Bearhawk LSA Control Stick Drawings Issues

[JakeP]

On drawing 26 (control stick assembly, revision 4-25-04), the C and D tubes are drawn on paper at something like 15-1/32" apart, at a scale of 1 = 2, meaning that they would be about 30-1/16" after scaling to reality. But on drawing 15 (fuselage top & bottom, revision 3-22-04), C and D are specified to be 30-1/2" apart. So it appears to me that C and D should have been drawn on paper at 15-1/4" apart, to scale correctly.

The biggest problem with this is that the plans do not directly specify the length of the torque tube, so we scaled from the drawings to make the original one 33-7/8", which might have worked but the rear rod end attach brackets didn't fit all the way on the tube as they should have. So we ended up with a final control stick assembly torque tube length of 34-3/8". Don't know if that's what was originally intended, but it seems to be at least approximately correct.

Also, a slightly separate issue from the same page (drawing 26), but does not appear to be a drawing error, just a builder issue: The rod end spacing is specified as 29-1/2" (which is apparently correct), but we wound up with something like 29-1/8" as built because of adjusting things to fit with the shock strut rod ends. It's a tight fit there, and fuselage tubes shrink and bend from welding, so I would suggest other builders might want to delay final welding on the rear rod end attach brackets to the control torque tube until after fitting the front rod end with the fuselage and shock strut upper rod ends. This way you can fine tune the rear attach brackets to suit the situation. Since we did not anticipate this being a problem, we made up the whole control stick assembly first, but then later had to grind off the rear attach brackets and do them over.

Also, another minor issue: Scaling off the plans, we wound up with the front stick being at least one inch too long to clear under the tube at the bottom of the instrument panel. I don't consider this very important since it can simply be cut to fit afterwards, but I figured it was worth mentioning, as long as I'm on the subject.

[John Massaro]

Good "stuff" all the way around Jake.

Thanks for sharing!

[stinger]

Jake, When one builds a aircraft from a set of plans. Not having the same jig as the factory or another builder ,we build to fit or as required. Often plans are a guide or clue when building a individual part . Just make it work ! Have Fun Stinger

[JakeP]

Yeah, we're "building to fit" for sure Just posting some gotchas that might save others a few hours.

While I'm at it, drawing 26 also says to use Aurora GMM-3M-680 rod ends for the elevator push-pull tubes. Those parts have a width of .500, which is not 7/16" as specified for the idler arm, and also specified for the elevator horn. So I'd suggest others buy their rod ends first and compare with the drawings before fabrication. We wound up making larger aluminum spacers and adding some washer shims for the elevator horn to make up the difference, but making a .125 offset instead of the .100 specified for the horn would have been preferred.

[epapa]

You are far ahead of me but I share your thoughts. Had I known that the blueprints were so poor, I would never have bought them. My RV4 plans dated 1982 are like a fine masterpiece compared to these.

[LukeS]

I own both 4-place and LSA sets of drawings, and am currently building the 4-place. When I'm done with that, I'll probably build the LSA. These drawings can be challenging at times because they won't spoon-feed you the information you want, and sometimes there are errors. I wouldn't consider these challenges a reason to regret purchasing them. All of Bob's designs show real beauty in the form of simplicity and adaptability. If you want to build this plane, know that you can do so from these "poor" (your words, not mine) drawings. Use this network of builders, and use the designer, who is exceptionally kind and helpful.

[JakeP]

Heh... My Bearhawk plans are sitting on top of my dad's RV-4 plans as we're building the Bearhawk. There is a pretty-close-to-finished RV-4 ("close" as in final painting then reassembly for flight close) in the same shop as the Bearhawk. Parts are intermingled, but they seem to be getting along fine

This situation begs a bit of explanation: We want an LSA in the hangar. The RV-4 has been in progress since about 1991. Unfortunately, as many others have experienced, it has become a hassle to deal with the medical over the years, and more expensive. We're both healthy enough to pass. Heck, I'm still young enough that I just have to show up (AFAIK), but I can't stand going to the doctor unless I'm dying. Which are some of the reasons why the LSA is being built and the RV is on pause. They will probably both be painted at the same time.

I agree, the RV-4 plans and construction manual are far more comprehensive. However, one thing I know is that the RV-4 does not build itself, and even though the plans are comprehensive, there are tons of things to figure out on it. So the RV-4 plans being as fantastic as they are, the build itself is still a great challenge.

Now, onto my take on the Bearhawk LSA plans and build. I completely understand frustration with the plans. I may be exaggerating, but it feels like we have spent 100 hours in the evenings in the shop, with Dad on the computer and me on my iPad, hunting down clues on the internet for the Bearhawk, oftentimes obsessing over seemingly small issues that we felt were pretty critical and should have been explained. Most of the time we just roll with the obvious solution and haven't been bit (that we know of), but sometimes we got bit. That is the precise reason why I signed up for this forum -- to pass some non-obvious things we've found, back, in appreciation for all the information and pictures that builders of other models of the Bearhawk have shared. The Bearhawk LSA is a new experimental aircraft. That I know of at this point, there are only two flying. The available resources and the drawings reflect that reality. The Bearhawk LSA definitely has given me the feeling that I am building a experimental aircraft that we have to "make up as we go along", unlike the RV-4 which almost feels like you just have to follow the recipe and you'll get an airplane in the end.

My opinion is that plans-building the Bearhawk LSA fuselage is not currently something for beginners. Fortunately for me, my dad is not a beginner. Knowing what I know now, I sure as heck could not possibly have done it myself... although I definitely can now, and I am thinking about starting another one, now that we've got most of the "engineering" figured out. I don't know about the wings, as we bought the QB wings from Mark. However, I did do about half of the aluminum work on the RV-4 wings and would have no worries about taking that on myself for the Bearhawk from what little I've seen of it, and seeing the mostly completed QB Bearhawk wings sitting in the hangar already (they appear to be nice quality work!).

With my criticisms aside, allow me to spend a little time gushing praise about the Bearhawk LSA plans and build for a moment. I have had an absolutely awesome time building this aircraft, so far. We're pretty much down to doing the aluminum work on the fuselage and welding attachment tabs to the fuselage for said aluminum, and just a few minor weldments like the gascolator and remaining stringers. I know it sounds hypocritical of me to say this after my criticisms above, but at this point I see the plans as not a source of frustration, but a work of art which needs a few touch-ups here and there. I understand them now. We started with some sheets of paper that had some scribbles on them by Bob Barrows, plus a few typos, plus a couple thousand dollars in steel tubing and small bits of sheet, and now after about 1000 hours of work, we have a beautiful framework of tubing assembled in the shop, that I can sit in and make airplane noises. I will never forget seeing it rolled outside on its own landing gear for the first time. Other builders know what this is like so I won't expand on it. But what I would like to say is that the design in the plans is essentially complete, and mostly correct (as far as we know), except particularly for some issues I posted here. There are a few other issues too, but certainly nothing that would get me to recommend against building the Bearhawk LSA.

[BTAZ]

I am just starting my fuselage build so appreciate all of the "Heads up" you can provide.

I built the wings from scratch and only ran into two "gotchas".

I work with fabrication/assembly prints during my day job and was bit by the aileron rib flange call out. In industry, there are "Fabrication" prints and "Assembly" prints. Fab prints have everything needed to know about a sub-component so it can be outsourced. Assembly prints are to take several "fab parts" and put them together. In the drawing package, there is a sheet for the aileron ribs which I assumed had all the fabrication information but, on the "Aileron assembly" sheet, there is a call out for flanging the lightening holes. I didn't discover the call out until the frame was riveted together (Bob said to not worry about it) but I would have expected the "Hole flange" requirement would have been on the rib fabrication sheet instead of on the assembly sheet.

Otherwise, the rod ends I purchased to use for Aileron hinges are thicker then the hinge spacing called for on the aileron sheet. Not a big deal(I just "joggled" the hinge brackets) but another lesson learned.

Beyond those two items, everything that was needed could be found in the plans while the techniques were in Eric's Bearhawk build manual.so the wing build, while time consuming, was straightforward for this first time builder.

[JakeP]

Hi BTAZ, Congratulations on the wings! That is definitely a huge accomplishment for a first time build. As I said, my first wings were RV-4 wings. They were kit wings from Vans, which were not pre-punched, just bent, plus some hardware. So I can relate to what you did. Again, huge accomplishment on your part. Also, thanks for the heads up on the aileron lightening hole flanges!

Best of luck with your fuselage. It's been fun for me.

Since you asked about other fuselage gotchas, instead of wandering too far off topic here, I started another thread: http://bearhawkforums.com/forum/bear...ge-build-notes