|
|
|
 |
RCCars |  |
Crack Roll | |
Flying Giants | |
RC Power | |
The E Zone | |
Lift Zone | |
Our Sponsors |  |
|||||
|
|
||||||||||||||||||
|
||||||||
|
Electrifly L-39 EP Ducted Fan Jet RxR™ Review
By Jim Walker
Jul 21, 2009, 04:59 PM
Introduction
I've built and flown just about every genre of flying model there is in our great hobby except one: a jet. If you're like me, you've dreamed of building and flying a gas turbine jet, but the reality is that very few of us have the time and money to go down that path, and the glow powered ducted fans of my youth were heavy, messy, underpowered and fussy to start. With the advent of electric power, it wasn't long until the technology advanced to the point where even electric powered ducted fan jet models were an option. These days, electric powered jets are rivaling their gas turbine powered counterparts in speed and ability. Though once again, the costs involved can be as prohibitive as the gas turbine models. Take heart though, the average flyer such as you and I is now in luck. The quality of the models and components has progressed and the costs have dropped. Wonderful offerings such as the L-39 in this review are readily available and quite affordable, and just about anyone who can fly has the opportunity to pilot an EDF model. But there's yet one more problem to which I'm sure many of us can relate: We love to fly and/or build, but there's just not enough time in our busy lives. A project gets started with great enthusiasm and then ends up sitting forever on the bench (I have several in such a state). Electrifly has come to our rescue with the new L-39 brushless RxR ARF. The L-39 is a proven winner, but now it comes in a package that allows pilots who have their own preferences and gear to get in the air quickly. Add to that the included brushless motor and ESC that guarantees top performance at a very reasonable price, and you've got something special. That was it for me, I had no more excuses. I invite you to join me in seeing how easy it was to get a high performance electric ducted fan model in the air!
Kit Contents
Electrifly Power Series 1250mAh 11.1v 20c LiPo
One of the items you'll need to complete the L-39 is a suitable battery. Though not included in the package, the Electrifly Power Series 1250mAh 20c battery was provided for this review. It is a fine choice at a reasonable price and could be purchased at the same time as the kit.
The shipping box was very attractive and informative, and it also protected the contents quite well on their journey to my house. Everything you will need to get the L-39 RxR ARF in the air is included except for the few components that most modelers usually prefer to choose for themselves. This configuration is really one of the main rationales for this new package.
Kit Requires:
Kit Contains:
AssemblyOne of the main reasons this type of kit is so appealing is due to its ease of assembly. In fact, the small manual is almost not needed for this jet.
Main Component AssemblyThe servos, pushrods, wiring and so forth were factory installed, and no additional work was required. The manual suggests 30 minute epoxy, but anywhere between 5 minute and an hour set time is acceptable. I chose 15 minute so I could simply hold it together by hand with a few minutes of adjustment time. The manual warns that tape will easily pull the paint off the foam, and I wanted to avoid that.
I chose to glue the tail assembly to the fuselage with the fan cover removed. This was to insure that no stray glue would get on it and make removal difficult. The fan area needs to be accessible for EDF unit and motor maintenance in the future. The cover fitted easily and snugly into place after the tail assembly cured. I chose 5 minute epoxy again for this operation, and parts keyed together nicely, and I felt that no adjustment time was needed. Total elapsed time including epoxy curing was 1.5 hours.
Radio InstallationA tube is embedded in the fuselage for 72Mhz antennas to be run, or if using 2.4Ghz equipment, there's plenty of room to position the two opposing antennas in the cockpit area. The elevator servo is also factory installed in the cockpit conveniently off to one side.
I've always had a problem with the Velcro adhesive backing sticking to AeroCell foam. The manual suggested a very light coat of thinned epoxy brushed onto the floor of the cockpit to solve this problem beautifully with no measurable weight gain. The Velcro has not released at all after repeated battery removals.
CompletionSmall ducted fans like this can't afford landing gear, so what do you do with it when not flying? Why, put it on the included display stand along with the really cool looking display canopy, bombs, and missiles of course!!
There were no problems with the first preflight whatsoever. A few movements of the battery pack with the L-39 on the Great Planes balancer had its CG right on the recommended starting position, and the size and weight of the Electrifly battery was the main contributor to the ease of this procedure. Of course the CG was set with the included flight canopy installed and all display items removed. A few more minutes checking servo direction, adjusting throws and zeroing center points had the Albatros ready for its first flight.
Flying
The Electrifly L-39 Albatros by Great Planes was already a proven winner, but this package comes with all the hop-ups factory installed. The Ammo brushless motor, Silver Series brushless ESC and high output LiPo Electrifly battery all coupled to the HyperFlow DF unit provided the Albatross with above average performance for EDF jets in this range! Even at the high altitude at which I live (nearly 4000' ASL), the L-39 performed. This amount of performance at such a low price is difficult to beat, indeed!
Basics
The Albatros was rock steady from the very start. Just a few clicks of up elevator trim and full throttle produced stable flight and crisp acceleration that got the L-39 to altitude in a hurry. Multiple attempts at stalling the L-39 failed to produce any negative behavior. Varied techniques were tried such as pulling up hard and chopping the throttle at speed, slowly backing off the throttle and gradually applying up elevator at the same time, and finally, climbing near vertically until all speed was lost. In each case the Albatros gently banked to one side or the other and immediately started flying again. No snapping tendencies were encountered. With stall characteristics ascertained, the CG was adjusted slightly forward and aft on subsequent flights. In the end, the CG suggested in the manual seemed just right. The manual does allow a small range to accommodate different tastes.
With plenty of confidence in the stall characteristics in hand, it was time to fine tune the throws. A word of caution: I agree with the manual that first flights should use exactly what is specified. The L-39 was very sensitive to small control inputs. However, after just a couple of flights, it was clear to me that there wasn't nearly enough aileron throw for my liking during high speed passes. I doubled the throws recommended in the manual and was satisfied with the roll response; however, landings became a bit twitchy. After a few more flights I decided to set dual rates with the recommended throws programmed on the low rate switch position. This proved quite desirable for slow roll work and landings. The high rate position with double what the manual suggested worked well for axial rolls at speed.
Next it was time to work with the elevator. The suggested starting throws on the elevator are quite small, and I was tempted to add more throw. I'm glad I didn't! The L-39's elevator was even more sensitive than the ailerons. Large movements of the elevator accomplished nothing but a quick stall and loss of airspeed. The Albatros definitely won't snap as reported earlier, but if you suddenly lose all your airspeed at low altitude, well, you fill in the blanks! After several flights it was decided to use dual rates on the elevator as well. Low rate was once again set to the factory specifications and high rate added about 20% more throw. However, high rates were only used during one aerobatic maneuver and even then weren't absolutely necessary. 99% of the time the factory throws were just right.
Next, slow speed flight was investigated. Starting high and then gradually flying lower and slower revealed the Albatros's characteristics which were quite pleasant and enjoyable. The L-39 won't slow down like a delta, but it is a jet which gives it great slow speed performance. For a real treat on a low pass, first slow down as if to land, then gradually and simultaneously pull up elevator and advance the throttle. The L-39's nose will come up slightly but instead of climbing, the plane will slow down quite a bit while maintaining altitude! It was also noted that as I'd heard, EDF powered planes lose airspeed and thus altitude in turns unless throttle compensated. There's not a propeller up front generating torque and thrust, just a little fan in there screaming away, so turning and burning required some throttle management. One could just firewall the throttle, which would be fun, but flights would have been quite short.
That brought me to the final basic flight observation; battery performance and suitability vs weight and duration. Two sizes and capacities of LiPo battery are recommended for this model. The one provided for the review was the larger of the two at 1250 mAh. After extensive flight testing I can't imagine using a different power source. The size and weight of this pack was perfect for balancing and keeping the AUW close to the minimum. AUW weight is a big consideration for EDF planes, and I wouldn't want to sacrifice any of the performance I experienced by adding weight. On the other hand, flight times were about as short as I'd want them with this pack. Firewalling the throttle for the entire flight cut the duration to 4 - 5 minutes. With throttle management and mixed flying I was able to get consistent 7 minute flights. The longest flight was 9 minutes, but the pack was completely discharged and hot which would severely shorten the life span of a lithium polymer battery if done repeatedly. The smaller 950 pack could conceivably be used resulting in a possible increase in performance. However, in my opinion, the negatives would greatly over shadow the slight increase in performance. First, the lighter battery could make it difficult to balance the plane. Second, and more importantly, the duration would be extremely short unless the pilot did mostly slow and level flight. Taking Off and Landing
Usually what one worries about the most with a EDF jet is the launch. I was no exception, and I spent several minutes before the first flight contemplating how I would hold the model and thrust it into the air. I'm happy to report that the time I spent was completely wasted. After many launches it has become clear that you may hold the Albatros however you wish. All that was required was to advance the throttle to full and firmly push straight forward with the nose level. The brushless EDF unit provides plenty of thrust for this model. In dead calm air the L-39 dropped ever so slightly after release as it accelerated to speed. With a slight headwind it climbed immediately after launch, a real pleasure!
Landings were just as pleasant as takeoffs, I'm happy to report. Since the Albatros had absolutely no bad habits, landings were smooth and solid. Since this is a jet model with no landing gear and thus flies relatively fast for a "parkflyer", some room was needed to line up and allow for slide. However, after the feel for the Albatros was acquired, all that was needed was to decrease the throttle to about 25%, keep the nose level and let it settle softly for a sliding landing. Chopping the throttle completely proved to be a bad idea as the fan became an airbrake and slowed down the model too fast. Grass or something equivalently soft was a must since the model is made of foam and has no landing gear. Which brings me to the one complaint and at the same time one of my biggest kudos for this model, strangely enough. Electrifly was very thoughtful concerning durability. The wing tanks look great, but would be trashed soon enough if they were permanently glued on. The solution was to have them held on with neodymium magnets, and it worked wonderfully. No one lands perfectly every time, and I'm no exception. Even on perfect landings a tuft of grass or some such can rear up and smite a model. However, each time the tank just popped off with no damage to the tank or the wing. At the same time, the magnets were plenty strong enough to hold the decorative tanks on during high speed flight.
Unfortunately, there was a severe durability problem with the servo arm covers. The servo arms and linkages project from the bottom of the wing, and thus would be destroyed on the first landing without some sort of shield. AeroCell is a great material that is super durable, light and easily repairable: the perfect material for molded model airframes. The problem with making the servo arm covers from AeroCell is that the covers are taking approximately 95% of the weight and friction of the airframe during landing. Foam is not very good at resisting abrasion and is not the best in compression.
The result was that the covers were obviously not going to survive long without some kind of attention. I design and build foam and carbon fiber airframe parts and frankly, I'm not sure what Electrifly's answer to this problem might be without significantly increasing the cost of the kit. So even though I'm pointing this out, I can't really say it is a design flaw. It's just something I feel might be better addressed before the first flight. My solution was to carefully remove the AeroCell covers, coat them inside and out with laminating epoxy, repaint and reinstall. This procedure has made them perfectly acceptable so far with just a minimum of weight gain.
Aerobatics/Special Flight Performance
Of course the real fun begins when one starts to explore the "jet-like" performance of a jet model! (No I'm not referring to flying the model around the garage by hand while making jet noises...) Of course, jets are supposed to go fassst! Does the Albatros go fast? My eyes are not calibrated and I didn't have a speed gun handy, but I'd guess this plane will do 60-70 mph diving into a low level fly by with no headwind. So is that fast? At the end of the day I can only give you my personal opinion, which is, the Electrifly L-39 brushless RxR package is just right. Hearing that brushless EDF whine as the Albatros whizzes by on a low pass gets the adrenalin up without scaring me to death like the last hotliner I flew!
This is a beautiful semi-scale model and should be flown most of the time as such. It also has only elevator and ailerons for control surfaces which eliminates certain maneuvers. In spite of that, the L-39 was quite agile and would do quite a bit more than the full scale plane could do. First and foremost, slow rolls on low rates were wonderful and surprisingly easy due to the model's great stability. That stability coupled with a responsive yet smooth elevator response was, in my opinion, the explanation for the ease of slow rolls. Switching to high rates was the ticket for high speed axial rolls. On low rates during the inverted part of the slow roll, quite a bit of down elevator was required. However, on high rates just a slight nose drop was noticed during the roll with no elevator input. Slamming the stick over at high speed and watching the L-39 twist was fun, but I still preferred the more scalelike slow rolls at the end of the day.
Loops were definitely an option. They required the plane to be at speed with full throttle however. An attempt at too tight, too big, or too slow a loop got the pilot a gentle bank as it fell out of the loop near the top. The model recovered nicely each time. After a few tries the correct speed and size were discovered, and loops became quite pleasant and even seemed to be within the character of the model though I wonder if the full scale L-39 is capable of loops. Inverted flight was also very doable and stable. This was where the optional high rate elevator switch was used. Using stock elevator throws on the low rate switch setting, the Albatros required full down elevator and full throttle to maintain altitude. At high rate the plane was able to climb slightly at full throttle, but overdoing it resulted in a stall which is not fun when you're upside down. After noting that the Albatros required full down and full throttle inverted, I saw no reason to attempt outside loops or split S maneuvers. However, the L-39 was rock solid inverted as long as it was kept within its flight envelope. Extremely low inverted passes will definitely be in the near future... a real treat with such a beautiful model!
Is This For a Beginner?This model is definitely not for the beginner. It has no self-righting abilities and is a "go where you point it" airplane. Though not super fast, it is definitely not a slowflyer. No rudder with only aileron/elevator control means that pilots need to have progressed past rudder/elevator trainers. This model is for the intermediate to advanced pilot or anyone who can comfortably fly A/E equipped planes and wants to try their hands at an EDF. Launches are easy, but I would recommend prior handlaunch experience with propeller driven models. If it happens to be the first jet for a pilot and the first attempt at handlaunching, I would recommend that an experienced launcher be used for that first flight. After that it should be no problem for the pilot to launch and fly simultaneously. Finally, heaven forbid there is a crash, molded AeroCell is very durable and easy to repair which lends itself very well to the first time jet flyer.
Flight Video
ConclusionI have nothing but good things to say about this package. It is aimed at the intermediate to advanced pilot who usually has his or her own preferences toward radio equipment and would probably end up switching out factory transmitters and receivers if included. All the commonplace components are already gathered, installed and are of high quality saving huge amounts of time and money. Construction is incredibly fast and comes close to "RTF" status. High performance "hop-up" brushless components are already installed at a noticeably low price precluding the need to buy cheap now and upgrade in the future. The model is simply beautiful in flight with scalelike appearance and performance. However, with brushless power things can be bumped up a notch for a little adrenalin fun. First time jet pilots can fly with confidence due to the rock solid flying stability and durable molded AeroCell airframe. Advanced pilots will enjoy the ease of transport and reasonable price which will allow them to get a quick "jet fix" anytime at the local field. Finally, because of all the extra display parts included at no extra charge, the Electrifly L-39 RxR ARF constitutes a simply stunning display model when not at the field. I highly recommend this package!
Pluses:
Minuses:
Last edited by Jim Walker; Jul 20, 2009 at 08:11 PM.. |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
|
|
Thread Tools |
|
|
|
Jul 21, 2009, 05:19 PM
|
#2 |
|
Registered User
Join Date: Dec 2008
Location: Florida
Posts: 176
|
good review, but its way under powered, with a don's wicked 5400 and it made it fly like a jet, it pulls 450 watts at 40 amps with a 2200 mah 25c 3s lipo, stock hyperflow fan, more info.... http://www.rcgroups.com/forums/showthread.php?t=720882
|
|
|
|
Jul 21, 2009, 05:23 PM
|
#3 | |
|
never gonna give you up!!
Join Date: Jan 2008
Posts: 2,499
|
Quote:
+1 that's the setup i use and it's a blast. |
|
|
|
|
|
Jul 21, 2009, 05:31 PM
|
#4 |
|
I can't hear you!!!!
Join Date: Jul 2004
Location: Tucson Avra Valley, Arizona, United States
Posts: 2,939
 |
Hey Jim,glad to see your back in the saddle!! Jet needs a peg in the wing,lol...
Excellent review! -Dave |
|
|
|
|
Jul 21, 2009, 06:19 PM
|
#5 |
|
that's how i roll!!
Join Date: Feb 2008
Location: las cruces, nm
Posts: 205
|
Great review, Jim! very informative and fun to read.
I have the xpd-81 with hyperflow fan and 4400 kv turnigy inrunner. Flies real nice. We should see which is faster sometime  Are you still doing the friday morning flying routine? I plan on going out there this friday. Maybe i will see you then.-Steve |
|
|
|
|
Jul 21, 2009, 11:38 PM
|
#6 |
|
Live, Die, FLY
Join Date: Jul 2006
Location: Kalispell, in the Rocky Mountains
Posts: 430
|
haha my buddy bought one of these and he made me fly it first. good little jet, but yes underpowered. my F-27C stryker was faster
|
|
|
|
|
Jul 22, 2009, 07:20 PM
|
#7 |
|
Registered User
Join Date: Apr 2002
Location: Canada's East Coast, "An Ocean Playground"
Posts: 3,762
|
|
|
|
|
|
Jul 25, 2009, 05:32 PM
|
#8 |
|
Registered User
Join Date: Feb 2001
Location: Fort Worth, TX USA
Posts: 1,975
|
Jim, Just curious.
Why are there no photos of the model flying with the clear canopy? "Flight canopy" does that mean the clear one is for display only? |
|
|
|
|
Jul 27, 2009, 03:21 AM
|
#9 |
|
Registered User
Join Date: Nov 2006
Location: Regina, SK
Posts: 1,011
|
The servo horn covers on the bottom of the jet can be easily reinforced if you put a thick layer of foam safe CA on the bottom parts.
It's proven to be a really tricky jet to hand launch in stock form because it has very little 'pull' even when at WOT. You (or someone else) launch it wrong and there isn't enough power to pull it out of trouble. Once in the air and up to speed it flies decently. 1300mah packs gets you about 5 minutes of flight time with careful throttle management. The stock speed controller has a really dumb arming routine where you need to throttle up, wait for it to beep and then throttle down and wait for more beeping. Rob |
|
|
|
Jul 27, 2009, 03:25 AM
|
#10 | |
|
Registered User
Join Date: Nov 2006
Location: Regina, SK
Posts: 1,011
|
Quote:
Rob |
|
|
|
|
|
Jul 27, 2009, 09:21 AM
|
#11 |
|
Use The Force Jim
Join Date: Jul 2001
Location: Las Cruces, NM USA
Posts: 2,319
|
Hi everybody!
Thanks for reading my review and I'm glad you enjoyed it. I'd like to answer some of the questions and respond to some of the statements made here for the benefit of any readers. Please understand that these are my opinions and I understand that each person perceives things differently. Dave, I'd like nothing better than to toss a plane with a peg in the wing, but I don't think this little jet would handle it too well  Maybe next year when I'm out of school I'll explore if my back can do it. It's nice to hear from you though!Several people have said that this plane is underpowered. While this stock kit is definitely not a screamer for veteran jet fliers, I definitely have to disagree that it is underpowered. Maybe these pilots are refering to the brushed version??? The RxR kit is a brushless setup and the plane in this configuration was adequately powered. Launches were a no brainer and the plane lost no altitude after the toss. This is my experience at nearly 4000' ASL as well. At lower altitudes I would imagine it has even more OOMPH. With a headwind it climbed immediately. At full throttle this model was plenty of fun and at half throttle was a stable kitten. No, I never flew this plane with the clear canopy. I considered that a display canopy only since it weighed nearly an ounce more than the foam only canopy. An extra ounce of dead weight in my opinion would have made this model underpowered in this configuration. Best to all, Jim |
|
|
|
|
Jul 27, 2009, 11:06 AM
|
#12 |
|
Registered User
Join Date: Dec 2004
Location: Crossville, TN
Posts: 2,314
|
My Electifly L-39 weighs in at 18 oz and has the stock Ammo 20-40-3500KV set up. The battery is an Enerland 3s PQ 1200XP 20C, servos are JR SM 22's. The ESC is a bit overkill..a BP40a.
It has an aftermarket clear canopy that I combined with the original. I used a couple of 1/16 ply 'fins' to protect the servo arms and linkage..works well. The stock wing leading edges were really rough and adversely affected performance. I added the matte finish Scotch tape to 'smooth' them out..noticeable improvement ! I fly it at 700' above sea level. Not nearly as fast as my hopped up Velocity and XPD-8's, but still fun to fly. |
|
|
|
|
Jul 27, 2009, 03:01 PM
|
#13 |
|
Registered User
Join Date: Feb 2001
Location: Fort Worth, TX USA
Posts: 1,975
|
Well that explains why it was not flown without the canopy, thanks
However the canopy that I was making a year before they added theirs to the kit is only .02 ounces heaver I'm forming it with .020 plastic, anything heavier would be overkill in toughness. Perhaps I'm using smaller magnets to hold it down. This model is definitely not underpowered but then again with a model this small; the need for speed escapes me. I am a lousy hand launcher and have never bounced the plane off the ground. ( at least 40 flights) I tried over handed, holding it just behind the wings and underhanded softball pitch style pinching it in front of the inlets and behind the canopy. Over handed is best unless you are facing a good wind. I ride this bird hard for about 5 minutes with a 1320 three cell pack and have a ball with it. The only mod I made beside the canopy is a cooling scoop in the nose and exit holes leading to the inlet. Before the mod the battery would get hot but not balloon, with it the battery comes back just warm. Nice review, I'm glad to see they don't consider this one to be at the end of its selling life. Better jump on one before they do though. I have a new one under the bed 
|
|
|
|
|
Sep 28, 2009, 04:13 PM
|
#14 |
|
Registered User
Join Date: Nov 2005
Posts: 74
|
I have nothing but great things to say about this jet. Right now I have 5 EDfs and I have the most fun with this little guy and my larger F5. I dialed the ailerons back to 70% expo and this thing flies great.....Ive always had problems hand launching planes, but the L-39 is effortless to get going. Anyone with a little low wing aileron experience will have no difficulty flying this jet.
I fly on the stock power system with a 3s 1320 20c thunder power pack and am getting 6 minutes or so with throttle managment. I feel that the speed range is great for someone like me who does not care about unlimited verticle....I like bringin 'em in close and "buzzing the tower". Highly recommended jet. Five stars in my book. |
|
|
|
|
Sep 28, 2009, 08:31 PM
|
#15 |
|
never gonna give you up!!
Join Date: Jan 2008
Posts: 2,499
|
I just received a dons wicked 4800 and 4S 2200 Batteries to power my L-39 with
hopeing for 105-110.
|
|
|
|
|
|
|
| Thread Tools | |
Similar Threads
|
||||
| Thread | Thread Starter | Forum | Replies | Last Post |
| Sold NIB Great Planes Electrifly L-39 ARF | happylandings | Aircraft - Electric - Jets (FS/W) | 4 | Feb 22, 2009 07:39 PM |
| Sold Electrifly L-39 Electric Ducted Fan Jet NIB | Flyin-Again | Aircraft - Electric - Airplanes (FS/W) | 9 | Jun 28, 2008 11:46 AM |
| Great Planes ElectriFly Mini Delta EP ARF | Dave Lauck | Product Announcements | 3 | Nov 25, 2007 11:53 PM |
| Great Planes ElectriFly Lancair ES EP ARF | Dave Lauck | Product Announcements | 3 | Nov 14, 2006 04:28 PM |
| Discussion **NEW** Great Planes ElectriFly XPD-8 EP ARF Jet & HyperFlow Ducted Fan Unit | Jim T. Graham | Product Announcements | 0 | May 30, 2006 11:48 AM |
|
|
Downloads
