Russ Erb's Bearhawk "Three Sigma"

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I discovered the Bearhawk in mid-February 1996 late one Saturday night in a Budd Davisson article in the October 1995 issue of Sport Aviation (as you can tell, I was a little behind on my reading...). It took about a day to get over the shock that someone had designed an aircraft that met my mission needs perfectly--primarily consisting of a 4 place airplane with STOL capabilities. The fact that it had a classical cool look was a bonus. With two small children (not so small now), I expect to finish it long before they move away from home (well, at least before they move away), hence I wanted four seats. At the time, I planned to retire from the Air Force eventually to a place my Dad has in Texas where we could put a couple of grass strips (660 ft into the wind, 975 crosswind) so I really needed SHORT takeoff and landing capability. I was scheduled to go to Nampa Idaho to sign ze papers for a Kitfox in March 1996, but that was always a compromise decision (only 2 seats). Needless to say, I cancelled that trip. This is a true 4 place airplane, meaning that you can fill the tanks, load 4 FAA standard adults, and still have about 200 pounds left over for baggage before hitting gross weight.

The wing is all aluminum, so I can relate to the RV builders. The fuselage and tail are tube and rag, so I can relate to the Acro-Sport builders. The wingtips are fiberglass, so I can relate to EZ, Q-200, and Pulsar builders. I figure wood will find it's way in somewhere. It's a scratch built aircraft (no kit) so I have time for all of our other builders (like Paul Rosales) to finish their aircraft (update--he's flying now) so that I'll have plenty of options for chase aircraft. The other benefit is that being scratch built, I don't have to wait another several years just to scrape together enough money to buy the kit. According to Davisson, the entire materials required will run about $6000 (I don't believe that anymore, inflation or not), or about 60% of an RV kit, and far less of a Kitfox kit. Although I bought the plans in February 1996, actual building did not begin in earnest until December 1996, thanks to a move cross-country at the request of the government.

NOTE: If you're interested in the Bearhawk but don't feel up to scratch building, you can now order kits ranging from parts to a full 51% quick build kit from AviPro.

At the bottom of this page you will find links to pilot reports and other information on the Bearhawk.

I don't know why everybody says that scratch-building is a lot of work. The Bearhawk only has a total of 168 ribs in the wing, flaps, and ailerons, and YOU GET TO FORM ALL OF THEM YOURSELF!!! After all, it only took about seven months...about a half year later and I was at the point where RV builders are when they open the box!
Both main spars mostly drilled and starting the first rear spar. Doesn't everybody build a four-place airplane in a one car garage? I do spend a lot of time reshuffling where everything is to make room, though.
Drilling the spar for the wing strut attach straps
The back ribs for the flaps and aileron on the parts rotisserie in the paint booth after application of Poly Fiber Metal Prime. Metal Prime is (was) a new waterborne primer for aluminum and steel. You can read my notes on my experiences applying Metal Prime. I really liked it, but apparently there wasn't enough demand, so Poly-Fiber pulled it from the market.
My parents and brother came out to visit over Christmas 1998. While they were here, Dad and I went nuts riveting. We got all of the ribs riveted together and most of the wing spars. Here you see me riveting one of the 5/32" rivets near the main spar root. Some people prefer to work with a partner to do the bucking. I've been successful bucking my own rivets with no major problems. For the large rivets, I'm using a 3 pound bucking bar, which is heavier than most bucking bars I've seen advertised for sale. The facial expression is optional. I'm not sure if it helps or if I was just not happy with the way things were going. In the end, we got all of the rivets in right. However, in the process...
No good deed goes unpunished. Here I am drilling out one of the many rivets that didn't make it up to standards. The two biggest problems were smiley faces and clinched heads. Smiley faces on the manufactured head can arise from bouncing the rivet set (not holding it against the rivet hard enough or removing it before the gun fully stopped), but most of mine came from driving the rivet too hard, such that the manufactured head is deformed between the rivet set and the spar (the spar is heavy enough to give some bucking bar effect). Clinched shop heads are formed when the rivet deforms to one side instead of straight down. The easy way to identify the problem: Proper heads are circular. Clinched heads are elliptical. I'm using a special form of microstop (available from Avery and other sources) designed for drilling out rivet heads. Proper technique (drill just enough to break off the head, drive rivet out with a punch) will remove the rivet without much damage to the hole. Thinner material is more likely to be damaged than thick bar stock.
Jigging up the flap drive and torque tube support for welding the torque tube bearings in place.
Tack welding an aileron hinge mount on the jig as shown in Bear-Tracks. The vise-grip holds the curved tube in place while the other end is tack welded.
The bellcrank after completion. The ends have been welded, drilled, and trimmed. The bearings have been installed in the pivot. There is a very important tube (not visible in this picture) around the pivot bolt between the bearings which takes the compressive load of the bolt so that the bearings do not carry a side load. This tube should be cut slightly oversized, then slowly sanded to length. The tube is the right length when the pivot bolt can be tightened and the bellcrank turns freely about the bolt with only very minimal freeplay up and down the bolt. If there is excessive freeplay, shorten the tube. If the bellcrank binds and does not turn freely, the tube is too short. Be careful, as the tube goes from too long to too short really quickly!

The large washers (AN970, also known as fender washers or wood washers) used on the pivot bolt and the rod end bearing for the pushrod are important safety features. At either bolt, if a bearing failed, the washers would keep the assembly from falling apart. The assembly would continue to work, albeit with higher friction and more slop. This could be critical to maintaining control to be able to land safely.

A family picture of all of the wing steel parts together.
A flap completely drilled and clecoed. I'm using a jig consisting of 2"x2" steel vertical members with 1"x1" steel horizontal arms welded to them. These jigs are clamped to an angle iron which is screwed to a 2x4 screwed to the rafters. The bottom end of the jig is bondo-ed to the floor. The jigs are carefully positioned to put the arms in the same horizontal plane, i.e. the arms are leveled and level with each other. This must be carefully done, because any misalignment will be transfered permanently into the part being fabricated.
MVP! (Major Visual Progress) Every now and then, you do an operation that actually looks like you've done something. While this wing frame looks very complete, this is probably only 10% of the way through assembling the wing. Even so, it looks cool! Of course, until the skin goes on, it won't look much different...
Because of the very limited space in my shop, I had to move the left wing out to make room to build the right wing. To transport it to the airport, I borrowed a flatbed trailer from a fellow EAAer. The wing is supported on ratcheting tie down straps stretched across the side rails of the trailer. Additional straps are used across the wing to hold it down and in place.
The left wing strapped up on the wall of the Kommandant's hangar. This wing shares the hangar with his very nice 1977 Cessna 180 Skywagon.
After finishing the other wing, I started on the welding. Prior to starting the fuselage, I built up the horizontal tails, elevators, and rudder. This shows the horizontal tail in the table jig.
Top of fuselage frame in table jig.
Bottom of fuselage frame on table after bending up to the bottom contour.
Top of fuselage frame on jig after bending.
Side view of fuselage in jig. Not a great picture, but about the best I could do with the tight quarters that are getting tighter. At this time, the second wing is still in the jig next to the fuselage. Next step--install the sides.
Primary fuselage tube structure tacked together. The fuselage was allowed to escape the garage workshop temporarily while the tables were removed to make more room to do the final welding. At this point, the fuselage still needs to go back in upside down and have the tacks on the bottom side done.
I had long planned a rotisserie for the fuselage to spin it around to make the welding easier. As the time approached, I realized the workshop wasn't long enough to support such a device. Therefore, I attached 4 2x4s to the engine mounts as suggested in the Poly-Fiber literature for covering the fuselage. Still very effective, and allows a minimum of four positions to choose from. Rotation is done by picking it up and manhandling it to the next position. So far I've been able to do it without assistance. Note that in this picture the fuselage is inverted.
Also per the Poly-Fiber literature, a simple sawhorse is used to support the tail of the fuselage.
Roughly five (5) years after starting on the ribs, I took this picture with the tail feathers.
Add another year and a couple of months and I've moved to a new house with a three-car garage, and finished the fuselage enough to bring the wings home and fit one to the fuselage.
Same thing, different direction.
Labor Day 2003--#164 finally has its own feet. Of course, it also has the Bearhawk standard alpha version shock struts--namely pieces of EMT conduit. It was good enough for the prototypes, it's good enough for #164. This picture was taken halfway through the process of turning the fuselage around in the garage. The tires are 6.00x6 with double puck Cleveland brakes and wheels. The brakes are not shown in this picture, but have since been installed. The real shock struts will be constructed after all of the parts arrive.

Two changes were made to the plans--to shorten and extend the length of the axles. On the shock strut end of the axles, the axles were shortened by one (1) inch, which is in keeping with a change made to the current plans sets now shipping. On the wheel end of the axles, I extended the axle by 7/16". As drawn on the plans, the axles are the absolute minimum length necessary to mount the wheels. The length shown on the plans requires the axle nut to be so close to the bearing that no normal tool will fit on the nut, and it would be extremely difficult to insert the cotter pin. Increasing the length of the axle allows use of a 1/4" piece of 1-3/4 x .095 under the axle nut as a spacer (as shown in the Cleveland drawings), which keeps the axle nut out where a standard tool can be used to tighten it, and it has one to two threads showing. Also the cotter pin can be inserted easily. The axle is still short enough to fit under the Cleveland hub caps. A minimal amount of weight is added, but the maintainability is increase immensely.

More Major Visual Progress! On 22 August 2004 the "impossible" has been accomplished. There were those who couldn't see how I could possibly build my own dynafocal engine mount, since that would obviously have to be done very precisely. I countered with it would be useless to order one of the kit-built mounts because 1) it wouldn't match my fuselage precisely since my fuselage was not built in the kit jig, and 2) the kit-built mounts are for a different Type of dynafocal mount. Details. Besides, if I could precisely build the rest of the fuselage, why wouldn't I be able to do this. Anyway, the proof of the welding is the engine hanging on the mount.
Yet More Major Visual Progress! On 6 November 2004 I mounted the prop for the first time. It took until now because that's how long it took for the prop to get here. You can also see some other advances. The ring gear, starter, alternator, carburetor, and oil quick drain can be seen. The prop governor is installed but hidden by the prop. Part of the baffles are seen here, which started out as Van's RV-10 baffle kit. The oil cooler has been mounted hanging from the engine mount. The ductwork for the oil cooler has not been created yet.

The main reason for mounting the propeller was to determine the position of the aft end of the spinner to define the location of the nose bowl. This piece of info is critical for defining the shape of the firewall and building the cowl and boot cowl.

On the right side you can see that I have also skinned the doors and installed all of the windows, including the wing root windows for viewing the fuel sight gauges.

One job that I knew was coming and was dreading for years was sandblasting and priming the fuselage. I was dreading it because I knew it was a big job and had to be done all at once. There was no way to break it up into smaller pieces. When it became inevitable, I scheduled the work over Thanksgiving 2005, when I would have Wednesday through Sunday (5 days with interruptions) off from work. I had hoped to have it done in that period with time to spare. In keeping with the revised Waldmiller rule (time for completion equals π times the estimated time for completion) plus my own personal distaste for any sort of finishing process, all that was complete at the end of the five days was the sandblasting and cleaning up all of the sand. Priming consumed the next Wednesday, Friday night, and Saturday. The primer is white Poly-Fiber epoxy primer.
Pink is such a manly color, as long as we're talking about Poly-Brush. This photo was taken after the interior fabric was applied and had received its first coat of Poly-Brush.
After completing the fuselage covering and painting, the reassembly really picked up the pace. Here you see the right side of the engine with the custom built exhaust system. Note also the stainless heat shield around the engine mount to protect it somewhat from the radiation of the exhaust pipes. There used to be a lot of room behind the engine, but after putting in all of the hoses and tubes, that space seems to have disappeared.
Left side of the engine installation.
The side of the fuselage fabric painted in its final colors.
The instrument panel after test fitting for a chapter project tour. Still not delivered are the two Dynon D-10As. The altimeter is off being re-certified. On the left side is the Hobbs meter and CO detector. Next is the airspeed indicator and the TruTrak ADI Pilot II autopilot. Under the altimeter hole is the Rocky Mountain Instruments micro-Encoder. The radio stack is a Garmin GMA 340 audio panel, Garmin GNS 480 GPS/Comm/VOR/ILS, Garmin SL40 Comm radio, and Garmin GTX 327 transponder. The engine monitor is a JPI EDM 900. Under that will be a slot for holding maps and such.
Aft of the baggage area are the batteries (2 because of using a dual Lightspeed electronic ignition), contactors, battery busses, external power plug, strobe power supply, and ELT. Not installed in this area yet is the autopilot pitch servo.
This was my solution for the rudder cable exit at the rear of the fuselage. Shown is a "Rudder Cable Fairing Sets For RV's" available from Avery Tools( part number 10728). Each set has two parts--you'll need two sets (one for each side). RVs use one of these on the side of the fuselage, but that doesn't leave enough room to get the cable eye out. Using two with one inverted solves this problem. The parts are white because they have already been primed. The holes are not required--they were for stringing up the parts for spraying.

The parts are Poly-taked to the fabric and covered with a doily, just like an inspection ring.

Rudder cable exit after completion.
The panel after the wiring was complete. After much work and outstanding support from my avionic vendor (, I managed to achieve the miraculous by getting seven (7!) computerized avionics boxes to all talk to each other. Sort of the "Accidental Integrated Avionics Suite". This is the same stuff as above, but here they are actually turned on! I've also been able to successfully download real-time data via RS-232 from the Dynon D-10A and GNS 480.
Cover plate at front of horizontal stabilizer.
N Number after application. These were a special order 3 inch vinyl number strip from Aircraft Spruce, P/N 09-00294. Application was very straightforward with no problems.
EXPERIMENTAL placard on left sidewall. This was a single-piece decal of 2" black letters on a clear Mylar base, Aircraft Spruce P/N 09-33400. According to 14CFR § 45.23 (b) "...the operator must also display on that aircraft near each entrance to the letters not less than 2 inches nor more than 6 inches high, the words..."experimental," applicable." I certainly consider this location "near" the entrance.
EXPERIMENTAL placard on right sidewall over rear door.
Instrument panel after covering with the upper boot cowl. I'm currently building a glareshield that will cover part of this and overhang the panel to support an electroluminescent strip for panel lighting.
Moving Day! Since it was only about two miles to the airport, I decided to just slowly pull the fuselage on its gear. After much thought, the simplest way to attach the fuselage to the van was to remove the tail wheel and bolt the fork to a hitch tube.
Apparently doing this sort of thing is illegal in the People's Republik of Kalifornia. Now they tell me that I should have gotten some sort of a towing permit to do this. They didn't cover this in my 1977 Texas Driver's Ed class. The legal test seems to be if an object has wheels on the road then it has to have some sort of registration. I'd hate to think what would have happened if I had used my first idea--to tow it with my garden tractor. The things I do for y'all so that you can learn from my mistakes.

Apparently "Screaming Yellow" is not a good color to paint your unlicensed trailer when you're trying to get away with something. If I did this at 0300 do you think that would have raised suspicion that I was trying to get away with something?

The remaining question is why was one of the California Highway Patrol's finest (i.e. not Erik Estrada) doing way back in a residential area at least a mile from the nearest major road? Hmmm...

Finally, "Three Sigma" arrives at its new home at Rosamond Skypark. It really enjoyed meeting new friends, including a Cessna 182, a Baron, an RV-6, Focke Wulf FWP-149D, Cozy, Bonanza, and some sort of biplane. The hangar owner seemed very impressed.
At the EAA Chapter 1000 Sixteenth Annual Scotty Horowitz Going Away Flyin (19 May 2007), "Three Sigma" finally got to be with her sister "Smokey Bearhawk." We know they are sister ships because they share the same spar cap DNA. The spar caps for both #164 and #232 were sheared from the same 4x12 foot sheet of 0.125 2024-T3 aluminum many years ago.
The unofficial non-meeting of the Southern California (SoCal) Bearhawk Squadron at the EAA Chapter 1000 Sixteenth Annual Scotty Horowitz Going Away Flyin (19 May 2007). From left to right, Chris Haley (#883), Brittney Haley, Penni Haley, Pat Fagan (#232), Carol Fagan, Tim Brien (#999), Anita Amsberry (Mrs. Tim Brien), Russ Erb (#164).
The SoCal Bearhawk Squadron non-meeting, with Penni Haley, Carol Fagan, Pat Fagan (#232), Russ Erb (#164), Anita Amsberry, Tim Brien (#999), Brittney Haley, Chris Haley (#883).
The fuselage continues to progress. Here the tail is fully installed and connected. The paper over the landing gear legs is to catch paint drops. I found that three of the door hinges were in the red stripe, so I had to remove the yellow paint, reprime, and paint red. It's always something.
Aren't those just the coolest 24" N-numbers you've ever seen? Too bad they don't count for the 12" N-number requirement for penetrating the ADIZ. I've been dreaming of what this would look like for years--it's really cool to finally seen it realized.
1 December 2007 was a landmark day in the history of "Three Sigma", the "Hanging of the Wings". For the first time in history, both wings would be on the fuselage at the same time. Both wings had been on the fuselage before, just not at the same time, since the garage wasn't big enough for that. To accomplish this task, I e-mailed a whole mess of my closest friends, of which 12 actually showed up. The day before was the first rainy day we had seen here in the desert for probably more than a year, but in spite of that I was able to get everything prepared and ready to go.

To move the wings, I called on yet another friend to borrow the same trailer I had used the previous four times I had moved the wings. The procedure was the same--suspend the wing above the trailer bed on ratcheting tie-down straps. Here the first of the painted wings has been positioned on the trailer and is about to be secured in place. If you can't find the wing in this picture, it's the red and yellow thing the four of us are pointing at.

At the hangar, this is the wingless fuselage as it started. Well, as it was after we lifted the tail up to the level attitude, which puts the tail an amazing distance up in the air. In this case we just wanted it close--precise leveling was not required. Raising the tail was required because the drywall lift that would be pressed into service as a wing lift would be holding the wings in the horizontal attitude. You could try it in the three-point attitude, but the wings might keep slipping off of the wing lift.
The drywall lift was rented from a local rental center. The rental agreement stated "Renter agrees to use this equipment in a reasonable manner, and only for the purpose for which it was intended." I'm sure these devices were originally developed for mounting wings on high winged airplanes, and later someone realized that there was a much larger market selling them as lifts for installing drywall. A piece of MDF (any plywood or OSB would do) was placed on top of the drywall lift to give it a larger bearing area, and a moving pad was placed on that to protect the MDF from getting scratched by the wing. Or was it the other way 'round?

The wing was then rolled over close to the fuselage and raised with the lift while being stabilized by several helpers. Small adjustments were made simply by moving the wing around on the lift.

To help align the holes, I had rods the size of the bolts that I ground to a taper at one end. Wiggling these rods around in the holes lined up the holes very nicely. The root attach bolts were put in their holes, and then the strut was installed. Not obvious in this photo is that one of the helpers has his right hand on the strut fittings, which are forward of the lift. Thus, the strut could be installed before removing the lift.

With this many helpers, you can easily satisfy the requirement for "observers observing observers".

In this picture we're inserting the last bolt at the base of the strut, but you can't really see that. The key point is at the far right of the picture. Here you see one of the ends from the rotisserie holding up a 2x4 with padding on the top that holds the left wing up while we were putting on the right wing. The support is located under the wing spar. The 2x4 is clamped to the stand with a couple of bar clamps. The padding at the top was some packing foam that was previously cushioning the new computers at work.

We didn't establish if this support was absolutely necessary, as it seemed the airplane would not tip to the side with only one wing attached, but just barely. It seemed like simple, cheap, and easy insurance to install it, so we did.

Then at last. Both wings are installed and fully supported by flight hardware, and the tail wheel is back on the ground. None of the non-structural connections between the fuselage and wing have been made, but I can do that later without needing an army of assistants.
The wing-hanging ne'er-do-wells. While this job could have been done by three to four people, it was such a significant event that I figured far more people would want to be present to observe and to participate. It was more of a party, a celebration, than a work detail. Hence the cast of thousands, or at least 13.

From left to right are Miles Bowen (Cessna 170 and Harmon Rocket), Chris Haley (883), Kent Troxel (Mooney M20C), Scott "Stormy" Weathers (RV-8A), Bill Irvine (Cessna 310), Russ Erb (164), Doug Dodson (Glasair IIFT), Randy Kelly (Cessna 182), Jack Creviston (Bearhawk Quick Build Kit), Gary Aldrich (Cessna 180), Pat Fagan (232), and Dave Vanhoy (Giles G-202). Not pictured because he had to leave early is George Gennuso (Pulsar).

Eric Newton (682) wanted to participate, but felt that his location in Long Beach Miss'ippi made that impractical. He did, however, consult on the written procedures.

The next big thing on the critical path was to trim and fit the windshield. Not exactly a low stress operation, since acrylic (Plexiglas) is more prone to cracking at colder temperatures, and temperatures (December 2007) were only getting up to 45 to 50 degrees F in the afternoon. After many hours with a cutting wheel on a die grinder and a sanding disk on another die grinder I managed (with experienced help) to get the windshield trimmed to the proper shape, as seen here, with no cracks. A significant contribution to this successful operation was the information given by Eric Newton (682) about his windshield trimming.

In between windshield trimmings I continued work on other items, including installing the wingtips, connecting wiring and hoses at the wing roots, and installing the doors. The paint lines lined up perfectly. The landing/taxi lights were tested successfully, as were the position lights. The strobes worked the first time they were turned on, which was nice since this was the first time that power had been applied to the strobe power supply that I had purchased almost two years ago.

In preparation for laying out the rest of the paint lines, the cowling was installed.

The fuselage was lifted up by two cranes to the maximum expected climb pitch angle to accomplish the fuel flow test. A funnel and tube (which my helpers immediately named "the beer bong") was attached under the open end of the fuel line at the carburetor. The stiffness and curvature of the tube would not let the gas container sit squarely on the floor, so a Gas Container Stabilizing System (GCSS) was rapidly conceived and assembled.

The remainder of the painted sheet metal was finally installed, resulting in a complete airplane, if you ignore the fact that it is currently devoid of seats.

Taxiing out for first flight...the first would take at least three taxi attempts to get the engine ignition all working properly and thus be able to start the first flight. This was early in the morning on 7 June 2008, which just happened to be the same day that Eric Newton of Long Beach MS and John Sample of Aquilla AZ first flew their Bearhawks. EAA even reported on the "Bearhawk Hat Trick", although the first flight was really in Rosamond CA, not Rosemead CA. On another unrelated note, 7 June 2008 was my 22nd wedding anniversary. Armed with that knowledge, you might be able to figure out the background behind the choice of N-number.

Yes, "Three Sigma" is capable of flight, albeit briefly. The first flight encountered trim tab flutter at 80 KIAS shortly after taking off. The flutter went away after reducing power and slowing below 80 KIAS. The flight plan was immediately shortened from about a one hour flight to once around the pattern to a full stop.

This picture was extracted from a video of the landing. You can see the video of the landing on YouTube, as well as the video of the takeoff.

The trim tab flutter was quickly traced to the trim tab pushrods which were not stiff enough. New pushrods were fabricated according to the January 2004 Engineering Change. A larger diameter tube was used, and the size of the bend in the pushrod was minimized.

The second flight was in the afternoon of 11 June 2008. The trim tab flutter problem was gone, but two much bigger engine problems reared their ugly head. For some reason, a large amount of oil was making its way into the cylinders where some of it was burned and the rest proceeded out the exhaust pipes, much of it depositing itself on the belly of the airplane. One observer commented that the resulting smoke trail looked like I had installed an airshow smoke system. Of even greater concern, the engine temperatures could not be controlled. CHTs were in excess of redline at full power before turning crosswind. After a brief effort to sort out the problem, the second flight was also cut short. During the flight, I determined that the airplane was balanced laterally (no heavy wing) and that the trim system seemed to work acceptably.

The initial ignition problems appear to have been oil fouling of the spark plugs, caused by the excessive amount of oil in the cylinders.

Shortly after the second flight, the engine was removed, boxed up, and sent back for warranty repairs. I thought this picture looked so comical, I submitted it to the Bearhawkers in search of captions. Here's what we got back:
  1. Sir, I think we may be aft of the cg limit (My initial submission)
  2. Damn, it was there when I taxied in.
  3. I thought it was kind of quiet on final.
  4. Yeah, but think of all the fuel I'll save.
  5. No, it cost so much I take it home every night.
  6. Next time I'm putting it in with Velcro
  7. I'm using 300 strands of Pirelli next time.
  8. ...and to think I could have been a piano player in a whore house instead.
  9. Well, it'll keep me off the streets...and the taxiways..and runways..and...oh, shut up!
  10. Golf is looking better and better.
  11. Tower, no I mean it. I really lost my engine.
  12. An observation more than a caption: If you just focus on the firewall and ignore the extraneous elements, it looks kinda' like Cthulhu.
  13. Stupid thieves! The boneheads went right by the avgas in the tanks and took that POS engine....
  14. What a Bearhawk looks like after blowing it's nose
  15. Don't leave home without it
  16. You should have listened when he said not to do a full power run up with the brakes on!!!
  17. She always said divorce was 50-50.
  18. Why didn't they leave me the cowling?
  19. Of course it did feel a little funny on final.....
  20. Yes, I am going to make Oshkosh this year.
  21. I thought sure he told me he needed my "rotor."
  22. Oh, come on! Sign it off for me! It's this close.....
  23. I was decisive on the entire build - until it came to the engine.
  24. Honey, who was that fellow that asked for the keys to the hangar today?
  25. The stolen airplane was found a few miles away, but with the hyper-warpitronic flapivator completely missing!
  26. James Dean's 550 Spyder engine was last seen on this airplane. Information leading to its recovery will be dealt with severely.
  27. Pilot thinking, "now that is what those bolts were for"
  28. Pilot telling tower "it was there when I went deep into IFR soup, then all hell broke loose"
  29. Pilot telling AI, "you mean those plug wires really have an order to them?--who thought that up?"
  30. For simplicities sake, I should have gone with an air cooled engine
  31. You should have made that last engine payment...
  32. Well, the plane was hanging on the prop when...
  33. F= M x A (Flight = Motor x Aircraft)
  34. What is missing in this picture?
  35. Gesundheit!
  36. With southern accent (I'm southern so can say it) while unscrewing pint of cheap Whiskey: "Dang Boy (insert spit of chaw here), there's your problem".
  37. Ah...guys...the Lord mounts are supposed to cover the holes, not go though them...
  38. YES SIR, we kept the engine wiring very basic, just barely enough to keep 'er running.
  39. I TRIED to tell you one of the drawings was missing.
  40. The brochure said I could lose weight fast, but Dayum!
    ...and my personal favorite:
  41. Theilert said my engine would be here soon.

The second first flight ended with a ground loop that smacked the right wingtip into the runway. This resulted in a crack on the top of the wingtip and abrasions on the bottom of the wing tip and the corners of the aileron.

Five months later the repairs on the wingtip and aileron were complete and they were re-installed on the airplane. (The white schmutz in the upper right corner is hangar dust.)

View of the wingtip after the repairs.

The tail wheel assembly after repainting. I was having trouble with the AN3 bolt that rides along the cam and pulls out the pin to free-swivel the tail wheel. The side loads on the bolt near the end of its travel were high enough that these bolts were routinely being bent over or broken. To address the problem, I followed the lead of Scott Weinberg of Scott-Iron Design LLC. As you can see on, Scott replaced this AN3 bolt with a shoulder bolt. Scott was all excited to tell me about it at Copperstate 2007 when I saw him there. While he said that his primary motivation was to get around the variances in AN3 bolts and use somthing that was more standardized, I think there is some strength to be gained from the shoulder of the bolt resting on the pin. The slot in the tube was widened to fit around the shank of the shoulder bolt.

Between using the shoulder bolt and a few other tweaks to the tailwheel assembly, the tailwheel seems to be releasing much easier and smoother under side loads. We'll see how it goes once I start taxiing again.

Here is a close-up of the shoulder bolt that I used. I got this from McMaster-Carr, catalog number 93996A416.
Ready to taxi out for the Third First Flight on 8 May 2009. This would be the last "first flight" as the flight ended by the pilot's decision, not because of an in-flight emergency.

Front page newspaper article from the local Antelope Valley Press (27 July 2009) covering my trip to Oshkosh 2009. Written by Allison Gatlin, a friend of mine and my favorite newspaper reporter. This is a highly unusual newspaper article because it is well written and absolutely 100% accurate. She prides herself for that and I have great respect for that. She knows what Oshkosh is all about--she attended in 2005.

The continuation of the above article. Look for the reference to Eric Newton and the Miss'ippi Mudbug.

After about 39 hours the bracket holding my alternator in place broke from cyclic fatigue. Apparently the alternator is in a high vibration environment. Unfortunately this was discovered at Rapid City Airport (KRAP) on a Sunday morning, the second day of the trip to Oshkosh. Fortunately, we found someone who could weld the bracket back together and with the addition of some safety wire we got the alternator strapped together in such a way that I could make it the rest of the way to Oshkosh.

While at Oshkosh I talked to the fine folks from Plane Power, who had come very highly recommended in a recent Sport Aviation article. They arranged to have an AL 12-EE70/B externally regulated alternator shipped overnight to my dorm. With my own tools and some borrowed from the plane repair station at Oshkosh I was able to install (in the rain) the new alternator with the much beefier bracket. As a side note, I finally figured out what the extra boss on the starter was for--to connect part of the alternator bracket to. About 50 hours later the alternator is still in great shape. Pricey, but a very high quality alternator. Well worth the expense.

After a PIO or two on takeoff, I finally decided that my pitch stick had way too much free play in it. Most of that came from excessive clearance between the lateral pivot bolt and the tube. I ground down the welds on the control stick to remove the old tube. The new tube had an inside diameter smaller than the pivot bolt. The new tube was welded in place and then reamed to a very close clearance on the pivot bolt. This greatly reduced the freeplay in the stick, down to an acceptable amount.

There was also a little bit of freeplay in the lateral stick because of clearances around the bolt I was using in the control stick to make the control stick removeable. I replaced the bolt with a taper pin which pulled the two parts tightly together. The taper pin is extra long because I didn't have sufficient information in the Aircraft Spruce catalog to fully determine the exact pin to use. Sure, I could cut it off shorter, but it's really not in the way of anything.

At 62 hours the cowl flap was found to have this big crack in the corner under the hinge. There were also marks on the flap indicating that the flap was being deformed by air loads and was beating against the mufflers. Both of these problems were address by making a new cowl flap with a stiffening flange along the front edge. At 87 hours the cowl flap was found to have a crack completely through the stiffening flange. With no time to build another cowl flap before a major planned trip, the crack was stop-drilled and several doublers were added to the flange. Apparently the air loads in this area are much higher than I imagined, but that's why I have the big "EXPERIMENTAL" decals posted in plain view of each entrance. There may be some more iterations of cowl flap design in the future.

Discussions with Scott Weinberg at Oshkosh and Eric Newton's experiences with his Bob Wheel breaking on the way to and from Oshkosh 2009 convinced me that I should strengthen my tailwheel yoke. This doubler was welded to both sides of the yoke per Scott Weinberg's recommendation.

Every airplane should be cursed with an Electromagnetic Interference (EMI) problem. Mine was an interference between the autopilot and the COM 1 radio. When flying with altitude hold engaged, if I transmitted on the COM 1 radio the autopilot would command a large and uncomfortable pitch-up. Even more fun, when the transmit button was released, the autopilot corrected with a just as large and even more uncomfortable pitch-down!

The initial recommendations I received guessed that that the problem was with the antenna being poorly matched to the radio. At the time I was using a simple stainless steel rod antenna. I tried adjusting the SWR by slowly cutting the antenna shorter and shorter. That really had no effect because that wasn't really the problem. Another suggested solution was to install a ground plane and a more purpose built antenna with a BNC connector that maintained the integrity of the shield all of the way to the antenna. The new antenna had a different mounting system so I had to modify the antenna mount. To do this I needed to get up to the fabric at the highest part of the fuselage where there is really no structure to support my weight. My solution was to build the "Bridge To Nowhere" which was supported on the edge of the fuselage and the first two wing ribs. The feet are padded by the no-skid rubber stuff sold for lining kitchen drawers. Not really visible here are the ropes tieing the front of the bridge to the windshield diagonal tubes (the windshield happened to be off for another repair) to keep the bridge from sliding down the fuselage out of position.

I'm enlarging the hole in the fabric for the antenna base.

My original plan for a ground plane was to just ground the antenna shield to the fuselage and allow the fuselage frame and wings to serve as the ground plane. Antenna expert Bob Archer had told me that this should work just fine. Even so, as I was trying to fix the autopilot EMI problem one of the suggested solutions was to install a sheet aluminum ground plane. Fortunately, because of the way I designed my trim system, I already had this large access panel that I could use to install the ground plane. I'm not convinced that this really made a difference, but it's not hurting anything either.

Since this picture was taken I had to bend the front and rear edges down because they were rubbing on the top fabric.

I would eventually determine that the EMI problem was caused by the COM 1 antenna simply being too close to the autopilot control box. Yes, Tru-Trak's literature says that the autopilot box is sufficiently shielded to prevent this problem, but I'm guessing they were assuming the transmit antenna was farther away than mine actually is. After a successful test of crudely wrapping aluminum foil around the box, I pulled the box out and wrapped it in aluminum duct tape. This isn't the gray fabric duct tape that was developed for sealing ammo cases in WWII and used for everything on Mythbusters. This is an aluminum tape that is sold to be used on actual HVAC ductwork. One issue is that the aluminum is electrically conductive but the adhesive is not. To be effective, an electrical shield must be conductive from any point on the shield to any other point. If not, you end up with each edge acting as an antenna and defeating the purpose. This box was spiral wrapped in such a way that the entire box (except the face, of course) was covered in one continuous piece of tape, thus ensuring electrical continuity.

This has mostly solved the problem most of the time, allowing me to transmit on COM 1 while using altitude hold on the autopilot. A couple of times the problem has returned to some extent, but then gradually disappeared on the same flight with no action taken on my part. I don't know what's up with that.

For the trip to Oshkosh, I had to fly at reduced power settings to keep the engine temperatures under control. After takeoff I would have to reduce RPM about the time I reached pattern altitude to keep the CHTs from getting too high above 435 degrees F. In cruise flight I limited myself to about 65% power to keep the CHTs between 400 and 435 degrees F. Even so, these temperatures were still higher than desired. After much time I decided that the problem was that even though the exit area of the cowl flap was sufficient, the path to the exit was very much crowded with exhaust pipes, mufflers, and a sea of SCAT tubes.

I figured that if I opened up additional paths for the cooling air to get out it might help with the engine cooling. I picked up a couple of pre-made louvers at the Avery Tools booth at Oshkosh. After getting back home, I installed the louvers in the location shown. I chose this location because it was similar to where I had seen other louver installations and it was the only semi-flat place on the cowling large enough that I could find.

There was a noticeable improvement in cooling. Now I can climb about 3000 feet at full power before the first cylinder approaches 435 degrees F. Cruise CHTs are now below 400 degrees F and under some conditions it is possible to close the cowl flap. Even so, I'm still not happy with the cooling in climb. These louvers have a very limited exit area, and are so low profile that I think they are fully within the boundary layer. Fortunately I installed the louvers with screws so they are easily removable. I'm working on another louver design with a larger exit area and that will reach out of the boundary layer to create a low pressure area to help draw more cooling air out. We'll see how it works.

As the ambient temperatures dropped, the "extra ventilation" of the cabin became less and less desireable. I applied weatherstripping in the gaps around the doors and windows. This made a large difference, but I noticed that the mouse doors still didn't seal very well because they were too floppy. I added this aluminum angle to the mouse door to stiffen it up. It doesn't seal perfectly, but it is a definite improvement. I'd recommend it to anyone.

At 93 hours while flying I noticed the forward edge of the left cowl door vibrating with a fairly large amplitude. After landing I inspected the door to find a sizeable crack around the first rivet on the hinge. Several things seem to have contributed to this problem. On this side the propeller, and thus the slipstream, is rising and thus lifting up the door. The door was cantilevered out rather far from the first rivet. This section is rather flat, so it doesn't get any stiffness from being curved. I stop drilled this crack and added this 0.032 doubler over the door. The doubler itself is cantilevered because of the joint between the door and the nose bowl, but not cantilevered as far.

Immediately after speaking at an EAA meeting at Whiteman Airport in Los Angeles, I was talking with Bill Berle about my louvers and how to get more cooling air out of my cowling. He suggested that I needed more aggressive louvers that would reach outside of the boundary layer. Not able to find suitable louvers already available, I did what any scratch builder would do--I figured out how to build them from scratch.

Each louver was bent up from a flat sheet of aluminum. The louvers were bonded to a backup ring of aluminum. Because the louver assembly would be sandwiched between the cowling and a ring of aluminum holding nutplates, there was no room for rivets between the sandwich. Therefore, the parts were bonded together with T-88 epoxy after scratching up both sides with 80 grit sandpaper.

It's really tough to do a meaningful test of how effective the louvers are since the CHTs are a significant function of the ambient air temperature. My Oshkosh copilot once claimed that my initial success with the first set of louvers was that I fixed my cooling problem by adjusting the calendar (cooler ambient temperatures --> cooler CHTs). On a flight from Rosamond to Chino with ambient temperatures similar to those seen on the Oshkosh trip, during the climb I reduced the RPM to 2400 but was able to get the maximum CHTs to stabilize around 425 degrees F. Even with the RPM reduction there is still more than enough power for a reasonable climb rate. After setting cruise power the CHTs stabilized with a maximum of about 356 degrees F with the cowl flap full open, significantly below the 400+ temperatures seen before. While I still need to pay attention to CHTs during climb, I think I'm in much better shape overall for keeping my engine happy. Maybe I'll eventually be able to fly this airplane without worrying about the engine overheating.

More than two years after first flight and even longer since the aircraft was painted, I finally did the last step of the original planned paint scheme. This was to apply a 1/8" wide black stripe along each of the color separations. That is, anywhere red meets yellow. It is really amazing the difference it makes. From a distance away you can't tell that there is a black stripe, but you can sense that something is different and it looks better. As a bonus, the black stripe covers up subtle imperfections in the paint masking. This was not my idea, but was part of the original paint scheme that I derived mine from.

Rather than spend years developing the skill to paint pinstripes, like many auto customizers I went with vinyl tape. I used 3M Scotchcal Striping Tape. Part number 70202 is black, 1/8" wide, 3 mils thick, and comes in rolls 40 feet long. To find a supplier, simply Google "3M Scotchcal 70202".

In this picture, the tape has been applied around the "6" but not around the "8". You should be able to see a subtle difference. The quality of this picture is not great because it was taken with an iPhone (no flash) as the sun was setting.

Why did I wait so long to apply the tape? My local auto body shop veteran told me that I should let the paint "out-gas" for several months before applying the tape for the best adhesion. I guess gasses coming out of the paint under the tape might somehow push it up or otherwise reduce the adhesion. So how did "several months" become several years? It took a while for it to work its way up the priority list. After sorting out various engine problems, repairing ground loop damage, and building necessary upgrades, by the time I was ready to apply the tape, it was much too cold. Wait several months for the temperature to come up. According to the product documentation, this tape should be applied between 55 deg F and 90 deg F. Be sure to clean the surface before applying the tape.

As of this writing, the tape has flown twice and has not blown off. If it ever does, it's not that expensive or difficult to replace the tape.

In April 2012 Brady Lane, EAA Multimedia Journalist, was on assignment nearby here in Southern California, so I went to pick him up in Three Sigma to take him to our EAA Chapter 1000 meeting. While there, Brady took this beautiful picture and a whole lot more. I have this picture printed four feet wide up on my wall.

Note the strut fairings and wheel pants are installed in their raw, unfinished form.

In April 2013 I *finally* finished filling and painting all of the fiberglass parts. Here they are finally installed. The fairings installed include the wheel pants, upper and lower wing strut fairings, and fairings over the landing gear shock struts.

Those wheel pants sure look like they were always intended to be there! It sure is nice, too, to have those strut ends covered up.

Tires make convenient step stools, but the wheel pants aren't built to hold up anybody's body weight. I know this, but to guard against someone else who might not know, I applied the decal to warn "No Step".

One of our Project Police officers noticed that there was a lot of volume in the wheel pants behind the wheel well. He suggested building in a storage compartment. I decided to do that, mostly because I knew of nobody else who had. Between the two wheel pants there is more than enough volume for the wheel chocks, tie-down straps, and Pitot tube cover. The best part is that the compartments are right on the cg, so this equipment isn't moving the cg aft.

(Note: this color scheme has been adopted. I'm leaving this here for the history) This shows my proposed color scheme as of early 2001. I like the colors, and I'm happy with the design now. I've never claimed to be a creative artist, so I prefer to use the design methodology of find something I like and liberally steal from it. (I have reason to believe I'm not the first one to use this method...) This design was adapted from the picture of Red Lerille's Clipwing Monocoupe on page 82 of the November 1994 Sport Aviation (See below). The cowling treatment required some re-design since I'm not building a radial engine Bearhawk. I didn't really care for my original treatment of the cowling area, so I eventually decided to call in the big guns. I contacted my favorite aviation artist Mike Machat (best known for his highly detailed historical paintings, many of significant flight test events) for his paid professional assistance. He made several suggestions, and we both agreed on the treatment shown here. Funny how I had to go to a professional to settle on the "obvious and simple" answer, but sometimes I just need slapped around like that. Mike's consultation was well worth the cost. Your color scheme is what most people will react to at fly-ins, regardless of what kind of wonderful job you did welding that strut link. Don't skimp when it comes to getting a good color scheme design. We kept what I had aft of the firewall, except that Mike suggested the location of the "Bearhawk" logo and carrying the scallops onto the tail. The proposed colors are Poly-Fiber #136 Lemon Yellow and #189 Madrid Red.
Yes, I know that 24" wing registration numbers have not been required since sometime in the 1930's. However, I decided that I wanted to give my Bearhawk the look of a 1930's era airplane. Previously I had wondered if when I took it to a fly-in, would the ground crew mistake me for just another production aircraft instead of directing me to the homebuilt section. Now this raises the question of will I get directed to the Antique/Classic Section? Oh, well, that's what the little signs are for...Wonder if I could convince the FAA and Transport Canada that 24" wing numbers would satisfy the requirement for 12" registration numbers for border crossings? Probably not, since, after all, that would make sense (I eventually asked EAA HQ this question, and the answer was, of course, no, they didn't count. However, the good news is that 12 inch numbers are not required to fly into Canada, since there is not an ADIZ between our countries. All hail NORAD...)...Note that this picture shows the top with the transparent roof. I expect that I will not install the skylight, but rather will continue the yellow fabric forward to the windshield. No need to bake in the desert sun. E-mail me and tell me what you think of my color scheme.
I wanted to see how different the bottom would look from the top.
The front view with the new cowling treatment.
I rotated the first picture to give an idea what the Bearhawk would look on the ground at your favorite fly-in.
WOW! Some days I amaze even myself! I had wanted to do this drawing for a long time, but kept putting it off because I thought it would be too hard to do. I finally just did it while trying to make a final decision on this cowling treatment thing. Working from the picture in the original October 1995 Sport Aviation article, I put my color scheme on complete with the shadows. The color scheme looked good in the 3-views, but I think it looks gobs better (a technical measurement) in the perspective view.
I'm (was) considering setting up my landing gear to have the option to install wheel pants for those long cross-country flights to hard-surface airports. To do that properly, I need to procure the wheel pants before I start building the gear. I made this drawing to help me decide which style of pants I liked best. The styles shown are four styles available from Aircraft Spruce that will fit a 6.00x6 tire. (I ended up buying one of these, then decided that I wasn't happy with it--didn't cover enough of the wheel. I'm building my own now...well, will continue after the airplane is flying. These are styled after those on the Monocoupe that the paint scheme was stolen from.)
Download the vector file of the above color scheme drawings. Additional pages have the outline drawings for drawing your own color scheme. Draw on them in Powerpoint or print them out and draw on paper. This file is a self-extracting archive. Save it in a temporary directory, then run the file. Tell it where to save the extracted file. The final file is in Microsoft Powerpoint 95 format, so it should work in any version of Powerpoint or most programs that claim to be able to read Powerpoint files.
Red Lerille's Clipwing Monocoupe from page 82 of the November 1994 Sport Aviation. This is the picture that when I saw it I knew this was (close to) the color scheme I wanted on my airplane. Oddly enough, that decision predated the Bearhawk, back when I was planning to build a Kitfox. This would have transferred on to a round cowling Kitfox very easily.
Download the vector file of the Bearhawk name as painted on the prototype and shown at the top of this page. This file is a self-extracting archive. Save it in a temporary directory, then run the file. Tell it where to save the extracted file. The final file is in Microsoft Powerpoint 3.0 format, so it should work in any version of Powerpoint or most programs that claim to be able to read Powerpoint files.
Designer Bob Barrows and the prototype Bearhawk on the big Alaska trip. Picture from Bearhawk Builder Tim Cramb in Cold Lake, Canada.

Pre-First Flight Checkout Reports

Initial Fuel Leak Check - 17 Feb 08, 18 Feb 08, 1 Mar 08
Oil Dipstick Calibration - 18 Feb 08
Landing Gear Tread - 23 Feb 08
Spraying Behr Premium Plus Interior Flat Enamel - 27 Feb 08
Brake System Servicing and Checkout - 1 Mar 08
Fuel Flow Test - 8 - 16 Mar 08
Multiple Checkouts - 21-23 Mar 08, including fuel seep fix, Pitot-static leack check, and autopilot ground checkout
Control Deflections - 29 Mar 08
Initial Engine Run - 6 Apr 08
Alternator and Tachometer Troubleshooting - 6 - 19 Apr 08
Engine Ground Runs and Taxi Tests - 20 Apr 08
Crankshaft Oil Seal, Shock Struts, and other stuff - 23 - 27 Apr 08
Induction Losses - 6 May 08, including splitting the nose bowl, governor RPM check, verify full throttle fuel flow, verify crankshaft oil seal, idle mixture check, compression check
Weight and Balance - 18 May 08
Compass Card Calibration - 20 May 08

Read more about the Bearhawk at Budd Davisson's

Original Bearhawk Prototype, 180HP
Second Bearhawk Prototype, 260HP
Pat Fagan's Bearhawk #232
Bearhawk as featured in Northern Pilot Magazine

Want to know even more about the Bearhawk? Are you a Bearhawk builder looking for more reference material? Then you need to order the Bearhawk Reference CD. A huge amount of information at a ridiculously low price.

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The Bearhawk can be built from plans (scratch) or you can buy a kit from AviPro (after you buy the plans).

Be sure to also check out Del Rawlins' progress. Del maintains the on-line version of the "Unofficial Bearhawk FAQ" (Frequently Asked Questions) at

EAA Chapter 1000 Home Page
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Contents of The Leading Edge and these web pages are the viewpoints of the authors. No claim is made and no liability is assumed, expressed or implied as to the technical accuracy or safety of the material presented. The viewpoints expressed are not necessarily those of Chapter 1000 or the Experimental Aircraft Association.
Revised -- 24 April 2013