bearhawkproject.com Matt Kunkel's Bearhawk Build Log

17Apr/104 hrs

Mounting the Horizontal Stab, Stab primer

Today Stacey helped out on the project.  We worked on mounting the horizontal stab so I was glad to have the help.  On our kit, the fuselage and carry-though tube are marked right/left but I couldn't find any markings on the stab halves so we had to figure it out.  The first way we mounted it, the left side slid on buttery smooth and lined up (figured it was too good to be true), however the right side would bind about halfway on.  I tried removing primer buildup from inside the tube but it didn't help and it became obvious it was a slight misalignment of the tubes that caused the binding, not primer.  We ended up flipping the carry-through tube over along it's long axis (keeping left=left/right=right) nothing fit at first, but then we swapped stab halves.  It went on but not without some name calling; in fact the only way to get the left side on is to make fun of it's mother.  Anyway the holes line up.  I ended up calling Mark at Avipro for re-assurance and he said to mount the elevators and see if they match since there's an oblivious left/right.   Well the elevators line up either way (with trim horn up and down left=right and left-left).  I'm still not 100% convinced it's right because the stab isn't square on the fuse (right side is lower) even though I re-checked both mount tubes and they're level.  The squareness may be something fixed with flying wires.

You can see in the pictures where I'm having to drill through the holes a bit.  I didn't re-drill, just removing primer from inside the holes.  A fractional bit was used (same size as the bolt) to keep a snug (light press) fit.  It's my intention to keep holes to the exact fractional size at first and only drill to the next numbered size larger (per AC43.13) if necessary.  I have some reamers coming next week that will help with this.

On a side note I must be being really particular about bolt length.  The lengths I'm ending up using don't match what's in cross reference at the back of the Avipro Manual at all.  Also, there are some sizes I don't have and need like AN4-22 for the fuselage->stab incidence spacer->carry-though bolt.  This isn't on the hardware list,  figure a -24 is intended but it needs 4 washers.  A shorter -20 bolt was used for now to keep progress going, but have it noted to order.  Others don't match up either.  Where possible I intend to keep things to 1 washer to keep weight down.  I can usually find bolts where the last thread just peeks through, add a washer, and it's good.

Finally, I found some places where the stab rubbed through the primer in shipping so I hit those with a bit of the Rustoleum.

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  1. Hi Matt. Is the “Avipro Manual” you are working from different than that available online (http://www.bearhawkaircraft.com/assemblymanual/index.html)? I’d like to follow along with your build, however the online manual starts with the gear and then moves on to the tail. Just curious!

    I feel your concern about things not lining up, incorrect bolt lengths, etc. I guess I was ASSuming that since it was a quickbuild kit everything would be such that a monkey like me could build it.

    Good luck!

  2. Sorry for the rapid succession of posts. Do you mind keeping a list of “unexpected” additional/different hardware you have to purchase? I’d really like to not re-learn your experiences, plus I bet Avipro would probably update their kit (they have a vested interest in continuous improvement and these would be very low cost changes from a business standpoint).

  3. That’s the avipro manual and the basic build order I’ll follow but everyone will take a slightly different path. I skipped the gear because I’m going to put my fuse on a rotator and do a few mods. I also didn’t buy wheels yet, holding out for a deal.

    I probably won’t keep a list of hardware discrepancies as that’s a little much to track. I’ll call it out as I see it but remember each kit is different. On the carrythrough bolts if they left it 1/8″ longer when grinding to length then that changes the bolt. The wicks kit is a good start. I would say that the bolts and fasteners by application list isn’t really close and maybe the hardware kit fits more by the fact that there are alot of bolts of different sizes.

    I do plan on keeping a descripancy list of stuff that’s missing in the manual. A quick check of the yahoo bearhawkqbkit group usually gets the answer and it hasn’t been updated in the manual. One item I found today is that the tailstruts use clevis ends and the plans / scratchbuildrrs manuals make them to fit with steel. No callout in the manual and the part numcer AN665-34R is nowhere in the book (not even the HW list). If you didn’t order off the wicks website list you’d never get it. That stuff Ill start a list of.

    Finally perhaps my tone is to critical. I REALLY like my kit. Quality is very good. And these small issues while they should be fixed, don’t really bother me because I was going to scratch build to an extent. Glad I have the kit. The manual is on par with other kit mfgrs (except vans). The only reason I’m pointing this stuff out is to hopefully help a builder down the road. The BH is a great airplane and we need more of them flying! I hope to get people interested in building and hopefully help a little along the way.

  4. Sounds good. Thanks Matt!


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