfect as if I had attacked it with a planer, jointer and an attitude of complete professionalism… but I don’t have a jointer or planer, and even if I did what that steam would do to cheap flat sawn boards would be a real downer. It works.
On the last several ribs I’ve been taking a different approach to gluing. Early on I found that trying to glue up two ribs in one night meant working with epoxy that was starting to get a little stiffer than I would have liked. I was using a popsicle stick to carefully spread glue in the groove, then on the braces, and assembling. I was also having to fit each brace piece as I went along. Each rib seemed to want about 10cc of glue, but I was getting a fair amount of it running down onto the plastic on the jig.
Now I pre-fit all the braces and mark them with their location. I mix up the glue, dip the ends in the glue and put them in place. I can work a lot faster and make less mess. I’ve been seeing more left-over glue than I would like, as much as half what I mixed up. I think about 7.5cc of glue per rib is more than enough. I mixed 15cc for one pair of ribs and only had a little left over. I’ve also been more careful about the glue mixing. I had the ratios close enough to work well, since T-88 is not too critical. Still, the darker B component was getting used faster than the A, and that tells me I’m not getting it completely right. The stuff is pretty viscous, B much more so than A, and it takes a while to level out in the mixing cup. Now I’ve been squeezing the B part into the mixing cup and walking away for a few minutes while it levels out. Then I add the A component, walk away again, check back in a couple of minutes. I can get it dead on 50/50 that way. I may see about building a 100:83 balance scale to get it even closer.
Not entirely dormant
I haven’t posted any updates to speak of this month. I did get out to the garage and spend a couple of hours sanding down rib geodetic stock.. What a pain in the ass. I really wish I’d gone a different route than I did on this stuff. I just don’t know what that route would have been. Anyway, today I started taping stacks of geodetic strips together and cutting braces. I’ll do as many as I can before starting to build ribs again, so hopefully when I can return to building I can get some momentum going.
I have to be honest… I look at some of the single-seat parasols and think, “Hey, I could be building half as many wings…” But I just need to stick t this. It will be worth it in the end. I’m working on an idea to semi-automate the sanding of the geodetic stock, I just need to fabricate a couple of guides and use a stepper motor to feed the stock through my sanding rig. That could increase throughput and give more consistent results, while I get other things done.
On the way… maybe?
Well, 24 days after placing my order Aircraft Spruce finally shows a tracking number for my capstrip stock. We’ll see if it actually shows up this week. For a while there I was afraid this would just be a blog about how difficult it is to obtain spruce… maybe eventually I will get to actually build some airplane bits.
So, note to self: Lesson learned. Always order wood at least a month ahead of needs, preferably two or three months. Looks like it’s time to start on the spar stock and the stuff I’ll need for the tail surfaces. That order might be here by the time I finish the ribs. There’s a time scale that obviously applies to wood construction that is quite different than what I’m used to. And it’s not like I can just run down to the lumber yard and pick out some suitable spruce or Douglas fir.
Strength vs. weight vs. work (rib geodetics)
While waiting (still) for my spruce to be shipped, I did some figuring…
Building from plans means not getting the wood factory cut and grooved. There are just some pieces that you can’t buy off the shelf. The Celebrity plans call for rib geodetic braces made of 3/32″ x 3/8″ Sitka spruce. ACS and Wicks sell spruce capstrip down to 1/8″ thickness, but not 3/32″. So the choices are to plane or sand down the entire length of the 1/8″ x 3/8″ strips, or use them as is and just sand the ends to fit the grooves in the top and bottom capstrips. So how much extra weight will we end up with if we just use 1/8″ thick pieces? It’s 1/32″ thicker, so we’ll do the math…
1/32″ x 3/8″ wide x 1464″ of capstrip = 17.25 in3 of extra spruce. Sitka spruce weighs about 28 pounds per cubic foot (or 1728 cubic inches), so 17.25 / 1728 = .009928 ft3 x 28 lb gives us a little over a quarter of a pound, less whatever gets sanded off on the ends and scrap, etc. So… around four ounces or less; I can live with that. Still, I’m thinking I may set up a spindle sander with a 3/32 gap to do the ends. If it works well enough I could run the entire lengths of the strips through it, then so much the better. Of course that would probably mean having to buy a new power tool. Oh, no! 🙂
Started rib jig #1
I spent some time yesterday working on the first wing rib jig. The workbench needed a new top surface, so I picked up a sheet of 3/4″ MDF at Lowe’s. They were nice enough to cut it for me. I ended up with one piece 3′ x 8′ for the bench, and two 1′ x 4′ chunks for rib jigs. Nice how that worked out.
I marked a center line on the MDF and laid out the rib setup from Sheet #1 of the plans over it, then trimmed the paper to fit the jig. I hate cutting up plans, but there’s an extra copy of that page for this reason. I made all of the little chunks of plywood for the locating blocks, and cut a few small pieces of pine stock as needed. Then I cut out the places where I would need holes to accommodate clothespins, marked those on the MDF and cut them out with a scroll saw. I used some spray adhesive to stick the plans down to the MDF. So far so good.
Next I had to find some clear poly to cover the plans sheet. I finally remembered the nearly 4′ long bag in which the plans were shipped; it fit just fine. With that in place I started nailing the locating blocks in place over the plan sheet. I got most of them done before knocking off for the night. I still need to make one more plywood block for the main spar locator, and make the blocks for the top and bottom capstrips. I haven’t decided for sure how to do those. I had thought about using a couple pieces of pine bent to fit, but that seems like a great way to mess up the jig trying to get them perfectly in place, and the jig needs to be as close to perfect as I can make it. I’ll probably go with closely spaced pine blocks, nailed in place.
It’s official!
I received a quart of T-88 epoxy yesterday, so the first batch of glue is covered. Today the mail carrier brought the plans, tightly rolled and somewhat bent from their trip from the nether regions of Canada. I will be building Celebrity serial number CE164. So now I have a number of jobs that need to be completed…
- Get the plans unrolled to flatten out so they’re usable
- Get an inventory of the drawings, figure out how and where to store them so that they’re protected. I may add tabs or some sort of externally visible identification so I’ll be able to quickly locate a drawing. One of the irritations encountered while working on the RV-7 was sorting through a pile of drawings to find the one I was looking for. That was a time waster. These drawings are in at least four or five different sizes, a few of them 16′ long. Fortunately, it does not SEEN as though I’ll need to frequently switch between several drawings as I did while building the RV.
- Replace the workbench top with fresh MDF. It’s a good solid bench, but the old hardboard top is scrap. As a bonus, a 4×8 sheet of MDF will be one foot wider than the bench, giving me a 1×8′ cut-off. That will make two 1×4′ wing rib construction jigs.
- Figure out where to begin construction.
- Order up some wood!
I’ll start with the wing ribs. They use only two sizes of stock, and construction is simple and repetitive. I can build the first two or three out of locally sourced pine, just to get the jigs built and get my process sorted out. I can scrap them or use them as wall decorations in my office. The jigs do not need to occupy the entire work bench, so the bench can be used for other things while working on the ribs.
Sourcing wood
While waiting for the plans from Fisher, I asked for and received a PDF copy of the bill of materials for the airplane. While I’m sure there may be some errors and omissions, it’s a good place to start in my efforts to obtain the materials I need to start building.
Much of the wood is aircraft grade Sitka spruce (naturally), and that I’ll be buying from expert and trusted sources like Wicks and/or Aircraft Spruce. There are a few (very few) other sources for aircraft spruce in the country, but those two seem to be the biggest and most readily available. There certainly aren’t any near here, so no running down to the local supplier with the truck to pick out my own bits and pieces.
There is, however, also quite a bit of pine used in areas where spruce is not required and there is some money to be saved. A good little bit of money, in fact. For instance, the outer frames of the fin, stabilizer, elevators and rudder are all laminated from 1/8″ x 3/4″ pine, as are the wingtip bows. You could use spruce as well, of course, but spruce doesn’t come cheaply. Just the pieces to make those laminations would cost over $155, plus truck freight, from ACS. Wicks seems to be a little cheaper for those pieces, but still well over $125 plus freight.
Finding clear, straight- and tight-grained pine won’t be easy, nor the boards cheap – compared to the so-called “stud grade” garbage typically sold at big box stores. That stuff is mostly more suited for a pulp mill than anywhere else. I’ll have to re-saw any pine boards I do find down to size, probably recovering only a small fraction of the wood as usable stock. Still, even if I could only get a few strips (these are 1/8″ x 3/4″, remember) from a typical select grade 1×6 from a local lumber yard, it could still cut the cost down by a hundred bucks or so. So, I think I’ll visit a couple of the local lumber yards to see what I can find. I have the option of slicing pieces from millwork like baseboard and flooring too, so I’m hopeful that I’ll be able to find something. I printed a chart to help me quickly figure out acceptable grain slope on two axes. That and my Incra ruler should help sort out any good boards I may find.
The worst case would be not finding anything usable at all. That just means I would instead use aircraft grade spruce for all the parts called out as pine in the plans. It would be somewhat more expensive, but certainly no compromise of quality, weight or difficulty. I figure about an extra $700-750 added to the build cost if I have to go all spruce, maybe a bit more or less. It’s not enough to derail the project, but it is enough to see what I can find and maybe make some sawdust.
Tooling up (part 2)
I spent some time today going through the table saw setup and adjustment. As it turns out, my saw (a Ryobi BT3100) has a pretty decent following. I did figure out why I’d never been happy with the rip fence. I’d always used the grooves in the casting to align it. As it turns out, this saw is not like others. You don’t align the blade to the table. You align everything off the blade. I got the miter slot (an optional part), sliding miter table, and front scale all adjusted to the blade, lubed the jack screw that raises and lowers the blade, and checked the rip fence. Turns out, it’s pretty close to dead nuts on and always locks itself in place perfectly aligned… you just have to ignore the grooves in the table. Who knew? Anyway, I cleaned it up and gave the table a coat of wax, and cut a feather board and some trim strips for a remodeling project. It’s awesome. One down.