I'm plugging right along with my tube-and-gusset 7/8ths scale Nieuport 11 and along the way I've learned some invaluable lessons:
1. Don't reinvent the wheel. If the way to do something isn't obvious, ask for help. Heck, if you think you know how to do something ask anyway.
2. Homebuilding is interdisciplinary. Building an RV is pretty far off from my project, but that guy has an insight on jig building, installing a gascolator, and a host of other tasks that are similar. Likewise, at the last EAA meeting I mentioned a technique on annealing aluminum tubing that caused a few eyebrows to raise in pleasant suprise. Never assume over specialization based on someone else's project.
3. Put in your head the quality of work you want on your plane before you begin. For me that means that I'll accept a solid, safe, flying aircraft with a few unimportant flaws that is in the air versus a glorious example of flawless craftsmanship scattered across multiple tables and several years from completion.
This leads to....
4. Learn to grade your work and decide what you'll accept:
Suitable: Correctly assembled/installed and within design tolerances. Not the prettiest work, but solid and safe. Examples include a tiny run in paint that someone will really have to look hard to see or a slightly asymetrical panel.
Good: Same as above; the tiny run in the paint is something only you will ever see. So what if the compass is 1/64th an inch to the left of center? It still points in a direction other than what you thought you were going; find another excuse for getting lost.
Great: Somebody else might have done a better job than you, but they're probably seeing a therapist for their OCD problem.
Perfect: The plane built by that OCD guy. Probably took him eight times longer to build his than yours. Or he has years and years of experience in that sort of thing.
I shoot for Great and wind up with Good a lot of the time. There are a few Suitables in there as well, usually from efforts to improve a Good part to Great standards. Hey, if it wasn't for craftsmanship on my level, how would we know what superior work looks like?
Which leads to...
5. When you're finished with a part or subassembly, stop messing with it. Quadruple checking is a solid build ethic, but if it's done and of acceptable quality "tweaking" it usually winds up turning into "redo it." Balance planned project timelines against the grade of what you've done. Building the same part over three times when the first was just fine is a huge time thief.
6. Know the difference between structural and cosmetic.
When I accidentally gouged one of the vertical tubes that the lower wing carry-through tie into there was no quibbling - it was replaced. It's a major load carrying spot on the aircraft and there is no way I'm risking stress fractures on a tube that is keeping a lower wing in its place.
When I bent the gusset/support for the front of the turtle deck I wound up with a sort of flat spot in part of the bend. The bend is true and the part fits, but it has this one inch long odd looking spot one third down from the end. Nobody will ever see it. I decided to shrug and accept it, as making a second one would take time, cost money, and not really improve anything.
7. Learn tolerances in the design. An example is my lower wing carry-throughs. Per the plans I was bumping against the lower longeron; fortunately the designer of my plane is the type to answer the phone and is happy to advise that there is a quarter inch vertical tolerance on them - and then warned that they must be equal distance horizontally to ensure the wings match on both sides.
There are a couple of other places where my efforts differed from the plans and I found out it was "gooder enough;" that is to say safe and within tolerance. Designers can't write "About 18 7/8ths an inch," for things - they have to give a solid number.
There are other parts, though, that have to be precisely by the plan for safety; knowing that is important, too. Just shake it off, take it apart, and do it over.
8. Thicken up thine skin. I'm sharing a blow-by-blow account of my build with a set of WWI replica builders, and feedback ranges from "excellent" to "I'm sure it will have a nice personality" to "unacceptable - do it over." All of it is appreciated, but the really valuable input is the criticism, especially since it is coming from folks who have more than one plane build under their belts. Some of it is silly, too, and one has to ignore it ("you should clean your tools better" kind of stuff).
Once the wings are done I'm inviting our local EAA tech advisor to critique my work; when I get close to final inspection I'm going to beg our chapter to come find mistakes, with prizes (first to spot a mistake, most mistakes found, etc.).
9. Occam's Razor is King. When presented with a problem, the least complicated solution is the right one. A few examples:
In placing the stringers for the turtle deck on the rear gusset, they're evenly spaced. The center was easy. The outer ones were easy. The two between them hurt my head. What's half of 3 and 5/16ths and how do I measure it? Solution: take a piece of paper, mark the center tube, the outside tube, fold it in half, unfold, and mark the gusset appropriately.
The support cables for the cabane struts have to be tight, but not too tight. Tension strength isn't listed in the plans, and I'm dipped to know how to measure it (though I know there are tools for it). Solution: start the bolts enough to hold, stretch the cable as hard as one can by hand, swag it, and then tighten the bolts, which will tension the cables appropriately. But no tolerance on the swags - use a go/nogo gauge on every single one.
Jigs are meant to hold things in place while they're being assembled or shaped. Most of the times in my build that can be accomplished just as well with a few pieces of scrap wood screwed down into the table versus a custom formed one that holds every inch of it.
10. Take stock of what you're doing! If you don't smile after saying "I'm building an airplane" three times slowly, sell your project; the fire has gone out.
Take a step back and look at your slowly growing airplane before getting six inches from the parts - pretty impressive, isn't it? There is nothing wrong with a satisfying sense of accomplishment.
So what gems do y'all have?