This essay started out to be about what it takes to build an airplane using wood, wire, dope and fabric. It's still about that, but it's also about why there shouldn't be a down-time aerospace industry, nor much of an air force, in the first decade or so post Ring of Fire. I say "shouldn't" because what actually happens is up to the fiction authors and, in my experience, when works of fiction are created, plot and drama trump the details of reality every time. Still, if you're going to break the rules, you should at least know what they are.
I earned my private pilot's license in 1966. At the time, it required a minimum of forty hours flight time. I qualified for my Airframe and Powerplant (A&P) mechanic's license in 1970—one of the very last groups of students to be formally trained in maintaining wooden aircraft. To earn my A&P license I went to school eight hours a day, five days a week, for fourteen months, then passed long and rigorous written and practical exams. Nearly all of what I learned in that time is orthogonal to what a pilot learns. The idea that J. Random Pilot from the twenty-first century would know anything about building and maintaining wooden aircraft is laughable. There were no A&P mechanics in the Ring of Fire—let alone any of my era—so most of what I'm going to talk about below is unknown in Grantville.
Further, as a mechanic I know how to maintain and repair aircraft using mostly off-the-shelf parts and materials. I don't know how to design one. For that you need an aerospace engineer and there is only one in the Ring of Fire, Hal Smith. (Mike Spehar managed to grandfather him in before the Grid became so rigid.) I don't know how to make the precursor chemicals for dope. For that you need a chemist. I don't know how to make the high quality steel to make the wires, nuts, bolts, etc., you need to hold an aircraft together. For that you need a metallurgist. Except in the most general terms, I don't even know how to make a propeller, let alone design one. Trial and error will have to serve.
The following description of the building and maintenance of fabric-covered, wood-framed aircraft is going to include a lot of fiddly details and requirements. Some of them are going to be difficult to implement in the seventeenth century. Whether they are implemented or not is up to the fiction authors, but they should be aware of this: A lot of airplanes crashed and a lot of people died to put those details and standards in place. None of them are entirely frivolous. If you want your airplanes to be credibly able to fly from Peetle to Pootle without crashing six times along the way and want your pilots and passengers to be anything but suicidal daredevils, you'll leave them in place. Also note that even modern private aircraft are inspected annually, commercial aircraft are also inspected every 100 hours of flight and military aircraft are inspected daily, so problems can be detected and repaired early. Finally, when feasible, every pilot does a walk-around inspection of his aircraft before taking it up.
It's been suggested to me that outside of Jesse Wood's air force, down-time pilots will be daredevils. Even if you aren't concerned about their safety, consider the safety of your precious engines, instruments and even rubber tires. You can't afford to build airplanes that crash and burn at every pause in the conversation.
So, let's begin.
First is a list of the minimum woodworking tools required to maintain a wood framed aircraft. Most of them should be available or makeable in the seventeenth century. Space limits prevent me from describing each one and its use. Mechanics learn about them in the practical shop part of their training.
Backsaw (14 to 18 teeth per inch)Small bucking barAuger bitsBraceC-clampsParallel wood clamps (Jorgenson)Scribe compass (10 inch, thumbscrew lock)Hand drillTwist drills (1/16 to 1/4 inch)FlashlightHammerMagnetic tack hammerPocket knifeBlock planeJack planeDiagonal cutting pliersCoarse wood rasp (half round)Fine wood rasp (half round)Dovetail sawCrosscut hand saw (10 to 14 teeth per inch)Keyhole sawRip saw (5 to 6 teeth per inch)ScrewdriversCombination squareStraightedge (36 to 48 inches)
The wooden frame is covered with fabric and the tools for working with that are the same as those used by a tailor or upholsterer. They include assorted needles, scissors, pinking shears, sewing machines and irons. The fabric, in turn, is covered with dope, which I'll talk more about under the materials heading. Dope is applied like paint, with brushes or, if available, a paint sprayer.
Even wooden airplanes have metal parts and fittings and for them you need the usual wrenches and screwdrivers and drills (oh my!). To fabricate the parts from raw stock, you'll need the resources of a machine shop or a blacksmith.
In addition to these mostly generic tools, there are specialty tools needed for doing things that only airplanes need done, like tensioning the wires and cables that hold the wings up (and down). I'll mention them as they come up in context.
Aircraft spruce is the wood most commonly used for wooden aircraft structures. Properly cured, it is light in weight and has high tensile strength for loads applied parallel to the grain. "Properly cured" means kiln dried to produce uniform strength and reduce moisture content evenly. To promote even curing, pieces to go in the kiln should be as small as feasible, given the parts they are going to be used to make. (Obviously, beams for wing spars and such are going to be pretty long.) If aircraft quality spruce isn't available, certain other woods may be substituted if they are of sufficient quality: Douglas fir, noble fir, Western hemlock and white or Port Orford cedar. Some of these are not available in seventeenth-century Europe.
In general, the wood should be straight grained and the grain should not deviate more than one inch in fifteen. Wood for spars and other large structural parts should be quarter sawed such that the end grain is nearly perpendicular to the sides of the board. The minimum number of annual rings per inch is six for most woods and eight for Port Orford cedar or Douglas fir. Look for trees growing on the shady side of a hill or in other conditions that lead to slow growth.
Aircraft wood must be free of decay, shakes and checks (splits) and compression failures. Minor defects like small, solid knots and wavy grain are tolerable if they don't appreciably weaken the part, but should be avoided if at all possible.
Most aircraft construction and repair uses glue to join pieces of wood. A glue joint should be as strong as the surrounding wood. Of the glues available in the seventeenth century, animal and fish glues cannot be used for aircraft work because they are not waterproof. Until synthetic resin glues are reinvented, casein glue will have to do. (The familiar white glue is usually a casein glue. It's made from milk, lime and salt.) It is satisfactory for the purpose as long as it is protected from fungus, usually by chemical additives (zinc borate or formaldehyde may be suitable). All glue left over from a job should be discarded.