TOP FLITE P-47D THUNDERBOLT GIANT
PRODUCT TEST REPORT
by Dick Pettit
Type: Giant Scale Warbird
Manufacturer: Top Flite Models, PO box 788 Urbana, IL 61803
Distributor: Great Planes Model Dist.
Suggested: Retail Price $429.99
Wing Span Advertised: 85", Measured 85 1/4"
Wing Area Advertised: 1327 sq. in., Measured 1347.5 sq.in.
Airfoil: Semi symmetrical
Fuselage Length: Advertised 75-1/2", Measured 76"
Req. Control: 4-6 (Ail, El, Rud, Throt)
Req. Engine: 2.1-2.8 glow, or 2.5-4.2 gas
Req. Weight: 20-22 lbs
Basic Materials: Balsa and plywood
Instructions: 64 illustrated pages
Plans: Two rolled sheets
Hardware Included: Control linkages, throttle linkage, formed plastic cowl, canopy, accessory parts, screws for servo plates, cowl mounting, and wing bolts.
Items Needed To Complete: Spinner, propeller, engine, engine mount and mounting hardware, fuel tank and lines, retracts system, main and tail wheels, retainers, hinges, control horns, 6-7 CH radio system with 10 servos, high capacity receiver battery, covering, finishing materials, and adhesives.
Finished Weight: 21 lbs
Wing Loading: 35.91 oz/ft²
Engine Used: US41 2.5 c.i. gas
Prop Shaft to Ground: 14" (held level)
Fuel Tank Used: Sullivan 21 oz
Radio Used: JR 8103 PCM with seven HD and three standard servos, and a 5 cell 2000 mAh battery.
Covering/Finishing Used: Goldberg UltraCote and Ultra Paint
Special Items: Robart retracts and air system, Du-Bro hardware and wheels, Tru-Turn prop hub, Stan's Fiber Tech fiberglass cowl and accessories, and the Top Flite cockpit kit
CHEERS: Great plans and instructions; sturdy construction design; good quality parts and materials; looks great on the ground...spectacular in the air; excellent flight characteristics; a great first giant scale warbird for an experienced large-model modeler.
JEERS: Wheels do not retract fully into wing.
"...if you want to send a picture of yourself back to your best girl in the states, sit on the wing of a P-51. If you want to return to that girl in the states, sit in the cockpit of a P-47"
The paraphrase just about sums up the rugged reputation of the Republic P-47 Thunderbolt. The "Jug" (referring to its mil bottle shape", was designed by two former Russians, Alexander P. de Seversky and Alexander Kartveli. By the end of the war, it had become a legend. Following their designs of several preliminary high performance aircraft, the P-35 and P-43, the new company, Republic Aircraft, located at Farmingdale, NY, introduced the XP-47B, which was test flown on May 8, 1941. What followed was major chapter in aviation history. The heaviest single engine fighter to see service in WWII was produced in greater numbers than any other U.S. made fighter. Its sheer strength and power allowed the P-47 to take hits from enemy funs, and either keep right on fighting, or allow it to limp home with the pilot ready to return the following day. Zemke? Johnson? Gabreski? Recognize any of those names? All of them became WWII Aces flying P-47's and they all loved the big Jug. With more than 2000 HP pulling seven tons of metal around the sky, it's easy to believe that the P-47 was one of the most popular of the warbirds. More than 15,600 were built after their entry into combat in March, 1943, clocking more than 1.35 million combat hours, during which they destroyed more than 9000 enemy aircraft, and untold thousands of railroad cars, locomotives, tanks, trucks, and other ground vehicles.
All of this seems to make the P-47 a perfect candidate for a giant scale warbird, and many modelers agree. Based on demands from a large number of giant scale enthusiasts (myself included), Top Flite recently released their giant scale Gold Edition P-47D.
At a scale of 1:5.7, with a wing span of 85", the new P-47 will indeed fill the need for another all wood giant scale warbird kit that requires no special building or flying skills. It can be built as either the popular bubble top version or the razor-back version I choose to replicate. All wood parts are included in the kit, but the razor back canopy is an extra cost option. Included in the kit are many die-cut and laser cut ribs and formers, a large number of sheet and stick balsa, a five piece plastic cowl (with the cowl flaps open!), two rolled plan sheets, two sheets of self adhesive markings, and another of the fine Top Flite illustrated instruction manual. The builder must purchase the hinges, control horns, wheels, engine, radio, and covering materials. I ran an inventory of the parts included with the kit, and found nothing missing.
I began construction by labeling all the ribs and formers with a ball point pen, even though most parts already have embossed marking. All the die cut parts practically fell from their sheets, while the laser cut parts only needed to be loosened by a twist of the sheet. I placed parts for individual assemblies into large freezer bags to keep everything together.
I called Robert Mfg. to order a complete retract set, including the mains, tail gear, air tank, and their adjustable rate control valve. A call to Tower Hobbies got a new US41 engine on its way, just as called for on the plans. This engine flew my 22 lb Top Flite Mustang quite well, so I felt it would be sufficient for the P-47 as well.
The real construction work begins by cutting and taping the plans together, and then cutting various parts from the big sheets. Sheeting skins are made up from balsa that's edge glued using yellow carpenter glue and tape. This is the first kit that tells you to make up the skins before you clutter your building board with all sorts of other stuff.
The horizontal stab and elevators are built first, all in one piece. The stab ribs have jig tabs which are supported over the plans by balsa framing sticks. You really don't have to cover the plans because the structure is held above the plans. Each rib was Zap'd to the trailing edge, followed by the leading edge. The top skins are then Zap'd into place, and the assembly, both the stab and elevators, is removed and flipped over onto cradles so the other side can be sheeted. Balsa blocks are added to the stab and elevator tips and sanded to shape. The elevator halves are cut free, and leading edges are added and drilled for Robart HD hinge points. The fin and rudder are built almost the same way, except there was a slight problem when flipping the fin over to sheet the second side. The cradle positions shown on the plans are incorrect, but most builders will quickly determine where they need to be placed.
The fuselage is built with the top half first. Shaped balsa edge pieces are pinned to the board, and formers are Zap'd into position, along with half of the engine and fuel tank box. Stringers are added, followed by epoxying the stab and fin into position. You must then choose between the bubble top or razor back version you wish to build. I chose the razor back, and added the formers called out in the book. Parts for either version are supplied in the kit, and the instructions make it quite clear as to what is to be done with each set of parts. Probably the most difficult part was bending the reverse curve into the top sheet where it meets the razor spine. I used a steam iron to soften the balsa enough to form it around this complex curved area.
The fuselage bottom was supposed to be next in line, but the retractable landing gear still hadn't arrived, and the tail gear has to be installed permanently. While waiting for the retracts, I went ahead and built the wing panels. The wing sheeting skins are assembled using 20 pieces of 3/32" sheet balsa, edge glued with carpenter glue. The instructions tell the builder to square up both edges of each sheet of balsa before joining them, but I found a better way. As luck would have it, my kit had several balsa sheets that were more than 1/4" away from being straight. But there were eight of these sheets, just enough to make four skins of two sheets each. I was able to match up all eight pieces within 1/64", and glue them together without straightening the edges at all. The other 12 sheets were joined exactly the same way, matching the curvature of one sheet to that of another. When dried, each completed skin was then squared off with a razor blade and metal straight edge, and sanded smooth. You may want to try this on your next kit.
Wing panel assembly is quite simple. With all the ribs and spars prepared, a main spar is pinned in place over the plan sheet, followed by the ribs and trailing edge parts. Once everything is in the correct location, the ribs are then supported by short sections of 1/4" sq. balsa on each side of the jig tabs. Each rib is then Zap'd into place to the spar and trailing edge. The shaped leading edge is added to the front of the ribs, and I was ready to add the top sheeting. The wing is sheeted from the spar forward and backward, using two separate sections of balsa sheet. I added the rear sheeting first...because it was closer to my side of the building table. I used yellow carpenter's glue on the ribs, and weighted the sheeting down with stacks of our favorite magazine. (I knew they'd come in handy for something!) The front sheet was a little harder to install, since the sheet butts up against the back of the leading edge. I used thin Zap to hold the sheet in place, and then added yellow glues to the ribs and spar, again held in place with magazines for weight. After about an hour, the glue was dry enough to remove the magazines, and inspect the wing for warps. None were found, so I went on to build the second wing panel.
I was soon to the point of adding the main gear retracts, but they still weren't available. The retractable tailwheel assembly showed up first, so I went back to building the fuselage. The retractable tailwheel assembly and its two air hoses were installed, and then the bottom of the fuselage was sheeted the same way as the top had been done. The servo tray, fuel tank floor, and firewall were then installed, followed by pinning the firewall to the engine box sides. After a little sanding, the fuselage was starting to look really nice, especially when the razor back canopy arrived. Placing the canopy on the fuselage produced lots of Oohs's and Aah's from all my fellow modelers who dropped in to check on the model's progress.
The main retracts finally showed up, so I went back to the wing panels. Retract mounting rails were added, and the units placed in position. I then noticed a problem with the position of the scissors on the gear legs. The plans show the scissors facing the leading edge, but the gear legs had them facing rearward. After taking a long, hard look at that I had, I decided the situation could be remedied by simply swapping the left and right gear legs. This correctly oriented the scissors and the offset leg.
The two wing panels were then joined using a laminated aircraft plywood joiner. No additional center section bracing is noted, but the builder may want to consider a wrap of thin fiberglass cloth, and resin or thin Zap. The completed wing was then sheeted with balsa, the edges trimmed, and the control surfaces separated from the main panel.
The wing jigs didn't seem to fit quite correctly, but after checking things like dihedral and wash out, I determined that a minor adjustment in the jig positions would cure the problem. Once the wing was complete, measurements confirmed that the wing was indeed built as shown on the plans, and that the jig positions must be adjusted to fit the individual wing.
The ailerons are to be hinged in the normal fashion using Robart giant hinge points, while the flaps use the hinge points in the V-arrangement on the underside, to simulate retracting flaps. Access holes for the aileron and flap servos and the retract mechanism were then cut into the lower sheeting, and servo mounts fabricated and installed. Hopefully, the builder has already installed the air hose for the retracts, and some paper tubes for the servo leads. (Yes I did!)
To mate the wing to the fuselage, the wing was set into place and squared to the tail. I sighted along the plane's center line to see how the stab lined up with the wing, and I have never had a plane come so close to being as perfect in alignment as this one. Holes for the nylon bolts were drilled and tapped, and circular dowel formers installed at the front. The fuselage to wing fairing is built in place using thin plywood and balsa sheeting. This looks a lot harder than it actually turned out to be, and was completed and ready to finish sand in just a couple of hours. The belly pan is now built onto the bottom of the wing, taking care not to inadvertently join the wing to the fuselage. I found a very minor problem with one of the formers, which didn't have all the notches cut. A few swipes with the razor saw took care of that, and the belly pan was then sheeted and prepared for final sanding.
Engine mounting was just a matter of mounting the US41 to the isolation mount, and bolting the whole unit to the firewall. Throttle linkage and fuel lines were installed, followed by a coat of thinned epoxy to the engine area. I got a beautiful prop hub and backplate from Tru-Turn, which included a drilled and tapped prop bolt. The prop hub looks great, and resembles the full scale hub found on the P-47. I used an 18x8 Master Airscrew wood prop, and measured almost 7500 RPM on the ground after two tanks of running on a test stand.
Since I was building the razorback version, a small amount of sanding on the top of the fuselage was required, and then the canopy fit fine. There was a little engineering necessary to get the cockpit interior to fit correctly, but it can be permanently installed after the plane is covered.
The multi-piece plastic cowl was sent to Stan's Fiber Tech to be used as a pattern for a fiberglass replacement. I received the new cowl in a couple of weeks, and was amazed to see the fine quality of the surface. It fit the nose of the fuselage perfectly, using the cowl mounts included with the kit. These allowed the cowl to be spaced about 1/2" away from the fuselage to allow the engine heated air to exit. I cut holes for the fuel filler, exhaust extensions, and for choking the carburetor. After a thorough cleaning and sanding, I applied a coat of white sand able primer to check for any pin holes in the fiberglass. Finding none, I lightly sanded the primer, and then applied silver Goldberg paint, which matched the silver UltraCote almost exactly. Then the black trim lines were masked and painted, using more Goldberg UltraPaint.
Final sanding was next, followed by a good wipe down with a tack rag, and then a thorough going over with a vacuum cleaner. A few high spots were sanded, a few low spots were filled, and soon the P-47 was ready to cover. Rather than apply a detailed epoxy glass finish and many coats of paint, I used Goldberg UltraCote silver covering. Its finished look resembles unpainted aluminum, which is just the effect I wanted. The wing required four rolls of UltraCote, but the scraps cut off the edges were enough to cover the control surfaces and the tail surfaces. Two more rolls were used on the fuselage, while the areas under the flaps were painted with metallic water base acrylic silver paint found in a craft store. The silver matched the covering almost exactly, so I used it on the cowl mounts and inside the wheel wells, too.
The control surfaces were attached with Robart large hinge points and Pacer hinge glue. The flaps required a little adjustment during the glue drying time, but they worked well when complete. Du-Bro large control horns were added, followed by the control linkages included in the kit. Each elevator half is connected to a separate servo via a 4-40 rod inside a plastic tube. The rudder has a single wire and tube, and the tailwheel is controlled by its own servo via a pull-pull system. I added a spring in each pull-pull cable to isolate landing shocks from the servo. The ailerons and flaps each have their own separate servo, wired in place using homemade extensions and locking connectors. One of the flap servos, and the tailwheel servo, needed to rotate in the opposite direction, so I electrically reversed them inside their cases. All of the air lines, the air tank, the control valve, and the retracts were then installed and connected.
I masked the canopy and sprayed a medium coat of black on first, followed by a couple of coats of silver. This resulted in a black pattern inside the canopy, and a silver pattern outside. This may not be scale, but it sure looks neat. The turbocharger outlet and two oil cooler vents, also available from Stan's Fiber Tech, were primed and painted with UltraPaint, and then attached to the fuselage using Pacer canopy glue. The stars and bars decals in the kit worked okay, but the ones for the fuselage just wouldn't conform correctly, finally tearing into several pieces. I contacted Bill Fulmer, at Grafix Custom Cut Lettering, who has made several graphics packages for previous test models. He made up a set of stars and bars, and also a set of Republic Aircraft "presentation airplane" markings for me. As you may or may not know, my late aunt built P-47's at Republic, and every so often the workers would purchase a plane using the proceeds from their war bond sales. This would be fitting to pay tribute to my aunt and all the workers who put planes together for the war effort.
I finally had all the parts completed and ready to assemble for final detailing. The Top Flite cockpit interior kit was cut to size, painted, and installed. The engine was installed, and a kill switch added to the magneto. The 5-cell 2000 mAh battery was installed near the fuel tank, after which the P-47 balanced exactly at the point indicated in the instructions.
I took the completed model outside to test run the engine, and found the plane easy to assemble on the stand, but difficult to lift and turn over. The air system was pumped up to 100 psi, and the retracts were tested and cycled. They all functioned flawlessly, with the adjustable control valve allowing the wheels to retract slowly, but extend a bit quicker. I filled the gas tank, primed the carb, turned off the kill switch, and the US41 roared to life after a few spins of the spring starter. There was plenty of power to drag the P-47 through the tall grass in my yard (when is she gonna cut that stuff?), so I decided that it was time to head to the flying field. A few minor adjustments were made to the tailwheel steering and kill switch, the cowl was reinstalled, and the P-47 was made ready to transport.
We headed for the field on a cool morning, hoping to get there before anyone else, so the test flights could be carried out without too many spectators. I assembled the P-47 in a few minutes, pressurized the retract system, filled the gas tank, and snapped off a roll of ground photos for this review. I range checked the radio system, performed a last minute pre-flight inspection, and after finding no excuses not to fly, I started the engine. By now a small crowd had gathered around, and many questions were asked and answered. Then I...we were finally ready for the first flight.
A few low-speed taxi tests showed that the P-47 was easily controllable on the ground, and that the tail lifted at a rather low speed. I taxied to the extreme west end of our 350'grass field, turned to point the model into the wind, wiggled the controls for reassurance, took a moment for a few religious incantations, and then slowly advanced the throttle. The Jug accelerated briskly, requiring only a small amount of right rudder to keep it straight on course. The wheels started to bounce a little, so with a slight tug on the elevator stick, the P-47 took to the air.
A moderate climb at full throttle was made, followed by a gently left turn to bring the plane back over the runway. Just a couple clicks of elevator and aileron trim were necessary to trim the P-47 for straight and level flight at 3/4 throttle. I then flipped the retract switch, and watched the wheels disappear. The model's air speed seemed to pick up dramatically without the drag of the wheels holding it back, but no trim changes were necessary, and I could then fly hands off at half throttle.
As my confidence built, I tried an easy roll. That was complete quite respectably. A moderate size loop required almost full throttle, but I expect the power to increase somewhat as the new engine breaks in.
I took the P-47 to a comfortable altitude, cut the power to idle, and gradually applied full up elevator. The nose dropped, but there was no noticeable falling off to either side, and the model was soon back to flying speed, with little altitude loss. Again at low speed I switched the transmitter to the "landing" position, which I had programmed for about 20 degree of flaps, and about 1/4" of down elevator to offset any ballooning. The plane almost came to a halt as the nose dropped ever so slightly. Added power kept the plane flying very nicely, though, so I was pleased with that. I raised the flaps and just flew around making high-speed passes of the crowd, and for my photographer. The P-47, especially the razor back version, looks absolutely huge in the air, but it was behaving more like an advanced trainer. I felt no lack of control authority at any time.
My transmitter timer started beeping at the 10 minute mark, so I made a low pass across the field, flipped the retract switch, and watched as all three gear legs came down fairly realistically. I reduced power, dropped the flaps a little, and on final added just a little more. The nose of the P-47 was aimed for the center of the field, and once the plane crossed the threshold, I cut the power and flared for a nice smooth landing. I remembered to pull up the flaps like you're supposed to taxing, and then shut off the engine from the transmitter.
With the plane back in the pit area, I inspected everything for loose or missing pieces. All I found, however, was a really nice oil stain from the cowl across the side of the fuselage. Yes, it was actually nice, because it looked very much like exhaust marks that all fighter planes get during a mission. This particular stain, however, came from unused gas sprayed back out the carburetor. Despite my initial surprise, I was still able to convince the spectators that I'd worked long and hard to achieve that special weathering effect.
Sadly, my final landing that day was not quite as nice as the others. I slowed the plane a little too much, it dropped a little to hard, so then it bounced back into the air, coming back down with its full 21 lbs. on the right main gear leg, while at nearly 45 degree to the runway. This mistake cost me a bent main gear, and luckily just a fractured plywood gear mounting plate. If that plate had been any stronger, though, it would probably have resulted in a mangled wing! The damage was repaired in an hour or so back home at the workshop. The gear leg mounting was straightened in a bench vise. The leg itself was not damaged at all. The Robart gear parts are plenty strong, and I'd much rather replace a plywood mounting plate than an expensive gear leg, or an entire wing panel. Having learned my lesson, all of the subsequent flights went very well...landings included!
The Top Flite P-47 was a good kit to assemble, since the materials, plans, and instructions were typical Top Flite quality, making the assembly quick and easy. Everything fit well where it was supposed to, and all the parts were usable, even though I chose to use a fiberglass replacement cowl. The completed model looks great on the ground, but spectacular in the air. I have no reservations whatsoever in recommending the Top Flite P-47 to any experienced giant scale modeler, as a first warbird project. I feel very confident that such modelers will like this kit as well as I do. It's a keeper!!
Reprinted with permission.
December, 2000 R/C Report
Editor: Gordon Banks