The Air Induction System

About a year ago Don Rivera, founder of Airflow Performance, hosted a Fuel Injection 101 course that I attended.  I am using their fuel injection system on my IO-540.  Don offered a perspective that stuck with me, "Engines are just air pumps".  Good airflow entering the engine is just as important as a good exhaust system that can carry spent air out of the engine.

Below is the standard "square" air box on most Bearhawk's.

I set out to streamline the air induction system for my Bearhawk and create a round ram type inlet, like this.

Engine Cowling

Time to install the engine cowling...  When building the Bearhawk, there are two sets of manuals.  The AviPro Aircraft "Builder's Assistance Manual" for the kit, and Eric Newton's "Bearhawk Builder's Manual" for scratch builders that was written in 2008.  Both manuals discuss the design and installation almost identically.  Eric Newton's scratch builders manual is a little more thorough on most everything, including the engine cowling.  But both are referenced for varying aspects.

Completed view of the engine cowling and nose bowl installation.

Engine Baffling and Plenum

After completing the baffling provided in the RV-10 Firewall Forward Kit, I installed the traditional Air Flow Fabric in order to seal the gap between engine cowling and the baffling.  Ultimately I was not happy with all the seams, gaps and crevices with the Air Flow Fabric.  Swiss cheese comes to mind.  Yes, 99% of piston GA engines use a flexible fabric to seal and cool the engine, but I was intrigued with a few carbon fiber plenums I encountered.  And considering IO-540's in tight Bearhawk engine cowlings are reported to run hot, I decided to take a stab at fabricating my own carbon fiber plenum.  

    The finished product...

Hanging the Engine

Previously I discussed some difficulty with the engine bracket and isolators.  Once resolved, the engine swung into place and was mounted in less than 20 minutes.  Whew!

Boot Cowl

I have two desired outcomes with the boot cowl.

1).  To have access to the back of the instrument panel from the inside top, after the windscreen is installed.  This will also allow the hinged panel to tilt rearward for greater access.

2).  To have access at the sides of the boot cowl for access to rudder pedals, fuel lines, brake lines, etc.

Engine Isolators - What a Debacle!

(UPDATE 8/30/19...  Several have asked and offered advise for installing the engine and isolators to the Type 2 bracket.  I successfully completed the engine installation after consulting several certified engine service manuals on the same engine and Lord J-9613-12 isolators.  All were consistent in detailing the sequence and that each AN-7 bolt should be fully torqued before moving to the next.  This proved very effective made the installation a non event.)


It WAS a debacle...  It's easy to describe the issue now after "going to school" on engine mounting brackets, engine case ears, isolators and isolator bolt lengths.  But this whole experience was a huge time suck and slowed my build progress down more than I would have expected.


The following video describes the entire engine mounting situation and explains why it took so long to hang it...  Get ready for an education on mounting an engine!

Gear Legs On ~ No More Rotisserie!

It's been a long summer and quite awhile since I updated my build blog...  I had a business trip in June, family vacation to California in early July, then a week in Oshkosh at the end of July.


Now that the fuselage has been painted, it's time to get some legs under her.  It is bitter sweet to remove the convenience of the rotisserie, but real progress to finally have the gear legs mounted.  Finally starting to look like an airplane!

Each of the main gear struts is comprised of a cylinder containing a high compression spring and a capped shaft.  The spring must be compressed into the cylinder, locked in place with a snap ring, then the cylinder is filled with ATV fluid.  This creates the hydraulic dampening system for the Bearhawk landing gear.

In my opinion, the most underrated component on the entire Bearhawk line is the ingenious landing gear system.  This gear is not "springy" and creates a sense of sticking to the runway on landings.

Following the Bearhawk Builder's Assistance Manual I installed the spring accordingly. 

Fuselage Fabric Covering, Fabric Filler, Prime & Paint

I used the Stewart Systems fabric covering and waterborne paint products.  And could not be happier!  It took me about six weeks to cover and fully paint the fuselage.  

I used the blanket method for covering the fuselage.  I began on the bottom, then the sides, the vertical stabilizer, and finally the top.  The transition from the leading edge of the V-Stab to the top was a little tricky, but again the Stewart Systems videos are exceptional for detailing the fabric covering and painting process.  https://www.youtube.com/channel/UCrlV5GMsw4S6zTn9bzjFwkA

I was prepared to accept a marginal paint job considering my experience and conditions.  So to say I am happy with the results would be an understatement.  The top coat came out PERFECT!  

I have to attribute much of the success of this paint job to the equipment I chose to use.  Stewart Systems say that 95% of bad paint jobs come from poor or inappropriate equipment.  So I selected everything they recommended including a high output air compressor that could keep up with long run times and maintain consistent pressure at the gun, high flow fittings and hoses, high performance air dryer, and a high performance HVLP paint gun with an inline pressure gauge.  

I cannot say enough about the Stewart Systems for fabric and paint!

9 Month Walk Around

March 2019 marks the 9th month of my Bearhawk build.  I am finally feeling like there is light at the end of the tunnel!  I know for certain that my next build will go much quicker having established tools and processes.  (I would like build a Bearhawk Patrol next). 

Here is a quick overview of my status as of March 10, 2019.  I thought this would be a good point to show the status of my build as I am almost ready to cover the fuselage with fabric. 

Eliminating the D Window...

This turned into a bigger job than I wanted.  I decided not to use the kit provided "D window" assembly and go for a more modern look.  (To me, the D window says Pacer or Super Cub). 

All of the fabrication took place on the port side of the fuselage.  Whatever I ended up with was copied and cut from the cargo door on the starboard side. 

The process I used involved a single piece of .05 aluminum as the frame.  I layered or laminated additional pieces of .032 aluminum for build up.  Finally I finished it off with aluminum angles attached to the inside for strength. 

Pitch and Roll Auto Pilot Servos

I elected to install a two axis Dynon auto pilot system, (pitch and roll).  Perfect for holding altitudes and headings.  Turns using the heading bug, or route changes while in AP mode, will be assisted with the pilot's foot on the rudder pedals in the appropriate direction to compensate for adverse yaw.

The roll servo is mounted under the pilots seat on a .050 aluminum plate.  The plate is secured using adel clamps.  Dynon provides brackets in their AP servo mounting kits.  The following pictures show the plate I fabricated and the Dynon provided bracket.

Static Ports and Lines

Most of the Bearhawk builders I've spoken to say that the static ports are most effective further down the fuselage.  I've heard of some installed on the boot cowl, but I would think that prop wash would interfere.  I made tabs from aluminum angles and attached the ports from the rear secured with flush rivets.

Antenna Mounting Locations

Antenna's mounted on this ship will include:

• 1 Comm (Avidyne IFD-540)
• 2 GPS (Dynon 10" Skyview HDX & Avidyne IFD-540 Navigator)
• 1 ADSB in/out
• 1 Transponder
• 1 ELT (ACK E-04 406)

I personally prefer no hair on the top of my airplane, consistent with my head. 😎The only comm antenna is mounted at the rear of the tunnel.  (Fuselage is rotated on the rotisserie)

The T3 Tailwheel Dual Coil Over Shock Suspension

It's been described, "like landing on a cloud!"  Maybe.  But I am pretty sure the T3 Tailwheel Suspension System will make for improved tailwheel dampening on landings for the Bearhawk 4 Place.  The B Model Bearhawk kit comes with a tapered round spring tailwheel suspension.  The large end of the round spring fits into a receiver built into the kit frame.  The kit does not include the tailwheel assembly itself and the builder will need to source their own.  I purchased my tailwheel for the round spring suspension from Eric Newton, owner and builder of Bearhawk Tailwheels, LLC.

Eric Newton's (Bearhawk Tailwheels, LLC) tailwheel assembly mounted to the kit included round spring suspension.  

Mid Build Interview

Bryan Walstrom from the Experimental Aircraft Channel stopped by not long ago for an interview of the Bearhawk build.  Be sure to subscribe to Bryan's channel and see his other great interviews related to amateur aircraft building.

Instrument Panel

I received the new instrument panel from Aerotronics last week.  Jason Smith was the lead technician and his team did a fantastic job building my panel.  I requested this panel IFR capable.  The AviDyne IFD-540 (WAAS GPS) makes that possible. 

The EFIS is the Dynon Skyview HDX with its own GPS, engine monitoring, ADSB in & out, ADAHRS and Magnatometer for complete attitude instrumentation. 

We also opted for the iPad mount with cooling fan. 

It's beautiful!