My E-Flite P-47 Thunderbolt

This winter, I built an ARF electric P-47 from E-Flite. After weeks of the bird sitting in my garage waiting on a break in the weather, I finally maidened her. Here are the specs:

  • Park 450 motor
  • Dymond 2100mAh LiPo. Yeah, there's no balance plug on these batteries, but they are cheap, work great, and seem to last a long time when recharged at around 0.4-0.5 amps.
  • Hitec Supreme radio (a little heavy for this bird, and behind the CG, so I'm going to replace it with something lighter)
  • Hitec HS-55 servos (4)
  • E-Flite brushless ESC
  • Master Airscrew 10x8E and E-Flite 10x8E props
  • Dubro scale wheel struts

Just so you know, I really like flying this bird. She's very pretty in the air, stays up for a good long while (up to 15 minutes on a 2100mAh battery, but I tend to bring her down at about 10 minutes because a lower depth of discharge preserves long-term LiPo life), and is a blast to fly. I'm going to list quite a few downsides, but it's in hopes that my bad experiences can help someone else

Positives:

  • Very easy build. I have very little build experience (I prefer flying to building), and found it very straightforward and well-documented for the power choices I made.
  • Once trimmed, she's very solid in a light wind.
  • The 10x8E prop is well-matched for this bird, even at 5000 feet elevation.
  • The Park 450 outrunner is a fine motor for this warbird. Very short takeoff rolls, and lots of power. At my elevation and with the extra weight of the Dubro scale struts and lots of nose weight (more on that later), I couldn't hover her using this motor, but nevertheless it provides a very pleasant flying experience.
  • Having a rudder available in a plane this size made my landing approaches in a crosswind much easier and prettier than in an aileron/elevator-only ship.
  • It's a damn pretty little electric in the air, even with a little fuselage and wing rash.
  • Inverted flight is fairly easy to hold. Not as easy as, for instance, a ParkZone Stryker, but with this motor on the front I never worried about not having enough power to push or roll out of the invert and maintain altitude.
  • Even with extra weight due to additional nose weight, epoxy, a heavy radio, she cruises just fine at 1/2 throttle doing lazy figure-eights and circles. At 3/4 throttle, she can do most aerobatics, and at full throttle she can do enormous loops.
  • For a warbird, she's very docile. The nose just mushes in a stall, rather than tip-stalling like the P-51. With factory throws, the roll rates are just slightly faster than scale at full deflection.
  • Landings were a non-event. I did four approaches to learn her glide path, then brought her right down on the fifth one. On the second flight, the first landing approach was perfect and she settled down at 1/3 throttle easier than my J-3 cub.
  • The battery bay fits a Dymond 3S1P 2100mAh LiPo battery perfectly. Since these are the same size as the Thunder Power 3S1P 2100mAh, those should fit fine too. If you have fatter packs than these narrow-form-factor ones, you may have better luck with not having to add nose weight, but you'll also have to hog out the foam in the nose a bit. Given that these narrow LiPos are almost exactly the same width as a 2/3A battery, you should also have good luck with NiMH packs. And hey, with a NiMH..... less nose weight required!

Negatives:

  • You're going to have to add substantial nose weight if you use the rudder option. From my bench balancing during build, with just aileron and elevator, no landing gear, the CG appears spot-on with the stock motor and prop; using a light brushless motor, rudder servo, rudder hardware, glue, and tailwheel affects the CG mightily. I'm thinking of building a second one in a pure slow-flyer configuration without gear, rudder, or brushless motor later.
  • The stock CG indicator is slightly too far forward for perfect hammerheads. Although easy to handle, yaw performance suffers. With the CG at the factory location (using a CG machine), the elevator required quite a bit of back trim to maintain level flight, and exhibited classic signs of nose-heaviness on landing approaches.
  • To balance at the factory CG, I had to use the full bar of clay, pressed around the nose, and several additional small weights. The weights will be going away one-by-one until I find the sweet spot on the CG; I suspect it's about 1/4" back from the factory-indicated CG.
  • Like most uncovered foam models, the finish is very easily damaged in the hangar. I already have a scratch from one of my fingernails, and a pretty ugly white-ish bruise on the side due to an accident with my CG machine while balancing.
  • Trying to pry the cowling off in order to mount my motor was frustrating. They need to let the paint dry just a little longer before shoving the cowling on at the factory. Or maybe they could wrap the fuse in tissue or something so that the cowling slips off easily.
  • The space is very tight, even for a razor saw, when trying to cut the engine mount stick. You're going to end up taking out a few small hunks of foam even if you're really careful. They are concealed beneath the cowling, so it's not a big deal.
  • The lack of a steerable tail wheel complicates landings a little; once the tail drops, your level of control drops, too. That lack also complicates takeoffs if you attempt to do a scale rollout at half or three-quarters throttle rather than the "jump into the air" full-throttle roll.
  • The two wing panels should really be saved for last in the build. If, as I did, you're going with a flaperon setup rather than a y-connector, the flaperon adjustments may require repositioning of your servo arms. And that double-sided tape on the wing panels really sticks hard! Note, however, that using flaperons as flaps is strictly optional. She floats lightly even in the full-house configuration and nose-heavy.
  • She doesn't handle high winds really well. Like most park flyers, if the wind is faster than 10MPH, you might want to consider keeping her on the ground if you aren't confident at the sticks. At higher wind speeds, this P-47 has a very pronounced weathervaning tendency.
  • The stock throws provide too much elevator and too little rudder/aileron for my taste. Your taste may vary, and luckily suiting that taste is probably just one adjustment away.
  • The stock landing gear location is susceptible to nose-overs on landing. Bending them forward so the axles line up with the leading edge of the wing when sitting on the ground (weight on the axles) clears this up just fine, while providing plenty of clearance for the stock prop.
  • The little black wheel holders suck. I replaced them with some nylon ones, because one of the wheels fell off during the second landing.
  • Some people report that the paper hinges are weak on the ailerons. Mine does not appear to have this problem, but I still don't like how they look.
  • The indicated location for the ESC and radio is rather far back. I put my ESC in the nose, and trimmed some foam to move the radio as far forward in its tray as I could.

Overall impressions:

The E-Flite P-47 is a solid, large-ish park flyer, a ton of fun to fly, and really good-looking in the air. Although fairly slow-flying, with the Park 450 motor it's really too fast to fly within a baseball field, but a large treeless park may do the trick. I fly at an abandoned runway, and there was more than enough space My personal bet is that, in an aileron/elevator-only combination without landing gear, on the stock motor, this bird will be a great flyer even in smaller parks.

With factory throws, rolls are scale-like and pretty. There's plenty of power to push through moderate winds, but gusts above 15MPH will easily throw her around in the air since she's so light. Like many other short-nosed warbirds, tail-heaviness can be a problem; you should be generous with the nose weight, at least for the first few flights, and aim for at or very slightly behind the factory-indicated CG location.

I like it!

P.S. You'll notice in the photos below that I have one that I've marked up a bit. This is to show you my hangar rash :) As many of you know, I'm a relatively new flier, and I learned quite a bit about the proper care and handling of a pretty airplane. Too bad it's not so pretty now, but at least it looks great in the air.

You may also notice that she no longer has landing gear. This is because I attempted to land on a very wet field, and it ripped two of the gear out of the foam! I should have taken the clue when it wouldn't rise off the ground, but instead just sort of flopped over on its nose when I tried to take off. Since I mostly fly from grass or salt flats anyway, I'm just flopping her on her belly for the time being. I'm going to buy a steerable tail wheel and re-outfit her with landing gear and bomb pylons again then.

AttachmentSize
p47_pilot_small.jpg36.9 KB
p47_diag.jpg100.2 KB
p47_front_wide.jpg76.28 KB
p47_cowl_marked_up.jpg81.91 KB

Great Job!

Great review - thanks Matt.

Follow-up

You're welcome! Here's my follow-up from http://www.rcuniverse.com/forum/m_3911105/tm.htm :

I have really enjoyed my P-47 for the month I've been flying it. It looks pretty in the air, handles aerobatics nicely, and can really haul butt with the Park 450 on the front. Good flyer, handles great in the sky.

The problems occur at or near the ground! I know people will tell me "it will either fly good or crash good, but not both", but with several birds in my shed that handle routine wear-and-tear better than this bird, I have a few comments. They are all related to reliability of this plane as a "daily driver", flying it every sunny day. I have never once crashed it, tumbled, or had even an exceptionally hard landing. I'm not sure whether the landing gear ripping off should be called "mechanical failure" or "pilot error". I've not had it happen, even landing on grass, since epoxying them. My buddy just nosed it over tonight on a landing in grass, which is the worst accident it's been in.

1. Landing gear. They just don't do a good job of securing the gear mounts in place in the foam. They rip out really easily. It looks as if they are attaching the mounts after they have painted the plane, and the paint is the only thing holding the glue.

Recommendation: I used the "pinprick" technique to secure my gear, and now they don't come out, grass or no grass. Basically, after your gear have ripped out (it's WHEN, not IF with this bird if you land on anything other than smooth asphalt), you mix some epoxy, then coat the tip of a wooden skewer and, re-coating regularly, jab the foam using the skewer inside the ripped-out landing gear bay. Then give a good healthy coat to the inside of the mount bay, and to the mount itself, then set. Six-minute epoxy works well for this. Ten flights+ using this method, and the wing will now go before those gear will.
Alternately, run without the gear, fiberglass or packing-tape the fuselage right behind the set screw, and belly-land in grass. This bird handles like it was made for belly landings. Never a broken prop if you kill the throttle before touching down, and the flare-and-flop (like flying a Stryker) works perfectly without the tip-stalling tendencies of the beautiful but nastily tip-stall-ish P-51.

Also, the full-scale P-47s landing gear line up with the leading edge of the wing. You should bend yours that way, too, if you don't like nosing over

2. Wing covers. These covers have a tendency to lift up at the lip near the body, and rip out in flight. All you have to do is one screaming dive and a pullout. The wing cover will pull out of its little slot in the body, and you're just a good gust of wind away from it ripping out in-flight. If it rips off, it will tend to hang on an aileron pushrod and just flap in the wind until you land.

Recommendation: I don't have one yet. The plastic wing panels are so heavy that I'm thinking of dispensing with them and just sealing some Monokote on instead. I won't have the nifty panel lines, but with the amount of hangar rash I've incurred (and the "stand-off scale" aspect of the bird), I'm far more concerned about flying habits than winning any scale awards!
A friend suggested simply using packing tape on the wing, at the root where it's inside and won't be seen. I like that idea, and I may do it if I buy another one of these birds due to the enormous amount of hangar rash I've incurred on this one.

3. Foam durability. The foam they use on this P-47 is brittle, weak, and subject to melting even with foam-safe CA! They should use the same variety of foam used on the latest version of the ParkZone Strykers. It's rubbery, strong, and handles foam-safe CA very well. A two-year-old walked up to my P-47 on a table today and broke off a big chunk of my elevator (like 1/4 of the right one, right up to a panel line), then walked away eating it. It's a lost cause, and I'll have to shape some balsa to replace the lost foam. I have similar rashes elsewhere on the bird, pretty much scratched up everywhere you look. My other foamies don't suffer nearly as badly from fingernail scrapes, for instance.

Recommendation: Fiberglass the following areas with 1/2 oz. fiberglass cloth and 10:1-mixed Minwax (polyurethane varnish):

  • Wing leading edge
  • Tips of wings. There's a really, really delicate area just outside the aileron, and the false lights rip off easily if you drag a wingtip or whack a weed.
  • Tips of the elevators. Don't do the whole leading edge, as it's really easy to make this bird tail-heavy.
  • The bottom of the fuselage, on the foam bit that holds the wing in place.

Just those bits should be enough to keep your bird looking relatively nice. I'm just really sad to see how banged-up my bird is from fairly routine use.

4. The cowling. They stuff it on the end of the plane too soon after painting it, and it's painted on solidly when you open the box.

5. The motor mount. I have very few nose-overs on this bird. One, exactly (and it was a friend flying, just tonight). The stick mount is really darn weak; even if you reinforce it, the foam it's in is brittle and icky.
Recommendation: Add a firewall of some sort. Going to do this tonight, with two layers of 1/32" plywood. My recommendation to the manufacturer would be to make the stick mount part of the bit you have to build, rather than having it hot-glued in. The hot glue had melted the foam badly around my stick mount, and no amount of epoxy seems to keep it secured.

Other than those five key issues, though, I really love my plane. I debated just scrapping it due to the incidental damage it's received, but I can't bear the thought Tonight, I guess I'm breaking out the epoxy, microballoons, and sandpaper to fix up the bad patches, followed by a healthy amount of painting. Hope I can find paint that comes close to matching so I can glass this and have it look OK. Wish the foam weren't so brittle; that one is really the key frustration issue for me with this plane.

Upcoming events

  • No upcoming events available