Hi all,

Anyone out there converting (converted) a Nexstar 46 Trainer to Outrunner?

We are in the process of doing this, and have the following setup...

AXI 4130/16 (390Kv)
CC Phoenix 80 Amp ESC
DM 5C2P 8000 mAH Lipoly

Trouble is, the Kv rating (390) on this motor selection is too low, and we can't put enough prop (Diameter) on it to pull the rated loads and clear ground. The max diameter is about 15 inches (leaving only 1/2 inch ground clearance). Should pull ~50 Amps at over 1100 Watts. We bought the setup on the recommendation from a "reputable" hobby shop specializing in electrics. They sold us a Master Airscrew 16x10-3 Blade prop to go with.

The MAS 3B-16x10 only loads it up to ~830 Watts, and pulls about 7-1/2 lbs thrust. Enough to fly, it seems, but way short of expectations. Bad part is, we need to jack this thing WAY up, or convert it to tail dragger to clear this much prop. This hardware will eventually go into our BME CAP Maniac, where we can swing a much larger props.

Tried an APC 15x10E, will only pull around 5 lbs thrust @ approx. 400 Watts. (sorry, don't have my notes with me for accurate numbers, going on memory). The OS 46 it came with makes about 1200 Watts (1.6 hp). So, the questions are:

a. Is 5 lbs thrust enough to fly this trainer? (I'm thinking not)

b. Has anyone converted this bird to tail-dragger?

c. Any ideas?

Appreciate any feedback!

Good Flying...

If possible you should switch to an 4120/18 or even a 2826/12 for your 5S pack. These will allow you to run more reasonably sized prop in the 13 -14 inch range.

I am using a 4130/16, 6S 4440 Tanics, 16*10 prop on a World Models Chipmunk 90S that weighs in at 8 pounds and it is not lacking for performance. The 4130/16 is more appropriate in a .60 size plane.

In very rough terms the 2826 is similar to a .40-45 two stroke, the 4120 is similar to a .45-.55 two stroke, and the 4130 is similar to a .61 two stroke. Actual results will depend on the battery and prop that are being used. However since the electric will use a larger prop at a slower speed it is more like switching to a four stroke. Less speed but more pull.

Thanks GWH,

Yea, we're stuck with this setup, looking for a way to make it workable. We took the dealer's recommendation, blindly thinking they knew how to set up. The motor has the power to do the job, it's just a propeller selection challenge. To get 1100 Watts out of this thing, we'll have to swing a BIG prop, probably 18-20 inch diameter. [X(]

But, since it has been set up and run, they won't take it back or exchange it, and battery was custom. I should have done calc's on it to see if they spec'ed it right, I didn't. I should have insisted on gang-wiring standard cell packs, I didn't. Shame on me. [:@]

You only need 500-700 watts in the Nexstar to fly very well. A 6.5 pound plane will fly on 5.5 pounds of thrust.

100 watts per pound is a rule of thumb for very good perfoamance with electrics. 75 watts per pounds is ok but not impressive.

The OS 46 that you are replacing does not really put out 1.6HP at any type of realistic RPM or resonable sized prop. If you read the fine print the 1.6hp is at 16K rpm with a small prop. Most sport engines are flown at 13K rpm or less.

Outrunners are normally flown at a maximum of 7-8K RPM. You will be on the low side at roughly 7200 RPM. Thus you will need to maximize thrust. Try some APC E props or Graupner mutiblade props with a high pitch.

The 4130 is not really a 1100 watt motor, especially on your battery. In order to get to 1100 watts on 5S you will need 60 amps. This motor does not like that type of loading except in a glider where the motor is run in short bursts and very little partial throttle time.

If you want to drag the tail, you need to mount the new mains so that the wheels are at the leading edge of the wing. Then add a tail wheel or at least a skid at the backend of the plane.

What is the pupose of this conversion? Trainer or electric test bed or both?

It were me, I would probaly get a 4120/18 to use with the 5s pack in the Nexstar then buy a 6S pack for the 4130/16 in the Cap.

GWH,

Yea, but the Nexstar weighs in at 7-1/2 lbs glow, and we add another pound for the conversion, so we are more like 8-1/2 lbs AUW. With 400 watts on a prop we can swing (APC 15x10E), that's real weak. We are below 50 watts per lb. What I was asking was, where is that limit where you could easily get in trouble by lack of power. I am used to flying with way more than 1:1 thrust to weight ratio for 3D aircraft.

Model Motors shows example loads on their site at 1154 Watts at 50 amps, and the motor is rated for 60 amp max, so the motor is good for it. Granted, our problem is the cell count is too low, hence rpm is well below optimum levels. Swinging a big prop or a high-pitch multi-blade is the only solution I suppose. We'll look at options on maybe a 4-blade 15 inch diameter, see what we can find.

This is my father-in-law's plane. He is a retired beginner pilot, wanting to fly his trainer without my help since glow is such a headache, and his digits are not too nimble anymore. He also has the CAP, and when he gets up to flying pattern and take-off/landings, he would like to move the gear over to that bird. I'm just tech support, builder and flight trainer.

Yea, buying the right battery or the right motor would be the best solution here... but, he has already invested a mint in this conversion. More cost is a last resort, so we'll explore options to make this hardware fly first. He might be singing soprano if he spends another $200 to make this right .

Found a MAS 14x9 3-Blade prop today at the LHS. We'll mount that up in the next day or two and see how she pulls...

Here's a setup that also works...

http://www.hobby-lobby.com/glow2econ.htm

NJ Flyer,

Thanks for the feedback...

Yea, we checked that setup out before we bought. Frankly, it's too weak to perform decent. Max load for the 2826/12 is around 550 Watts. That works out to less than 75 Watts per pound, which is very marginal for performance.

We were shooting for more like 130-150 Watts per lb to make the bird fly nice and strong, and the hardware would be useful in an acrobatic plane later on. The Model Motors AXI spec's recomended model weight for the 2826/12 motor is 2000-3000 grams (4.4 to 6.6 lbs), clearly well short of the e-conversion weight at around 8.5 lbs.

We are attempting to get the dealer to exchange the 4130/16 for a 4120/18. That gets us closer, with a 510 Kv rating and 55 Amp capacity @ something over 1000 watts. Not what we hoped for, but a workable compromise. The ideal solution to match the battery would be a 560-600 Kv motor capable of 1100-1200 watts continuous, but nothing in the AXI line does that [].

To get this motor to work, and turn a reasonably sized propeller (14-15 inch 2-blade) I guess we could consider tearing the battery apart and re-wiring for 6 or 7 cell. We would need to buy a couple more cells to balance the pack going up. A 6C2P 8000 mAH pack would only require 2 more cells (heavier). Or, we could just make it a 7C 4000 mAH, shorter fly time, leaves 3 cells left over, lighter, but marginal on current delivery. Need to find out what C rating these cells have in the 5C2P 8000 mAH pack we bought.

An update...

The LHS was kind enough to exchange the AXI 4130/16 for a 4120/18. Put on an APC 15x10E and it now pulls a respectable 1045 Watts. The AUW is 7.8 lbs, and we are measuring thrust at approximatly 7.2 lbs. Still using the 18.5V 5S2P 8000 mAH. This thing it wicked scary to play with on the bench. Nice and quiet, but that mean hum warns you of the danger.

The 4120 is about 3/8" shorter, so we had to put a bushing on the shaft to clear the front of the fuse sidewalls. Still, it worked out nicely. Lighter than planned. Moved the Rx over on the right side wall over the servos, mounted with velcro. The battery is sitting on the Rx tray now, and we added a triple ice-cream stick beam forward on the lonerons in the lower front fuse section. Put down a foam pad, and strapped the battery with a velcro belt. Stays put well enough. Balance is on the forward marker with the center of the battery dead under the leading edge of the wing.

It's ready to fly. Hope to get some time this weekend to take it for a spin.

I guess I never came back and updated here. The bird flies just like it did with the OS46. All is well. Love it.

Here are pict's of the install.

Hi I have converted one using a E flite 46 with 13.8e prop and a jeti 70 amp opto using 2 Thunder Power 7.4 4200 mah batteries at 14.8 volts Fight time on this configure is 25 minutes at about half throttle and a couple of touch and goes. With the Thunder power 14.8v 8000 mah battery I am exspecting 40 minutes flying time. I use only TP batteries as I have tryed other off name brands and have seen less than half flight times. You get what you pay for and they stand behind there batteries.
steve

I used an Axi 2826/10 in mine and it flies like a trainer with a TP 3s 4200mAh lipo brick. Weight is just over 6 pounds. There is little or no vertical but it runs around the track just fine and I can get 3, 10 minute flights from a charged battery.

I have the E-Flite 46 with the castle 60. 5s1p4000 lipo and 10 x 7 APC prop. 28 amps WOT lots of power with good vertical flight. People are amazed how fast and well it flies, I will probably rip the wings off one of these days