My dad had three-dimensional wood puzzles that I played with as a kid. Sometimes they would kick my butt because what appeared to be the obvious solution was not the solution at all. Sometimes I would luck into the solution. Sometimes I would study and fidget with the pieces and find success. Sometimes I would give up and blame the loose puzzle pieces lying around on my little sister. Those puzzles helped prepare me to maintain British cars and build airplanes.
There are times during the construction of an airplane when a step appears simple but requires thought to execute. An assembly won’t slip into place as expected, its fitment seemingly hindered by existing structure. You will need to figure out how to get it into place via an indirect route, like maneuvering into a tight spot in a narrow parking garage. Creativity with tools, to gain access to a nut, screw, or rivet, may be needed. A part may need to be twisted and turned until its path into position is unlocked. For me, such challenges are part of the fun of building, unless it’s the result of poor design. (If you want real “fun,” change the stock oil filter on a left-hand-drive Triumph TR6.)
Case Study
The Sonex Onex plans call out the vast array of hardware that secures the four forward corners of the fuselage, but make no mention of order of installation. Like (probably) every builder before me, I installed hardware until I was humbled by a nut that had no way to engage its assigned bolt, its approach blocked by a preexisting nut. In one instance, the threads of a screw bumped into a neighboring bolt before the screw’s head sat flush on the surface. Challenges accepted!
Each conflict had its own solution, found by sifting through the possibilities:
- Change the order of hardware installation. Like the three-dimensional puzzles I played with as a kid, some bolts had to go in in a specific order or failure was ensured.
- Place the washer and nut over the hole before inserting the bolt or screw. This worked when there was no unobstructed path to install the nut after inserting the bolt/screw.
- Get creative with tools. When a standard socket or wrench would not fit, I would grab a thin-wall socket, small-profile wrench, or even modify a box-end wrench.
- Substitute an AN364 low-profile lock nut for an AN365 lock nut.
- Shorten the threads of a bolt/screw. (This, together with a low-profile nut and a thin washer, allowed the desired 1.5 threads to protrude from the nut.)
Some builders would call this a problem with the plans. I call it homebuilding. The plans represent a perfect world. We live in an imperfect world. We humans make it so. However, we must pass our time on this planet in some manner; building an airplane that frees us, if only briefly, from its surface seems like time well spent. An extra 20 minutes to suss out the hardware was not a hardship and probably spared me 20 minutes scrolling influencer videos. To me, that is a win.
In a bolt/nut situation sometimes a thick flat blade screwdriver or chisel will hold the offending party immobile whilst sufficient torque is supplied to tighten the pair. Grease, gasket compound, masking tape, magnetic and other various and sundry solutions may present themselves. No difficult job is ever completed without some sacrifice of blood from a finger, knuckle or forearm. Keep the hydrogen peroxide handy with bandaids or at least paper towel and tape. And, when the job is completed and you’re almost asleep, the obvious answer dawns on you. Then, hopefully you can fall asleep.
I agree with all of your solutions except “ Substitute an AN364 low-profile lock nut for an AN365 lock nut.”
This should not be done without consultation with the designer. The shear area of an AN365 is roughly 50% greater than for a 364 and is designed to develop the full tensile capacity of the bolt the nut is attached to. An AN364 is not designed to develop the full tensile capacity of the bolt it is attached to. If an AN 364 is substituted for an AN365 in a highly loaded tensile application, the result could be quite bad.
A good designer will only specify AN 365 where their additional tensile capacity is needed. Otherwise, one is just adding weight without benefit. Therefore, when you see an AN 365 specified, you should assume the designer did so for a good reason and you should not remove 1/3 or so of the fastener capacity by using an AN 364 without the blessing of whoever performed the structural analysis on that fastener.
Yes, the AN364 is intended only for shear, not tension, applications. However, an MS21042 reduced hex nut may fit where a standard nut won’t, and is actually stronger in tension than the standard nut.
And much more fun to work with!!
True, but that wasn’t the recommendation in the article.
The bolt pattern inside the Vans RV8 gear towers has this kind of interference.