FlyingRC.net is a
Top-Flite Giant Scale P47 Razorback – Segment 3
Filling up the fuselage
Text, photos and video by Tom Hintz
Posted – 2-14-2016
The elevators come already hinged to the horizontal stabilizers. Those are supported by a pair of aluminum spars that have a very tight fit in the stabs and through the fuselage. Once I applied epoxy to all of the parts they went together somewhat easier but still required some effort. The instructions say to hold these pieces steady with masking tape which I did even though once seated I could not get either stab to move outwards.
The vertical stab is factory installed but to keep the box a reasonable size hinging the rudder is left to us. Good-sized “Robart style” pin hinges are supplied and the necessary holes were drilled at the factory. I had no issues getting the rudder mounted with virtually no hinge gap because everything fit as it should with no “coaxing” or “fitting” needed. Top Flite® keeps impressing me with quality of the components and the preparation of the kit itself.
While the epoxy at the tail feathers cured I installed the servos for the elevators, rudder, throttle and tail wheel. The instructions include good photos of the servo layout as well as the servo arm lengths needed to get the control deflections specified by Top Flite® for the Giant Scale P47 Razorback. This layout along with the tubes that carry the control rods to the tail make installing the servos correctly the first time a snap. The servos all mount in an elevated tray that offers lots of room to store/hide the excess servo cable lengths beneath the servos and out of the way. The elevators and rudder are controlled using long steel rods supported by factory installed tubes within the fuselage. The rods are threaded on one end and plain on the other end so we can trim their length to fit and solder clevises on that end. Having the guiding tubes pre-installed simplifies this process and before long I had my rear control surfaces working. I made sure I had a good amount of initial throw on these surfaces. Later once the Top-Flite Giant Scale P47 Razorback is fully assembled I will go through all of the control surfaces a final time to set their travels per the instructions.
Retractable Tail Wheel
This was also a good time to install the Robart retractable tail wheel. Here again the quality of the Top-Flite Giant Scale P47 Razorback kit showed through. Despite the tail wheel looking like it would never squeeze into its cavity it did and it fit nicely. The only issue came when I installed the pull-pull cable system that steers the tail wheel. Incidentally, the pre-installed tubes for the cables made this one of the easiest cable-stringing jobs I have done.
Unfortunately, in the glee of the moment it never occurred to me to put the tail wheel down before I made the pull-pull cables. Later when I did try to lower the tail wheel it moved just a little and the automatic amp-out system in the Robart retract shut the motor off. The tail wheel needs to be down when you size the pull-pull cables so this was my bad all the way. I was able to turn the servo around and shorten the cables enough that they snugged up with the ail wheel down. Getting up to start working on the plane at 2:30am occasionally has some liabilities.
The instructions say to use a Y-cord connecting the rudder servo and the tail wheel servo but I decided to separate the steering servo to an open AUX channel and then set up a mix of the tail wheel steering servo to the rudder servo. People who are experienced with the Top-Flite Giant Scale P47 Razorback have been telling me that the tail wheel steering is sensitive so with this mix I can adjust the steering without changing rudder deflection.
The EME 60 was mounted using the stand offs that came with it. The Top-Flite Giant Scale P47 Razorback instructions call for a 171mm firewall to prop washer distance and these standoffs produce exactly that dimension. However, the carb is pointed back as on many single cylinder engines and there was precious little space between the carb and firewall. I considered adding 1/4”-thick spacers to move the EME 60 forward but that creates issues with fitting the cowl and setting the CG. I opted for boring a 1-7/8” diameter hole in the firewall aligned with the carb to let the motor breathe. A depression was also carved in the firewall to allow full motion of the choker lever. Then with the motor placement set I could install the throttle servo, throttle linkage and my hand-made choke rod.
The stock muffler that came with the EME 60 was too wide and would protrude through the side of the cowl. I had a Bisson wrap-around Pitts style muffler and that fit much better. Another plus for this muffler is that it has baffles in it that reduce the decibel level of the engine noticeably.
I am a huge fan of the RotoFlow fuel tanks so am installing a 24-ounce capacity RotoFlow tank along with their trick Quick Fire Fuel Balancer and Filter system. This filter is designed to hold ¼-ounce of fuel at the carb for quicker starts.
The Top-Flite Giant Scale P47 Razorback it offers a removable hatch that provides access to the fuel dot and On/Off switch. I also like being able to see the fuel tank so that during the initial flights I can better determine safe flight times with this combination.
I mounted the Quick Fire filter first because it was easier with the tank out. One end of the filter has two nipples and gets a line from the fuel dot and another to the fuel tank. The single nipple end has a line going to the carb. Nothing fancy in terms of the plumbing but I am hopeful the fuel this filter retains will make starting easier on those days when nothing seems to want to run.
I mounted the RotoFlow tank with a strip of foam secured to its bottom with double-sided tape. I also added two hook and loop straps to secure it. On these tanks I run the vent line around the top of the tank, secured to the hook and loop straps and then down to a vent dot on the bottom of the plane. Nothing fancy, just as clean and secure as I can make the installation. Plumb it decently and the RotoFlow tank will keep the plane flying reliably in virtually any attitude.
The Top-Flite Giant Scale P47 Razorback cowl is very well made from what appears to be quality fiberglass. It certainly not flimsy or cheap. The paint job is very good and the cowl arrived without damage. I recognized my inability to cut a cowl for exhaust with any degree of finesse so I have secured the help of Dennis Shaver, one of the finest builders/fliers in the RCWingers club I fly with.
The dummy engine needed to be mounted in the cowl before the cowl was mounted and cut to clear the exhaust so I put that part of it together. The dummy engine for the Top-Flite Giant Scale P47 Razorback seems to be made of the same thin plastic used to make many other f aux engines and interiors. I am certain that this plastic can see me coming and morphs itself into an exceptionally brittle state that splits, cracks and pretty much blows up when I try to work with it. That bit of paranoia probably insures disastrous results but I pushed ahead nonetheless. I was gratified to see that if you stand well back, the dummy engine looks sort of normal. I suspect that done by someone with skills this material can worked into a good looking f aux engine. If my faux engine looks funny to you it is all my bad.
Here endeth this part of the Top-Flite Giant Scale P47 Razorback build. I am getting down to the small stuff now but some that can still kill a plane if forgotten. That’s why I always stop at this point and go back at it the next day. I need to set the CG, set the throws, make sure I have everything in the DX9 the way I want it, confirm that my ignition kill works and then fire the motor up to be sure the fuel system is working without leaking. Always a good point.
See the previous Top-Flite Giant Scale P47 Razorback build and maiden stories
Have a comment on this Review? –Email Me!
All Flyingrc.net written, photographic and drawn materials are property of and copyright by Tom Hintz and Flyingrc.net 2013-2017. Materials cannot be used in any way without the prior written permission of the owner.