RCU Review: Hangar 9 33% Pwnee 80cc ARF


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    Contributed by: Andrew Griffith | Published: September 2012 | Views: 32920 | email icon Email this Article | PDFpdf icon
    Andrew Griffith
    (BarracudaHockey)

    Email Me




    Hangar-9
    Distributed through Horizon Hobby
    4105 Fieldstone Rd.
    Champaign, IL 61822
    Phone: (217) 352-1913

    www.hangar-9.com/


    The Piper PA-25 Pawnee was designed by Fred Weick in 1958 and was produced in a number of variants by Piper Aircraft Company between 1959 until 1982.

    Designed for the agricultural spraying industry, the Pawnee is simple, rugged, and easy to maintain.  The Pawnee features a single engine and fabric covered tubular steel airframe construction.

    Aside from the Pawnee's primary crop dusting duties the PA-25 has also served widely as a glider tow plane as well as pulling advertising banners.  One of my favorite airplanes, my earliest memories of the Pawnee are of one towing banners up and down the beach while spending the summers of my youth on the beach in Ocean City, New Jersey.

    Hangar 9 had already offered an IMAA legal 80" Pawnee that I had considered building when I got wind of the larger one third scale 80cc Pawnee that was on the horizon (no pun).  There are several members of our club active in scale glider towing and I fly both gliders as well as the tow planes.  As soon as I saw the previews for the new 33 percent Pawnee I knew that my search for a new glider tug was over.

    Our Pawnee will be powered by the recommended Zenoah GT-80 80cc twin.  RC Extreme Power provided an electronic ignition conversion for the review as well.  I've seen the GT-80 run very well with the stock magneto ignition but the the EI conversion is both lighter and the spring starter makes me a bit nervous.

    I often see two full scale Pawnee's in the Jacksonville area so there is no shortage of scale inspiration or subjects locally.  One is the primary tow plane for the local glider club and the other I see almost every weekend towing banners at the beach or around the Jaguars football stadium.

    Photo courtesy of WikiPedia


    • Accurate scale outline.
    • Functioning scale landing gear struts and shocks.
    • Flexible motor mounting setup allows choice of engines.
    • Flies like a big baby!
    • Outstanding covering job.
    • High amount of pre-fabrication
    • Massive 2 piece aluminum wing joiner.
    • Easy access to radio system
    • Wing installation and removal is fast and easy.
    • Even with some added lead, a pilot figure and tow release, the Pawnee still came in UNDER the recommended weight limit.


    • Wing jury struts required some modification to fit correctly.
    • Wing anti-rotation pin holes in fuselage were not aligned and required some work to get the wings to plug in and the incidence correct.


    Skill Level:

    Time Required to Build:

    Frustration Level:

    What do these ratings mean?



    Name:33% Pawnee 80cc ARF

    Price: $1249.99

    Stock Number: HAN5190

    Wingspan: 130 in (3.30m)
    Wing Area: 2620 sq in (169 sq dm)
    Weight: 34.0-38.0 lb (15.5-17.3 kg)
    Length: 94.0 in (2.40m)
    Center of Gravity (CG): 8.5" to 9" from the leading edge
    Radio Used: JR 11X 2.4 with Spektrum AR12110 DSMX Power Safe Rx
    Servos Used: (9) Spektrum A6020 Digital Servos.
    Battery Used: (2) WrongWay RC A123 Nano Phosphate 2300Mah
    Channels Used: 7 total - Elevator, Aileron, Throttle, Rudder, Flaps, optical kill switch, glider release. (On the review plane each aileron, elevator half, and flap is on its own channel and mixed using the 11X channel mate feature)
    Weight Range: 34-38 Lbs (15.5 -17.25kg) 
    Flying Weight: 35lbs 5oz ZFW (16kg)

    Options Added: Red Aero RC Pilot figureRC Extreme Power electronic ignition conversion kit, IFlyTailies glider tow release.

    Control Throws: HIGH

    • Elevator: 1.75" (45mm)up /1.25" (32mm) down
    • Ailerons: 1.5" (38mm) up/ 1" (26mm) down
    • Rudder, right/left: 2" (52mm)
    • Flaps: 2" (52mm) Max, 1" (26mm) mid

    Items Needed To Complete

    • 5-channel radio (min) w/ Receiver
    • 60-100cc 2-stroke Gas Engine w/ Propeller
    • 2700mAh receiver battery
    • 2000mAh ignition battery
    • 8 high-torque servos
    • 30-Min Epoxy
    • 3 3/4" Spinner
    • Medium and thin CA and Canopy glue
    • Common modeling hand tools
    • Thread Lock





    I was a little worried when Fed-Ex called and asked if a tractor trailer could get into and out of my street to deliver a package!  The driver seemed surprised for some reason when he realized he was delivering a model airplane, I think he thought it might have been an ultra light! 

    The PA-25 Pawnee arrived in three very large boxes.  The painted fiberglass cowl occupied it's own box, the wings were in another, and a box the size of a coffin contained the fuselage, tail feathers, and everything else to assemble the plane.

    I did a quick inspection for damage and finding none I set about making sure everything I needed was present and accounted for.

    The Pawnee is constructed of a mixture of laser cut balsa and lite-ply.  The wing features a flat bottom airfoil and curved fiberglass wing tips.  The fuselage has hatches in all of the right places including the main cockpit windows that are hinged for easy access.  There are two hatches near the tail that house the three tail servos and a large battery compartment that appears that they were expecting the Pawnee to be nose heavy.  It's a good thing because my dual battery packs ended up back there along with some lead.  The advertising for the Pawnee indicates the forward hatch is to access the fuel tank and the tank is indeed right there at the CG, but it's a good thing it's there as removing the hatch is the only way to access the forward two wing bolts.  The hatch is pinned at the front and held in place by two button head hex screws so it's easy to remove for tank or wing bolt access.





    There is a lot of work already completed for you.  The ailerons, flaps, and elevators are already hinged for you.  Much of the articulated scale landing gear is assembled as well.  The motor box features a laser etched template with the mounting bolt locations for several popular engine choices including the recommended GT-80 already marked. 

    The engine mounts to the motor box which then can slide in or out like a drawer to the proper position to accommodate the length of the engine of your choice.  All of the included hardware is of excellent quality and of adequate size for the giant Pawnee.  The size of the Pawnee was intended to give the builder a wide choice of engines and Horizon has flown the Pawnee on all of the appropriate engines that they sell as well as the DA-100.

    The fuselage and wing is covered with white Ultracote with red and blue trim in the scheme used by the Wabash Valley Soaring Association.  All of the decals and trim are already applied.  The trim paint on the cowl matches the Ultracote perfectly in color and lines up exactly.

    If this is your first crack at giant scale, you shouldn't have any problem getting the Pawnee ready for flight.  Though if this is your first giant scale, please have your aircraft checked over by someone with experience with large planes as this large aircraft could do significant damage to persons or property if something were to go amiss.


    Manual


    The manual for the Hangar 9 Pawnee is exactly as I have come to expect from my experience with Hangar 9 models, that is to say, it's outstanding.  The well written manual has is photo illustrated at nearly every step and includes mechanical drawings where needed.

    The manual covers everything that I think is essential for a great manual: a complete inventory, concise instructions, clear photographs, center of gravity, control throws, and most importantly product support contact information.

    I always make a habit of checking online to see if there are any updates for the instructions for the kit I'm working on but as of this writing none were available for the Pawnee.  As soon as I learned that I would be reviewing the Pawnee I downloaded and examined the manual and I didn't find any areas I thought would benefit from freelancing the assembly sequence.

    Download the Pawnee Manual here

    (2mb - requires Adobe Acrobat Reader)









    Our Pawnee will be assembled with all of the Hangar-9 recommended components with just a few minor deviations.  I'll note any deviations as we go along. Where adhesives are required I'll be using Zap brand CA and Pacer Z-Poxy 5 and 30 minute epoxies and RC-56 canopy glue.  Remember that  when you are working with modeling chemicals and adhesives be sure you have adequate ventilation.

    When building or repairing a gas airplane, always use thread locker on ALL metal to metal connections!

    Before you unpack anything make sure you have enough room to work on the Pawnee.  The wing panels are 60" long each with a 20" chord, and the fuselage is nearly a foot wide and over 90" long.

    Once I had my work area laid out I set up a new model in my JR 11X 2.4gHz radio and bound it to a Spektrum 12210 Power Safe receiver.  The 11X (as well as several other of the high end radios) makes setting up multiple servos for one control a snap with the surface mating feature.  The Pawnee uses 2 aileron servos, 2 flap servos, and 2 elevator servos.  Using the mating feature eliminates setting up a program mix and ensures that any trim or mixing applied to the master channel affects each surface equally.   Having the radio ready to go allowed me to set up each control surface as the build moved along.






    Wings

    The first step to building the Pawnee is assembling the massive wing panels.  Remove and mark each hatch for location and orientation and use the provided hardwood blocks to install the servos.  If you're using the Spektrum servos and JR arms the servo arm comes with a hex head screw that replaces the easily stripped phillips head screw provided with the servo.  To complete the installation I used the hex screw from the servo arms and the star washer from the hardware provided with the servos. 

    When installing the aileron servos the recommended servo extensions are perfect.  Also there is string provided to pull the aileron servo extensions through the wing.  Use some heat shrink or dental floss and secure the servo extensions to the servo wires so nothing becomes disconnected at an inopportune time.

     





    The flap servos didn't get the factory string and I think there's a misprint in the manual because the indicated 3" extension for the flap servos is barely long enough to reach the wing root and I replaced them with 12" extensions.  I could probably have gotten away with 6" extensions here but the 3" were definitely too short.  I used a piece of music wire with a hook on the end to fish the wires through for the flaps but a string and large nut would work just as well as it's a straight shot through the ribs to the wing root.

    In the "wow that's a nice touch" department, strings are provided to pull lighting wiring through the front of the wing if you wish to add a scale light kit to your Pawnee.  I have a set of E-Z Lights on order from East Coast Vario but they were not received in time to make the review.  I did glue the included clear lenses on with RC-56 canopy glue so that they would be easy to remove once it was time to add the lights.

     





    Installing the 4 control horns is straightforward.  I found it convenient to have an electric screw driver on hand to run the counter-sunk screws through each control surface.  These call for epoxy and whenever you use epoxy around the Pawnee's nice white covering job, take care to have some alcohol and clean paper towels handy to remove any excess glue before it has a chance to set up.

    The wing jury strut installation is where I ran into one of the very few problems I had with the kit.  With the attachment points installed on the wing as indicated, and the struts oriented correctly (I checked several times to make sure I wasn't doing something wrong), the strut simply would not sit far enough into the mount for the screw to clear.  I reluctantly took the struts to my bench grinder and had to remove about half of the material between the bolt hole and the bottom of the strut so that the bolt would pass through both the mount and the strut. 

    The Pawnee kit uses a set of bolts, fuel tubing, and cotter pins to attach the struts to the wing.  The fuel tubing slips over the bolt and when the bolt is passed through the hole and the cotter pin is installed, the tubing compresses and keeps everything tight.  The same connection is used to attach the struts to the fuselage during field assembly and I found it to work very well.  In fact, I saved one of the clear servo boxes and carry the bolts, cotter pins, wing bolts, and front hatch bolts all in one place when the Pawnee is disassembled for transport.

    When you have everything connected, install the strut covers with RC-56, tape them down with painters tape and when the glue is dry the wings are done!

     





    Fuselage/Tail

    Generous hatches are provided at the rear of the plane for both servo and battery access. The Pawnee uses one servo for each elevator half and a pull pull system for the rudder.  Considering where the CG ended up on my plane even with the heavy spring starter components removed, I'm glad they designed the plane with rear mounted servos in mind.  The battery tray was just an added bonus or I surely would have been fabricating one back there.

     





    When you build the pull pull rudder cables the manual recommends a crimping tool for the brass sleeves.  I didn't have one handy so I simply used vice grips.  One thing I did end up doing that made it harder on myself than I needed to was to try to use the least amount of cable possible on the servo end to make the connections.  I need not have worried as there was plenty of cable left over and its easier to have a little more cable and cut off the excess when you're done.  Take care to thread the cable fittings into the ball link ends equally so you end up with the proper geometry when you're done.

    If you read ahead in the instruction manual you know that you're going to install the tail struts to the two forward servo hatch bolts later on.  You can either fish two of the brass strut fittings out now and install them, or leave them for later.

    When you're done buttoning up the tail it's time to move on to the scale landing gear. 





    Hangar 9 took the time to faithfully reproduce functional scale landing gear for the Pawnee that replicates the real thing while being very easy to assemble.  There is no bending, soldering, or fussing; the whole thing goes together like an erector set.  Add the large tires and the Pawnee should be able to handle almost anything that resembles a runway.

    About the only advice I can give you is to make sure the bolts are tight enough so there's no free play, while not so tight as to prevent the gear from freely articulating.  Where the shocks mount to the frame up inside the fuselage, use a good thread locker and use caution not to over tighten the bolts where they thread into the blind nuts.
     

    The scale landing gear is one of the features that has gotten the most attention from folks looking (drooling really) over the Pawnee at the flying field.  The shock absorbers are so cool it's a shame they are buried up inside the fuselage.

     





    On the subject of easy to assemble, the stabilizer and elevator installation is about as simple as it gets.  The elevators are pre-hinged at the factory like the flaps and ailerons so that chore is already done for you.  Simply fit the tubes in the correct holes (short one to the front) and bolt the stabilizers in place.  I double checked the incidence when I was done and they were square and dead on.

    Assemble the elevator pushrods just like the ailerons.  The Hanger 9 ball links, standoffs, and turn buckles are of very high quality and I haven't had any issues with the hardware in this kit.  Though it wasn't specified in the manual, I went ahead and applied epoxy to the bolts here as well where they went through the elevators.

    When assembling the elevator servo arms, make sure everything is sub-trimmed so that the arms are 90 degrees to the servo body on both sides.  If you try to eyeball this you're likely to have uneven elevator throw.  Attention to detail here will pay dividends later on.





    The tail wheel bracket and hardware appear robust enough to take the rigors of every day Pawnee flying.  The rudder and servo are isolated from the tail wheel by the use of springs.  The springs provide tail wheel steering while not passing the shocks of landing on to the servo gear train.

    When you're done installing the tail wheel it's time to make up the eight tail strut rods.  I'm not sure if they are functional on the model but while it's a little bit tedious getting them all tight enough not to rattle while not being too tight, it's worth the effort because they really do look good when you're done.  They are a scale detail that is included on the full scale Pawnee in any case.

    It's time to prepare the rudder for installation.  The rudder is the only surface where you have to install and glue hinges but the holes are already drilled for you.  In order to prevent inadvertently gluing the hinges I coated the pivot points with Vaseline petroleum jelly.  Also, since you're going to use epoxy to install the hinges you can work with one side at a time to make sure the alignment is perfect.  I glued the hinges into the rudder and when they were dry I installed the rudder to the fin.

     










    RC eXtreme Power Electronic Ignition Conversion




    I had complete confidence in the Zenoah GT-80 as it came out of the box but I had worked with Milton from RCXP before on gas engine projects and when I told him what I was working on he offered me one of his electronic ignition conversions.  This allows the big twin to be flip started, and puts the engine on a weight loss diet as well.  The coils, spring starter, large flywheel, and one way bearing all come off the engine and an electronic ignition module, sensor, and flywheel from RCXP get installed.

    All of the parts needed for the conversion are included in the kit and you get a free ignition test unit.  The ignition also has a lead so you can attach a LED tach (sold separately) to the unit and mount it in the aircraft if you wish.  The conversion took me about 30 minutes as the big Zenoah wasn't in any hurry to part with it's stock flywheel.




    The RCExcel ignitions are sold by RCXP with a 2 year warranty covering defects and a 2 year half price crash replacement warranty.  The ignition conversion also allowed me to install an RCXcel optical kill switch which allows me to shut down the engine from the transmitter as well as killing the motor if the radio system goes into fail safe.

    One of the nice features of the magneto system is that it eliminates installing and charging an ignition battery.  Since I was planning on installing dual receiver batteries and one was going to do double duty powering the ignition I didn't consider this an inconvenience.





    Zenoah GT-80 Engine Installation


    Peter Goldsmith and Hangar 9 designed the Pawnee to work with a variety of engines from the G62, Evolution 80, GT-80, to a DA-100.  The unique sliding drawer style engine mount allows you to get the proper alignment with very little work.

    Our review model will be powered by the Zenoah GT-80 twin.  This opposing cylinder simultaneous firing twin ran smooth and pulled the Pawnee around with authority.

    The laser etched mounting template provided in the kit shows proper mounting locations for the various engines. Since this is the engine recommended for the Pawnee all of the photographs in the manual are based on it.

    The first step is to locate and drill the mounting holes, install the blind nuts and mount the engine to the sliding drawer.

    Slide the engine and box into the drawer and mount the cowl.  Then put the spinner backplate in place and slide the engine until you get the proper clearance.  Without disturbing the motor, remove the cowl and mark location on the motorbox. 

    The instructions say to epoxy the motor box together but I also drilled and glued in 4 hardwood dowel pieces to pin the box in place.  Since it swells up as it dries I used carpenters wood glue to install the pins then sanded them flush to the motor box.  This was for my own peace of mind since I plan on towing some expensive gliders I want to make things as bullet proof as possible.

    Zenoah GT-80 Twin Spotlight

    Overview:

    The GT-80 features an increased bore diameter, increasing displacement to 80cc�s and boosting horsepower to 5.5. Dual rings on each piston give a superior seal, while the self-contained Quartz ignition gives a reliable spark without the hassles of charging ignition batteries. Starting�s a breeze with the rear-mounted spring starter, just wind the prop clockwise one turn then release. And this simultaneous firing twin runs so silky smooth from idle to full power, you can forget about vibration- related airframe and electronic problems.

    Key Features:

    • 4.88 cubic inches of power in a smooth running twin

    • Ball bearing-supported crankshaft

    • One-piece chromed cylinders

    • Magneto-driven CDI ignition system

    • Delivers a whopping 6 horsepower to drive a 24x10 APC at 7500 rpm

    Specs:

    • Type: 2-Stroke

    • Bore: 1.60 in (40.50 mm)

    • Stroke: 1.22 in (31.00 mm)

    • Displacement: 4.88 cu in (80.0 cc)

    • Practical RPM Range: 2,000 - 17,000 rpm

    • Crankshaft Thread Size: 1/4 x 24

    • Total Weight: 108 oz

    • Engine Only Weight: 123 oz

    • Muffler Weight: 15 oz

    • Practical RPM Range: 2,000 - 17,000 rpm

    • Prop Range: 22x12 - 24x10

    • Fuel: Gas/Oil Mix

    • Mounting Dimensions: 192 x 257 x 205 mm

    • Cylinder Type: Twin Chrome Plated, Ring

    • Carb Type: Walbro WJ-64

    • Crank Type: Ball bearing

    Warranty:

    Exclusive Warranty- Horizon Hobby, Inc., (Horizon) warranties that the Products purchased (the "Product") will be free from defects in materials and workmanship for a period of 3 years from the date of purchase by the Purchaser.

    Download the manual in PDF format - Click here





    I have been using rubber sealing washers to mount fiberglass cowls and in other applications on gas airplanes for some time now.  I was really glad to see that Hangar 9 included sealing washers to hold the cowl and hatch of the Pawnee in place.  These hold well and don't eat away at the fiberglass and most importantly; they stay put.

    If you're running the Zenoah engine there is a cut out for a throttle servo right on top of the motor box..  To get proper throttle geometry my engine guy ended up making an extended throttle arm (it pays to be friends with a machinist!).  I have always found the carb arms on our gas engines annoyingly short and nearly always install some sort of extension so I get increased end points for better throttle resolution.

    To actuate the choke I considered adding a separate choke servo underneath and I had one channel left on my 11X but in the end I elected to stick to the manual method. 

    Though it's not documented in the manual, located in the fuel tank access area are servo cut outs that are provided if you use a different engine and the top mounted throttle servo won't work for you.  They also provided a pushrod for that purpose.  I purloined that pushrod, cut it off, and ran it out the bottom of the cowl and attached it to the choke actuator.  Its nearly invisible and works like a champ.  When I found out I was nose heavy even with the removal of the spring starter parts and two batteries in the tail, I was glad I didn't add any more weight to the engine compartment.





    The stock GT-80 magneto plug caps will fit completely inside the cowl but the electronic ignition conversion included longer plug caps that required a little cowl hacking.  When the plug cap was clear we went ahead and mounted the mufflers, made a template from manila folder, and cut out the cowl for the exhausts.  There's a pretty generous area between the bottom of the fuselage and the bottom of the cowl so I thought we had enough exit area for the cooling air to flow out of the cowl.

    Tru-Turn provided a gorgeous aluminum 3 3/4" P-51 style spinner which looks terrific on the Pawnee and matches the cowl perfectly.  They also sent along the proper propeller adapter bolt.  The drive plate on the Zenoah has pins that fit into the predrilled hole in the spinner back plate and the entire system has been flawless.

    The fuel tank was already assembled and mounts in the generous front area right on the center of gravity.  I mounted the tank on self adhesive foam insulation strips available from any home supply store.  The only modification I made was to cut the feed line to the carb and install a Tee fitting along with a Gem-Dot machined fuel dot.  Use tie wraps or safety wire on all of the connections as tygon fuel line can swell over time.  The vent line was routed to the bottom of the cowl and I installed a rubber grommet for it to pass through.

    When the time came to put everything together I found the second area of my kit that needed some extra work.  With the aluminum wing joiner installed on the right wing and the wing slid up to the anti-rotation pins, only one pin would seat, the other pin wouldn't align.  I had to use a Dremel tool and a sanding disk to open up the hole, top to bottom a bit.  Fore/aft alignment was fine.  The left wing was out even farther.  Before I set to work on the holes I used a incidence meter to see whether the front or back needed to go down a bit.  It turned out to get equal incidence I needed to enlarge the back hole slightly.





    Radio Installation

    With the engine installation completed all that remained was to install the rest of the radio equipment and balance the plane.  I have been using A123 battery packs from WrongWayRC for some time in my aerobatic gas planes so I contacted Richard and discussed the power system for the Pawnee.  We decided to go with dual 2300Mah A123 battery packs feeding the R12110 DSMX Power Safe Reciever.  In addition one of the packs will have an output that goes to a JR HD charge switch, then to the RCExcel Optical Kill Switch, to a WrongWayRC ignition voltage drop diode, then on to the ignition.

    The Power Safe receivers from JR/Spektrum provide a reliable battery redundancy system.  The switch itself is unique as well, when the switch is closed a small current goes through the switch and this holds the receiver in a power off state.  When the switch is open the receiver is powered on.  Since the failure mode of most switches is open, if the switch fails the power to the receiver stays on, which sure beats the alternative!  The other side of that coin is that when you're storing the airplanes, the batteries feeding a power safe receiver should be disconnected as that small current will drain your batteries down over time.

    Since only high rates were specified in the manual I made a few guesses as to low rates.  Flight testing proved I didn't need them and I have been flying in the recommended rates since half way through the first test flight.  I did add 35 percent expo to everything to give the Pawnee that smooth scale flying look.  Flap throw was set per the manual with .7sec delay set between steps on a three position switch.

     





     

    An RCExcel optical kill switch was installed and the receiver was bound such that the throttle was set to full low and the ignition was set to kill in the event of a fail safe event.

    There are switch cut outs provided all over inside the Pawnee.  You merely have to decide where you want your switches based on your particular radio equipment layout.  One of the things I really liked is that the switch cutouts land squarely on the blue stripes so they don't stand out like sore thumbs on the white.  I installed the soft switch for the Power Safe receiver and the JR Heavy Duty Charge Switch for the ignition system.  Hangar 9 provided both the large and small switch cutouts so it's clear the equipment flexibility extends to the radio system as well as the engine mounting.  In addition to the switches I drilled a small hole and mounted the LED indicator light for the electronic ignition system and the Gem-Dot fuel dot.

    The last thing to install was the Red Aero RC pilot figure.  I fabricated a deck made out of plywood and epoxied it to the bottom of the cockpit window rails.  The pilot bust was secured by making a plywood stringer and attaching it with self tapping wood screws.  If I had realized in advance I was going to be making this deck in the cockpit, I would have mounted the switches for the radio on the the deck the pilot is sitting on to clean up the outside of the fuselage.

    It came as no surprise that it took two of us to balance the big Pawnee.  With the batteries initially sitting below the cockpit the Pawnee was seriously nose heavy.  I soldered up extensions for the batteries and installed them in the rear access hatch.  This was a lot better but it still required 3 full sticks of Kwik Stik lead as far back as I could hide them.





    Tow Rig Installation

    Since the Pawnee was going to be doing duties similar to its full scale counter part, IFlyTailies.com provided a glider tow relase for the review.

    The tow release is made in Germany and appears to be very sturdy and very high quality.  This release is unique in that it is a two step release that can be used for a number of applications aside from glider towing or could even be used for towing more than one glider.

    Installing the tow release in the Pawnee meant removing two bays of covering on the bottom and some of the foam that is applied to the balsa sheeting on the turtle deck.  Once we got down to bare wood where we were going to glue, we built a bulkhead and supports out of plywood.  Once the bulkhead and support were glued in place we fabricated a mount for the servo out of plywood.

    When everything was checked and double checked I recovered the bays and headed to the field to do a day of glider towing.

    While the above steps make it sound simple, it took two of us about 8 hours of work to custom fabricate, glue, and test everything related to the glider tow release system.  Since this was beyond the scope of assembling and flying the Pawnee for the review, I did not count this time towards completing the project.  Indeed, the review flights were done the weekend prior to the installation of the tow release and the glider towing portion of the review.  Thanks goes to my engine guy Joey for his help and expertise in modifying the Pawnee for the tow release.

    The Pawnee is a natural glider tug as you will see from the videos we shot with the GoPro HD camera.  I have flown a number of tow planes and the Pawnee gives a very stable and predictable tow and it's generous fuel tank has plenty of capacity for knocking out several tows before needing to land and refuel.  The day we shot the video we were towing a quarter scale KA8B built and flown by Steve Betts of Jacksonville.  We have a number of scale gliders in our club so the Pawnee will be doing regular tow plane duty.



    Assembling the Pawnee at the field consists of removing the tank hatch, sliding the unique aluminum wing joiner into each wing half, fitting the wings to the fuselage, connecting the 4 servo cables, and installing 4 each wing bolts and strut bolts and cotter pins.  When you're done you have to reattach the tank hatch and you're ready to pump fuel.

    New review planes always attract attention but it's looks and size make the Pawnee the center of attention almost every time it's at the field.  Be prepared to answer questions and wheel the Pawnee out to a nice clear spot for pictures.  The Piper Pawnee attracted a lot of attention any time I took it out of the trailer.  How big, what engine, how many channels, how much does it cost?

    Since I was starting with a brand new engine I mixed up a gallon of 32:1 Lawnboy oil to let the cylinders heat up and seat the rings.  With the choke on, ignition on, and the throttle at about 1/4 the GT-80 popped after about 8 flips, with the choke off it started on the third flip and was purring like a kitten without touching the needles.  I ran it for a few minutes, shut it down, checked everything over and refueled and did a few taxi tests.  The Pawnee handled well in the grass but I would prefer a bit stiffer springs because the steering felt a bit "mushy" on the asphalt.

    With the Zenoah idling reliably and providing what felt like plenty off pull, I lined the Pawnee up on center line and advanced the throttle.  The tail wheel was off the ground almost instantly and the rudder has authority very quickly.  The takeoff roll was short and the Pawnee was climbing away in no time.  Unfortunately as soon as I turned down wind one of the doors was flapping in the breeze and shortly thereafter departed the plane, I turned final and did a no flap landing to see what happened.  It appears on my kit that the stringer on the bottom of the door didn't have enough glue and the stringer and hinges were still attached to the airplane.  The latch at the top of the canopy stayed put, everything else was on the hill.  We retrieved the part, made some field repairs, and I lined every window joint with RC-56 canopy glue.  Nothing else came loose or had any issues for the rest of our testing.

    With the cockpit door fixed the rest of the flights that weekend were much more enjoyable.  The Pawnee flew like a low wing Cub.  The GT-80 pulls it around with authority with the recommended 24x10 propeller.  Low passes at full throttle then pulling up into a hammer head stall turn like the crop dusters look great and the big twin really sounds the part. 

    I fly a little of everything but high performance is my thing so I couldn't help but try a few aerobatics with the Pawnee.  Rolls took surprisingly little down elevator, so little that my first attempt had the nose and wheels headed skyward because I way over estimated the amount of down to keep the nose level.  The ailerons are big so it has plenty of control authority but the wings are huge so don't expect it to roll like an Extra.  While the Pawnee certainly doesn't have unlimited vertical it will pull decent looking up-lines and do nice big loops.  Wingovers and hammer heads look great as well.

    I took her up high and pointed the Pawnee into the wind, dropped the throttle and added elevator to see where she stalled.  Anyone that flies large planes knows that the bigger they are the closer they mimic the real thing and the 33 percent Pawnee is no exception.  If you get it slow enough, it will drop a wing.  You have to really be mushing along before that happens and the Pawnee will let you know you're going too slow well before you get into trouble.

    It was time to set up for my first landing so I dropped the flaps and noted that the promotional buzz was true, there is no trim change at all when the flaps come down.  The Pawnee settled on the runway on it's main wheels and came to a stop in about a hundred feet.  Wheel landings and three point landings both look great and three point landings produce almost zero roll out.  When the glider tow line is attached I like to drop full flap, come in steep and flare into a 3 point landing so I don't have to taxi back to attach the next glider in line.

    As the afternoon grew late I spent most of a flight doing one of the things the Pawnee does best; touch and goes.  I tried no flap approaches and landings, half, and full flap.  The more flaps you use the steeper you can come in without building up too much airspeed.  Come in too fast and the Pawnee will float to the next county before it settles down.  I had a dead stick or two while breaking in the motor and had side slip in to kill altitude and not over run our field.







    The Piper PA-25 Pawnee is a great subject for a civilian scale model and Hangar 9 has done an outstanding job with this kit.  The covering, fit, and finish are outstanding.  The Pawnee can fly well on a number of engines from scale flying to enough power to take off an accelerate straight up depending on your engine choice.  The accurate scale outline and open cockpit area would make an excellent starting point for a scale project.
    If you're new to giant scale, the Pawnee is a great kit to start out with.  The roomy fuselage has easy access to all of the internal areas, much of the work is already done for you, and it's flying characteristics will get you comfortable flying large airplanes quickly.  I invited a variety of people at my club to fly the Pawnee and everyone had the same smile on their face after just a few minutes.
     


     


    Hangar 9 Models
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    Zenoah Engines
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    The comments, observations and conclusions made in this review are solely with respect to the particular item the editor reviewed and may not apply generally to similar products by the manufacturer. We cannot be responsible for any manufacturer defects in workmanship or other deficiencies in products like the one featured in the review.

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