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Hobby Lobby JPower A-7 Corsair II ARF RC Jet

Hobby Lobby has added one of the less often modeled Vietnam era jets to their rapidly growing selection of EDFs, the JPower A7 Corsair II 70mm EDF.

Splash

Introduction


Wingspan:32-1/4"
Weight:30.5 oz.
Length:36-3/4"
Wing Loading:18 oz/sq. ft.
Servos:Four JPower 9G Servos (Included)
Transmitter:Spektrum DX7
Receiver:Spektrum AR500 Full Range 2.4 Ghz Five Channel
Battery:14.8v 2200mAH Lipoly (Included)
Motor:2950Kv Brushless Outrunner (Included)
ESC:JPower 40 Amp Speed Controller (Included)
Manufacturer:JPower
Available From:Hobby Lobby
Price:$269.90

I have been flying radio controlled Electric Ducted Fan jets for several years, and I love them. My first EDF was an Alfa Mig 15, and I still regularly fly it. The Mig is in the 60mm fan class, and pretty much all of the jets in my fleet have been in this same size and class. But lately there has been an observable trend towards the larger 70mm fan class EDFs. Hobby Lobby has been steadily expanding their selection of these 70mm jets, and when the less often modeled A7 Corsair II showed up, I knew it was time for me to leave the sidelines and get out on the playing field to see what these larger EDFs are all about.

A Little Background on the A7 Corsair II

I was two years old when this aircraft entered service and began seeing active duty in the skies over Vietnam. Wikipedia provides the following bits of interesting information and errata:

It was one of the first combat aircraft to feature a head-up display (HUD), an inertial navigation system (INS), and a turbofan engine.

The A-7 enjoyed the fastest and most trouble-free development period of any American combat aircraft since World War II.




The A-7 Corsair II was tagged with the nickname "SLUF" ("Short Little Ugly F(ill in the blank)") by pilots.

In Vietnam, the hot, humid air robbed even upgraded A-7D and A-7E of power. Takeoff rolls were lengthy and fully-armed aircraft struggled to reach 800 km/h. For A-7A aircraft, high density altitude and maximum weight runway takeoffs often necessitated a "low transition," where the aircraft was intentionally held in "ground effect" a few feet off the runway during gear retraction, and as much as a 10-mile departure at treetop altitude before reaching a safe flap retraction speed.


All above photos from Airliners.net

Kit Contents

This kit is really a Receiver Ready model; the only thing lacking in the box and necessary to fly is a receiver. The foam airframe comes out of the box pre-painted, with the decals already applied. The detail of the airframe is very nice, with panel lines molded into the foam. The parts count is very low: fuselage, two wing halves, two horizontal stabilizers with elevators already hinged and attached, the vertical stabilizer (no rudder), canopy and a bulbous black nose cone. All of the electronics, including the four servos, are already installed. The same is true of the power system. The assembly manual covers the basics in a very abbreviated manner but there is not really much instruction necessary to ready this Corsair for flight. My kit arrived in fine shape, although it did not seem very secure in the box. I was fortunate that apparently it had not shifted around very much while in transit.


The 2200mAH 4S lipoly was encased in a protective cocoon of bubble wrap. I could find no identifying markings or labels with specifications on either the battery or the speed controller/BEC, so the published numbers have to be assumed as correct.




In The Box

  • Foam fuselage, wings, empennage and nose cone
  • Two piece Plastic and Lexan canopy with magnetic retention
  • 40 Amp Speed Controller with inline BEC
  • Four 9G servos already installed (two for elevator, two for ailerons)
  • 70mm class fan with 2950Kv brushless outrunner motor
  • Black and white instruction and assembly manual
  • Small accessory bag with push rods, glue and four round foam plugs to cover wing screws








Required for Completion

  • Receiver with channel minimum of four channels (Aileron, elevator and throttle)

Assembly

Though the model came with a tube of glue, I could not be sure exactly what type of glue it was. I opted to go with my tried and true adhesives, namely five and fifteen minute epoxies and foam safe CA.

Fuselage

The fuselage itself really requires no assembly. It comes with a pair of elevator servos already installed, as well as the entire power system. All of the wiring is routed down the center of the fuselage in a channel cut along the top center of the wing saddle.




The canopy attaches to the fuselage by means of four little metal c-clips that are attracted to four magnets in the fuselage. The c-clips are just clamped loosely to the canopy and if not careful, you may lose them when handling the canopy. A drop or two of CA will help prevent this from happening. Though the A7 comes out of the box pilotless, there is a decal applied inside the canopy to simulate the A7's control panels and instrumentation.

Wing

The wing comes out of the box in one large piece. There is a two piece spar glued in place. This spar is also the CG location, at the wing root. The two aileron servos are already installed. All that remains is to make up the push rods and connect them between the ailerons and the servo horns. The included clevises thread onto one end of the push rod and the other end of the push rod has a z-bend. The horns are already mounted to the ailerons. There is a fair amount of lateral slop in the clevis after snapping it onto the aileron control horn, as the spacing between the two jaws of the clevis is substantially greater than the thickness of the control horn. I always use small nylon ty-wraps as security retainers on clevis' if none of the more conventional type are supplied in a kit and they work very well.



The servo leads lie flat in precut channels. The servos are mounted inboard very near to the fuselage, and the servo leads thus quickly disappear into the fuselage with but an inch or two exposed.

The center groove in the fuselage supplied for all of the wiring gets a little crowded, and when attaching the wing to the fuselage, care must be taken to ensure that all of the wiring is lying as flat as possible. This will allow the four wing retaining screws to fully seat the wing to the fuselage. Strangely, the four supplied screws were too short to even begin to grab the plastic insets mounted on the fuselage. A quick rummage through my parts box turned up four longer screws. I then noticed a small gap at the rear of my wing, even though the screws were all tight. Removing the wing revealed an impression in the rear bottom of the wing that matched the outline of the ESC. I carved a small pocket in the exact location of this impression to provide the ESC with a little extra breathing room. Having done this, the wing now mated nicely with the fuselage from front to back. The four foam plugs provided are nice. They even have the same panel lines that pass through each corner of the wing.

Tail

Attaching the three thick tail surfaces is a snap. They are are sturdy, and each one of them fits tightly into their respective locations. In fact, they fit so snugly that I was comfortable using foam safe CA to attach them. The two elevator halves come pre-hinged and pre-attached to the horizontal stabilizers. The vertical stabilizer does not come equipped with a rudder, though adding one would be pretty easy.




Assemble the two final push rods and attach them to the two elevator servos and control horns, paying careful attention to the alignment of the two elevator halves in relation to each other. With both elevator servos in the same neutral position, sight along the elevator halves to make sure they are both in the same neutral position. These two servos are attached to one common servo connector and will share one channel on the receiver.


Radio Installation

As mentioned, the A7 is pretty much a Receiver Ready kit. There is a fairly large receiver compartment molded into the foam fuselage near the leading edge of the wing at the wing saddle. My Spektrum AR500 full range receiver fit with plenty of room to spare. I ran the longer antenna out of the receiver area and along the wing saddle, holding it in place with a few pieces of 3M Blenderm.



Power System

Though the complete power system comes wired and installed, my curiosity drove me to extricate the fan and motor for a closer look and some close up photos. Access to the fan and motor is gained by removing two small screws, which then allows removal of the hatch located on the aft belly of the fuselage. The motor is a 2950 Kv brushless outrunner motor, which is mated to a five blade impeller. The fan unit is a 70mm class fan.




The speed controller comes with an inline BEC attached to it. Both are already installed in the aft section of the fuselage wing saddle.




Completion

Wow, that was QUICK! Thanks to the factory applied paint and decals, this A7 goes together right quick. One short evening spent building will have the Corsair ready for an early morning sortie the next day. While the manual does show what the center of gravity needs to be, it does not offer any information on suggested throws for the ailerons and elevators. SO, I set my ailerons for about 3/8" throw on low rates and 3/4" on high rates. I programmed in 3/8" worth of low rate travel on the elevator, with the high rates getting set at about 9/16". I like to run about 40% expo on my EDFs. Slipping the 4S 22200 lipoly battery into the battery compartment is easy. I found it necessary to position it pretty far back, otherwise the canopy would not seat properly. Positioning it just far enough back in the battery box to permit the canopy to snap down in place resulted in the proper CG being achieved.

The AUW (All-Up-Weight) RTF (Ready to Fly) of my JPower A7 came in at 30.2 ounces.




Flying

Taking Off and Landing

Pushing the throttle stick forward the first time in preparation for launch, resulted in the motor stuttering and sputtering as it struggled to build RPMs on it's way to wide open throttle. No matter how I worked the throttle stick, it just could not seem to find its way to any kind of smooth and steady RPM. After reconfirming that the lipoly pack was indeed fully charged, I reached for another 4S series lipoly battery. With an alternate battery, the power system successfully surged to life, although not without a bit of mid-throttle hesitation? Some have suggested that a simple timing adjustment on the speed controller will probably solve this problem but with no real directions on how to program the ESC included, it is difficult to attempt to make such programming changes. (The "burbling" of the power system at some mid-throttle positions can be heard in the review video below.


With the pedal to the metal, I raised the A7 over my head in my left hand and heaved it straight forward. The high wing configuration and overall shape of the A7 fuselage results in a model with quite the natural hand grip. The output of the included power system is satisfying and strong and the big 30+ ounce airframe climbs out very nicely on launch.




The high wing configuration, coupled with a light wing loading, combine to create a aircraft that will slow nicely on landing. There are no worries that you will snag an aileron servo or push rod in the grass when landing this A7. They are high up out of harms way. The one caution that must be exercised is to try and protect the inlet lip on the front of the Corsair. I was able to flare mine in such a way that the very aft end of the long fuselage would contact the grass first, scrubbing speed and velocity as it drug itself through the grass. With the inlet lip and front of the aircraft dropping to the ground last, the chances of any real damage to it are minimized.





Curiously, several of my launches saw the big A7 pull hard to the right. Most of the time I was able to compensate, correct and climb out with hard left aileron. In one instance I was not able to save the launch, however, and the A7 crunched in hard on her nose and inlet lip. Ouch! Most of my launches have been non-events, with the A7 climbing out just as calmly and tamely as you would like. I like to launch with the elevator on high rates and the ailerons on low.

Aerobatics/Flight Performance

It is always interesting to send the Eagletree eLogger up for a check ride, to gather some in flight numbers and see what the power system is actually doing. The factory power system in my A7 Corsair is producing a maximum output of around 450 watts, with maximum current peaking in the low 30s range. Though this does not give the plane unlimited vertical climbout ability, it does more than adequately push the big foam fuselage along at an exhilarating pace. During one media gathering flight, I accidentally violated controlled airspace and brought the big Corsair in directly over our heads in a high speed, low pass. The blast of energy generated by the the A7 as it roared by just a half dozen feet over our heads made us both spontaneously burst out in uncontrolled laughter. (Audible in the video soundtrack) This plane really does have great presence in the air!

(DO NOT try THAT at home. We RC Groups Authors never intentionally compromise safety or AMA protocol during the making of these reviews!)


Lacking a rudder, knife edge is out of the question. But, nice, large loops are easy, especially with a very slight diving entry. The ailerons on the JPower A7 are located inboard, in the location normally reserved for flaps. The result is rolls that are just a little less than axial. Experimenting with some aileron differential will probably clean them up a bit. What the large A7 really excels at is flights spent at WOT. The power system seems to handle it with no complaints and the lipoly battery never came down excessively hot after streaking around the sky for a full flights worth of mAH.

Is This For a Beginner?

Beginning EDF pilots may be comfortable flying this larger offering. Its high wing configuration and lighter wing loading mean easy launches and landings. At the same time, the speeds possible with this 70mm ARF are nothing to sneeze at, and right out of the box, it is probably peaking at 70-80 MPH, so your reflexes had better be tuned up and in tip top shape or the Corsair could get out in front of you before you know what is happening.

Flight Video/Photo Gallery












Downloads

Conclusion

Hobby Lobby's JPower A7 Corsair II is one rockin' 70mm EDF. It comes out of the box just about ready to rumble and in just an hour or two, you will be ready for launch. The paint and decals are all applied at the factory and they look great. They faithfully recreate the look of a vintage Navy color scheme. The factory power system really helps the A7 pour the coals on but at the same time, it needs a little massaging or tuning to smooth out the mid-RPM blues. I decided to swap the factory ESC out with one of the Castle's excellent Thunderbird 54 speed controllers and a Castle BEC. With these components installed, the motor and fan ran smoothly, from 0 all the way up to 100% full throttle.

I absolutely LOVE the way the A7 looks as it comes in on a hot pass, its fuselage "hanging on the wing". It is downright beastly, but in a very, very cool way. Its full throttle passes will get the adrenaline going, and yet it will allow itself to slow down nicely for easy landings on its long belly. I recommend a flying site with nice, soft green grass in order to not damage the intake lip. Keep the nose up on the flare and all will be fine. The high wing design of the airframe makes for easy hand launches. Sadly, many of the EDFs offered today do not come with a pilot figure. This is true of the A7 too.

Pluses:

  • Nice rendition of a less often modeled aircraft
  • Larger 70mm class model provides exhilarating high speed EDF performance
  • Expert builders will have her ready for the catapult in 60 minutes or less
  • Factory power system pushes the A7 along at a more than satisfying speed
  • High wing configuration means easier hand launches

Minuses:

  • Power system sounds a little unhappy at mid-throttle settings
  • Manual is a little lacking in detail and omits important details like factory recommended control throws
  • No speed controller programming instructions to permit changes to motor timing


Last edited by Angela H; Dec 19, 2008 at 06:23 AM..

Discussion

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Old Dec 19, 2008, 10:48 AM
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brati4's Avatar
Wichita,Ks
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Nice review Jon, been waiting for this one. What took you so long? ...Just kidding.. Good review for a good plane.
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Old Dec 19, 2008, 10:59 AM
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Great review Jon! I love my A7 (version 1) and believe it's one of the nicest flying and looking EDF airframes currently available.

Doubletap
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Old Dec 19, 2008, 11:25 AM
US Navy AT2 1987-1995
USNAviationjay's Avatar
Houston Texas
Joined Mar 2008
1,329 Posts
Man having worked on the real A-7E for 4 years with VA-105 I gotta get one of these.. this is too cool.
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Old Dec 19, 2008, 11:31 AM
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brati4's Avatar
Wichita,Ks
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USN: it is definitely one of the most docile EDfs I have ever flown. The only issue is the ESC as Jon has stated. Many have bought the ARF kit and put in their own electronics.
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Old Dec 19, 2008, 11:31 AM
KK6MQJ
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Quote:
Man having worked on the real A-7E for 4 years with VA-105 I gotta get one of these.
You actually having worked on A7s is what is really cool!
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Old Dec 19, 2008, 11:42 AM
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Jon: have you experimented with the Diff to get the rolls better?
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Old Dec 19, 2008, 11:51 AM
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West Central PA
Joined Dec 2008
2,140 Posts
I've kicked around the idea of getting the bare airframe version, but with they'd come down to under $100. I've flown similar high wing delta jets like this, and the airframe is really nice to fly. As Jon says, it's probably one of the better suited EDF entry jets.
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Old Dec 19, 2008, 11:53 AM
KK6MQJ
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No I have not toyed with the differential yet. It is on my rather lengthy list of things to do though!
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Old Dec 19, 2008, 12:13 PM
Balsa just crashes better
Cub Fan's Avatar
Bradenton, FL
Joined Nov 2004
599 Posts
Nice review - Great looking plane in the air. Thanks for keeping the background music low enough so we could hear the motor at work- a very nice touch. I keep avoiding getting an EDF but planes like this are very tempting

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Old Dec 19, 2008, 12:20 PM
KK6MQJ
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C'mon in Cub Fan...the water is fine.

Personally, I cannot get enough of the EDFs right now.
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Old Dec 19, 2008, 12:40 PM
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Quote:
Originally Posted by BARNESJONR
C'mon in Cub Fan...the water is fine.

Personally, I cannot get enough of the EDFs right now.
umm........yeah, that's my problem too. I picked up 3 kits in the last couple of weeks (Windrider F-35, Blitz F-117, Blitz SR-71) to add to a growing collection of unbuilt kits. What can I say, I'm an RC junkie and EDF foamies are my "crack du jour".

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Old Dec 19, 2008, 12:49 PM
Lipo abuser ... smoke on!
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Joined Feb 2005
1,909 Posts
Great review Jon! I've seen this thing fly, and I'm always impressed by how good it looks in the air. I hope manufacturers take note of the growing popularity of these 'larger' foamys

Don
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Old Dec 19, 2008, 01:23 PM
US Navy AT2 1987-1995
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Quote:
Originally Posted by BARNESJONR
You actually having worked on A7s is what is really cool!
A-7Es F/A-18A, C, and Ds and S-3Bs =D

yeh they were a neat aircraft.
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Old Dec 19, 2008, 01:28 PM
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That was a good review and an awesome video. My wife is not going to be happy with me.
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