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Cox Models Christen Eagle ARF Review

Thomas Blakeney visits Cox’s newest addition into their R/C line – the Christen Eagle. This PNP-style model comes preloaded with a complete brushless outrunner power system and a 3 cell 1800 mAh Lipo battery.

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Introduction


Wingspan:33.6"
Wing Area:400 sq. in.
Length:28.75"
Spec:Advertised:Actual:
Weight:23-25 in oz23.5 oz.in.
Wing Loading:
oz./sq ft
8-98.4
Servos:3 Hobbico B-8
Transmitter:Futaba 9CAP/
DX-6 conversion;
Spektrum DX-7
Receiver:Spektrum BR6000
Battery:3C 12.6v 1800 mAh Lipo (pre-installed)
Motor/prop:110 watt brushless outrunner and 10-4.7 prop (pre-installed)
ESC:18 amp brushless ESC with BEC (pre-installed)
Manufacturer:Cox Models
Available From:Cox Models and local hobby shops

Cox Models, an industry name historically associated with small glow motors, plastic control line RTFs and entry level R/C models has recently begun to offer a series designed to please both the novice and experienced R/C flyer.

One of these models is the new Cox Models Wing Series Christen Eagle. This small foam ARF biplane nicely captures the look and spirit of this classic and colorful aerobatic biplane. Cox makes it extraordinarily easy to get the Christen Eagle model into the air The model arrives highly pre-assembled with even the decals already in place.

Notes on the Full Scale Christen Eagle

The Christen Eagle series of aircraft are based on modified Pitts Specials. They have been re-engineered for easier construction and with some structural and styling improvements by Frank Christensen. The single seat Eagle I aircraft were never offered as kits, but were built to promote the Christen Eagle line of two seat kit aircraft.

The Christen Eagle aircraft are very well known to all aviation enthusiasts, due in large part to the Eagles Aerobatic Flight team. The Eagles team, consisting of Tom Poberezny, Gene Soucy and the late Charlie Hilliard, entertained airshow attendees everywhere with their brilliant multi-color bird-like plumage and precision formation aerobatics with the single seat Eagle 1 aircraft, performing at more than a thousand airshows from 1979 until 1995. These performances made the Christen Eagle as instantly recognizable as a Piper Cub to airshow attendees everywhere, and also helped to make the aircraft very popular in the R/C world.

Kit contents:

This aircraft is closer to an RTF, or PNP, than an ARF in a lot of ways. The kit comes with a 110 watt brushless outrunner with an 18 amp brushless ESC with BEC already mounted and ready to go. Further value is provided by the included 3 cell 1800 Lipo flight battery. All kit-supplied electric components are plug and play. All the builder has to do is to add the TX, three 9 gram servos and a suitable RX unit, plus a very small amount of assembly time.

The first thing that caught my eye were the spectacular decals that give the Eagle its proper scale colors. Someone at this ARF factory is very good at applying very thin water transfer decals!

The Kit Contains:

  • upper wing assembly with all decals pre-applied
  • lower wing assembly with decals applied
  • fully pre-built fuselage
  • landing gear assembly
  • 3 cell 1800 mAh Lipo battery pack
  • spare 10-4.7 prop
  • brief 8 page instruction manual
  • small bag of hardware

Pre-Installed:

  • motor, prop, ESC
  • tail surfaces & tail-wheel
  • pushrods & torque rods
  • hinges
  • interplane struts already in the lower wing

Kit Requires:

  • 4+ Channel transmitter (Spektrum DX7 and Futaba 9CAP)
  • matching receiver (Spektrum BR6000)
  • 3 9g 17 in. oz. sub-micro servos (reviewed with Hobbico B8)
  • tester Gloss clear coat can of paint
  • appropriate battery charger
  • Phillips screwdriver/pliers/hobby knife
  • a desire to fly without doing a lot of work beforehand!

The four ailerons even had fittings already in place for the pushrod that connects the upper ailerons to the lower ailerons.

The pre-installed unbadged outrunner that turns a 10-4.7 slowflyer type prop, offering up about 110 watts on a 3 cell lipo. Also included is an 18 amp ESC with BEC that is hardwired to the ESC. The ESC and battery are pre-wired with some type of Deans connector clones that work well with each other, but not well with authentic Deans connectors. Be forewarned.

The battery is a 3 cell 1800 mAh Lithium Polymer pack. No max draw rating is supplied. No balancing taps are provided.

Assembly comments and observations

Preparing this model to fly is amazingly simple. I suggest that you charge the flight battery right away, because the model will be ready to fly before the charge is complete! Most modelers will be able to assemble this model in about 30 minutes, not counting the hour or so for the clear gloss to dry.

Assembly Snapshot

  • clearcoat the foam
  • press in the servos
  • attach the receiver
  • hook up the supplied control linkages
  • insert the landing gear
  • tape on the canopy
  • bolt on the lower and upper wings
  • install the flight battery
  • adjust flight controls...
  • FLY!

I was a little surprised at the instructions to use Testor's gloss clear gloss to the model. I thought this lacquer-type coating was not ideal for using on foam. However, used in light coats, it worked perfectly to seal and protect the decals and did not harm the foam. The kit instructions suggest removing the cowl before applying the Testors gloss clear, but I skipped this step and still obtained nice results with the clear coat.

I found that the elevator, and the rudder to some degree, had stiffness in the hinges which required some extra trimming. This is not uncommon with foam models that have a compressed foam area at the hinge line.

The strip aileron linkage arrived mounted on the upper surface of the lower wing, and it does show a little bit on the finished model. There is no linkage height adjustment on the strip aileron horns, so I had to ensure I used a servo arm that offered the needed amount of throw.

I secured the interplane struts to the top wing with a screw at the back of the strut and a zip tie at the front of the strut. A zip tie probably wouldn't have been my first choice, but it did work.

With that big canopy, a lightweight pilot figure would be nice to have. I chose to temporarily tape my canopy on until I have found a suitable pilot figure.

I elected to save a touch of weight and not use an aileron extension, as I planned on leaving the model assembled most of the time, anyway. The landing gear assembly, with wheels and wheel pants pre-installed, friction fits into a socket in the lower fuse. I decided to add a little bit of epoxy to the landing gear socket to help retain the wire gear.

The kit instructions showed a clever method of using the included length of red ribbon to help extract the lipo battery from the tight fitting compartment in the lower fuse ahead of the bottom wing. I taped the ribbon to the battery to keep it where it was needed. The battery compartment has a neat little hinged hatch that closes and clips shut and some folks have reported that their hatches do not latch properly, but mine has worked great from the beginning. The battery compartment is a tight friction fit for the supplied 3 cell 1800 mAh lipo and it would be difficult to install a larger battery without some significant modifications.

There is another compartment with a latching hatch right behind the battery compartment that is not mentioned in the instructions. My best guess is that it is the original battery hatch, with the other forward battery hatch being a modification to help the model have the CG in the proper location.

I did manage to break one clevis in the aileron pushrods and another in the aileron interconnection pushrods during assembly. The nylon clevis hardware provided is a little more brittle than typical hardware. If you are concerned about installing these parts, boiling them prior to installation may make them less brittle.

One thing that several people have noted about their finished Eagle model is that the upper wing gets pulled into a faint amount of anhedral, apparently due to the interplane wing struts being a little bit too short. On my model, it was only barely noticeable and I did not feel it had any significant adverse effects on performance or looks. My lower wing had a little bit of dihedral.

The CG worked out per plan at the aft limit with no nose weight required, but I later added some expo on the elevator, as it was fairly sensitive to input. A more forward CG may have been a good solution.

Flying:

I almost hate to say it because the readers hear it over and over again in reviews, but the model required only a small bit of down elevator trim to fly perfectly.

Take-Off/Landing

The club field had a nice grass strip that was smoothly mowed. As small as the wheels are on this model, grass takeoffs were still easily accomplished. I advise flying off closely mowed grass or pavement only and you might need to give a small push at the start even on the best grass surface.

The Cox Eagle is easy to slow and fully controllable at lower air speeds and so proved to be especially nice in handling during approach and landing. The plane lands so slowly that it rarely flips over in the grass despite the very small wheels.

Aerobatics/Special Performance

The Cox Eagle is not overpowered with the stock brushless power system, but there is plenty of power at hand for all basic aerobatic moves. This model is more suited to replicating classic full scale airshow moves than modern 3D aerobatic moves, however. There is not enough thrust to hover, but the Eagle was never designed to hover in any case.

Stall turns were easy to execute and this little model excels at them.

Cuban 8's: No problem, but on windy days, it would be nice to have a little more power at hand to keep the back half of the figure close to the front half.

Loops inside and out: no problems!

Slow rolls and 4 point rolls: no problems here at all, except for some proverse roll coupling in the knife edge parts of the rolls (model wants to roll in the direction of applied rudder) and a need for some elevator expo to reduce the pitch sensitivity of the model. Very little down elevator correction is needed for inverted flight.

The model will almost but not quite maintain extended knife edge flight on the stock power setup. The proverse rudder/roll coupling shows up here as well. Mixing could be used to adjust for this.

Loops with snaps at the top (avalanche) are effortless. Horizontal and vertical snaps break fairly crisply when properly timed but bleed energy quickly due to the light weight and modest power loading of the model.

I have flown the model in gusty winds up to about 15-18 mph. The Eagle handles wind with confidence, but does get knocked around a little. The in flight video was filmed on this very windy and gusty day and shows what you can do with this little Eagle when other parkflyer models are often grounded.

Is this for a beginner?

NO! Did I mention, NO? Trying to learn to fly on a small aerobatic bipe would just be a lesson in frustration when there are so many more fitting models are out there for beginners. That said, the Christen eagle has very consistent performance and could easily be a first bipe or first scale aerobat for a modeler comfortable with a low wing basic aerobat.

Video Gallery

Downloads

Conclusion

Overall, this was a very enjoyable build with even more enjoyable flying! The PNP style setup is very close to "plug and play", allowing me to use my reusable radio gear, but having the power package already installed and ready to fly.

I have had a lot of fun throwing the Eagle around the sky. This model requires at least basic flying skills and is not suitable for a first or second model, but once you can handle a model with some sensitivity in roll and pitch, you will not have any trouble flying the Cox Christen Eagle.

Plusses:

  • PNP-style completeness with pre-installed power system
  • Extremely attractive scale decals
  • Nice level of finish and detail design for a foam model
  • Fidelity of scale, for a small foam model
  • Superb ease of assembly
  • Excellent flight performance given the modest stock brushless power setup

Minuses:

  • Zip tie strut rentention on the upper wing not up to the standard of the rest of the kit
  • Slightly brittle nylon hardware
  • No balancing plug on the 3 cell 1800 mAh lipo battery
  • Clone versions of popular connectors not compatible with the real connectors

I would like to thank Richard Ng (Richard N) for his superb in-flight photography and Ron Pope (dawnron1) for his equally great effort in creating the video for the review!

Last edited by AMCross; Mar 22, 2007 at 09:32 PM..

Discussion

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Old Apr 05, 2007, 03:07 PM
Registered User
Indianapolis, IN, USA
Joined Oct 2000
523 Posts
Great review! I have one of these in my garage just waiting on my to get out there and put it together. I'm looking forward to it even more now!
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Old Apr 05, 2007, 03:39 PM
Electric Coolhunter
Thomas B's Avatar
United States, TX, Fort Worth
Joined Jun 2000
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thanks!..It really is a great little model. I am keeping mine...
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Old Apr 05, 2007, 06:09 PM
Addicted to RC
YarSmythe's Avatar
USA, TX, Houston
Joined Nov 2003
2,719 Posts
Nice. Glad to see it finally online. It appears we had very similar 'minor troubles' during the assembly. Flies very nice though. I'll let you know when I upgrade the motor! VRRROOOOMMM.
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Old Apr 05, 2007, 06:23 PM
Dr. Dave
USA
Joined Nov 2005
1,316 Posts
Very well done Tom. Great detail in the text. Lots of great information.
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Old Apr 05, 2007, 06:59 PM
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Thomas B's Avatar
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Thanks..I will quietly say that I do not agree with some of the final edits made by our recently departed editor....some are a little jarring and out of place.
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Old Apr 05, 2007, 07:15 PM
North Central Positronics
badbill's Avatar
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Joined Dec 2002
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Quote:
Originally Posted by Thomas B
Thanks..I will quietly say that I do not agree with some of the final edits made by our recently departed editor....some are a little jarring and out of place.
What edits were these? Ann Marie has passed away??? What????


Bill Davenport
AMA 28141
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Old Apr 05, 2007, 08:18 PM
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Thomas B's Avatar
United States, TX, Fort Worth
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Don't panic...AM Cross is alive and well....she is moving on...Billy Hell's wife is taking her spot.

Can you get into the authors forum?
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Old Apr 05, 2007, 08:50 PM
The sky is my playground.
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United States, NH
Joined May 2005
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It sounds like you were flying in a hurricane...
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Old Apr 05, 2007, 11:51 PM
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Well, it was a hurricane for the little Eagle, pretty much....
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Old Apr 06, 2007, 07:35 AM
North Central Positronics
badbill's Avatar
USA, GA, Centerville
Joined Dec 2002
3,307 Posts
Quote:
Originally Posted by Thomas B
Don't panic...AM Cross is alive and well....she is moving on...Billy Hell's wife is taking her spot.

Can you get into the authors forum?
What is the author's forum? What was edited out, negative comments about the airplane?

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Old Apr 06, 2007, 09:15 AM
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Thomas B's Avatar
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No negative comments about the model were edited out. The content was not edited.

The editors misspelled a word and added some clumsy verbage and changed the style too much in places.
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Old Apr 06, 2007, 12:12 PM
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juanmartinez's Avatar
San Francisco, CA
Joined Aug 2002
254 Posts
Awesome, awesome.. my experience with biplanes is that the top wing has to be reinforced, how is the wing reinforced on the christen?
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Old Apr 06, 2007, 12:41 PM
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The upper wing does not have a spar and really does not need one, in my opinion. This not a depron wing, bt an injectioned molded EPS wing.

Some people reported, as mentioned in the review, that their model's upper wing was bowed down a little. Mine had almost none of that issue.

The foam itself is fairly strong on a small model like this. The lower wing has a short fiberglass rod spar and the interplane and cabane struts make it all into a box structure.

If you were going to really overpower it with a replacement motor and add much weight to the model, I might consider adding some functioning flying wires or some extra spars.
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Old Apr 06, 2007, 01:16 PM
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I'm sorry, what I meant is not reinforcing the to wing but keeping the wing from detaching while doing loops or high G maneuvers.
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