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Saturday, November 12, 2011

P-38 1.4m EPO Warbird w/ Retracts Plug-&-Fly Flight Review

Update:  After flying a lot of foamie warbirds belonging to me and others, the J-Power P-38 wins as Z8RC's overall best foam warbird.  

This plane could have easily won Z8RC Best 4-Channel Aileron Trainer, too.  The reasons I didn't choose it are the complexity and potential failure modes of the twin engine design.  Ironic isn't it, that twin motors are supposed to be safer but they really never are:  you have at least double the chance of engine failure, usually more than double, and twins never fly well on one motor--or they would only have one.  If you do my counter-rotation mod, below, the plane becomes even more docile, and you can always switch back to co-rotation to learn about torque.  One last thing, the retracts present the possibility landing gear up and the stock retracts cannot adsorb a hard landing, or even a light landing on a rough surface..  

If you don't mind a little build complexity, rolling the dice on motor failure, or dealing with cheap stock retracts this P-38 could make an even better aileron trainer than the Z8RC favorite Cessna 150.

This fantastic J-Power/Hobby King P-38 cost me $137 with $0.01 USPS Priority Mail shipping to the USA (made known during checkout from their USA Warehouse).  The same ARF is available from Banana Hobby in the 'States, but for about twice as much money considering HK picked up the shipping charges.  

No doubt about it, the P-38 is a gorgeous warbird and this model shows it off properly:
This ARF kit is a bit of a handful to assemble for a foam plane, don't expect to be flying in under four hours from opening the box.
The hardest part of assembly is running the included Y-connectors to the servos and motors, and then neatly embedding the wires in the wing channels, as you build the airplane.  It takes a bit of thought as you hook everything up and test it, before dry-fitting the structure.  The good news is that everything you need is included, and the cursory, poorly translated instructions aren't really needed once you understand the basic idea--which is--hook up airleron, rudder, and elevator servos via a Y-connector to your choice of Rx.

More good news is the beautiful finished product:

The motors and ESCs are powerful, but the prop is scale instead of max efficiency.  The detail on the props alone would make most models green with envy, but the entire plane carries a few more finishing touches than other foamies from the usual suspects, which usually cost more than a little bit more.

This P-38 is a heckuva bargain at less than $140 including USPS Priority shipping.

On the Ground:
The EPO foam is better than Horizon Hobby's Z Foam, because the surface is harder and more rubbery.  You can apply and remove tape without affecting the durable paint scheme.  There is a full wingspan carbon fiber tube embedded in the bottom of the wing and painted.  The plane is very well built for a foamie, and the inherent bracing of the design is more sturdy than a single fuselage airplane.

The twin motors are already installed, they appear to be roughly 450 size generic brushless outrunners.  Each motor has its own ESC in the fuse behind it.  The twin ESCs are not marked with Amp capacity, but each only carries half the load of the single battery solution via the included Y connector.  The battery is located in front of the cockpit, with a battery hatch conveniently on top.  The battery bay is perfectly cut for a 2200 mAh 3S, but a longer battery is no problem with a 10 second removal of a thin foam divider. 

To my pleasant surprise, the power system is 4S ready.  My 2200 4S Venom battery fit very snugly, but without issue.

The propellers are some of the best looking scale 3-blades I've seen, but unfortunately you have to assemble them.  Each blade hub gets sandwiched by a sturdy, two-half radial motor facade.  A screw holds each hub in place.  The hub slides onto the spinner shaft, and a shaft nut holds it all in place.  The only defect with my model appeared here, one motor was wobbly on it's motor mount.  I removed two screws holding the cowl in place, slide off the cowl, and tightened down two loose motor mount set screws--finished.
TheP-38's maiden voyage was uneventful and a lot of fun.  After trimming the model for straight and level, the P-38 displayed perfect balance as shipped.  The Lightning is a graceful and stable flyer.  It doesn't feel nose heavy while it tracks positively, like most warbirds. 
In addition to twin motors, the P-38 has twin everything electronic.  Each side fuselage has mirror image electronics, including main gear electric retract servos.  Included Y harnesses carry each half of the plane's signal to the center fuselage, where each channel meets at a single servo plug into the Receiver, which sits in a large opening under the canopy.

The only mildly confusing piece is the dedicated nose wheel steering servo, which must Y off of another Y that goes to the twin rudder servos.

After all the electronics are connected, it is time to slip a fuselage on each main wing.  The wing inserts from the inside-out, and as the fuse slides into place, all the Y connector leads have to be tucked in, one by one, to a grove under the main wing.  Getting all the wires in the grove looks like it'll be a lot harder than it really is.

The landing gear deserves a special note, as it is very flimsy, as are the gear doors.  The gear doors are paper thin plastic on spring loaded hinges.  The system allows the gear to function, but the gear doors hang open in the airflow, once speed hits about 45+ mph.

The end is a nicely redundant twin everything, not just a twin engine.
In the Air:

My maiden, shown here, is on 3S to make sure everything worked properly.  It was uneventful so I upped the cell count to 4S for the second flight.  On 3S the plane climbs strongly, perhaps 70 degrees nose high, but one still gets the impression the plane is flying mostly on the wing.

While the plane climbs well, on 3S there is an underpowered feel during sharp maneuvering.  The plane manages to fly well on 3S, mostly due to a very competent, slippery and forgiving core design. 

With 4S, power and speed and noticeably improve.  But the custom props still don't seem to bite that hard.  I recommend 4S to keep the crowd pleased during pass and review.  The additional battery weight seemed negligible, given the pretty large scale of the airplane.

Loops and rolls are graceful and stay mostly uncoupled.  Min turn radius is surprisingly small.  If you pull too hard, the plane rolls out involuntarily.  This 38 can actually hold a reasonably uncoupled 3S knife edge indefinitely, given a fresh battery.  Flat turns are tricky but can be done impressively with the twin rudders digging in.  Loops are a breeze to fit any size requirement, and only need a hint of right rudder over the top.


I thought this was a twin engine?  Well, guess what, the prop's are both pullers, so there is no way to eliminate torque using counter rotation.  My next round of props will be a pusher/puller combo with one engine reversed.  When you induce counter-rotation, be sure to make the props spin inward at the top of the prop arc, so P-Factor fights any asymmetrical or single engine thrust, instead of compounding it.

Aerobatically, this P-38 is better than the both the Fw-190 and the Spit that I recently jousted. The plane's manners are exceptional for a WWII throwback. While a warbird is never going to perform like a true aerobat, the Lightning behaves very well indeed and is agreeable to some varsity level stuff -- snap rolls, inverted spins, wings-level 360s, and knife edge flight are within bounds. Due the perfect out of the box balance and thrust line, inverted flight is no sweat with minimum forward elevator, and the fight path stays arrow-straight when chopping or gunning the throttle. Overall, I'm impressed. I've never owned a P-38 before, I wonder if they all fly this good.

If you are in the market for a real head turner that won't dent the bank, flies beautifully out of the box, and includes a few extras like rickety retracts, twin motors and double-servo rendundancy, this airplane could have your name on it.

Appearance: A
Impressive presence.  Great paint scheme.  Classic WWII fighter. 

Airframe: A+
Great flying warbird.  Perfect balance as set up.  Quality aerobatics.

Power System: C+
No counter rotation??  Mild asymmetries.  Weak on 3S but 4S ready!

Build Quality/Durability: C+
Expect usual foam degradation.  Lots of servos.  Lousy retracts.

Value:  B+
$139 price goes a long way, + free shipping.   Two motors.  Extras.

Overall Grade: A
More than worth the C & L note.  Fun basis for hop-ups.  Flies great!

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