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Building Sequence... Does it Matter?
By Tony Bingelis (originally published in EAA Sport Aviation, November 1993)
It is natural to assume there is a logical sequence for constructing an airplane. Indeed there is, but such an assumption is only partially correct.
The logical sequence for building or assembling a homebuilt’s basic structure is a traditional one. It is one where the tail surfaces are built first, then the wings and, finally, the fuselage. Sometimes the fuselage may be built before the wings.
But does it really matter whether or not you follow this basic building sequence for your own project? It may, but maybe not as much as you may think it does.
Actually, it will depend more on the design of the aircraft and whether you are building from a kit or from raw materials (scratch building). In addition, available work space and your personal preference can certainly influence the building sequence you choose to undertake.
Obviously, you cannot fly the airplane until all construction is completed. That is, all of the various component parts must be built, and the various systems fabricated, and installed before you can fly it.
Since that is the way it is, what difference would it make which structural component you decide to build first?
Well, just think about it for a minute. Until you construct the basic structure (fuselage, wings and tail surfaces), you will not have any place to install the controls, instruments, radios, landing gear, brake system, engine, canopy, cowling, propeller, and all the other goodies that make up a flyable airplane.
Logic would have it, then, that building the three basic structural components first is the way to go for most builders.
Although this building sequence works well when building from a highly prefabricated kit, it may not be the best sequence to follow for some projects or, for that matter, some builders.
What Kit Builders Should Consider
Anyone electing to build a homebuilt from a complete kit package will have several purchase options to choose from. Which of these he buys first will, essentially, limit his/her building schedule to the particular kit purchased and on hand.
Kit manufacturers divide their kits into several "easy to buy" packages.
In general, there will be a tail kit (usually their smallest and least expensive building segment), a wing kit, a fuselage kit, and a finishing kit. In some cases there may even be an instrument kit and an engine installation kit.
Of course, if as a prospective builder your confidence and finances permit, the complete aircraft kit package consisting of the several kit options may be purchased at one time. Then you would be free to build from any of the sub-kits you choose to start with.
However, not many builders are in position to expend as large a sum as would be required for a sophisticated, high performance, homebuilt kit project. We are talking of big bucks which nowadays could range up to $50,000, or more, for one of those luxurious homebuilt kits. Nor would many builders be in position to clutter their work area with all those crated kits at one time.
In some respects immediately buying the complete aircraft kit is a good idea. You can then be assured you will have all the parts and materials needed to complete the aircraft . . . even if the kit manufacturer goes out of business.
Unfortunately, this sort of thing has happened too often in the past. And it always leaves the unfortunate builders in a quandary with no plans, materials, or parts for finishing the projects.
On The Other Hand
On the other hand, when the kit manufacturer is well established (and can be expected to be in business even after your kid is old enough to build his/her own aircraft), buying the complete kit right away may not be the best idea.
Here’s why. If you buy the complete kit early on (as soon as you start the project), you may be "cheated" out of subsequent design improvements.
Aircraft designs, and kits, too, are subject to changes - often for the better. The Kitfox, Avid Flyer, Glasair, Lancair, and other highly fabricated and comparatively complete kit designs, have undergone a considerable number of changes and improvements since they were first introduced years ago.
Here’s just one example to make my point. The current Kitfox kit fuselage is roomier and stronger than the original product. Those who purchased the earlier kit were furnished with a prefabricated welded fuselage which would be difficult to convert to the newer configuration. A similar situation may also be faced with most any other design.
So, you see, buying the complete kit to protect yourself in the event of a possible business failure of the kit manufacturer or, for that matter, as a hedge against the seemingly inevitable future price increases may not be as clever as you think.
Why Start With The Tail Kit?
Like most builders, you would probably elect to build the tail kit first, particularly if the kit has no pre-assembled components. And, why not? It makes good sense.
The tail kit, being the least expensive of the kits, will enable you to acquire considerable confidence and experience without worrying about the potential risk of ruining some of the more costly parts making up the larger kits.
Actually, one kit manufacturer has recently seized on the confidence building idea by offering a Rudder Starter Kit for first-time builders. His intention is to prove to them that they, indeed, have the skills to work with sheet metal and successfully build . . . and fly . . . their aircraft.
At any rate, as completion of the tail surfaces nears, you will have to decide whether you want to build the wings or the fuselage next.
What Next? Wings? Fuselage?
The kit manufacturer will probably steer you in the direction he wants, influenced, in part, by his inventory and the assembly instructions written into whatever manuals he provides with the kits.
The main thing to remember is this:
If a pre-fabricated fuselage is provided or you elect to build the fuselage first, your wings (and tail surfaces) must be made to match and fit the dimensions you have already built into your fuselage.
Naturally, you will follow the plans and will try to maintain the correct dimensions. And you may, in the beginning, even resolve to build it as perfect as you can but, let’s face it, small differences will sometimes creep into your best effort.
If you must have a rule, here it is: once you start your project and build something . . . anything . . . all of the mating parts you make thereafter must be made to fit what you already have!
Another consideration may influence your planned building sequence . . . space or rather the lack of it. For example, a fuselage, once it is built, will continue to occupy considerable work space, whereas a set of wings can be built and easily hoisted up out of the way or be stored vertically on a mobile rack.
My own personal choice would be to opt for building the fuselage early in the project. It can do much to keep your enthusiasm at a high level because you can sit in it and daydream a bit. In addition, it will provide you with the opportunity to make quite a few small installations that don’t take a lot of hours to accomplish.
After all, since the wings and the tail have to be fitted and connected to the fuselage anyway, building the fuselage first has considerable merit.
In designs where the landing gear is attached to the fuselage and/or engine mount, building the fuselage first is even more advantageous.
Once the fuselage is on the gear, it can be easily moved around to better utilize your workshop space. Unfortunately, if the landing gear attaches to the wing, your building sequence will have to be altered to cope with that problem.
Of course, if you have plenty of work space and have both the wing and fuselage kits on hand, you can start building both of them at the same time and switch working from one to the other any time you get tired of working on the wings or vice versa.
As a matter of fact, I find that to be an excellent way to enjoy my project to the fullest.
Building From Plans
This is the way it used to be. Aircraft kits were very scarce and relatively incomplete. Builders had to make everything or find someone who could fabricate parts they could not. It was and still is a far greater challenge to build an airplane from scratch (plans) than it is to assemble a highly developed composite kit where virtually all the components are partially or completely prefabricated.
Some of the more popular designs for which plans are available may also have a few prefabricated components available, for sale, from the designer or from some builder who has already completed a project.
Engine mounts, landing gear parts, exhaust systems, cowlings, and canopies are usually the extent of the prefabricated parts available to the plans builder.
Building from plans will permit you, as the builder, to start anywhere you want with the minimum expenditure of funds. Remember, everything must be built and installed before you can fly the airplane.
Where do you begin with a plans-built project?
Anywhere you want, of course, but the most popular starting place is with the wing ribs. Builders are intrigued with the idea of completing all the wing ribs first.
You could, instead, make all the fittings, brackets, ribs and similar small parts. At the same time you could be shopping around for the various instruments, fittings and hardware you will need.
Take heed of this observation. The building sequence where you make all the small parts first is not for everybody.
After all, you will not have any major structure to look at or anything to show off that looks like an airplane . . . maybe for as long as a couple of years.
That less than exciting prospect can be discouraging to all but the most dedicated of builders.
In short, if you are a frugal builder you can save a considerable amount of project money provided you are willing to develop new skills, are not in a hurry to fly, and don’t mind all the extra work.