Building Sequence . . . Does it Matter?
Sport Aviation - 11/93
By Tony Bingelis
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.
