Idratherbeflying89

Ok so after testing the voltage I know I have the power. I think the key is a proper hand launch. I've heard that with a 4s battery there is even less effort required to launch itbut I think that will make me nose heavy. I could get a 4s and add weight to the back but Im afraid of adding too much.

boneviator

Hi guys,

I have been flying mine for 3 years, and a few rebuilds, the plane is severely underpowered with the stock motor and 3 cell LiPo, HobbyKing Rhino 1550 4 cell made the difference, but I also went for a turnigy 3900 kv motor, again less then a $10 upgrade, and a 45A esc, another $30, and she is a totally different plane.

Bone

TechyJoe

Hi all

I have a question on the electrifly L-39.

I flew mine for the first time this past Monday. It really flew pretty well and fast but it seems extremely loud. I have another EDF and it is not nearly as loud as this plane. It sounds like an EDF firing a machine gun.

I typically fly in the early mornings at a local park but I'm afraid someone is going to complain about the noise level. It doesn't seem like anything is rubbing (like fan blades on the shroud) but my model also was delivered with several defects such as a bad ESC and a flaky aileron servo so I wouldn’t be surprised if there is another issue.

The plane is neat but I found the quality control on it lacking and I submitted a complaint to Tower Hobbies about my issues.

wind junkie

My Feedback: (1)

try removing the spinner. They are notorious for being out of balance. You can go futher and try to balance the rotor if you wish, but that's where the noise is coming from.

If indeed I am right about the spinner, when you remove it the noise should go away and the performance you gain (RPM) will offset the slight benefit of the aerodynamic fairing the spinner would provide, plus you will have a quieter airplane as you desire.

TechyJoe

I tried another flight on the stock L-39. This time I had bad luck. I launched the plane and it immediately crashed.

It wouldn't have been so bad except for the fact that it rolled over then dove nose first into the ground.

First flight went reasonably well so the only thing I can determine that changed was the climate conditions. First flight was heavy humidity with a slight breeze. Today's flight was low humidity with NO breeze what's so ever.

Bottom line in my opinion is that it seems that this plane needs the mods as set forth in previous entries of this blog.

It's ashame because this plane was suppose to be "ready to fly". Maybe if the conditions are "just right" this plane will fly stock.

TechyJoe

Has anyone taken any bench measurements for this plane?

I measured the following using a 3s lipo 1300mah pack and a standard Digital Volt Meter:

Vmax = ~8.36 volts
Imax = ~7.22 amps

calculated power:

P = V * I
P = 8.36v * 7.22a
P = 60.35 Watts

Seems way under powered, even for this motor.
Motor specs state it can handle constant 133watts

Does anyone concur or object to these values? I would like to know how others measure brushless motors.

boneviator

TechyJoe,

Like I said, It only comes to life with a 4 Cell battery,

Secondly, there is a lot of resonance off foam construction, a unbalanced fan will make a lot of noise, and the foam amplifies this noise, you will also find that the fan might not be off balanced but nor running true, will give off a lot of vibration (noise)might not touch the fanshroud but will severely affect the fan.

* Go 4 cell, 1750 mah is about as big as it will take
*balance the fan and make sure it is running true
*CA that nose back together enjoy

TechyJoe

A few more bench notes:

wind junkie was correct. Removing the spinner did remove the noise and reverberation level of the fan on the foam (now it sounds correct).

I received my new Turnigy 1300mah 4 cell battery from Hobby King ($11.99). On the bench I used only 3/4 - 5/8 throttle and received ~10.0v and 11.0amps. That gives 110watts. Way better then ~70watts with the 3s lipo.

I was afraid to juice the throttle to full because I didn't want to "blue smoke" my small 11.1v, 18amp rated ESC.

Bottom line, you should be able to run this model stock with the stock 25amp ESC and changing the battery to a 4s lipo pack. I don't think there is a need to change the motor. The stock Ammo motor is rated at 130watts. However, I may clamp on an additional heat sink to my ESC.

I'm going to run this for about 5 minutes on the bench to see how hot things get, then we will see how things go in the field.

Thanks all for your input.

wind junkie

My Feedback: (1)

Glad it worked for you TechyJoe.

Great Planes uses the Hyperflo fan in their new F20, and I noticed they don't have the spinner supplied with that plane. Instead, they have a fairing molded into the intake which conforms from the intake splitter to the cylinder of the fan hub (replacing the spinner in effect).

I believe they'e invested too much in the hyperflo fan to deal with the issue of spinner vibration, so it doesn't surprise me they've eliminated the spinner altogether.

TechyJoe

L39 in the Field

It, worked pretty well at the flying field even with the small 18amp ESC. I used the power from the 4s Lipo to get into the air and then I could cut the throttle way back.

I flew for about 6.5 minutes and only used ~750mah of my 1300mah battery.

I calculated an average of about 7-7.5amp draw and calculated that for my next flight, I should be able to get almost 10 minutes of run time using moderate throttle.

The ESC was a little hot but not too bad. I think it helped that I added the extra heat sink. No air flow into the electrics compartment so no doubt things will get hot. I have been experimenting with adding some small intake holes in the nose to get some air inside the compartment.

Landing however is an all together different issue. I need some practice getting the glide path and landing speed correct.