Nitro Epic Lt-120 Jet Prop. - RC Groups
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Apr 14, 2008, 01:22 AM
Done it all
Build Log

Nitro Epic Lt-120 Jet Prop.

This is a very short build detail on the Nitro Epic Lt-120. The purpose of starting this thread is to provide information as to the overall good quality of this kit. I flew the maiden today and it flies as good as it looks.

The Epic jet weighed out, including batteries at 11 lbs 6 oz converted to electric.

The stats:

75 inch wingspan
8S lipos
Turnigy or HXT 50-65c motor
Master Airscrew 3 blade 15X7 prop.
Projected weight out the door 10 lbs 7 oz.
Small size Robart air up spring down retracts

Pictures follow
Last edited by SCALEFAN; Apr 14, 2008 at 01:49 AM.
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Apr 14, 2008, 01:37 AM
Done it all
The build is pretty straight forward:

The fuse is fiberglass and painted with gellcoat.
The wings are covered wood.
The rudder feels like it is plastic or thin fiberglass.
The build is very straight forward and there is lots of room inside the fuse with the large canopy removed.
The servos mount toward the rear of the compartment on a large servo tray, the batteries mount forward in the same area.
The plane has no real balance problems or considerations.
The plane flies like it is on rails, very smooth, and has flaps for landing. However, it will float without the flaps.

The plane left the ground in about 200 feet and climbed with authority, a few down clicks on the elevator and it flew perfect. The comments from the peanut gallery were "Hey, it flies like a real jet" ......Shortly after the 3 minute mark the HXT motor froze up and the prop came to a screeching halt. I kept the plane straight, made a very long glide, and landed off runway in some 1 foot weeds with the gear down. NO damage...NONE.

After talking the motor apart, it seems that I overheated it at 8S lipos, and small plastic spacers put between the magents were melted or gone. I'm retro-fitting the motor with a E-Flite 110 ...only because I have a spare.

Anyhow this plane flies great, it's a keeper...I didn't mention that the kits comes with LED lights, only I didn't install them.

The reason for this thread is to make public that the Nitro Planes Epic is a good plane and a very easy electric conversion...we all know that there are some real lemons out there.
Last edited by SCALEFAN; Apr 14, 2008 at 01:52 AM.
Apr 14, 2008, 04:59 AM
Registered User
Haze_b's Avatar
Awesome, congrats on your maiden. I was wondering about this one, with quite a bit of interest. Good to hear it's worth a closer look.
Apr 14, 2008, 09:12 AM
Recruiter - 60 Amp Club
Ed Lyerly's Avatar
Congratulations on your successful maiden. Your Lt-120 is a beautiful looking bird ! After the overheating issue, I assume you will be making provisions for additional cooling air over the motor and out of the fuselage. Please share the details.
Apr 14, 2008, 09:45 AM
Done it all

I wish cooling was a problem, but it wasn't. The front of the cowling has simulated vents, I opened them up to make them usefull, I also cut a 1 inch square piece out underneath to the rear of the cowl. To go one step further, I also drilled out the cowl where the exhause stacks are mounted and the exhaust stacks are also vents.

I have 3 more of those HXT motors, and they are rated for much larger props and 8S lipos, I'm going to install another and do some voltage/amps/watts tests to see what went wrong. The E-Flite 110 motor is pretty heavy and I don't want to use it if it can be avoided.

Apr 14, 2008, 10:11 AM
Done it all
I dug up the stats for the HXT or Turnigy 50-65C motor and it appears that I ran the motor at it's upper limits which could have been the problem.

60 amps max.
1200 watts max.
29.6 volts max.
Suggested props at 8S 16X10
ESC recommended 80A.

Obviously I over stressd the motor, no sense in testing it any further. However, I may go to a Hacker 60s as a replacement, it appears to be lighter than the E-Flite 110.

See what happens when construction was rushed, I stuck this plane together in one week, working three hours in the evening at the most.

If you splurge and pay Nitro the 200 plus bucks for this plane you will be very happy. Oh, I forgot to mention, the wings are removable, they slide on and off with two aluminum wing tubes.

I wasn't planning a build thread on this plane, but, it was so easy to make, has so much potential, and it flies really good, I just had to comment.

More pictures later.

Apr 14, 2008, 06:03 PM
Recruiter - 60 Amp Club
Ed Lyerly's Avatar
IMHO, in addition to a different/more efficient motor, you need much more cooling than you show here. Consider some ducting and baffling similar to the
photo below. The air exit needs to be 3X the area of the entrance.
On the motor choice. Turnigy HXT 50-65C = 414 gm, Hacker A60S = 595 gm,
A50L = 470 gm, Power 110 = 490 gm, Power 90 = 450 gm.
The reason the Turnigy fried was that it was running very inefficiently (63%).... see E Calc profile. I suggest you have a look at the Power 90 and a 16x10 2 blade prop .... see E Calc prediction (82%). Only 1.3 oz weight penalty .
Apr 14, 2008, 11:20 PM
Done it all

I'll think about the increased air venting. If I can do it without destroying the lines of the cowl, or weakening it, I'll add more exhaust venting. The exhaust tube vents actually will will work like sucking the air through, like a device for bailing the water out of a boat while it is moving. Vent facing the rear, and the air will be sucked past the motor. Creates a low pressure area.

So, your vent is a ram air vent, my vent is a combination of ram air vent and exhaust venting to create the low pressure sucking out the exhaust tubes. Sounds good doesn't it? LOL

Re: motors, there is is a prop size limitation due to nose wheel clearance, thus, a 16 inch prop might be cutting it close, that is why I went to a 15 inch three blade. Besides the Master Airscrew looks more like a turbo prop.

For the first time in all my calculations Motocalc let me down. I won't go into it, but, I tried for hours this afternoon to make one of my "on hand" motors work with Motocalc. Beleve me, I have several different motors that would work in this 11 lb plane. So, in all fairness to the 50-65C, I decided to actually test the setup and take readings. I have three more of these motors, so, to sacrafice another for testing was acceptable.

To answer the question, why did the first motor fry?

With 8S lipos and the 3 blade Master Airscrew 15X6 prop. the tests disclosed that the amps hit 60 amps, 1400 watts, and the volts form the 8S lipos were at max for the motor. RPMS at full throttle were in the low 8,000 range. Two out of three factors were at the max, or over max, for the ratings on thjis brand motor. The motor was too hot to touch after the short run.

OK what happens using the same motor and 7S lipos?

50amps, 1200 watts, 7200 RPMs and I was able to put my had around the motor without a problem, heat wise. The adjustment was simple and the plane will still fly great.

Motorcalc said the plane would not fly with this combination.....????? Well, it flew fantastic with 8S, and based on the tests, it will still fly fantastic on 7S.

I used the smaller brother of this motor, the HXT 50-52b on the KMP B-25 and the VQ P-61 with 14X9 Master Airscrew 3 blades without a problem, on 6S lipos.

So, Motocalc is not the complete answer, actual tests and reasoning is the answer.

Thanks for the input.

Last edited by SCALEFAN; Apr 14, 2008 at 11:26 PM.
Apr 15, 2008, 08:52 AM
Recruiter - 60 Amp Club
Ed Lyerly's Avatar
Thanks for the clarification.
From your tests, it sounds as if you will try the same setup again, this time on 7S.
Good luck with your efforts. Please keep us posted on your progress with this beautiful airplane.
Apr 15, 2008, 01:59 PM
Registered User
Coastwatcher's Avatar
Hey ol Buddy ...... Nice looking bird there. I'll shoot the pics over to Mr Dave at our field. Sounds and looks like a plane he'd want.

Don't know anything about your motors , not sure what they are equal to in AXI or Eflite language. I suspect the three blade prop may be a bit hard on the whole system. Since its a JET maybe a grey or clear electric prop two blade prop would help with power. Ed has good ideas on cooling .
Apr 15, 2008, 03:35 PM
Registered User
You will be down on Pitch speed with 7s (~47mph).

A 15x10 2-blade will perform a lot better.

Apr 15, 2008, 05:54 PM
Registered User
mpope1's Avatar
Al, Im running a hacker a60-22s in my yak, on 10s with a 16x10 master airscrew 3 blader. About 2000 watts, that motor I think is the highest kv in the a60s line. Probably would work good on your plane if you can get the prop clearence. I tried a a50-14l on 9s with a 16x8, but it was too much for that motor, thats why I switched to the a60.
Apr 15, 2008, 07:01 PM
"Each Day Is A Lesson"
diver don's Avatar

Nice job a usual on this new bird.

I have had the same problem with MotoCalc since my last upgrade.

It also keeps telling me the batteries are frying which I know is not going to happen with the amps being shown.

But; If it says it will not fly, just get to the "Workbench" page, and plug in your motor and other info.
It will then tell you under "Opinion" if it will really work or not.

Hope that helps,

Last edited by diver don; Apr 15, 2008 at 07:19 PM.
Apr 16, 2008, 09:51 AM
Done it all
Thanks for the input, looks like the research and development department is still in business.

Heather: I agree a two blade prop might be better, but, this ia turbo prop plane......I just can't do it. A 4 blade prop perhaps.

When I read that some of you guys used LEDs, landing lights, all kinds of do dads I really thought "overkill". However, this plane is such a mellow flyer and can be made to fly fast, or slow, the options are remarkable. There is enough room inside for any battery configuration, even A123s. If I can get a video , you will all see that evern with 30 or so oz wing loading this plane is a glider in a power off situation.

It's too late to modify this plane, so, this will be the research project. I will order another immediately which will be fixed up with all the do dads. It's no WWII attention getter, but, it's sleek, looks and flys good, and can be easily modified to suilt anyones special desires, including a cabin door with stairs.

Best part, it's easy to fly.

Apr 16, 2008, 10:59 AM
"Each Day Is A Lesson"
diver don's Avatar

At least put "Barbie" in the pilot seat.


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