I found your RC Universe post on the Avistar conversion. It was quite useful in guiding my upcoming Avistar project and my current project: converting the Aero-Phibian which is a 40 sized high winged trainer that has an undercarriage that is quickly convertible from tricycle wheels to twin floats. I built and flew the tricycle version with pretty anemic power from this setup:
Wingspan: 53 inches
Wing Area: 530 sq inches
Weight: just under 6 pounds ready to fly with the batteries listed below
Motor: AXI 4130-20
ESC: Jeti 70
Batteries: two, Thunder Power LiPo's in series each a 4 cell, 4200 MaH pack (I tried them in parallel too but of course it produced less power)
with a 40 yard take off she lumbers into the air, barely. She is slow and hesitant to climb and my test pilot (very experienced) brough her down after two orbits of the pattern for fear of stalling. On her maiden flight last weekend I had used two TP 3s3p 6000 MaH packs in series but the extra weight in the packs and the lower voltage to the motor made her performance even worse if that's possible. I feel pretty confident from reading this forum that I have a big enough motor. The ESC should be fine so is it the batteries? Oh yeah, when I hook up a Medusa wattmeter I get only 80 watts at full throttle from the twin 4200 packs. If I want 150 watts per pound I need 800 not 80. Any ideas? What ever help you could provide would be greatly appreciated. I want to get out of Rookie-Hell but this plane is holding me back. WD

Lax

With an AXI 4130-20 the KV is low and the torque is high. You need a very large prop and a lot of batteries.

Prop 16x10 or 17x8

Battery 8S to 10S lipo's that's 24 to 30 Nicads. Too much weight for this plane. I am using that setup in my Funtana 90 a 9 pound plane.

With this combo you can get 800-1000 watts. 4S is no power at all for theses large motors.

4S packs are great for an AXI 282610 and a 12x8 prop. You will get 450-500 watts. I fly my Avistar on a 444 watt system.

interesting, so I need a smaller motor? I would not have guessed that was the solution. I guess I'm still learning. I just happen to have that motor you recommend so I'll mount it and see. I can't keep the 4130 and change the prop as I don't have the ground clearance with the tricycle undercarriage. I have much to learn...

Stephen what if I were to use 5s (18 volt) packs with my 4130? would that be enough power? one or two packs? if I connected them in serial would the system take the voltage/amps?

Lax

The less volts you use, the larger prop you need. Hobby Lobby's catalog only shows a low voltage of 8S and a 13x11 prop for the AXI 4130-20 motor. If you are getting only 80 watts, I have to ask. Are you testing with a prop on the shaft?

Yes it was tested with a 13" prop.

should I try more volts? Would it be insightful to hook up a couple of 18 volt packs in series? Would my system (ESC, Motor) be fried by this power source? Is this a way to get a better reading on my Wattmeter even if the packs' weight would be too much for this plane to lift off the ground? I'd be curious to see the result if you think my components are up to it.

80 watts of power dont seem right to me. Is it 80watts of power per pound, or 80watts on your meter?
I have a 4120/14, and I have a 13x8 prop on it. I am using a 5s 6000mah Li-Po pack and I get:

true reading throttle settings:

1/4 throttle 20.6v - 2.7 amps - 57watts
1/2 throttle 17.8v - 18.1amps - 351watts
3/4 throttle 17.8v - 49amps - 891watts
full throttle 17.4v - 63amps - 1112watts

80 watts total NOT 80 watts per pound at full throttle. I tested the power output with the engine mounted in the plane with a 14.5" Graupner Cam Prop. My test instrument is a Medusa Research Power Analyzer II. Unless this instrument hyphenates the watt data and there is no documentation to indicate its readout is shortened from 3 digits to two.

Does that instrument give you a current and voltage reading at the same time. If so then for 80 watts with a 4s or 14.8volts you should be seeing a current draw or amps of 5.405 amps.

Another way to check it is:

If you have an ampmeter that can handle up to 80 amps, then you can put it in series and measure your current. Then put a voltmeter in parallel under load, and measure your voltage. Then multiply the current with your voltage to get the watts. I think that measurement of 80watts total is not correct.

Cubano8,
Thanks for taking an interest in my dilemma.
I didn't mention that I bent the nose on landing so I had to dismount the motor. I remounted in on a test stand
ESC: Jeti 77 advanced opto plus with seperate receiver battery
Prop: Graupner Speed Cam 14.5-4"

and came up with these readings:

test one
source: 18.1 volts
80 watts
3.9 amps

test two
20 volts
80 watts
3.9 amps

test three
25 volts
80 watts
3.1 amps

test four: test of maximum power:
source: single TP 5s3p 6000 mah
20.9 volts
145 watts
7.1 amps

test five:
source: two TP 3s3p 6000 mah in series
25.0 volts
240 watts
9.6 amps

test six
source: two TP 5s3p 6000 mah in series
42.1 volts
540 watts
12.1 amps

Any insights that you can provide will be greatly appreciated.

The math adds up. I think its time to change that prop to a higher pitch, to get those amps up. That 4130 can handle 40amps with a 60amp burst. Those TP's can handle 10-12c discharge, and burst of 20c's, so you should be fine.

BTW, I like your choice on that 4130, assuming this is a nose gear plane. With that heavier motor in the front you dont have to add too much weight up front for balance.

Hey look at my max power test amperage, its way low I think. At 540 watts only 12 amps! Do you think this esc has a limit/governor on an input or output? Is that possible?

Cubano8 OK I'll try a different prop. What diameter and what pitch do you suggest? Which of my TP packs are you refering to and is a single or two in series?

That ESC is fine, I'm using the Opto 70, and I thought it was a bit overkill. your single 5s3p 6000mah is what I have, it can handle 60-72amps continuosly with a 120amp burst. your doubles should be fine. That motor can handle a 14x10 thru a 16x8, the ? is are you going to have the ground clearance with the 16inch prop. My tests with the MA 13x8 on post #58 showed a 1112watts with 5s3p TP 6000mah pack that should give you 185watts per pound on your 6lb plane. It should fly like a rocket. I usually calculate a figure of 100watts per pound on my conversions.

If you go that route, I would really like to see your results. A video would be nice.

Good Luck,
Sam

Thanks Cubano8 but I'm not getting that kind of output from that setup so something is amiss, isn't it? Certainly there was no heat in any components not the batts, not the ESC, nor the motor. Slightly warm to the touch at the end of all testing but certainly not hot. I'll try a bigger prop on the test stand and see what that gives me. Yes ground clearance is a limiting factor beyone 14" dia. prop. I will tell you that when I connected the two TP 5s3p 18volt packs in series (42 volt on the meter) the motor was much more "alive" than with a simple 21 volt two pack series. But Stephen's post was right on those big TP 5s3p's are too heavy and their weight would tear the wings off a plane this size (40 size, 53" span, 530 sq inches area) and under 6lbs with a single TP 6000 mah 3s3p pack. I guess his advice is sound; drop in a smaller AXI and use 4s 14.8 volt batteries. Thoughts?

Take a look at this video of my WM SS 40:
[link=http://www.ercflight.com/wmsp40.wmv]http://www.ercflight.com/wmsp40.wmv[/link]

It's using an AXI 2826/10 with a TP 4s 4000mah Li-Po on a 10x7 APC prop. I think its max at full throttle too 600watts.
The plane weighs 5lbs 10oz, I had to add 10oz of nose weight to the front, to get it to balance. But this is not going to be my final setup on this one, I'm going to end up using 2 shorter TP li-Po packs, and move them forward for balancing.
I'm using this setup now to test some AXI 2826/10 motors out and some new ESC(CC HV-45 and Great Planes 45) that came out recently. So when I'm done I should be able to reduce some weight and get better performace.

As Is, the plane has a hard time taking off from grass field, but once in the air, I'm satisfied with the performance.
It shouldn't have any problems taking off from a paved strip.

Maybe you might want to consider the AXI 2826/10

Lax

I used a AXI 282610 with 4S lipo's and a 14x7 prop on my 4.5 pound Modeltech Magic and had unlimited verticle.

The Bigger 413020 takes a lot of batteries (8-10S)and a large prop (16-17 inches) to get high watt yield. I don't think a 8S lipo pack is do able even with some Kokam 3200 mah 20C packs in series. There isn't enough room inside.

Yes that seems to be the conclusion from all posts. This has been extremely helpful and I'm very appreciative to all who have taken the time to analyze this detail and offer advice. No doubt you have saved me much time, money and aggravation. Thanks to all! I'm dropping back to an AXI 2826-10 and 4s packs. That should work.

Hi,

Where did you obtain that metal brace that wraps around the top of the motor and screws into the engine mount?

Thanks,
SAFZERO

SZ


Maxxprod.com or espritmodels.com. Look for a 36mm motor mount. It is about $6.00