TOP FLITE P-47 THUNDERBOLT
FIELD & BENCH REVIEW
by Vic Olivett
A Warbird That Flies Like a Sport Model
When I was a kid some 40 years ago, my dad would build these big rubber-powered planes and hang them from the ceiling of my bedroom. The first one I learned to recognize was the P-47 Thunderbolt. As I watched this thing rotate on the string, I dreamed of being a fighter pilot some day. Well, I did not become a fighter pilot, but I have enjoyed this hobby for the past 30 years. When I was asked to review the new Top Flite Gold Edition P-47 Thunderbolt, I agreed—"No Strings Attached"!
|Manufacturer:|| Top Flite|
|Model Name:||P-47D Thunderbolt (razorback version) |
|Wing Area:||713 sq.in.|
|Wing Loading: ||33.9 oz./sq.ft.|
|Engine Req'd: ||.60-.90 2-stroke or .91-1.20 4-stroke|
|Engine Used: ||SuperTigre .90 2-stroke|
|Radio Req'd: ||4- to 7-channel with 4 to 8 servos (Rudder, Elevator, Ailerons, Throttle - optional, Flaps, Retracts, and Tank Release)|
|Hits:||High quality; easy-to-follow instructions; well-drawn plans, just plain fun to build.|
|Misses:||Slightly misaligned fuselage jig (has now been corrected by Top Flite).|
The wood is of high quality and the die-cutting is very well done. Having built all the earlier Top Flite kits, I can say there is no comparison between the older kits and the new Gold Edition ones. The plans are well-drawn and very easy to follow, and the instruction book is well-written and gives you plenty of hints on little tricks of the trade. They call them "Hot Tips", and believe me, they do help.
Top Flite gives you all kinds of options to build the P-47: fixed gear or retracts; flaps; and the razorback- or bubble-canopy version. The razorback-version canopy is provided, but you can order the bubble canopy from Top Flite. I decided to build the razorback with flaps, retracts and a drop tank.
Tail surfaces. Some of us who have been building for years think that we know it all, but this was new to me: Top Flite suggests that you remove all the die-cut parts and mark them with the part number or the size before you start the construction. Guess what? It makes the building go much faster and easier. The ribs for the stab all have jig tabs on the their bottom edges, and this results in a true, straight, flat surface. (This is very important on any plane, but even more so on a high- powered warbird.) The computer-aided design ensures that the parts for the stab fit very securely, and they can almost be pre- assembled before using any Zap. If you follow the instructions carefully, you'll find that even a stab that at first looks difficult can be very easy to build.
The stab and fin are built first; the elevators and rudder are cut and separated later. The plans include templates for the elevators, the fin and the ailerons. Remember to cut them slightly oversize. You will also build a bevel gauge that's included in the kit. The gauge will show you the rib end point and the joint for the skins. If you do everything correctly, you will have great results.
The elevators and rudder have 7/8-inch-thick balsa blocks for the inboard tips. This is to ensure that the elevator joiner and control horns will be well-supported.
Fuselage. Building the fuselage involves two basic steps. The top half is built right over the plans, and the bottom is built after the top has been sheeted.
The crutch system is very important because it sets the alignment for the entire fuselage. Use caution because there are left- and right-side parts to ensure you have the correct amount of engine thrust.
The entire fuselage is built around the assembly. I used medium Zap for this step. Zap the rest of the formers, the cockpit deck and the 1/8-inch plywood stab saddles into place. Spend a little extra time on malting the stab saddles perfect; your efforts will pay off later. This is the time to decide whether you want to build the razorback version or the bubble-canopy version. The rest of the fuselage is easy to complete using the stringers and sheeting. Medium Zap works well for this step. Here's a sheeting tip: before you try to curve the sheeting around the formers, make it more pliable by soaking it in a 50:50 mixture of water and alcohol.
When you've trimmed the sheeting to conform with the stab formers, trial-fit the stab into place. If necessary, sand the stab to obtain a perfect fit. Do not change the angle of incidence set by the inner stab saddles. Remove the stab, and trial-fit the fin. If necessary to ensure a good fit, trim and sand the fin and mate it with F-9. Remove the fin, put the stab back on the saddle, and trim the sheeting on the fin to fit the top of the stab. When you're satisfied with the fit and alignment, glue the fin and stab into place using the 1-3/8 inch filler blocks and 30-minute epoxy. Complete the top of the fuselage and fit the canopy.
If you have built the top of the fuselage straight, the bottom will be very easy to build. Again, test-fit the crutches and the lower formers to ensure they fit properly, and sand them lightly if you need to. Use a straightedge to align the formers from top to bottom. Glue the formers and wing saddles into place. The tailwheel bracket is well-illustrated on the plans and in the instruction manual. When soldering the brass piece to the tailwheel bracket, take your time because it won't be accessible when the fuselage has been sheeted and finished.
On Top Flite kits, the tailwheel assembly has always been a nice setup. Install the elevator and rudder pushrod tubes and pushrods according to the instructions. Sheet the bottom of the fuselage. Check the pushrod movements. When you are satisfied that all is as it should be, glue and shape the rear fuselage block.
These new Gold Edition kits use a unique engine-mounting approach. The old kits had one-piece firewall glued to the front of the fuse; the new kits have an engine-mounting box. This is much stronger and easier to work with; just follow the instructions. I chose a SuperTigre* .75 engine, but Top Flite told me that the P-47 flies very well with a.61 to.90 2-stroke.
The wing. The wing is very straightforward and easy to build. Just make sure that it is straight and flat on the jig tabs. Page 55 of the instruction manual shows a sketch of the retractable-landing-gear modification; I used Century Jet Models* retracts. Medium Zap works well here. The aft spars are interlocking and fit well. The wingtips include ribs W-12 and 13 with a separate interlocking spar.
To sheet the wings, follow the instructions, and when you join the wing-skin sheets, use Top Flite's "Hot Tip" method; it works well, and you won't have ripples and warping. Before you glue the skins to the wing, remember to sand them.
Before you join the wing halves, cut away the portion of rib W-1 that's behind the dowel plate and cut away 1/16- inch behind the main spar. This will make room for the dihedral braces to pass through the ribs. Test-fit the wing-bolt plate for the rear of the wing, and sand the wing to fit if necessary. When you're sure that everything fits well, use 30-minute Z-Poxy* to join the wing halves and let it cure.
The flap installation is unique and works extremely well. The flaps are built as part of the wing and then separated after the wing sheeting has been applied. The removable servo hatches have the servos mounted directly on them; this hides all the pushrods and horns. When you install the Robart* hinge points, take your time. Hinge location is very important to proper flap operation; the kit includes drill jigs so that you can position the holes for the hinges accurately. Use it!
When you've installed the ailerons and flaps, glue the tip blocks into place on the wing, then cut and sand them to shape. Following the contour of the wing gives the proper amount of washout for the tips.
Suggestion: instead of using the linkage shown on the plans, use a servo for each aileron. It's an easy modification and well worth the effort.
When you're happy with its fit, center the wing on the fuselage and drill the holes for the wing screws. The wing fillets are easy to build using the templates provided, and they add to the plane's good looks. I decided to use the optional belly tank, and the release mechanism is installed on the center stringer of the belly pan. You can run the flex cable from the release to the servo mounted in the wing. The plans show this installation.
The ABS cowl provided is one of the best plastic cowls I have seen in a long time. Its three pieces fit together very well, and it was designed to give maximum cooling to the engine. The cowl mounts that are fastened to the firewall allow the air to flow over the engine and exit around the cowl's aft edge. With any cowled engine, the exit is just as important as the inlet. I used plastic Zap to glue the cowl and then after sanding the seams, I smoothed them by adding filler. Sand the cowl with 220-grit sandpaper, and prime it with automotive primer. For the final coat, I used Coverite's 21st Century silver paint. The same finishing method is used for all the ABS plastic parts.
The radio installation is easy; follow the instructions, and you'll have a good, clean, efficient installation. I used a JR* 10SX PCM radio and JR 531 servos with a JR 1100mAh pack. With the 10SX, final control throws are easy to set.
I sealed the wood with Coverite's Balsarite and then covered the model with Top Flite MonoKote. For the exposed areas such as the firewall and the wheel wells, I used 30-minute Z-Poxy and mixed in a little oil-based paint of the right color to match the MonoKote. I did this after I had covered the plane; it also seals the edges of the MonoKote.
The final touch is panel lines cut with the Top Flite SmartStripe, which works very well. This was the first time I had used this tool, but it wasn't to be the last; I have since used it for all my pinstriping. So don't throw away all those little pieces of MonoKote!
In my opinion, the Top Flite P-47 is a great project for anyone who's looking for a warbird. They have really done a great job on this Gold Edition kit.
FLIGHT PERFORMANCE by Roger Post, Jr.
After correcting an uneven flap deflection, checking the radio, landing gear and engine installations, I put the plane together and checked its balance. With the battery pack installed just behind the radio compartment's forward bulkhead, the P-47 balanced perfectly.
When considering an engine for your P-47, chose one that won't overheat when placed inside a cowling. I had trouble keeping the SuperTigre .90 running with the muffler configuration provided. A switch to a SuperTigre .75 solved the problem, allowing a solid engine performance without overheating.
Takeoff and Landing
Even with the engine size reduction there was still plenty of power to pull the P-47 along. During the takeoff roll and climb- out, a good amount of right rudder was necessary for straight tracking. Once at altitude, I added some down-trim and left- aileron trim to maintain level flight.
When the flaps were deployed, there was no noticeable pitch change. In the landing configuration, the P-47 was rock solid and extremely stable. Unlike some other fighter models of this size, the P-47 showed no signs of a tip stall anywhere during the approach path. Dr. Michael Selig's wing design is outstanding.
When landing your P-47, come across the threshold with the throttle at 1/4 power and the flaps fully deployed. This will give you a very comfortable approach speed; a few inches from the ground, reduce the throttle to idle and flare for a three-point landing. If you can land an Ultra-Sport, you'll have no problems landing this plane. Just be sure to control the plane's descent rate with the throttle.
Low Speed Performance
With the flaps fully deployed and the engine at 1/4 power, the P-47 flies quite slowly. I was anticipating all sorts of wingtip dropping with this configuration, but the wing didn't budge from its straight-and-level attitude. The power-off stall was straight ahead; I pulled the stick all the way back, and the plane just mushed along until the stall break. All controls remained effective throughout this test.
On the deck, straight-and-level high-speed strafing runs are this plane's forte. I flew the entire test flight (except for takeoff and landing) with the throttle set at 1/2. There was plenty of power for climbs, dives and other maneuvers. There was no sign of a high-speed stall, and I would say the only time you'll need to use full throttle is on takeoff.
I confined the aerobatics to scale-like warbird flight. The loops were large, and the wings remained level; left and right aileron rolls were fairly axial and seemed to have the same roll rate; and there was plenty of rudder authority for stall turns or hammerheads. High-speed dives and passes were certainly the order of the day—all topped off with a climbing 90-270 procedure turn at the end of the run. I'm sure the P-47 will do some of the more violent maneuvers in the book, but I was in a scale-like flying frame of mind that day, and the P-47 captured this beautifully. It's truly a fine flying machine—just like its big brother.
Reprinted with permission.
November, 1996 Model Airplane News
Editor: Gerry Yarrish