Getting Started in Homebuilding, Part 7 of 11


Budd Davisson, EAA/Experimenter, 1994

The Plan

Alright, picture yourself standing at one end of your newly completed, nicely finished workshop. Laying in the middle of it is a neatly stacked pile of "something." What that something is is a function of what you see yourself building. If it is a Pitts, there's a lot of tubing stacked there. If a Cozy, blocks of foam, jugs of liquid and bolts of cloth take up the middle of the floor. The pile will be different, but it will be there.

That pile practically reaches out to you and whispers "build me" in your ear in a sensuous, come-hither voice. It says grab some tools and start whacking, whittling, welding. It says start building. But where? On which piece?

Almost without exception, the first piece anyone starts building is the fuselage. Builders want something that looks like an airplane as quickly as possible. For some folks this is so they can see progress. For others, it is so they'll have a place to sit and make airplane noises with their lips, as they imagine themselves off for Aspen, Palm Beach or Cincinnati.

For the vast majority of builders, the fuselage is the wrong place to start. This is especially true if this is their first airplane. Actually, beginning anywhere is the wrong place, if the builder hasn't already given at least some cursory thought to a logical order of progress for the airplane.

Some of the more complete kit planes come with a recipe book attached. They lead the builder through the process in such a way the best approach to building is already spelled out so he doesn't have to stand there scratching his head each time he hits a crossroads. This is not true for about 98% of the homebuilts out there.

For most airplanes, the homebuilder can start anywhere, so it is imperative, he look at the airplane and the building environment and layout a road map to follow. It doesn't have to be complex and it isn't cast in concrete, but he/she should at least give it some thought. We think ahead, when we fly, why shouldn't we think ahead, when we build?

Exactly where we start in the hands-on construction of the airplane is driven by four basic factors, each of which has a couple of sub-categories to be considered. These are:
· Skill and experience level
· Work shop space
· The mechanical interface of certain parts
· Finances

Each of these has some sort of effect on the way the project is approached and it is the combination of these that dictate what is done first and what is done last.

Skill and Experience Level
As we said earlier, most builders almost immediately start on the fuselage. Let's look at that decision in the hard light how much skill and experience a builder brings to the project.

First let's say it is his first airplane project. He is building his first airplane yet the first thing he builds is the fuselage, which means he is tackling the wing fittings, engine mount and the primary structure which both aligns and contains all the rest of the airplane. The backbone of the airplane is the first thing he builds. That means, by the time he is done building the fuselage, he is going to be really good at what he does, so he can start on the tail.

Does that seem a little backwards?

A far more logical approach, at least where skill is concerned, would be to build smaller components first, developing skill on parts that are easier to build. Notice, we didn't say they were less important or less critical. There are no unimportant parts in an airplane. However, if the tail is the first thing built, then, when the builder jumps on the much larger fuselage, he takes with him the skills learned in building the tail. Then, when he is finished with the fuselage and he looks back at the lower craftsmanship he demonstrated early in the project on the tail, he has the option of building a new tail. That is not true if the does the fuselage first. He will be half way through it before his skill increases noticeably. When he is finished, he is not likely to junk it and build another one just because he can do it better.

One of the basics to building a good airplane is the willingness to build a part for a second, or even third, time, if it isn't up to our standards. When that part is something smaller, like an elevator, it is much easier and less painful to build another one. Since mistakes are much more likely to happen while a skill is being developed, why not try to contain those mistakes in components that are more easily redone?

Even if a builder is experienced, there are times, when the skill level is down simply because nothing may have been built for a while. There aren't many builders who jump right out of one airplane and into another. There is always a time in-between where more attention is paid to flying than building. So skills slide downhill. The welding isn't quite as fluid as it should be and there's a slight tendency to bounce with the rivet gun. All skills need to be practiced to stay sharp. For that reason, it even makes sense for the super builders among us to jump in to a new project slowly, with small parts first. Maybe the tail. Maybe an aileron.

Space considerations
It is one thing to be able to build any part. It is something entirely different to have a place to put that part, when it is finished. No amount of skill is going to make up for the fact that where simply isn't enough room to store everything. The old scientific principle that two things can't occupy the same space at the same time applies here.

Isaac N. had a certain amount of common sense.

If space is no consideration, then skip on to the next paragraph, but there aren't many of us who aren't constantly fighting the work space problem. We can either aggravate or help that space problem, depending on the order in which the airplane is attacked. Build the big pieces first and they lay around underfoot while the little ones are being built. Build the little ones and they can be hidden under the upstairs beds until ready for use.

Tails are almost never a serious space consideration, when building an airplane. But, they shouldn't be ignored. Most horizontal stabilizers are between six and eight feet long but fairly thin. So, they store easy. But, try to build one, when the shop is already filled to the gunwales with fuselage and wings. It is amazing how big they get.

The usual big question is whether to build the wings or fuselage first. This depends, to a certain extent on the design. Even a long, one piece wing, like the top one on a Skybolt, can be hung on a wall. In a pinch, they can even be securely bolted to the ceiling or made into a nice wall hanging for the living room, although that might be stretching it. If attached to the ceiling, protect with a layer of plywood. It is easy to forget it is up there and ding it up.

When the wing is being built, it takes up a lot of shop room, but stores easy. The fuselage never takes up less room than it occupies when being built. Once it is stuck together, the builder is stuck with it. They are also a lot more noticeable, if sneaked into the living room.

So, if space is a problem, unless there is a good, safe dry place to store the fuselage outside the workshop, do the wing first. Otherwise, building the wing is going to get really cramped.

Parts Relationship
Let's face it, some parts simply can't be finished until the part it is mated to is finished. It is, for instance, chancy to weld the mount bushings for a tail in the stabilizer and the fuselage without having both components together for final fitting.

Also, in some designs there is a natural progression to the way things are at least finished, if not in the way they are built. The fuselage and the tail, for instance could be built separately, but the mating parts left until the last, when both components are finished. A lot of wing fittings call for final drilling and reaming "on assembly."

Obviously certain parts can't possibly be made until their mate is finished. Cowlings, for instance, can't exist without the firewall for cross sectional shape and the rest of the fuselage for curvature and continuity. Most of the time, the engine will even have to be mounted in its final position on the mount, before the cowling can be completed.

Even if a pre-made component, such as a cowling, is purchased, there is no guarantee it will fit until it is placed up against the airplane, engine in place. Every homebuilt is slightly different and although every pre-made component is made to the same set of plans, still there is going to be a natural difference just because of tolerances and the differences between human beings. There is no such thing as "exact", especially in hand made items like airplanes.

The ability to build components separately, without mating them to the rest while building ,is also a function of how old the plans are and how many airplanes have been built from them. If a hundred airplanes have been built of a particular design, then it can be assumed the last set of plans will reflect at least most of the mistakes found in the earlier versions. So, the dimensions will have been consistently improved until components built separately will come close to fitting.

However, that all assumes nothing moves during fabrication. Aluminum airplanes have a tiny bit of creep built into them during the riveting process, but not usually enough to create serious dimensional mismatches. This definitely cannot be said for welded structures. Depending on the structural configuration of the tubing, the type of welding (TIG versus oxy-acetylene) and the skill of the welder, the parts will range from being dead on to missing by half a bolt hole.

The expansion and contraction caused by welding makes every experienced rag and tube builder nervous just because he never knows exactly where some of the parts will wind up. For that reason, attention has to be paid to planning which welded parts are going to be finished first and which will have to be finished and aligned on assembly.

Certain parts of an airplane naturally cost more than others and, if cash flow is a problem, planning should include it.

The engine is the obvious cash-problem because it sucks up so much in a single gulp. Therefore, since the cowling and all the firewall plumbing need the engine so they can be completed, plans should be made to build what can be built while cash is being diverted to an engine fund.

In some cases, especially with the composite kits, the ability to hold off big cash hits is limited because the kit installments, themselves, represent such big cash lumps. This is much less of a factor with aluminum because the material costs are less and the installment kits reflect that.

In rag and tube airplanes the ability to control cash commitments is practically infinite. If enough cash is available to build ribs, ribs are built. If enough tubing can be purchased to build a tail, then it's tail building time. Actually, this is true of any plans-built airplane, regardless of the material.

Planning Makes The Homebuilder's Life Simpler
It would take less than an evening to digest the plans and place them up against the primary factors effecting what is built first. During that time, the builder gets his mind in synch with the project and begins to see it in his mind as a well defined path, with certain decision paths at certain cross roads. He will know what to do ahead of time.

If he just jumps in and starts building, he will be working from crisis to crisis. Not only can that will take a lot of fun out of the project and can slow it down to the point that it mires down because parts were finished out of sequence and don't fit. The lack of planning and continuity is the reason many homebuilts don't get finished.

Devote one evening to planning, then be prepared for one of the most enjoyable experiences of your life.