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Hobby Lobby Alfa P-39 Airacobra ARF Review

Alfa has released the P-39 Airacobra ARF to their impressive lineup of models. Hobby Lobby carries these remarkable looking ARF's that fly even better than they look!

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Introduction


Wingspan:33"
Wing Area:~202 sq in
Wing type:- Semi-symmetrical foam
AUW weight:Advertised 16.25oz Actual - 15.9oz (450g)
Length:28.75
Wing loading:~11 oz/sq. ft.
Cube loading:9.25
Transmitter:Hitec Aurora 9
Servos:eRC 8g
Receiver:Hitec Optima 7 channel
Battery:POWERWING 1600 3s LiPo
Motor:eRC 400 brushless outrunner motor
ESC:Art-Tech 20 AMP ESC
US distributor:Hobby Lobby International
Alfa P-39 Airacobra ARF:Alfa P-39 Airacobra
ARF Price:$119.99

Hobby Lobby has been importing the impressive Alfa models line for many years now. These remarkable ARFs are produced from molded sheet foam which allows them to remain very light. For those concerned about the foam look, I can assure you they do not look like any common ARF foam model. Their unique molding process allows for a harder shell and very smooth surface that is expertly painted. Along with that comes the excellent Alfa markings with multiple schemes. You certainly can see what makes the Alfa lineup a step above the rest.

This P-39 Airacobra continues the Alfa tradition of stunning models with that exceptional finish and look. This is a highly prefabricated ARF model ready to fly within a few hours. They look fantastic, and what is better, they perform in the air since they are so light weight. With today's market of brushless motors, you can use many different power systems, but in my opinion a light brushless setup really makes the Alfa models come alive. This review will test the P-39 coupled with an excellent new motor from Hobby Lobby, the eRC 400.

The review package shipped from Hobby Lobby and it arrived in perfect condition. It was exceptionally well packaged, double-boxed and the contents in the box were isolated and protected from shifting during shipment. One key note, the P-39 is secured via the wing bolt to the box. Make sure you unbolt the P-39 from the block to which it is secured. Alfa uses this excellent protection system to assure items do not shift in transport.

Alfa produces a high quality exceptional ARF, all of them are headturners, with the splendid attention to detail and exceptional markings.

Kit Contents

Excellent text manual the typical Alfa parts blow up and a clear outline guide that helps with assembly.

ARF includes:

  • Stunning pre-painted foam fuselage with tail surfaces attached
  • Foam one-piece wing painted and ready to go
  • Clear canopy pilot ready (pilot included but not painted)
  • Factory hinged ailerons and elevator with horns factory installed
  • Hardware (Push rods, torque rods, keepers and horns)
  • Factory markings with 6 scale choices
  • Clear well-written outline guide

ARF requires:

  • 100-150w brushless motor
  • 10-20amp ESC
  • 2s-3s LiPo battery 900-1600 recommended
  • 2 micro servos (Ailerons and elevator)
  • 3 channel minimum receiver
  • 3 channel minimum transmitter
  • 1 3"-6" servo extension for aileron servo (may not be needed depending on receiver placement)

Included for this review:

<font size=-2>eRC 400 brushless motor</font>
eRC 400 brushless motor
Type:Brushless outrunner
Weight:47g
Output shaft size:3mm
Cells:3S Li-Po
RPM/Volt (Kv):1200
Maximum Current:20A
MSRP:$19.99

<font size=-2>eRC ERCS800 sub-micro servos</font>
eRC ERCS800 sub-micro servos
Type:Analog
Torque:13.89 oz/in at 4.8V
Speed:.14 sec/60 degrees at 4.8V
Weight:8g
Gear type:Nylon
MSRP:$7.99

<font size=-2>POWERWING 3s 11.V LiPo battery</font>
POWERWING 3s 11.V LiPo battery
Capacity:1600mAh
Voltage:11.1V
Number of cells:3
Weight:4.5oz
C Rating:20C
Max. Continuous Current:32A
MSRP:$18.99

Assembly

The Hobby Lobby Alfa P-39 Airacobra encompasses true meaning of ARF. The difficult work was all completed for you at the factory, right down to the impressive paint finish. This ARF was highly prefabricated, including a molded foam fuselage also beautifully painted. It has the foam tail surfaces already attached to the fuselage. The wing is one piece foam molded with integrated spar.

All of the surfaces are attached, hinged and come with the pushrods assembled and attached to the horns. Check the security of the horns, I found one lose one on the P-39 and a tiny bit of epoxy had it fixed.

Most will find the Airacobra can be assembled in just a couple of hours. This just like all the other Alfa models is impressive and detailed really a work of art. This is a very stunning model!

Done by the factory:

  • Surfaces hinged
  • Surfaces have pushrods and horns attached
  • Entire model is expertly painted

The builder needs to:

  • Install the servos
  • Install the motor and ESC
  • Install and paint the pilot figure

Fuselage

The fuselage on the Alfa P-39 was impeccable, representing the full scale version very well. The P-39 has distinctive lines and I was impressed how well they were duplicated. This rounded, sleek bird certainly was not easy to replicate and it represents scale detail, including panel lines very well.

The work here was simple, install the elevator servo and power system. The P-39 has a factory installed tray for the battery and the elevator servo. The elevator is actuated by two separate pushrods and wires attached to each elevator half.

Be sure that you secure the servo end of the elevator pushrod tubes, which is essential for proper operation of the elevators. If the ends of the push rods are not secured they can bend inside the fuselage under flight loads. Do not omit this critical step!

Power System Installation

The Alfa P-39 had the firewall factory installed. A note, since we are using the $19.99 eRC 400 motor, some modifications were necessary. Use of the AXI motor would not have required that, but think of the money we saved using the budget priced eRC motor! The modification was simple, with the proper tools.

Since the eRC motor is slightly longer than called for, a simple modification was necessary. These steps took me about an hour and allowed me to use a $20 motor, rather than the more expensive AXI motor. It was well worth the small amount of work.

Of note - if I had skewed the "X" mount, the process would have been even easier: The bulkhead that was installed to sure up the firewall would have been missed completely.



eRC 400 Motor Mounting

I have also included the official Hobby Lobby instructions for mounting the eRC 400 brushless motor to any of your Alfa models. Click on each picture to expand.



As you can see when you twist the X mount and point the wires straight down, it will miss the support beams that provide some additional support for the firewall. This powerful, tiny motor is big on power yet remains light enough for use with the Alfa models. I was very pleased with this motor and highly recommend it!



Battery Tray

The factory installed the battery tray is made from quality lite plywood. The balance point of the model turned out to be very close to the CG. So the battery will need to go near the elevator servo.

Canopy and Pilot

Since this is a scale model I added a pilot figure that I had from a previous model. I wish I could take credit for this awesome painting but alas I have no talent here. Doug Cohen an expert figure painter and friend of mine did this pilot for me!

Wing

The wing comes completely assembled and ready for a single servo for both ailerons. Alfa uses a rather unique but very effective single servo technique used on most of their models. I like using one servo for the ailerons, as it saves money!

Power system

The recommended eRC 400 brushless motor was a perfect light weight, budget power system for the Alfa P-39 Airacobra. The motor is very powerful!

Amp draws

The included brushless motor was perfect for use with 3s packs. With the POWERWING 1600 mAh 3s pack and the following propellers it produced the following results:

Motor statistics on 3s
Propeller Amps Watts Voltage
APC SF 8x6 18.7 214 11.4v
GWS HD 8x6 15 175 11.6v
GWS HD 9x5 15.7 180 11.5v

As can be seen, this is a very powerful little motor. As can be seen the APC-sf propellers tend to draw more amps and I felt that was more power than needed. I settled on the GWS HD 8x6 propeller and it has been an excellent choice. I prefer the smaller propellers with all of my Alfa models as they tend not to have as much "P" affect on these small ships.

These power levels gave the Alfa P-39 Airacobra ~175 watts per lb performance, more than enough for spirited performance in any any model let alone this lightweight Alfa! The power and performance of the eRC motor was impressive.

Battery

A single 3s 1600 MAh POWERWING LiPo battery to provide power. This pack weighs in at 4.6oz/130g. Performance of this pack was stellar as can be seen it provided great voltage under at the 15 amp load. Maintaining 11.5+v of power was excellent.

Finish

The Alfa models all come factory painted, and they include various markings giving you the choice on final look for your model. Since the P-39 was flown by many allies there are a good number of choices, including some excellent Russian schemes. Many will recall the Russians flew this model aggressively in the cold north areas of the war where it proved excellence as a combat machine!

Took the Alfa P39 Airacobra ARF outside for some more pictures - it just looks stunning!











CG

With the 3s 1600MAh pack placed nearly over the CG putting the battery near the elevator servo but still allowed for adjustment without weight being added. Alfa places CG indicator marks on the bottom side of the wings. While this is a great positive indicator you must balance this plane as all other low wings, with the airplane inverted. It was easy to measure and transfer small marks to the wing tops.

CG is somewhat a pilot preference so adjust as needed. The recommended CG was perfect for me.

Rates and transmitter setup

I used my Hitec Aurora 9 and Optima 7 channel receiver for the Alfa P-39. I can't wait for the Minima receivers Hitec is releasing soon, as their size and weight will be more suited for the Alfa sized park models.

Rates were set as recommended in the manual with ailerons at 10mm up 9mm down and elevator at 10mm. I also added the recommended 1mm of reflex in the ailerons.

Exponential rates were set at my preferred 25% for both the ailerons and elevator. The ailerons were responsive in flight but nothing too concerning. The pitch authority was also very good, perfect for my preference in fact. I appreciate it when manufacturers spend the time necessary to test models properly and give you recommendations that work.

Control surface throws are again a bit of personal preference, so adjust yours at will. It is nice to know Alfa has a great starting recommendations for you.

The flight timer was set to count down from 7 minutes giving an audible warning to land before the battery was depleted. The 1600 mAh pack was able to supply the eRC 400 motor with full throttle runs with no ill effects.

Flying

The P-39 is a small, quick and nimble airplane in fact it really moved out! As with all the Alfa models they are fairly small so you need to keep turning so you can maintain orientation.

In flight pics come from Ronnie - thanks for these fantastic in-flight shots!



As with all the other Alfa models (I have flown almost every one) there are no bad habits to report with the P-39. It goes where you point it, gets there in a hurry and is capable of any aileron, elevator aerobatics you can think of.



Takeoff and Landing

This Alfa must be hand launched as it has no landing gear included. The weight and drag of the gear is not something we need in this size model. It was very easy to hand launch as the powerful motor really takes it out of your hands. A level toss was all that is needed. Keep the wings and nose level and apply about half throttle. Full throttle is not needed or desired for the Alfa models. It will fly right out of your hands!



Landing is a thing of beauty with the Alfa, it is so light is slows down very well. Line up and realize that it will take some time to bleed off extra speed as this is a slippery ship. With light packs the Alfa can be slowed to near jogging speed for landings.


A small amount of throttle keeps some propeller blast over the surfaces and helps to make a smoother landing with more control response.



Special Flight Characteristics

The P-39 Airacobra is able to perform any elevator aileron maneuvers you can think of including loops, rolls, inverted flight and split-S aerobatics. Loops and rolls are very easy with the Alfa P-39. Rolls are magnificent and quick thanks to the responsive rates on the ailerons.



The plane stalls very predictably for a model with a ~12 in/oz wing loading. Recovery is a non-event with the smooth application of power. With the light weight P-39 it was flying again in a second.


Recommended power system

Power on 3s voltages was stunning and it did not leave and desire for more power. The eRC 400 motor with an GWS HD 8x6 propeller was a perfect combination for this Alfa.

Is this plane for a beginner?

The Alfa P-39 is for an intermediate pilot with some flight time under the belt. It does not exhibit any self correcting ability and is intended for someone with flight experience.

Flight Video

Downloads

Conclusion

I have owned many of the Alfa models. For those new to the Alfa world, I can assure you the quality and assembly time of these models is impressive. What is more they look great out of the box and they fly with authority.

Assembly of this ARF was quick and straightforward. The pre-fabricated parts fit was excellent making the assembly process simple and smooth. Everything fits due to the expert engineering of the Alfa models.

It was great to see that Alfa has gone to all magnet canopy attachment system making battery swaps a simple task. The battery hatch is oversize allowing easy access to the servos and battery. There was room in the battery tray for CG changes without adding weight for balance. The battery will be very close to the CG if you use this motor. Keep that in mind for placement of the receiver.

The eRC 400 Brushless power system and POWERWING 1600 mAh battery made a great combination for this Alfa. I have also used much smaller batteries, in order to save some weight and the model performs admirably. I really like the Alfa's performance with light 800-1300 3s packs. These smaller packs still allow decent flight times especially considering I rarely use full throttle.

The Alfa P-39 is also extremely attractive, a trait we expect from our Alfa models. They are expertly finished with military paint schemes that are period accurate and attractive. Since the builder has 6 choices on markings, all included, you can make your version unique.

Alfa has another winner on their hands. The P-39 Airacobra was fast to assemble, looks fantastic and flies like a war bird, with authority. Add this newest Alfa to your hangar today.

Pluses:

  • Looks fantastic with several scale marking choices available
  • High quality hardware
  • Spinner with canon!
  • Short assembly time
  • Excellent performance and budget price using the eRC 400 motor

Minuses:

  • Would be nice to have the firewall about 5mm shorter for use of longer motors

Check it out the hobby shop or buy direct at Hobby Lobby.

Last edited by Angela H; Feb 21, 2011 at 12:55 PM..

Discussion

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Old Feb 21, 2011, 02:32 PM
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JonteSvensson's Avatar
Sweden
Joined Aug 2009
718 Posts
Ah, a nice Alfa post. Will enjoy this review so much. Thanks!
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Old Feb 21, 2011, 03:54 PM
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wattman's Avatar
Evansville Dress Reg., Indiana, United States
Joined Jun 2004
1,078 Posts
Nice review and video , looks like a great airplane , a P-39 , which is nice for a change , thanks .
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Old Feb 21, 2011, 03:59 PM
Team Compass/KBDD Team Pilot
Ah Clem's Avatar
Joined Mar 2005
3,335 Posts
I have never owned an Alpha model before this one, but I agree with all of your conclusions. This is a very nice model that looks right and flies very well.

This is my first Alpha, but will not be my last!
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Old Feb 21, 2011, 04:35 PM
Never stop
Ottawa, ON, Canada
Joined Jan 2010
747 Posts
How does one mount a GWS HD prop on these motors? Use a prop reamer or another trick?
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Old Feb 21, 2011, 04:43 PM
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pda4you's Avatar
USA, TX, Trophy Club
Joined May 2002
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Thanks guys for the nice comments - this is a true Alfa - goes together quickly and flies like a dream!

Quote:
Originally Posted by Left_Drift View Post
How does one mount a GWS HD prop on these motors? Use a prop reamer or another trick?
Yes the GWS HD prop just goes on a standard collet type propeller adapter and you must use a reamer (or drill bit) to enlarge the hole.

I wish GWS would use the prop adapter rings like they do with their 3 blade HD offerings. Much easier to keep the hole true and centered. Reamers work well also, but drilling takes some time and talent to not allow the drill bit to run on you.

Mike
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Old Feb 21, 2011, 04:51 PM
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stuart warne's Avatar
Hong Kong, Hong Kong Island, Central And Western District
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Mike thank you for another great review. How would you say it flies compared to other Alfa's you've flown?

S.
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Old Feb 21, 2011, 04:59 PM
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dude_109's Avatar
Houston, TX
Joined Jan 2008
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Mike,
With the wing shape tapering some towards the tip, is there any tip stall tendencies?

I thought I was done with Alfas as my interest has turned to EDF in the last year but every time I look at my FW190, I see how beautifully scale it is as well as how stable it flies that really want to make room in my hangar for just 1 more...

By the way, just so those who might be scared of making firewall cuts (like lazy me) to get the motor to fit with good spacing, there are other economical motors that are practically drop in. So don't let that part scare you away from Alfas.
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Old Feb 21, 2011, 05:37 PM
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stuart warne's Avatar
Hong Kong, Hong Kong Island, Central And Western District
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Mike, one quick question. Why not just mount the motor mount behind the firewall? then the motor would still be set further back and you wouldn't have to had to cut it.

S.
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Old Feb 21, 2011, 05:37 PM
Never stop
Ottawa, ON, Canada
Joined Jan 2010
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Quote:
Originally Posted by pda4you View Post
Thanks guys for the nice comments - this is a true Alfa - goes together quickly and flies like a dream!



Yes the GWS HD prop just goes on a standard collet type propeller adapter and you must use a reamer (or drill bit) to enlarge the hole.

I wish GWS would use the prop adapter rings like they do with their 3 blade HD offerings. Much easier to keep the hole true and centered. Reamers work well also, but drilling takes some time and talent to not allow the drill bit to run on you.

Mike
Thanks, Mike.
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Old Feb 21, 2011, 05:40 PM
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Quote:
Originally Posted by stuart warne View Post
Mike thank you for another great review. How would you say it flies compared to other Alfa's you've flown?

S.
It certainly shows its Alfa heratige and really has no bad habits. It is a touch more pitch sensitive that other Alfa's, but nothing remotely concerning. It has likely not dethroned the F4F as my favorite admitting that would be a tall task.

It looks so cool in flight though. So unique with the long sleek nose and the nice rounded wing. It just looks stunning.

Mike
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Old Feb 21, 2011, 05:44 PM
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Quote:
Originally Posted by dude_109 View Post
Mike,
With the wing shape tapering some towards the tip, is there any tip stall tendencies?
Nope... Alfa just has these small birds figured out. They clearly engineer them to fly well, test them and get any bugs out before release. They all fly well IMHO.

Quote:
Why not just mount the motor mount behind the firewall? then the motor would still be set further back and you wouldn't have to had to cut it.
Stewart this firewall has no holes or anything cut in it. So you will have to cut or drill either way. The other reason is the motor will then be a bit too far back and you have no way of getting at the inside to attach it to the rear side. That is one LONG slender nose.

To be honest the mod was very easy. With a Dremel or other rotary tool and a sharp knife it was done in a snap.

You certainly can use another motor - but I can tell you I am loving this eRC motor! Powerful and light. Very nice.

Mike
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Last edited by pda4you; Feb 21, 2011 at 05:53 PM.
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Old Feb 21, 2011, 05:49 PM
buy a lot, fly a little!
stuart warne's Avatar
Hong Kong, Hong Kong Island, Central And Western District
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I thought that might be the case. Thanks for clearing that up. I hear you about the F4F though, I've yet to find a warbird that is as smooth as she in flight, but good to know the P39 is not too far off

S.
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Old Feb 21, 2011, 05:51 PM
Registered User
Burlington, NJ USA
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EPO foam?
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Old Feb 21, 2011, 05:54 PM
buy a lot, fly a little!
stuart warne's Avatar
Hong Kong, Hong Kong Island, Central And Western District
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Nope, molded styro foam with plastic reinforcement in the contact area's, belly,underside of nose etc. Very smooth, no foam cell skin. Only problem is it won't take an impact like EPO, but it looks a lot better for it IMO.

S.
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