HobbyKing.com New Products Flash Sale

Great Planes L-39 Albatros Jet EDF ARF Review

Great Planes has released a very nice looking sport scale EDF that includes the HyperFlow ducted fan unit and an Ammo in-runner brushless motor, all for under a hundred bucks! Jon Barnes lets us know if this one was worth the wait.

Splash

Introduction


Wingspan:25"
Wing Area:141 sq. in.
Weight:17.5-18.5 oz.
Length:31"
Wing Loading:17.9-18.9 oz/sq. ft.
Servos:Futaba S3114 Micro HT Servos (3)
Transmitter:Futaba 9CAP
Receiver:Futaba R156F FM 72MHz Micro Receiver
Battery:Great Planes ElectriFly LiPo 11.1V 910mAh 20C Power
Motor:Great Planes Ammo 20-40-3500 In-Runner Brushless Motor (Included with kit)
Fan:Great Planes HyperFlow 370 EP Ducted Fan (Included with kit)
ESC:Great Planes Silver Series 25A Brushless ESC 5V/2A BEC
Manufacturer:Great Planes
Available From:Great Planes distributors or your local hobby shop
Price:$99.99

Great Planes has released a very nice looking sport scale EDF that includes the HyperFlow ducted fan unit and an Ammo in-runner brushless motor, all for under a hundred bucks. The plane is composed of a unique closed cell foam called Aerocell. It is not as brittle as more conventional forms of foam and can be glued with standard CA. This model comes out of the box pre-painted, but it is marketed as having a smooth, paintable surface, should you wish to alter the factory paint job. This low parts count kit comes from the factory with most of the work completed.

According to Wikipedia:

The Aero L-39 Albatros is a high-performance, jet trainer aircraft developed in Czechoslovakia to meet requirements for a "C-39" (C for CviãnØ - trainer) during the 1960s to replace the L-29 Delfín. It was the first of the second-generation jet trainers, and the very first turbofan-powered trainer produced, and was later updated as the L-59 Super Albatros and as the L-139. The design is still produced in an evolved state as the L-159 Alca, while more than 2,800 L-39s still serve with over 30 air forces around the world. The Albatros is versatile, seeing duty in light attack missions as well as basic and advanced pilot training, and is the most widely used jet trainer in the world.

Kit Contents

As I dug into the kit contents, I soon began to understand why this ARF may have been a little slow to arrive. It would appear the factory spent a little extra time on the kits, completing many of the steps normally handled by the customer. Control surface horns? Already mounted. Elevator push rod? Factory installed. It is not even necessary to hinge any of the control surfaces, nor to glue two wing halves together to make up the wing. All you must do is attach the wing and tail, insert your radio gear and power system, and fly it!

In the box:

  • L-39 fuselage, one piece wing, empennage, canopy and fan hatch
  • Great Planes ElectriFly HyperFlow Fan Unit
  • ElectriFly Ammo 20-40-3500 brushless in-runner motor
  • Assembly manual
  • Detachable armaments and drop tanks
  • Display stand
  • Decal sheet

Needed to complete:

  • Minimum 3-channel radio with micro receiver
  • Three micro size servos
  • 25 amp Electronic Speed Control
  • 11.1 volt Lithium Polymer battery capable of providing approximately 20 amps
  • Two six inch servo lead extensions

Provided for this review:

  • Futaba S3114 Micro HT Servos (3)
  • Great Planes Silver Series 25A Brushless ESC 5V/2A BEC
  • Great Planes ElectriFly LiPo 11.1V 910mAh 20C Power

Assembly

For your convenience, ElectriFly makes a copy of the L-39 assembly manual available online HERE. Great Planes' assembly manuals are always very thorough, and this one is certainly no exception.

Make no mistake about it, this plane is one quick build. Almost all of the normal tasks have been completed for the builder by the factory. A few hours and a little epoxy, and you are ready to fly!

Motor/Fan

 Electrifly Ammo 20-40-3500
Electrifly Ammo 20-40-3500
Type: Brushless In-runner
Number of cells: Li-Po 2s-3s
RPM/V: 3500
Weight: 65g (2.3 0z.)
Max Efficiency: 89%
Motor Diameter: 20 mm
Shaft Diameter: 2.0 mm
Maximum Constant Current: 12 A
Maximum Surge Current: 25 A
Max Power(watts): 133 W

The first order of business is to assemble the HyperFlow ducted fan and motor. An electronic copy of the assembly instructions can be found HERE.

The HyperFlow fan is designed to accept 370 sized brushed motors, as well as 20mm and 24mm brushless motors. The HyperFlow fan comes with three different fan rotor adapters, allowing it to mate up to several different motor shafts. The motor that comes with the L39 is the Ammo 20-40-3500, a 20mm diameter 3500Kv in-runner.

There is an adapter ring which must be mounted on this 20mm sized motor to center it in the HyperFlow fan housing. Use thread lock on all fasteners when assembling the EDF unit. At 35,000 RPM, you really do not want anything to work its way loose! This fan will also accept more powerful motors, and the performance you can expect from the larger 24mm brushless motors is well documented in the HyperFlow manual.

Once the fan is completely assembled, it gets glued into the fuselage and is accessible via a hatch that is tightly retained with magnets.

Wing

The one piece wing comes with a spar glued internally, and it is surprisingly rigid. The 3114 Futaba servos fit into the cutouts perfectly. A little hot glue, and they were locked into place. The aileron push rods are short and attach at the servo control horn with a z-bend. This technical note appends the procedure and tools for preparing the aileron servo arms for the push rods:

On page 6, step 1 of the manual, the drill bit size used to enlarge the outer holes of the aileron servo arms should be a #58 [1.06mm]. A 3/64" [1.2mm] drill bit could also be used but would result in a slightly loose fit of the aileron push rods in the servo arms.

The other end attaches to the aileron control horn by means of a quick link with an oversize thumb screw with a knurled perimeter.

Foam covers protect the servo control horns from impacting the ground on the belly landings that the L-39 will be undergoing. The wing gets glued to the fuselage with 30 minute epoxy, but only after the fan /motor assembly is mounted into it. This is because the three motor wires get passed into the forward part of the fuselage and become somewhat captive once the wing is attached.

Tail

Assembly of the tail involves little more than gluing the tail surfaces with epoxy after ensuring that you have them square and properly centered in relation to the fuselage and wing. The modular construction of the L-39 will assist you with the correct positioning of them, but use your eye and a tape measure to verify that they are perfect. Once the epoxy has cured, connect the preinstalled elevator push rod to the elevator control horn and move onto the next step.

Fuselage

All of the radio and power system gear is accessible through a pair of magnetically retained hatches. The canopy hatch covers a very roomy battery compartment, and the speed controller and receiver get mounted to the rear of this compartment. There is a foam box into which the elevator servo gets glued. You will need to bend a small offset into the elevator push rod to get it to cleanly connect to the elevator servo horn. This connection is made with an included quick link. I elected to not use servos extensions for the aileron servos, as they would just reach the receiver if I positioned it to the very rear of the canopy opening.

Completion

The L-39 is relatively small and this allows you to place it atop a table or desk with ease. It looks great sitting on top of my computer desk. Attach the removable missiles and drop tanks, and it looks quite menacing.

Now is a very good time to check the CG and set up the control throws. Stick to the recommendations in the assembly manual until you have a few flights under your belt.

The L-39 is engineered very well. I say this because inevitably folks want to go faster, and the L-39 is up to the task. In fact, Great Planes even recommends specific larger and more powerful propulsion systems if you feel the need for speed. In addition to speed modifications though, you need to look at the amazing canopy and pilot upgrade available from Keith Sparks. I really like the colors of the stock canopy, but if you want to change the canopy and add a few pilots, Sparky has you covered. In case you have not come across his work here on RCGroups, Keith is a master builder/designer and also is very adept at creating plastic pieces that are in themselves works of art. If you'd like more information, have a peek HERE. This is a sport scale plane, but with a little extra time and effort, you can really detail it up and make it look even more authentic.

Flying

Basics

Taking Off and Landing

This plane does not come with any options for installing landing gear since doing so would only add extra weight (which is not a good thing for a plane of this size). It is necessary to hand launch the L-39.

I have a confession to make: I am not very adept at hand launching EDFs, and my first effort to launch the L-39 ended up being more of a test of the durability of the Aerocell foam. One very short flight and one hard landing later, and the only damage was a small crack in the foam at the rear of the canopy opening. Impressive!

The manual gives pretty thorough instructions on how to launch the L-39 with an underhand toss. I have seen it done in this manner successfully, but I have had better success with an alternate method of launch: It involves holding the plane in much the same way you would hold a shot put and hoisting if forward and upward. The advantage may be related to the fact that it starts out with over six feet of altitude instead of the three feet of altitude that comes with the underhand toss method. Please watch the video below to get a better idea of my method.

There is no threat of a prop strike when hand launching an EDF powered plane. Unlike a pusher prop, the spinning element is completely contained within the fuselage. So go ahead and give it almost full throttle for the launches. Once launched, EDFs take a few seconds to "get on step". Resist the urge to feed in any up elevator at first, and instead concentrate on keeping the wings level and allowing the speed to build. Once you have a little momentum, feather in a some up elevator, and start the climb to altitude.

Alternately, you may enlist the assistance of one of your fellow flyers. Just make sure they do not heave it up at too steep of an angle. Straight and level, with perhaps just a slightly nose high orientation will work best.

The plane and power system provided for this review are undoubtedly the lightest possible combination, so the wing loading is extremely light. Landing this review plane was as easy as turning final and killing the throttle. The L-39 would glide in with no sign of any surprise. If I felt I was going to come up a little short, a little throttle would extend the glide. Check the landing in the video to see just how nicely it slows down for landing. Due to the exposed aileron linkages on the bottom of the wing, it is a good idea to get into the habit of checking the tightness of the linkages after each landing.

Going with a more powerful power system will add weight, increase the wing loading and require holding a higher speed on landing.

Aerobatics/Special Flight Performance

With elevator and ailerons, the L-39 is capable of loops and rolls. Watch your speed at the top of the loops: A slight diving entry will help you carry enough to get completely over the top. Rolls are slow and scale with the recommended throws. I increased my aileron throws a little to expedite the roll rate. With the light weight set up, the L-39 will slow down nicely. I was amazed at how slowly I could cruise by, especially with a little bit of a headwind. If you have not already heard the scream of an electric EDF jet as the throttle gets pushed to maximum in preparation for a high speed pass, you are missing a very exciting and addictive sound. The L-39 screams along at a very satisfying speed when running at full throttle. I really enjoyed racing along a few feet off the deck at full throttle and then aggressively pulling up and climbing heavenward.

Is This For a Beginner?

EDFs can be a little difficult for a beginning pilot. The launches take a little bit of finesse, an EDF does not instantaneously respond to throttle changes, and there can be a bit of lag from the moment you initiate a throttle change to the time the aircraft actually responds. Once in the air and flying, the L-39 is certainly not a difficult plane for anyone used to flying with ailerons. It is a rather compact model at 25 inches of wingspan, and that, coupled with its relatively high speed, can mean it gets small fast.

Flight Video/Photo Gallery

Downloads

Conclusion

I will emphatically answer YES to the proverbial question, “Was it worth the wait?” I am completely amazed at what Great Planes will give you in exchange for a one hundred dollar bill: a sturdy and sharp looking electric ducted fan ARF that includes the fan and motor. It is an incredible value.

Pluses

  • Incredible value in an Electric Ducted Fan ARF
  • Less than a hundred bucks for plane, motor and fan
  • Great sport scale looks
  • The majority of assembly is completed at the factory
  • Aerocell foam stands up to those less than perfect launches and landings
  • Included armaments and display stand
  • Plentiful use of magnets for retention of canopy, hatches and armaments

Minuses

  • Assembly manual says the armaments are for display purposes only (wink, wink)
Last edited by Angela H; Jun 20, 2008 at 02:59 PM..

Discussion

Reply
Thread Tools
Old Jun 20, 2008, 07:28 AM
what it do everybody?
zaskarkid's Avatar
a swamp naturally
Joined Mar 2008
664 Posts
Terrific review, and an accurate video showing how it'll fly with the stock motor. Thanks! Now I'll go finish mine.
zaskarkid is offline Find More Posts by zaskarkid
Reply With Quote
Old Jun 20, 2008, 07:47 AM
Wonderfully Wicked
The Don's Avatar
Willoughby, Ohio
Joined Jan 2002
13,087 Posts
Excellent job! Well done!

Don
The Don is online now Find More Posts by The Don
RCG Plus Member
Old Jun 20, 2008, 08:35 AM
KK6MQJ
Bajora's Avatar
Joined Sep 2004
13,663 Posts
Terry and I had a blast shooting video and photos of this one. Thanks for the assistance TR!

I am building another L-39 and should have it finished today. It has a slightly hotter set-up, as many guys have already found the L-39 will handle with no problems. This one comes out of the box strong enough to handle more power, with only minor modifications necessary.

I used some Blenderm, top and bottom, on the aileron hinges.
Bajora is online now Find More Posts by Bajora
RCG Plus Member
Last edited by Bajora; Jun 20, 2008 at 08:52 AM. Reason: typos!
Reply With Quote
Old Jun 20, 2008, 08:42 AM
BVM Viper Fever
pdawg's Avatar
United States, OH, Dayton
Joined Apr 2004
5,516 Posts
I want one! great review Jon....as usual
pdawg is online now Find More Posts by pdawg
Reply With Quote
Old Jun 20, 2008, 08:58 AM
Si Vis Pacem Para Bellum!
Doubletap's Avatar
PRC (People's Republic of Commiefornia)
Joined Jul 2005
9,602 Posts
Thanks for a great review! I was kinda on the fence over the GP L-39 but because of you, I will be $100 poorer. For me, the most striking aspect of this model is the undeniably excellent value considering the quality and completeness of the kit compared to the current crop of overpriced (IMO) and mediocre quality RR/ARF EDF jets coming out of China.

Doubletap
Doubletap is offline Find More Posts by Doubletap
Reply With Quote
Old Jun 20, 2008, 09:43 AM
Pro Horder
turbonut's Avatar
upland CA
Joined Dec 2004
7,386 Posts
Nice review Jon...as usual...and they are a great plane(no pun intended) for the money!
scott
turbonut is offline Find More Posts by turbonut
Reply With Quote
Old Jun 20, 2008, 09:45 AM
Grumpa Tom
Kmot's Avatar
United States, CA, Los Angeles
Joined Sep 2003
23,348 Posts
That is the 'best' Top Gun track beginning I have ever seen!

Man, what a beautiful flying site you have.
Kmot is online now Find More Posts by Kmot
Reply With Quote
Old Jun 20, 2008, 10:16 AM
Registered User
Cohoes, NY
Joined Dec 2003
36 Posts
Great review. FastAlJr. and I had the same good experience with ours. Best $99 I spent at Toledo. We are also talking about buying a second to add a little more giddy-up to. Thanx goes to G_rod22 for this one. I did add an exhaust shroud to the fan and a battery cooling duct under the nose and out through the fan inlets, just as a precaustion from past experience with EDFS; otherwise ours was box stock.

A Mostek Sr.
Cohoes, NY
KingCobra11 is offline Find More Posts by KingCobra11
Reply With Quote
Old Jun 20, 2008, 10:43 AM
KK6MQJ
Bajora's Avatar
Joined Sep 2004
13,663 Posts
George is batting 1000, eh?! Reactor Bipe and now this? I love 'em both!

My hotter L-39 has a JS with 5 blade Alfa fan and a 4S lipo. I am mointing the ESC right in front of the fan for optimum cooling.

May have video by end of day!!
Bajora is online now Find More Posts by Bajora
RCG Plus Member
Old Jun 20, 2008, 12:00 PM
Wind Powered
george@dream-flight's Avatar
United States, CA, Goleta
Joined Oct 2004
538 Posts
Stop it!

First class job Jon!
Right on!
george@dream-flight is offline Find More Posts by george@dream-flight
Reply With Quote
Old Jun 20, 2008, 12:23 PM
Speed Freak
Spid's Avatar
United States, OH, North Olmsted
Joined Nov 2005
1,311 Posts
Excellent review Jon. Well done!
Spid is offline Find More Posts by Spid
Reply With Quote
Old Jun 20, 2008, 12:32 PM
Registered User
Michael Heer's Avatar
Stockton, Ca. USA
Joined Apr 2001
9,434 Posts
Very nice review Jon. Mine will have to sit in its box until I can restock on servos and ESCs as I am using all I had on hand for reviews in the pipe line. Mike
Michael Heer is offline Find More Posts by Michael Heer
RCG Plus Member
Old Jun 20, 2008, 02:12 PM
Almost out of epoxy
Done Crashing's Avatar
Salt Lake City
Joined Sep 2007
606 Posts
If you build it 3oz heavier, and even if you beef up the motor, it's a bear to fly. Keep it light. I destroyed mine cause I went with a bigger battery.
Done Crashing is offline Find More Posts by Done Crashing
Reply With Quote
Old Jun 20, 2008, 02:31 PM
KK6MQJ
Bajora's Avatar
Joined Sep 2004
13,663 Posts
Thank you very much, thank you, thank you!

The L-39 is the real star here though!

A GREAT EDF!!
Bajora is online now Find More Posts by Bajora
RCG Plus Member
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Article Great Planes Electrifly Mini Slinger Flying Wing ARF Review gwh Electric Plane Talk 51 Aug 22, 2011 01:31 PM
Article Great Planes Fling DL Hand Launch Glider ARF Review Goinav8n Sailplane Talk 42 May 31, 2009 02:37 AM
New Product New Great Planes Jet!: The L-39 Albatros SwissBoy Foamy EDFs 7 Dec 28, 2007 02:48 PM
New Product Great Planes L-39 DiabloKid Foamy EDFs 4 Aug 16, 2007 01:24 AM
New Product Great Planes L-39 Wasja Foamy EDFs 0 Aug 02, 2007 06:12 AM