Beartracks 2026 Issue 1 – Technical Q&A with Bob

Technical Q&A With Bob
Builder Matthew Brennan asks about Bob’s use of aramid composite floorboards in his latest plane, instead of aluminum. Matthew says, “Curious if the Kevlar floorboards “sound” any different than aluminum when in flight.  Is “drumming” reduced?”
Bob says, “I wear ear plugs when I fly and it’s hard to tell for sure due to all of the rest of the noise, but the composite floorboards should help dampen some of the noise.”

Builder Collin McDonald noticed some ambiguity about the hardware to use when securing the round tailwheel spring to the fuselage, and made a post on the forum to seek clarity. Should those be AN5 or AN6 bolts? 
Bob says, “We’ve used 5/16 and we’ve used 3/8 bolts there, and we’ve never had any problems with those bolts. We’ve used 5/16 on the lighter planes and 3/8 on the heavier planes.” Bob has used 5/16 bolts there on his own planes, and adds, “That stinger is hardened steel. It’s a really big job to drill those out. You don’t want to have to do that.”

Fabricating a Replacement Tailwheel Locking Pin

Source: 2023Q3 Beartracks, Jared Yates
As we know, the Bearhawks (especially the 4-Place and Five) are heavy on the tail when parked. The main wheels sit somewhat forward, so it is very difficult to nose over with a Bearhawk, but the heavy tail is a tradeoff. One Bearhawker years ago told me that he would clean, inspect, and lube his tailwheel assembly every 50 hours. This may be appropriate depending on how the airplane is operated. I try to stick to a schedule of every year or 50 hours depending on which comes first.
Two days before we were to leave for Oshkosh, (isn’t it always?) I noticed that our tailwheel was not locking and unlocking very freely. It turns out that an insect had made a nest inside the tube where the locking pin resides. There was just enough room in the area occupied by the spring, but once we started steering, the nest was broken up and the dirt dispersed in that tube. It didn’t take long for the loose dirt to jam the pin in the locked position. This isn’t a big problem to fix, but it required removing the hex-head screw that connects the locking pin to the bushing that rides on the unlocking cam. When I went to remove it, that little screw snapped off. You can see the results in the lower part of the picture below.

This was not optimal. I knew that Eric Newton at Bearhawk Tailwheels would be happy to sell me a replacement locking pin and screw, but that would take a few days. I used to keep a spare of each, but hadn’t thought to resupply those spares since the fire. If we were going to fly to Oshkosh, I’d have to make new ones. I started with a long grade 5 zinc plated bolt from the hardware store, which had a nice unthreaded shank section. The first step was to drill a new hole to receive the screw. With a milling machine this would be an easy step, but with hand alignment it took two tries to get an acceptably-located hole. The hole needs to be centered, and I found that grinding a tiny flat spot gave the center punch, and subsequent drill bit, a little landing pad. Not having anything like the original screw, I used an AN-3 bolt, so I tapped the hole for fine threads. Once the hole was threaded, I cut the new pin to length and deburred the edges. The next problem was the bushing. I found that a stack of three AN washers looked just about right, and worked great. I added just a little thread locker to the AN bolt, and worked some grease in to keep the pin moving freely. Once it was all back together, I packed the locking pin tubing with grease so that the next insect wouldn’t find it to be an attractive housing vacancy. While it was an inconvenience to have to make the new parts on short notice, I’m thankful that we found the problem at home and not while trying to maneuver in the campground or at a fuel stop while on the trip.

Installing the Round Tail Spring

by Steve Busby, Aerolite Flight Services
The tail spring for the Bearhawk Patrol and Model B Bearhawk 4-Place has two pre-drilled holes, one at each end, to accept AN4 bolts. The socket for the spring, on the fuselage, has a hole pre drilled as well, so its a simple matter of lining up and bolting. The tail wheel has two holes so you will need to drill the second one once the spring is inserted. Make sure the tailwheel is properly standing vertical with no leaning to a side before drilling. And confirm the final hole sizes/bolts required by referring the the plans.
The spring is made of 17-4 Stainless Steel hardened to approx 44 Rc. Though it is tough, it can still be drilled. Use a new HSS drill bit, turning slow with steady pressure and some form of cutting fluid. A cobalt drill bit is preferable (NOT carbide) as it handles the hard, tempered material better.

Builder video from Ken:

Builder Bruce Case drew this nice diagram of Bob’s tailwheel assembly:
Bearhawk Tailwheel Exploded Diagram

Airframes Alaska Tail Wheel Suspension Unit

Source: 2017 Q4 Beartracks, Mark Scott
About a year ago I heard about new tail wheel suspension units offered by Alaska Airframes. I was often getting tail wheel shimmy if I was over 2300 lbs. I tried everything to fix it to no avail. After reading about a couple other Bearhawkers’ experiences with the tail wheels suspension unit I decided to give it a try. My hope was to eliminate shimmy and soften the ride in the back of the aircraft. Fortunately both worked out. I returned from 50 hours of flying it in South Dakota, Montana, and Idaho. I did not get shimmy once on any surface at any gross weight. It also considerably softened up the ride in the back as we flew off a lot of gravel strips. The design has been updated with stiffer springs and shocks based on prototype field tests by Mike Creek. Though I never really punished it much, videos of the tail wheel on landing show little deflection as it soaked up bumps nicely. I think it could take much more abuse and work well. The first picture shows the completed installation. Note that I have a ventral fin installed for added directional stability. With 260 hp and an 80 inch three bladed prop the directional stability is slightly reduced. I added the ventral fin a while ago to boost stability back to where I like it.

Fortunately I did not have to change my tail wheel control arms much. The first thing I had to do was bend the arms out to a shallower angle. This minimized the interference. However, there was still some contact. In the second picture you can see the out-line marking the area I had to trim away.

I measured the maximum force my springs can make at full extension. I calculated the arm edgewise bending stress increase with the cut out at max load and it is still quite low. I did move the control chain links in about half an inch in to keep the throw the same. It steers the same as when I had the leaf springs. The overall weight increase is only one pound. This ended up being a special order from Airframes Alaska. They were not set on their dimensions yet. I had to send back the first one to get modified to match my hole pattern. It fit well the second time. If you do order one make sure they have my dimensions handy. Dave Lenart ordered one and has had some difficulty getting it to fit.

Selecting Tires, Wheels, Brakes, and a Tailwheel

Brake Selection
You’ll need to have some brakes and tires fairly early in your build process if you are planning to install the gear legs and keep the plane on its gear. The best strategy is to find a run-out set of any kind of tires that will fit your wheels. Use those until you are ready to fly, which may be years from now, and then purchase a fresh set just before your first flight. Rubber ages unfavorably whether you use it or not. Check at your local flight school for a set of 600×6 tires, which is the size most often used on the main wheels of small Cessna trainers.
Just as with choosing an engine, deciding on your wheels and brakes will require deciding on how you plan to operate the airplane. The financial outlay is not as big as it is with an engine, but it is still significant. The main players for the 4-Place Bearhawk will be Cleveland, Alaskan Bushwheel, and Matco.
Cleveland sells two suitable wheel and brake kits. The 199-62 package will fit large and small tires, and the 199-60 kit will only fit 6.00×6 tires. There are two differences in the kits. The 199-60 has a brake disk that sits ¼” closer to the tire, and the torque plate has shorter lugs. This set is ideal for wheel pants, since the overall width is less. Most Bearhawk builders will be better suited with the 199-62 package, which includes the deeper brake disk and torque plate with longer lugs. See 2016 Q2 Beartracks for more details on the part numbers.
Alaskan Bushwheel makes a wheel and brake package that is interchangeable with the Cleveland 199-62, and sometimes their price is lower. In any case, they are still very expensive.
Grove wheels and brakes are very popular with Bearhawk builders. They are available as single puck brakes (for use with normal aircraft tires up to 8.50’s) or double puck brakes which are required if you ever want to use bigger tires than 8.50’s. Groves are available in aluminum or magnesium.
Matco also offers a package that is suitable for the Bearhawk.

Tire Selection

There is a real tendency to think big tires are necessary to land on grass and dirt runways, which simply isn’t the case. The normal 6.00×6 tires will handle most surfaces 95% of Bearhawk builders will ever see. If the landing surface is called a runway by most people, then the smaller tires are fine. If you’ll be landing on rutted or rocky surfaces, the bigger tires will be necessary. Moving up to 7.00×6 tires will give you added margin and will cost almost nothing in performance. Below is a chart comparing the commonly available tires and their rolling diameter. Notice the big jump from 8.00 to 8.50 x 6.

Tire Size Diameter Width
6.00 17 6.3
7.00 18.25 7
8.00 19.2 7.95
8.50 22.1 8.85
26” Goodyear 26 10

Tailwheel Selection
The Bearhawk is designed with the main wheels pretty far forward, which greatly mitigates the chances of nosing the plane over. The other side of this trait is that there is a lot of weight on the tail. Many tailwheel assemblies that were designed for light taildraggers are simply not up to the task. There are only two tailwheel options that we recommend. One is the assembly designed by Bob and available from BHTailwheels.com. The other candidate is the Scott 3200 (pictured last), though many builders don’t find the Scott to be as cost-effective.

Installing the Tailwheel (Leaf Spring)

The Bearhawk 4-Place (pre-Model B) uses a 1.5” wide leaf spring for tailwheel suspension. The Model B kits come with the round tail spring like the Patrol & LSA. But the spring is thicker (1″ vs 7/8″) when compared to the Patrol or LSA.
When installing the tailwheel start with this spring. There is a large bolt in the front, and a “U” clamp (provided by Bearhawk Aircraft) in the back.
Preparing the Tail Spring
The tailwheel assembly is held to the aft end of the spring assembly with a single bolt. On this aft end, it is necessary that the holes in the springs have an oval shape, as to relieve any scissor action that may occur between the two leafs when the spring flexes. See the drawing to the right and verify that your spring has the correct shape hole. If yours was part of a very early kit, the easiest way to open up the holes is with a rotary tool or die grinder and a small grinding stone or carbide bit, although a large chain saw sharpening file works too. Look down through the two leaves and grind the holes into an oval that is about 1/8” bigger, fore and aft, than the hole was, with the original dimension side to side.
Installing the Spring Clamp
The “U” shaped spring clamp will nest around the spring, but just barely lacks touching the mount that’s welded to the tail post. That’s on purpose, so the AN4 bolts on each side can pull the spring up tight. The gap should be no more than .032” and bolt tension will take that up.
A Note About the Bolts
The bolts in this part of the plane are subject to serious loads in operation, so be sure to check them regularly for proper torque. The only way to visually check the bolt condition is to raise the weight off of the tail and give the assembly a wiggle. If you find that the bolts were loose, replace them, since they will likely have been worn by the movement of the parts. Keep a set of spares on hand. When the weight is on the tail, the bolts will appear to be tight whether they are or not.
Attaching the Tailwheel to the Spring
The “Bob” tailwheel body has thick side plates that are welded to the main attachment plate. Ensure that the tailwheel spring is seating fully on the main attachment plate, and not rubbing on a weld bead. This can be done by applying a radius to the top of the top tail spring. If the tail spring is resting on a weld bead and not making full contact with the main adjustment plate, in service the weld bead will wear down and the assembly will become loose. The steering springs to the rudder horn should have just enough tension that there is no slack in the chains.

Builder Bruce Case drew this nice diagram of Bob’s tailwheel design:
Bearhawk Tailwheel Exploded Diagram

2000 Beartracks Mailbag: Q&A with Bob

Bob, Enclosed is a check for Bear-Tracks for another year. I do have a few questions:

1 – What is a good method to use to transfer the airfoil shape to the wood to be used for the form block for the wing ribs?

2 – What is the recommended radius for the wing rib form blocks? I believe that 1/8″ would be about right for both .025 and .032.

3 – Do you have an e-mail address and if so do you answer e-mail correspondence?

I have a piece of 1″ thick hard maple for the form block. I just need to transfer the airfoil shape to the wood and cut it out. I am ready to start with the ribs. Is Proto II in the air? I bet the performance is really great – Thanks for your time.

Paul Foster – #289 – Monte Vista, CO

Paul, Thanks for your questions and newsletter renewal. As for your questions

1) The best method to use is to glue drawing #7 to your form block with contact cement or Plyobond.

2) a 1/16″ radius will work best for both thicknesses of the aluminum.

3) I do not have an e-mail account. Proto II is flying great -look for a flying report in this issue of Bear-Tracks. -Bob

This letter was pulled from the Bearhawk E-group. For more information on the Bearhawk E-group see page 7.

Well, after several days of non-stop building, 023 is on the main gear. I stumbled across a new Scott 3200 tailwheel in some stuff my Dad purchased from someone’s attic. He got a bunch of stuff (including a 65 hp engine, prop, landing gear, etc) for less than the price of a new Scott! What a deal.

Anyway, related to tail leaf springs, after much discussion and some consulting with Bob, I have decided on purchasing a PA25 tail spring from Univair (part number PA25TWS1) for approximately $90. 1 decided on the PA25 because Bob recommended two leafs all the way to the tail wheel bolt. Taper rod was attractive but with the Scott tailwheel, side loads should not be a big problem – it will go to full swivel if a major side load occurs.

My plan on putting a Continental 0470 on my Bearhawk has been changed. Finding an engine mount damaged or not – is not easy. Any found, even damaged, seem to run between $500 & $700. The Lycoming 0540 seems easier to make an engine mount following Bob’s newsletter. Also, Bingelis only talks about Lycomings!

Compressing the landing gear shock strut took some thought. I used a bar clamp – very long – and it worked fine. Later Bob told me he used his drill press with the table moved off center – I wish I thought of that! Oh well, some days I make things harder than necessary.

Piper TriPacer Seats also took some work to find. I ended up paying $60 each – frames in very good condition and but they need covering. Seemed like allot but finding seats was not as easy as hoped. Salvage dealers did not have any. My source has a couple more sets if anyone is interested.

Well, that’s my story for now. If anyone is near Cincinnati (actually Florence, KY) or Elkton, Ky, let me know. I build my parts in Florence and assemble in Elkton. It would be great to have some other builders close to discuss building, etc.

Bill Johnson – #023 – Florence, KY

Hi Bob, So glad to hear that you are ready (perhaps already have) to fly #2. Our second wing is going together quickly. Should have both sides, including control surfaces before the end of the year. Looking forward to starting on the fuselage.

The photo is my left wing with control surfaces installed. I am starting to look for a wind damaged Maule or C180/182 to scavenge for the engine and other needed parts. Still having a ball with the whole project.

Pat Fagan – #232 – Pearblossom, CA

Also from the Internet -I have most of the systems hooked up or at least roughed in. All the flight controls are working. I am finishing up the fuel system now. #75 is being powered by a (1996) Ford Taurus 3.0 24 valve engine that I modified with a polybelt GT. The engine has run with no propeller but hasn’t been run to RPM or load yet. Items needing to be finished are the fuel system, engine control linkages, a few things left on the cowl, and trimming everything. I am installing a removable interior for complete inspections in the future. I know that a lot of little details need to be worked out yet.

I am in the process of moving again. This time I am going to build a house and hanger at an air park. I hope to continue working on the Bear hawk through out the house project and get it in the air by at least late summer. How is everyone else doing on progress?

I will be happy to answer any questions the group has and give my opinion of what I may have done different. I will say as far as the plans I have followed them to the line and had very good results, The project gets more interesting when you start to improvise beyond the main part of the plane, i.e. engine controls and all the other goodies. Enough for now. Happy building.

Tom Yeoman – #075 – Apache Junction, AZ

Hi, Bob,
Things are moving along, not on schedule, but forward.

I was saddened to hear of Ray Thurston’s passing – It was like hearing about a family member.

The enclosed picture shows the flanging tool I used for the rib “holes” – it was made from a standard flycutter and worked great! The wood handle was used to exert pressure on the bearing. Steel washers were glued to the form bloc to serve as bearings for the center pin. This might be helpful to other builders so I am passing it along. All the Best,

Walt Draxler – #082 – Arlington Heights, IL

Bob, I hope this letter finds you and Mike in good health and fun flying in your Bearhawks. Enclosed is a check for my newsletter renewal – I have been so busy that I forgot to send it in. I’ve finally got a good start on my Bearhawk. I have all my small steel parts cut out. I am just finishing all my ribs and I am about to start on the wing spars. My goal is to have the wings done by the beginning of winter. I am enclosing some long overdue pictures of my project. I will be looking forward to seeing you and Mike at EAA again this year. If you need a place to stay for a couple of nights you can stay at my place. I am about 40 miles from Oshkosh. Maybe that is too far, let me know. I sure would like to hear your comments about my project. I can take criticism. I hope to have the wings framed up by then. I have a question about the fuel tanks. I noticed in one of the newsletters that you weld and rivet them. Is the riveting necessary? Can I just weld them? Is the riveting for added strength or just to hold them together for welding?

Ray Gabriel – # 334 – Greenleaf, WI

Ray, thanks for the nice letter and your newsletter renewal. Your parts look very good in the photos that you sent. Mike and I might be able to stay over at your place for one night while at Oshkosh, check with us at Oshkosh. It would be interesting to look over your project. The rivets in the fuel tanks are only to hold the sheets in place for welding. ~ Bob.

Ray Gabriel using a Liebert Hole Cutting Machine. Ray reports that a user can cut all the holes in all the ribs in about 3 hours with this machine. Also pictured are all the 4130 steel and a few of the aluminum parts ready for bending and drilling.



Bob, I have been meaning to write for sometime to thank you for the information in your newsletter. I have been working on my seating arrangement. The front seats incorporate a “captain’s table” arrangement for the mounting. Adjustments are made by pulling a side lever to the right and sliding the seats back and forth. The back of the front seats fold forward to allow entry to the rear passenger area. The back of the rear seat is adjustable. I used 3/4″ x .035 square tubing for the windows and door frames. I know that it costs a little more but it sure is easy to work with. I’ve got to relocate the rear window frame 2″ higher.

The engine is a Lycoming 0-540 of 235 HP. It will be pulling a fixed pitch McCauley 8452 Prop. I hope to have it up and running by October 2000.

George Anderson – #153 – Daphne, AL

Hello Bob, Just got the Jan 2000 Bear-Tracks. I am always looking forward to receiving the next issue. Sorry that we didn’t make it to the fly-in in Oct. We were planning on coming down to the fly-in and visit relatives but I came down with the flu – so maybe next time.

Thanks for the information in the newsletter – It must be nice to have two Bearhawks!

Thank you for coming to our cook-out last summer and I hope you can make it to our next one sometime in June this year. Since the cook-out there have been 4 of my neighbors talking about building Bearhawks. My daughter and son-in-law are planning on building one as soon as they finish their Cessna 140. We might have to change the name of the airport from Hale’s Landing to Bearhawk Landing!

I have been busy working on the 1959 Cessna 172 that I am restoring – it’s almost done. The Koala 202 is almost ready to cover and I have most of the 4130 steel hardware for my Bearhawk wings made. I have too many projects and not enough time or money to finish them all.

Do you have plans for any future modifications for the Bearhawk? If so what? How about plans in the newsletter for seat frames and tracks. I have found that the Tri-Pacer seats are hard to find.

Dan Riffee – #267 – Hale’s Landing, WV

Dan, Sorry to hear that you were sick and couldn’t make it to the fly-in. Like you say maybe next year. Mike and I really enjoyed our trip to Hale’s Landing last year and are looking forward to it again this year. When you firm up a date – let us know.

Currently I have no more modifications to the Bearhawk design planned. Your idea for seat drawings is a good one and I will work on that for a future newsletter. -Bob


Bob, Enclosed is a check for the 2000 newsletter, also I have a few questions:

1) The part of the nose ribs that form the leading edge, have you noticed on the prototype or do you forsee a problem with fretting because the metal is not secured together at the leading edge tip?

2) On the plans it calls out a 1.25″ flange on the main spar and a 1″ on the rear. The newsletter has instructions for laying out spar blanks : Width = web finished height PLUS 2 x flange width PLUS 1/16″. This will give a larger flange than calls out in the plans, the same also with the 9/16″ and 1/2″ marker for the rib flanges. I wonder if it makes a difference or would I have clearance problems later?

3) Are the spar webs square on both ends or do the root ends have the shape of the wing attach fittings to fill the gap between the fittings?

I have started slowly on the wings, having trouble getting consistently sized ribs but getting there, I have all my tools and shop set up so far and having a lot of fun.

Mark Skiba – #349 – Camarillo, CA

Mark, Looks like you are really getting into the drawings and giving them a good going over. As for your questions: 1) Fretting has not shown to be a problem on the prototype and I don’t see any indication that it would start. 2) Slightly larger or smaller flanges will not cause a problem. 3) The spar blanks have the shape of the wing attach fittings.

Your ribs should be consistent within about 1/32″, let me know if you are still having trouble with the ribs. Maybe I can give you some more pointers for rib construction. ~ Bob

Mike and I received notice that Ray Thurston’s #005 BEARHAWK project has been purchased from his estate by John H. Dugdale. Ray had completed a tremendous amount of work on his BEARHAWK and it would have been a shame to see it go to waste.

Hi Bob,

I’m making good progress on the BEARHAWK. I’m on the wheels and rudder hook up to the pedals (I had to move the rudder pedals back from the firewall for brake cylinder clearance). I have a 0-470 and Prop and a good lead for the mount.

The seats are installed and I’m rigging up the rest of the tail. I have included a few photos of me forming the T25 ribs 1/8″ bend with a steel mandrel on the anvil.

Do you have a date for the fall BEARHAWK Cookout?

Will Graft – #365 – Wadsworth, OH

Wil, good to hear from you. I mention the distance used on my rudder pedal setback on page 5 of this issue. As for the cook out – we are still working out the best date as October has suddenly become very busy. We will have a firm date by Sept 1. ~Bob


The following post is from the BEARHAWK e-group.

Today I had to go see the IA who helped my brother restore his Citabria and I mentioned the e-mail list discussion of reverse engineering a set of EDO floats. The one hassle which he could see, would be forming the “hoop” stiffeners which give the rounded top of the floats their shape. He showed me an old partially torn up EDO and it looked like they were formed in a brake and then formed into their rounded shape, similar to how the fuel bay wing skin stiffeners are made for the BEARHAWK wings, only with a LOT more curve. So it would be a lot of trial and error compensating for springback, and it would have to be redone for each size hoop due to the taper of the floats. Not an insurmountable challenge, but probably easier to copy a float with flat top and sides.

He did mention that in the EDO line the model 2425 is not rounded like the others, and might make a good candidate for duplication. If the model number is also the displacement, that might be a bit on the small side, but may be close enough if you don’t increase the gross weight above what is specified for the landplane version.

Other than the hoops the rest of the float looked pretty straightforward and ought to be easy to copy if you could get the right extrusions. The one thing I noticed was LOTS and LOTS of closely spaced rivets. I think I would prefer to build my floats in fiberglass if a set of suitable plans become available. Matter of fact, my friend the IA asked “why don’t you just design your own?”

Del Rawlings – #316 – Cordova, AK

Bob,

#232 is really coming along well now. I bent the top frame as you suggested and was pleased to find everything lined up! I almost have the entire frame tacked together.

I was wondering, do you call for any special bolts, like close tolerance or high strength in the wing struts or landing gear?

I am planning on an 0-540 for a powerplant, will any 0-540 core serve for setting up my motor mount or do I need the actual engine?

Pat Fagan – #232 – Pearblossom, CA

Pat, good to hear that the process worked, as for the special bolts question, the answer is no. The airplane was designed to use standard AN hardware. The actual engine would be best – short of that, make sure that the engine that you use is set up the same as your core and that it has the same mounting bosses that match your motor mount ~ Bob

Another note from the e-Group:

Has anyone perfected the “Barrows Method” of flanging the @#$% lightening holes?

Mike’s book as well as “BearTracks” makes this look real simple.

“Barrows” Method:

1. Wax it up.

2. Using the flange tool, lift the hole 30 degrees by smoothly going around it about 2-3 times.

3. Flip the rib over and push it down with the back of your flanging tool to lock in the 30 degrees and tame any bends.

4. Sit back, admire your work, and realize that you’re God’s Gift to the Bearhawk community and builders world over.

“Romanko” method:

1. Wax it up. (Even I couldn’t screw up this step)

2. Fail at smoothly taking the flanging tool around the @#$% hole. Instead, use the flanging tool like a soda pop opener and go around the @#$% hole lifting it up in increments equal to the width of the flanging tool.

3. Admire all waves you just put in the @#$% hole.

4. Wax it again, and go around the @#$% hole with the flanging tool, realizing the waves will never come out.

5. Flip the rib over and push the waves with the back of the flanging tool until you realize you really are having a hard time judging 30 degrees with your eye at 0400 in the morning. Induce more waves.

6. Sit back in amazement as you realize what was once a straight rib has turned into an oil can. Go outside. Look up. If you see stars, leave for the airport and get in some quick flying before work.

I know that some of you have built elaborate dies for forming your holes, but I really hate the thought of spending time doing that. Frankly, I’d prefer to keep everything “Barrows Simple”. I keep looking at Bob Barrows as my example. If he built THREE sets of wings using this method, it’s good enough for me. I think it’s just an issue of practice, but I really thought I’d have it down by now. Until I do, I will continue to refer to them as the @#$% lightening holes.

Bob Romanko – #399-Charlottesville, VA

Bob, Bob and I have agreed to conduct a personal workshop with you to perfect the “Barrows Method” of rib flanging. I got it on my first try. ~Mike

I found some rod ends at Sun & Fun for $12.00 each. Talked to the surplus dealer (Russell). He has about 1000 more of these jewels. The part number on the rod end is RE4H6-2 made by Fafnir (look at the Spruce catalog and you will see these are the right ones). If you would like to purchase, fax an order to Russell AT2 Surplus (847-432-6847). He said it takes time for him to fill orders so be patient.

Bill Johnson – #023 – Florence. KY

Bill, you look good sitting in that fuselage. I was able to confirm the rod end information with Russell – Order what you need builders! ~Mike

Bob, I’m enclosing some photos of my Bearhawk. I have completed the fuselage, both wings, wing-tips, fuel tanks (installed), nose bowl, and the seats. All cables are hooked up and operational.

I constructed the seats myself with 4130 tubing and
zig-zag springs for the seat bottoms and backs. They are fully adjustable front and back with a hinged back for access to the rear seat compartment.

I’m getting ready to mount my engine on the Bearhawk.
It is a Continental 0-470. I hope to have my Bearhawk in the air by next fall – God willing.

Things seem to be going very well building from your plans. I cut my first tube three years ago.

Sorry I missed seeing you and the prototype in May when I was on the east coast. Maybe it will work out better on my next visit. God Speed,

Boyd Newgen – 264 – Ontario, OR

Boyd, What a great letter to receive the day I return from Oshkosh! Thanks for all the great photos and keep them coming. I am glad to hear that you are making such good progress, ~Mike

Hi Bob & Mike, I have had the Bearhawk plans 5 years and I am only now just starting. I have done a Kitfox and a Thorp T-18 (which took People’s Choice at Oshkosh) in the early 80’s. I want my Bearhawk to do the same.

You mentioned that you stayed at Blackhawk Field in WI during your trip to Alaska. I hangared there for two years prior to coming to Oregon.

I am a steadfast promoter of the Bearhawk. Why someone didn’t think of it the 30 years proceeding Bob remains one of life’s mysteries!

Don Schindler – 068 – Springfield, OR

Dear Bob, Please send me a copy of the Utility Door Plans ($25 M.O. enclosed).

I have been studying the plans at great length, trying to create and assemble the aircraft in my mind. In this way I feel I will have an understanding of the aircraft as a complete idea and not just some parts to make and slap together. This activity alone has been a source of great entertainment for me.

I expect to be full bore into parts construction by the end of December.

I have a couple of questions for you concerning the plans – At the root end of the spars you show the .032 web is to be continued all the way under the spar end plates and the spar end inside plates. Also you show the web flange ending at the top and bottom of the spar slightly short of the corner angle of the end plates. this creates and inside right angle cut at the top and the bottom of the web material at the end of the flanges. Is this inside right angle cut a possible source of future web cracking from stress? Should I radius it or continue it as a gentle curve up to the flange?

Do the line diagrams of the fuselage tubing depict the inside, centerline, or outside of the tubes?

And finally are there any unusual cluster arrangements in the fuselage tubing joints?

Bion T. Rodgers – 436 – Mount Royal, NJ

Bion, You should have your utility door drawings by now – let me know what you think. As for your questions: You make a good point about the spar flange. There should be no sharp inside corners on ANY aircraft metal part. Use a 1/8″ radius or larger. The fuselage line drawings depict the CENTERLINE of each tube. And there are no unusual cluster joints used in the Bearhawk frame as designed. ~ Bob

Dear Bob, I was pleased to have made your acquaintance on the telephone the other day. As indicated I have purchased Ray Thurston’s Bearhawk project but have not yet collected it from Blenheim. I will collect it soon, in the meantime Mrs. Thurston has sent me the plans and I am studying these.

Ray has done a lot of work on his project and it is a tragedy that he was not able to complete it. I hope to be able to pick up where he left off and continue the quality of workmanship. I am not a trained engineer, but enjoy a challenge and have always had a “hands on” practical tendency to make and fix things – boats, engines, travelling irrigators amongst others.

We live on a small block (14 acres) about 14 miles from Christchurch. While we are within the Christchurch International Airport Control Zone, there is a possibility we could fly off the block (it is 515 meters long (that’s 1690 feet to you and me)). The big thing will be to not annoy the neighbors as the area is in the process of being divided into smaller and smaller blocks with people moving here from the city.

So far as the Bearhawk is concerned, I have not decided what engine to use yet. Personally I am not keen on air cooled engines, but there is considerably less work and less uncertainty involved in sticking with the Lycoming. I am also not keen on reduction drives as many of these seem to have some problems. I quite like the idea of an inverted, direct drive, alloy V8, such as Steve Whitman used in his Tailwind. No doubt this would take some development too. A Rover 3500cc can be stoked and resleaved to give over 5000cc and this would give enough HP, but this too would take some development.

I would appreciate if you could provide me with a bit more specific performance data re: the Bearhawk than is contained on the websites. If this has been published in the newsletters do not bother to repeat it (I am awaiting receipt of the back issues from Mrs. Thurston). I am interested in the specific performance of the prototypes – e.g. estimated HP of the engines and the cruise speed at 2400 RPM for each, climb rate, fuel burn at cruse. Do your take off and landing figures represent literally lifting off the ground or are they the traditional 50 foot obstacle clearance? Also can you supply some data on the Bearhawk’s ability to handle cross winds. I look forward to meeting you someday in the U.S. or in New Zealand

John Dugdale – 005 – Canterbury, NEW ZEALAND

John, Thank you for the introduction and I hope that you find the Bearhawk to be to your satisfaction once you begin construction. I considered Ray to be a very good friend even though he was on the other side of the planet and I am pleased to learn that all his hard work will not go to waste. I think that you will find the answers to most of your questions in the back issues of the newsletters. My performance figures represent actually lifting off the ground. I personally think that the Bearhawk handles crosswinds quite well. The nearest production airplanes that would be close in crosswind competence would be the Husky, Super Cub or Citabria. ~Bob

1999 Beartracks Mailbag, Q&A with Bob Barrows

Source: 1999 Beartracks, Bob Barrows

Bob,

Thanks for the note of 10/17 and yes, the struts arrived safely this time. The outer wrap had a small tear that didn’t penetrate to the metal.

I usually work on the Bearhawk between 10 am and 6 pm with the odd interruption to run into Kent (South of Seattle) to Boeing Surplus, a good resource for used tools, new aluminum and such. I just picked up a 61″ x 151″ x .125 sheet of 2024T3 for $185. I am cutting main spar caps, splice and filler plates and attachment plates from this. The savings more than justify the 225 mile round trip.

I have joined the local 430 EAA chapter, but have not yet met the tech counselor. I will have to get them over here soon as I am close to completion of ribs. The spar blanks are ready, caps, slices, and other necessary parts should be cut this week-end so that riveting can begin. The 1/2″ x 1/2″ angles need cutting to length and riveting too.

I took time out to turn a set of punches and dies out of firewood (Alder, Maple, Madrona) to form lighting hole flanges. The photos show a couple of them and the drill press used as an arbor press.

I am ready to order the remaining aluminum needed and the 4130 tubing. I want to talk to some of the other builders in the state to see if my buying plan is viable. I bought the first batch from Airparts in KS and enjoyed their rapid and professional response. Cost are reasonable too, in my judgement.

Enclosed is my check for next years Bear-Tracks, an enjoyable and necessary adjunct to the plans. I am having FUN! Mostly because of the loving support of my wife, not to mention Dan Donovan of All Form Welding, who has given me free run of his shop and Joe Ritter, who has made his shop (2 doors away) available as a good neighbor! Now – if I could just line up a good bucker. Best Regards,

Jack Piggott – #347 – Sequim, WA



Dear Bob and Mike,

Enclosed is my renewal check for Bear-Tracks and a photo of my Pile-O-Ribs. After finishing the ribs, stiffeners, attach angles I got got tired of forming aluminum and have been having a good time making some of the flat 4130 pieces for the wing hardware. I am hoping to run out of my last order of material about the same time I start my flying lessons in early ’99.

I do have one question for you – I’ve looked over the plans and newsletters and can’t seem to find any detail on the tail spring anywhere, other than how to attach it. Did you make the spring, or is it a salvage unit from a production aircraft? The reason I am asking so far in advance of needing one, is if time allows I plan on doing some parts scrounging while I am in the states and have been making a list of items to be on the lookout for.

After further examination of the new struts and the revised drawing, I think an additional thank-you is in order for making them available to your builders. I really was not looking forward to making and attaching the original design fittings. I’ve constructed a substantial crate to store my struts in so that they should be safe until I need them.

Del Rawlings – # 316 – Cordova, AK

Del,

Thanks for the photos of your wing ribs, they look nice. Regarding the tail spring, I used some that were found at the airport here. It depends some what on the tail wheel you use. Also if you can’t find one that will work – you can have it made at a local auto spring fabrication shop. I will be providing more information on this subject in future newsletters.

Also we are now testing a homebuilt tailwheel assembly we designed and built. If it continues to work as good as it has been we will provide drawings for same with spring details.

~Bob

NOTICE: In an effort to get builders to send in photos of their projects we have decided to try and bribe you guys! Starting with the October issue if you send in a photo of your project your name will be put in the running for a very nice BEARHAWK HAT! We do not care what stage of construction you are currently at – we would just like to see your progress. Even if all you have done is your wing rib form block send in a photo!

Bob, Well after many other projects finally out of the way #235 is under way! The shop is heated and finished, my first shipment of aluminum is here and I have started cutting out nose ribs. The aluminum sure is a lot cheaper when I buy it through work at wholesale prices. It is less than half what I’ve seen advertised for. Sorry that I missed you at Oshkosh last year, I was only there for 10 hours on a charter flight. I did speak to Mike briefly, sounds like it was a great trip to Alaska. If you decide to come look at some land up here (your dollar is still valuable) drop me a line. I’ve enclosed an international money order for the newsletter renewal.

Mike Guthrie #235 – Ontario – CANADA

Hi Bob, I have a question about building the control surfaces I hope that you can answer. What kind of a jig did you use while assembling them? I am trying to build the ailerons, but keep having to start over, trying to keep everything straight and aligned. Any kind kind of suggestion you can provide would be appreciated. We are almost done riveting the skin on the left wing.

Pat Fagan #232 – Pearblosson, CA

Pat, Good to hear that you are progressing smoothly on your wing skinning. We did not build a jig to align the flaps and spars. Find a perfectly level – flat table to assemble the flaps and ailerons. Start out by skip riveting the nose skins along the spar every 4 – 5 holes to keep the movement of the parts to a minimum. Check the fit to the wing and drill out rivets on the top side of the skin and re-cleco and c-clamp as needed. continue to skip rivet and rechecking fit until all rivets are in place. The pull rivers are to go in last. I think that you will find this method to work best with minimum re-dos on the rivets.

From the Internet:

On drawing 20 1 had not closely looked at the tube sizes. I thought that a larger tube slid over the front horizontal stab tube and was welded to it. Now I realize it is two 7/8″ tubes of different thicknesses butt spliced together. Is this the intent? For slightly less than 1 pound extra weight, I will make the entire tube out of the .049 material. This will have the added advantage of being more resistant to rock strikes. I had some nasty dings to patch there on the Maule that I rebuilt. Drawing 16 shows the airfoil shaped trim made out of 1/2 by 1/2 .032 channel, I am wondering what method you use to get a smooth bend around the nose of the airfoil? I have access to a shear and a 12′ brake at work now so I brought a 72″ x 18″ sheet of .032 4130 with me to make all the T25 channel pieces with. They gave me a bit of a hassle about checking it on as luggage on the company 737 but I got it here. In a fit of insanity I agreed to an extra week of overtime, so I am imprisoned at Prudhoe for 3 weeks this time.

Rod Smith #246 – Wasilla, AK

Rod, For the more punishing environment that you will be flying in it is OK to bump up the tubing thickness to .049 – the thicker tubing will be a bit harder to work with and you are adding weight back. Since you plan on a electrical system though the weight penalty should be negligible. As for the airfoil shaped trim piece, it is made out of 1/2 inch channel. Numerous “V” shaped cuts were made to make the bend for the airfoil shape. The notches were then welded together. This trim piece and allows for a tight fit of the windscreen so it is OK to file the welds flush. ~Bob

Bob & Mike, Enclosed is a renewal check for Bear-Tracks and the landing gear shock strut seal and snap ring kit. I enjoyed meeting both of you at Arlington and I am glad to hear that the whole Alaska trip went well. The opportunity arose for me to buy all the tooling and miscellaneous hardware from an RV builder who became ill and won’t be building any more airplanes. I also picked up a Scott tailwheel and other miscellaneous items. I’m real anxious to finish my shop and classic car projects so I can work on the BEARHAWK only.

Wayne Halliburg #266 – Centralia, WA

Hello Bob, Another year has come and gone and more BEARHAWK parts are being made. After a short slow down to add on to the house and other “little” things I am now back at work on my project. I spent 8 hours on a Bridgeport milling machine last week squaring and cutting to length all the web supports (1/8 x & 1/4″) for both main spars and next week I will do the same for the rear spar. We squared up the inner front attach plates and I laid them out and they went together easy, the jigs for the spars should be simple. I ordered the fiberglass wing tips from T.Q. Fiberglass.

April 12th will be 2 years into this project, but I’ve only got about 330 hours into it to this point. As for powering my BEARHAWK I’m leaning towards the Franklin 205 HP engine, everyone that I’ve talked to seems to think a lot of them.
I was glad to hear your trip to Alaska was a success and I enjoyed reading about your adventures in the newsletter.

Sonny Cilley #234 – Royalton, VT

Sonny, Good to hear that everything is going together so well. It looks as if you are keeping a good record of your build time and you seem to be right on track hour-wise to a 2000 hour build time. If you just find a couple of hours every day you will get more done than trying to work on it 8 hours on one day.
We found the T. Q. Fiberglass wingtips to be of first class quality and hope that you do to. Let us know how you like the quality and the service that you received. -Bob.

Howdy:

Just set up the jig for my wings today. Took the whole day to get everything square and level. Will spend next weekend finishing and fitting the fuel tank and determining where the holes for the lines will go and double checking the fit of the tank straps and then, finally, I will put the 1st wing in the jig.

I had, as did others, a problem with the aileron cable at the pulley located at the web splice that takes the cable down the wing strut. I solved the problem by clamping the bracket to a solid work bench with 2 LARGE c-clamps. Then I tapped the top of the bracket with a hammer just a bit in the direction that was needed. When I reinstalled the bracket and pulley, to my amazement it lined up dead on. It only took a small tap as the misalignment is very small.

Tim Neil – # 209 – Uniontown, PA

Tim: Thanks for the update on your wing construction – you should really enjoy the skinning process as it progresses.

Regarding the pulley/cable line up. I have investigated this problem and found that the bracket as drawn on the prints is not located properly. This condition has been in use on the prototype and has not shown a wear problem yet. Your fix sounds like a simple effective way to modify the bracket for the builders who have already made this part.

I will be working up an engineering notice on the bracket in the next issue of BearTracks. ~Bob

Mike and Bob,

Would like to thank you for taking the time to show me the BEARHAWK. I’m sending you the info I have on procuring alodine. You can order the crystals from a chemical supply house for approximately 30 dollars. It will probably last you a life time or divide up cost among people you know. Alodine is chromic acid and you can normally get it in clear or yellowing. I use the yellowing to verify coverage. I believe I found this info in Sport Aviation (August 96). 1 tore out the page and I’m no longer sure which aviation mag it was out of. If you have problems locating supplier drop me a line. Best of Luck

Chester Abbott Ocean Springs, MS

To BEARHAWK dreamers and doers,

I had the pleasure of spending the holidays with Russ (Erbman) and his family. I also had the distinct pleasure of helping with the riveting procedure on the rib stiffeners and the wing spars.

You must realize that I was trained (50 years ago) to SPRAY EVERYTHING WITH ZINC CHROMATE primer. I have seen the development of epoxy primers. In both cases solvents are needed for cleanup. I don’t care what anyone else says, I DO NOT want aircraft solvents around a house that my grand children (and their mother) live in.

I had difficulty reminding myself that the white parts were primed and not top coated. They were not green.

I may be prejudiced, but Russ did a beautiful job of spraying the parts. I was impressed with the working life of the primer when we were brushing a coat of primer on the mating surfaces and then riveting. The sealing of the edges between the cap strips was excellent for the initial seal.

In case you did not catch on, I think the Poly Fiber Primer is Terrific. I forecast that within 5 years after the commercial release of the primer, it will be the most specified primer on new designs in the aircraft industry.

Lee H. Erb, P.E.

Wow – Give you guys a little incentive and you really come through. We had about 10 entries for the BEARHAWK hat drawing. If you sent in a photo – your name got tossed in the hat (the very one that you could win). Mike drew the winning name on Oct. 12. The winner’s name is on the last page of this issue. We will do this again for the January 2000 issue – so send in those photos.

Bob, As per our phone conversation the other day I am sending you these questions as you asked to include in the newsletter.

1) There seems to be a 1 1/2″ – 2″ gap between the wings and the fuselage and I wondered how you went about covering it?

2) With the rear window frame, do you have the outside of the frame flush with the door frame and if so how do you get the window in?

3) On the plans it looks like the aluminum fairing on the landing gear legs only covers to the rear leg. Is the front section covered with fabric? Do you run your brake lines inside the fairing?

4) Could you give me the details of the tail spring, length of spring and height of fuselage from the ground?

5) Do you have your rudder cables run along the lower inside of the fuselage with fairleads and do you use a turnbuckle on each side?

6) How do you attach elevator and trim levers inside the the fuselage when it is covered?

7) How many inspection holes do you have in the wings and what areas and size?

8) By the photo it looks like you have a fairing around the top of the landing gear to fuselage, also top and bottom of the wing strut, are these all fiberglass?

9) With the strut at the front of the rear stabilizer is the top just flattened or is there a piece welded to it?

10) The lead balance weight in the elevator, did you mold the lead piece in place or mold separately and attach later?

Merv Hargraves – #362 – Queensland, Australia

Merv – Thanks for sending in the questions, and the photos of your project. In regard to your questions:



1) I used .025 2024 T3 aluminum to cover this gap. It is similar to the fairing used on a Piper Tri-Pacer or Pacer. Attach to the wing with screws.

2) The rear window frame is just slightly outside of flush to allow the window to slide in.



3) The gear legs are covered with fabric and the brake line is inside mounted on tabs to the rear leg.



4) The tail spring is similar to those used on Maule aircraft. 3 or 4 sections 1 1/2″ wide 1/4″ thick, with the two main sections about 16″ long. The fuselage is 18″ off the ground.

5) Rudder cables run inside fuselage until about 19″ in front of tail post, where they exit the fabric to connect with the rudder horn. I used four fairleads located at Sta C, D, F & H to support the cable.

6) Make an access cover 9″ x 8″ on each side of the fuselage at a location centered on the top longeron and about 2″ in front of the tailpost.

7) 1 used 6 inspection holes in each wing one at each pulley, aileron bellcrank, flap spring attach points, flap arms and the strut attach fitting on the front of the spar.

8) The fairing at the top of the landing gear is .025 2024 T3 aluminum attached to the T25 channel and the .032 fairing support with screws, use rubber edge material around the top of the fairing so as not to damage the fuselage fabric as the gear moves. The fairings at the bottom of the struts are fiberglass (see ad in the back of this newsletter to order).

9) The strut is just flattened, bent and welded around the edge.

10) I molded separately and cut to fit but it could be molded in place if you like.

Bob Triplett’s 4-Place Bearhawk

Source: 2015 Q3 Beartracks, Jared Yates
15q3fOshkosh can be a busy and hectic time, usually with too many exciting things to see and do. This year, I had time for a leisurely discussion in with Bearhawk builder Bob Triplett, as we sat comfortably in the shade under his recently-completed kit-built Bearhawk 4-Place. Bob comes to the airplane building hobby with plenty of experience, with airplanes specifically, and fabrication more generally.
He has been a machine shop teacher since 1977, and has worked as a tool maker and machinist for many of those years. This meant building custom manufacturing machines, and in one case, he made part of the extrusion die used to make Lucky Charms cereal. These days Bob is “supposed to be retired,” but he spends lots of time working in a high-end antique auto repair shop. He showed me some photos of a recent timing chain for a 1924 Voisin that he built link-by-link, modifying an existing chain to accommodate a non-standard width. Bob is a maker of things.
The Bearhawk is his “fifth or sixth” airplane, and it follows a Tailwind, an intensive Cub restoration, a Cessna 170, 172, and 195. The 195 was a literal basket case, which he acquired as several baskets of parts. He enjoyed the wide and spacious cabin, but in 350 hours of operation he replaced multiple cylinders, and always had oil leaks. This was part of why he chose the Bearhawk. The slightly smaller Bearhawk cabin is still plenty large for his cur-rent needs, and he says that both are able to handle the same amount of wind. The operating costs are obviously much lower on the Bearhawk.
15q3gThe empty weight of N94RT is 1395, which includes auxiliary fuel tanks, autopilot servos, 8.50 tires, a 10-inch tailwheel, and a well-apportioned interior. Bob started with a Scott 3200 tailwheel, but upon investigating the source of a noise it made during operation, he found that a piece of it had cracked. He made a Barrows-designed tailwheel to replace the Scott, and has appreciated the slightly flatter ground attitude. I asked if the axle had nuts on both sides to facilitate attaching a towbar. Bob machined his own axle by cutting threads on both ends. “I could have used a bolt,” Bob said, “but then I’d have to buy a bolt.” Bob adds a recent update: “I recently made some changes to the wheel by making new bolt to bearing bushings that extend all the way through the wheel with a sleeve on either side to hold the wheel in the center of the fork and changes out the elastic nuts for castle nuts and cotter keys. This will be a better long term solution. I installed this wheel 30 minutes before leaving for Oshkosh. There may be two additional changes that I may make to the wheel before I get totally finished with it.

Bob's fiberglass landing gear fairing, and fancy interior

Bob’s fiberglass landing gear fairing, and fancy interior


Left: Mark Johnson studies the engine installation. Center: Bob Barrows prefers more frequent fastener spacing on wing inspection panels, similar to rivet spacing. Right: The cabin heat is fed from two muffs into a custom-made Y manifold. It gets cold in Wisconsin!

Left: Mark Johnson studies the engine installation. Center: Bob Barrows prefers more frequent fastener spacing on wing inspection panels, similar to rivet spacing. Right: The cabin heat is fed from two muffs into a custom-made Y manifold. It gets cold in Wisconsin!


The engine is a parallel-valve Lycoming 360 that Bob removed from a Pitts. He replaced the cam, which required replacing the cam gears, and replaced the oil pump gears and installed new ECI cylinders. The prop is an 80” MT (MTV15B210). At 2400 RPM and 23.5” MAP, he sees 10.5 GPH and 115 knots, with CHTs in the low 400s. He’d like to see lower CHTs, and has tried installing a plenum above the cylinders. His next step is to try measuring the pressure in the cowl to see if the airflow should be adequate for cooling. Oil temperatures started out high, but he’s switched to a high-density 8-row oil cooler, and after that he’s seen temperatures less than 190 degrees F.
The paint job turned out very nice, with Polytone on the fabric and Aerothane on everything else. The interior is very classy, with lots of specially-made touches. Parking next to his airplane would make mine seem pretty ratty.
Bob used the new Additional Pilot provisions of AC90-116 for his initial flight testing. Bob’s Qualified Pilot (QP) handled the stick and rudder tasks while Bob monitored engine parameters and the overall situation. The QP had thousands of hours of experience in general, but no experience in the exact model. Like many other first-time Bearhawk pilots, he was surprised by how soon the airplane lifted off in the takeoff roll. The two completed a pre-designed test plan in about an hour of flight time. Later that day they repeated the process. One of the landings was a little bit firm, but the airplane was well-suited to absorb the energy. Of all of the planes he’s owned, Bob prefers the Bearhawk’s landing gear, due to its dampening and forgiving nature.
Bob had a great parking spot on the line at Oshkosh, and he had lots of visitors. It sounds like he is enjoying his Bearhawk, and I certainly enjoyed talking with him about it.
15q3j