Thursday, August 17, 2017
Home » Bonus Content » ECOMRC Piper PA-25 Pawnee

ECOMRC Piper PA-25 Pawnee


DISTRIBUTOR: Troybuilt Models

TYPE: Sport-scale ARF

FOR:  Intermediate sport-scale pilots

PRICE: $429.95


Eight high-torque servos, minimum of a 5-channel radio system, 30-40cc gasoline engine, suitable propeller, spinner


Sullivan smoke pump, smoke muffler, pilot, volt watch, engine kill switch, scale instrument panel


Familiarize yourself with the manual. There is not a lot to read, just a lot of pictures. Get a feel for the assembly process and use common sense. When it comes to the hardware I separated all the nuts and bolts by size in 2oz mixing cups. Saves time and you don’t have to rummage through the whole bag every time you need an item. The aileron, flap, rudder and elevator hinge spots are all pre-slotted. You just have to glue the hinges in place. The control horns for the ailerons and flaps had to be adjusted. The shafts were too long.  If not shortened, they would have poked through the top covering. I cut about ¼ in. off the ends before gluing them in place.

The rudder control horns also had to be modified along with the rudder itself. The slot in the rudder was too narrow and not long enough to receive the sandwiched shafts of the control horns.  The Dremel was pulled out to enlarge the slot to receive both shafts. They are sandwiched in because of the pull-pull set up. When installing the tail wheel assembly it interfered with the bottom hinge, so I had to relocate the hinge. I didn’t quite understand the section on wing assembly and the attachment of the wing to the fuselage. It starts off by having you check the wings dihedral and its squareness to the fuselage. I can’t see how one can change the dihedral because the wings slide into a wing tube with preinstalled pegs to set the angle of attack. So when the wing is plugged in, nothing can be changed. The manual also wants you to glue the wing permanently to the fuselage. How are you going to transport the plane? This is where you have to use common sense or you’re in trouble. It’s like building a boat in you basement and you can’t get it out when finished! When you attach the vertical stab make sure you remove the covering where it’s going to be glued to the fuselage so you get a good glue bond wood to wood.

In the installation of the G26 I used a method I feel puts less stress on the air frame. The manual suggests mounting the engine on standoff brackets at the four corners of the engine back plate. I don’t like them because of the torque the engine puts out which is then transferred to the air frame. The extenders act as levers increasing the torque pressure thus increasing the energy transferred to the air frame. This can cause premature fatigue to parts of the air frame. I use pine block stock and plywood to get the correct distance to the tip of the cowl. The block is glued to the fire wall. The block spreads out the torque load which minimizes torque stress.

Working with the canopy you have to treat it with loving care when cutting off the excess to fit on to the fuselage. The canopy is very fragile and can crack easily. The cowl placement also takes planning and patience with a sound game plane. The blind nuts have been factory installed so the cowl has to be in the correct position when you drill the holes in the cowl. I apply painter’s tape on the side of the fuselage and run it up past the blind nut. Then a black dot is applied at the center of the blind nut. The tape is then peeled back and the cowl is then placed in the proper location. The tape is then folded back into its original position over the cowl. At the black dot I then drilled a 1/16” hole then inserted a pin to make sure I was in the blind nut hole. Once all four holes were drilled the cowl was removed and the holes were opened up to receive the 3mm nuts.

The landing gear needed some tweaking at the ends. The ends had burrs on them which prevented the wheel collars from slipping on the axel, so out came the Dremel to smooth the ends.  Also the wheel holes had to be enlarged by one bit size so they would spin freely on the axel.

In setting up the flaps, I used a Y harness 6 in/ reverser distributed by Horizon Hobbies. This saves a channel on your receiver and works well.

The installation of the Sullivan smoke system was a snap. The instructions are easy to follow. They suggest you blow into the check valve to get the proper oil direction flow. On occasion I’ve been accused of having a lot of hot air! I couldn’t get air to go through in any direction, so I put the check valve in line and let the pump figure it out. In my first attempt of course it was backwards. It’s recommended to set the system up outside the plane and run it to get all the bugs out of the system. All worked fine on the first try.  What a great feeling.  I used a Sullivan 16 oz boat fuel tank which was thin enough to place along side of my fuel tank. You couldn’t ask for a better fit.. Saddle tanks can also be used in tight places. The system was then placed into the fuselage and hooked up to the Bisson smoke muffler. The on-off switch is the landing gear switch on my radio.

To get the wing tube to slide onto the fuselage tube with little or no resistance, I had to sand the inside of the wing and fuselage tubes. To accomplish this I used a dowel with sand paper wrapped around it. It took about one hour to enlarge the tubes in both wing panels and fuselage so they would slide on and off the spar tube easily.

To establish the correct CG the fuel and oil tanks were installed over the CG in the fuselage. I hate to add lead to a plane and I work my best not to. If I’ve need to add weight, I might as well use something worthwhile like extra juice for the servos and smoker. I placed two JR 2800Mah batteries under the pilot in the bottom of the fuselage. Not an ounce of lead had to be added to the craft. Finally, to dress up the cockpit, I inserted a Vintage plane pilot which just looks like me. In my shop I found a scale like instrument panel and after some trimming it popped into place. Some grey Naugahyde was added to finish off the interior. The high clear canopy really allows the details to stand out. Having some black tread traction tape which is used on stairs, I placed a strip on the wing walk area land it looked just like the full scale wing walk area. These add-ons really dress up the plane and makes it one of a kind at the field. On a field note, bring extra 3mm bolts, so if you lose one in the grass or in the air your flying day is not cut short.

During the construction phase there were a couple of areas that could be improved. These problems didn’t take any aesthetics away from the finished product. One just has to use his building expertise to complete the construction area. First of all the shafts of the control horns for the flaps and ailerons had to be shortened so as not to poke through the top surface.

The rudder shafts also had to be shortened, and where the shafts were to be inserted into the rudder, that opening had to be elongated and widened so they could be sandwiched together for the pull- pull set up.

Another area that required tweaking was the carbon fiber tubes. The carbon fiber spar tube did not slide easily into the fuselage and wing tubes, so I had to find a dowel that would  allow me to wrap sandpaper around it, so the inside of the tubes could be widened in the wings and fuselage. It took me about a hour of sanding to get to the point where I could slide the tube into the fuselage and wings with minimum resistance. Other than those problems the plane went together well.  When the plane was finally completed with all my add-ons, it looked great .