So today, more than two weeks after placing an order for wood from Aircraft Spruce and five days after contacting their customer support to ask where the hell my order was, I finally get a response that they will be shipping three more days from now. That will be a full three weeks from the time I placed the order, and also means I go yet another weekend without any supplies.
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! 🙂
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.
Plans ordered
I don’t know where all this will lead. Maybe I’ll end up building and flying a new airplane. Maybe I’ll end up with some interesting wall decorations. All I know is, I feel the need to explore this and see where it goes. Yesterday I ordered a set of plans for a Fisher Celebrity.
I’m already thinking about various modifications… mostly trying to de-drag some of the structure by using streamlined tubing or even wood for struts and such. And I’m keeping an eye out for possible engine choices. I’m kind of torn on the whole electrical system question. part of me says keep it light and simple — no electrical system, no transponder, handheld radio. The other part doesn’t want to have to hand prop the engine.
We’ll just have to see where it goes. Who knows? Maybe I just end up making really cool looking furniture and never finish it.