Friends, it's been quite a while since my last post. I injured my back during a home improvement project about a month ago, and have been unable to work on the plane until this week...but now I'm back at it!
Below are the seat pans I was working on just before my injury. Both my .032" and .040" stock was getting pretty banged up in the shop, so I decided to finish off the parts in those thicknesses. The polishing marks are all the scratch removal I had to do. Most of the scratches were cosmetic, and I was just being picky, but there were plenty that had to be buffed out for structural reasons. I laid these Seat Pans out 4 different times before finally cutting them and forming them. The reason for the number of layouts was to confirm my suspicions that one of the measurements in the blueprints was off. I explain further below, but these had a single coordinate for locating one point on the bottom flange that resulted in a taper that isn't shown in the final part. I changed the measurement to correct the tapering flange. I really hope they fit!
Seat Pans:
As I've progressed in the build, the parts are getting more and more complex, geometrically speaking. There are less and less right angles, with lots of strangely shaped parts. While much of the plane's structures can tolerate some variation in part dimensions, most of the cabin structures cannot. The cabin structure parts fit together more like a complicated 3D puzzle rather than a simple skeleton structure like the wings and control surfaces. I've noticed a decent amount of errata in the blueprints when trying to make the more oddly shaped parts, such as the Seat Pans above and the Arm Rests below. Certain bend lines aren't located with measurements on the drawings, or other measurements/coordinates are just plain wrong. Consequently, I believe the formed Arm Rest below is going to be too short. With both the Seat Pans and the Arm Rests, there are wrong measurements that don't add up correctly when you lay out the parts. I had to make an educated guess as to where the measurements had to be located by examining the exploded drawings and assembly manual. There are lots of places where the sizes of holes to be drilled for bolts or other things aren't specified. Sometimes, they're missing altogether, or you have to hunt for them in other parts of the blueprints or assembly manual. And in still other places, the holes aren't even located with measurements! For the most part, the Zenith blueprints are excellent. But there are still some deficiencies. Other scratch builders have had these problems too, with these same parts, so it's a known issue. However, due to the variances of the construction process for us scratch builders, we have to come up with a lot of our own corrections. I'm not looking forward to solving the known measurement problems with the baggage compartment parts. My solution, for now, is to leave some of the affected parts unformed until I start to assemble them. That way, I should be able to determine final measurement/bend locations.
Arm Rest Side Blanks, with one potentially usable formed Arm Rest:
The next 3 pictures show the balance of parts in .032", .040" and a
couple in .063". With these parts now complete, I have nothing else to
make in .025", .032" and .040". All of the parts for the wings,
elevator, horizontal stabilizer, flaperons and firewall. I now only have
to cut the skins for those structures, but the rest of the pending
parts are strictly for the cabin/fuselage. Pretty good progress!
Another example of errata in the plans is the Torque Tube Bearing Support shown below. The part itself is simple and all the locating measurements are spot on. However, no diameter is given for the torque tube pass through hole (barely visibly in the cross-hairs next to the flanged lightening hole). The hole size for the bearing block and bearing block doubler are given at 28.6 mm, so I assume that the hole in the support will either be 28.6 mm or maybe slightly larger for clearance for the torque tube, but it is nowhere in the drawings. The hole diameter is simply missing, even though the coordinates for its location are plainly labeled.
Torque Tube Bearing Support, Upper & Lower Elevator Control Horns & Elevator Trim Tab Horn:
Below is the Central Firewall Stiffener. I had actually already made the blank for it, drilled all the lightening holes and piloted the bungee pin holes. However, when I was drilling the pilot holes for the bungee pin larger, I ended up chewing up the hole with an oversized bit by drilling at too high of a speed. I learned that while the smaller holes in thin stock benefit from a high-speed drill, .040" with a 5/8" bit does not. I had already rolled and stored my .040", so I waited until all the .032" parts were done before I got it back out to re-make this part. An inconvenient setback (one of many!), but not the end of the world.
Central Firewall Stiffener:
I took a close up picture of the following part, the Elevator Trim Tab Control Horn, just to give it some scale. This is a rather small part, as one can see. It's not terribly complicated, but opposing bends are hard to do. I bent the tab with the hole in the brake, but then had to hammer form the other bend in the vise with a 1/8" round over oak board. There was just no way to do this thing entirely with a bending brake. Many parts require some creativity and/or alternatives to be able to finish. Although this part is pretty minor and very small, I was rather proud of how it turned out!
Close-up of the Elevator Trim Tab Control horn:
Anyway, enough of this ridiculously long post! With AirVenture coming up, it will likely be another 2-3 weeks before I update again, but rest assured, I'm back in full-swing on building. Since I have all the parts fabricated to assemble everything except the fuselage/cabin, I'll have some exciting visual progress in the coming months.
Cheers!
