[Hover]

Hello all, I'm back in the hobby after being away from it for quite a few yrs. Electric is new to me. I have started construction on a Sig 1/6 scale Cub. I bought an E Flite power 46 Outrunner motor & 60 amp ESC to go in the plane. I was thinking of a 4000 ma 4s lipo also, which I have not acquired yet. I am building it to look like the L4, with full span wing, greenhouse windows and will cover it with Solartex fabric. I'm using a Futaba 6J with standard size servos, one in each wing. I am looking for slower scale style flight, with long flight times...more than 10 minutes. Here are my questions...

1. Is this 46 too much for this plane( even if I throttle it back)?
2. If so, should I get the E Flite 32?
3. Is my battery choice a wise choice?
4. Should I be looking at 2- 2000 ma batteries, instead of a single 4000 ma?
5. Still unsure of what charger to purchase, I do have an Onyx235 I could use, but would like to upgrade for quicker charges...can anyone give me some charger recommendations with some charging times, assuming I use the above mentioned batteries?
6. Any recommendations on where to buy lipos and chargers in Canada at reasonable prices?

Thanks in advance!

[rcav8r71]

Welcome back!
Unless you want to fly your Cub like a 3D acro, the Power 46 is WAY too much power for the Sig 1/6 J-3. I've got the same plane, clipped wing, with a Power 25, 60A ESC, on a 4S 3600 battery, and get almost unlimited vertical at full power. Most takeoffs are done at 1/2 throttle. Flight times at 1/2 throttle are 12-15 minutes without totally draining the pack.
Those Sig Cubs are great, light weight models that fly on the wing. They don't need a gross amount of power to perform well.
Jon

[michaely]

Hover,

Welcome back.

I returned back to r/c after dropping out in the early 90s, when, as far as electric flight was concerned, we were using brushed motors, heavy NiCad cells for power and an on/off switch triggered by a servo for in flight motor control.

What I have learnt is that current electric flight has a challenging but accessible learning curve... in learning about motor and battery choices, their effect on flight performance, safety issues, etc.

The information you need to figure out for yourself what to put in which plane for your desired flight performance is all online but it is scattered.

One big aid is any of the various online electric motor/propeller/battery/electronic speed control calculators that are around.... according to many, their use will get to within 10% of the real life performance of the model and motor package.
Here is a link to a page of one such online calculator - the limited free version - punch in the wing area, likely all up weight, the esc and motor you currently have, then "play" with different battery packs, such as 3 cell lipos in addition to 4s, and different props
\http://www.ecalc.ch/motorcalc.php?castle&lang=en

I recently subscribed the paid version of the same calculator program - with listed choices of motors, batteries, esc, and props - for around $5.75 Cdn. a year.

Second, you need to buy a test instrument typically called a wattmeter, that you use on the ground with specific choices of motor/battery pack and prop to ensure that you are not overworking the choice to the point that you burn up the motor and/or esc. A glo engine typically gives some advance warning of self-destruction from a lean run but these brushless motors, apart from getting hot, do not.

Your charger will work with the batteries you are contemplating..... perhaps wait until you learn a lot more about batteries, charging and what you will be doing longer term with electrics before you buy your "ultimate" charger.

Here is a link to a good online site with information on chargers, connectors etc.
http://www.tjinguytech.com/

Where to buy.... once you know what range of items you want, buying used stuff right here on this forum has worked out well for me; typically your costs will be between 25 and 50% of retail.

A tip on lipo cell size: you can buy 4 and 5 cell lipos and even, at the extreme end, 10 or 12 cell packs.
But probably the most common cell size is a 3 cell pack and the double multiple of this size, a 6 cell pack. And you could put two 3 cell packs with serial connection, to make a 6 cell pack - just as you could put two 3 cell packs of 2000mah each, with parallel connection to make a 3 cell pack of 4000mah capacity.


good luck

[Max]

Its a good thing others have spoken up because I was going to suggest a 5 cell pack instead of a 4cell. But rcav8r71 has hands on experience with your size cub and the same motor. By the sounds of it, you should do OK with 4 cells. As for me, I am using a Rimfire 45 on an LT40 (about the same size and weight as your cub) and I prefer to use 5S packs. I HAVE flown it on 4, I just like 5's better.

Originally Posted by Hover

1. Is this 46 too much for this plane( even if I throttle it back)?
2. If so, should I get the E Flite 32?

Stick with the 46. Its better to have too much power and throttle down a tad then not enough power and have to fly at full-bore all the time just to keep it in the air.

Originally Posted by Hover

3. Is my battery choice a wise choice?

Given rcav8r71's comments, I would say "yes" for now. If you find you need more "oomph" later, you can always try a 5 cell pack

Originally Posted by Hover

4. Should I be looking at 2- 2000 ma batteries, instead of a single 4000 ma?

NO! I tried that in my early days. 2x 2 cells for a 4 cell, a 2 + a 3 cell for a 5 cell. Its not worth the effort. All those batteries to sort out and change cell counts when you charge. You also have to keep the cells matched all the time- a real pain in the butt after a while. You are better off buying 4 cell packs (and 5 cells if you decide later) as a single pack. As long as you take care of it, you will be better off than making a 4 cell out of 2 IMHO.

Originally Posted by Hover

5. Still unsure of what charger to purchase, I do have an Onyx235 I could use, but would like to upgrade for quicker charges...can anyone give me some charger recommendations with some charging times, assuming I use the above mentioned batteries?

Anything over 3S packs, you need good power. You can BARELY get away with a basic 50W charger to charge ONE 4S pack at a time, each taking about an hour-and-a-half. If you are OK with this, then your standard 50W b6 charger will work. But for most, that wont be enough. If you want to charge one 4S pack in 1 hour you need AT LEAST a 80W charger. My first high power charger was an Icharger 106B. This will do 250W, meaning at most 2 6 cell packs in parallel at 10A. 2 packs in under an hour? not bad.
Icharger 106B:
http://www.hobbyking.com/hobbyking/s...e_Charger.html

Lately I have purchased a Mega 400W x2
http://www.hobbyking.com/hobbyking/s...ger_800W_.html
This is now my go-to charger for my large packs. With this I can parallel charge 4 6S5000's one one side and 5 5S 5000's on the other, ALL in under an hour!!!

The only problem with the larger power charger is they NEED a high power power supply. I bought mine from a fellow here in the RCC classifieds for a good price. You will need one as well if you go for anything over 50W charger.

Originally Posted by Hover

6. Any recommendations on where to buy lipos and chargers in Canada at reasonable prices?

I get my stuff from HK, but if I had to buy Canadian, I live near Rotorquest, and they ave great prices on batteries. If you need something local, try your local hobby shop? If not, shop around for Canadian hobby suppliers online

[Hover]

Thanks everybody, I am working some numbers in Ecalc. If I go from a 4s to a 3s lipo, 4000ma, and change nothing else, the flight times actually increase significantly. This is with an Eflite Power 32. I thought the opposite, am I missing something? Also seem to get longer flight times with the Power 46 vs the 32. Maybe I haven't played with the prop specs enough...?

[michaely]

Originally Posted by Hover

Thanks everybody, I am working some numbers in Ecalc. If I go from a 4s to a 3s lipo, 4000ma, and change nothing else, the flight times actually increase significantly. This is with an Eflite Power 32. I thought the opposite, am I missing something? Also seem to get longer flight times with the Power 46 vs the 32. Maybe I haven't played with the prop specs enough...?

hi Hover,

Again, there are better informed people to respond.... but here's link to some basic information on powering our r/c planes with todays' brushless motors and lipos:


http://www.wattflyer.com/forums/showthread.php?t=24238

Probably the most significant change in performance issue you mention - longer flight times -in going from 4s to 3s size lipo battery packs, is due, in a roundabout way, to a quality or specification of the electric motors we use, its constant velocity or Kv.
Kv is the revolutions per minute (rpm) that an electric motor will turn a nominal/tiny prop for each applied volt.

The Eflite 32 has a Kv of 770 rpm per volt; for a 3s pack, using a load voltage per cell of 3.7, the rpm that the motor will try to run at is 3x3.7x770=8547
and with a 4 cell pack, 4x3.7x770=11,396.

If you were flying a streamlined, fast plane you would likely go with the 4 cell battery and a smaller diameter, higher pitch prop for high speed (and lower torque at slower speed).
But if you were flying a higher drag, slower speed model such as J-3, you would get better performance - including longer flight time - by using a 3 cell pack and a larger diameter and probably lower pitch prop.

Note that the Eflite 46 has only a moderately lower Kv of 670 which would also be of further help in a bit longer flight time (with a suitable prop/and throttle use) out of a high drag/lower speed plane but it is the dropping down from a 4 to 3 cell pack that makes a bigger contribution.

The Kv specification of an electric motor works in the same way as the stroke to bore ratio in the two stroke glo/nitro engines. Most engines from the 60s to 90s had an overbored ratio - the bore (area of the piston top) was greater than the stroke (distance between top and bottom of the combustion stroke) - and performed better at relatively high revolutions with smaller diameter props.
Relatively few were "long stroke" engines that performed better with larger props with a lower pitch - at lower rpm - suitable for high drag/slower speed models (and with a less objectionable noise footprint).

Aside from electric motor size, their Kv and prop sizes, cell size of battery packs and the performance outcome of flight duration, do look at other bits of information these motor/flight performance calculators generate, such as performance indicators such as thrust, pitch/stall speed, thrust/weight ratio, wing loading as well as safety factors such as motor temperature, max amp/watts, etc.

Again, do pick up a wattmeter as way of ensuring you are not pushing a motor or esc below their capacities.

good luck,

[Hover]

Originally Posted by michaely

hi Hover,

Again, there are better informed people to respond.... but here's link to some basic information on powering our r/c planes with todays' brushless motors and lipos:


http://www.wattflyer.com/forums/showthread.php?t=24238

Probably the most significant change in performance issue you mention - longer flight times -in going from 4s to 3s size lipo battery packs, is due, in a roundabout way, to a quality or specification of the electric motors we use, its constant velocity or Kv.
Kv is the revolutions per minute (rpm) that an electric motor will turn a nominal/tiny prop for each applied volt.

The Eflite 32 has a Kv of 770 rpm per volt; for a 3s pack, using a load voltage per cell of 3.7, the rpm that the motor will try to run at is 3x3.7x770=8547
and with a 4 cell pack, 4x3.7x770=11,396.

If you were flying a streamlined, fast plane you would likely go with the 4 cell battery and a smaller diameter, higher pitch prop for high speed (and lower torque at slower speed).
But if you were flying a higher drag, slower speed model such as J-3, you would get better performance - including longer flight time - by using a 3 cell pack and a larger diameter and probably lower pitch prop.

Note that the Eflite 46 has only a moderately lower Kv of 670 which would also be of further help in a bit longer flight time (with a suitable prop/and throttle use) out of a high drag/lower speed plane but it is the dropping down from a 4 to 3 cell pack that makes a bigger contribution.

The Kv specification of an electric motor works in the same way as the stroke to bore ratio in the two stroke glo/nitro engines. Most engines from the 60s to 90s had an overbored ratio - the bore (area of the piston top) was greater than the stroke (distance between top and bottom of the combustion stroke) - and performed better at relatively high revolutions with smaller diameter props.
Relatively few were "long stroke" engines that performed better with larger props with a lower pitch - at lower rpm - suitable for high drag/slower speed models (and with a less objectionable noise footprint).

Aside from electric motor size, their Kv and prop sizes, cell size of battery packs and the performance outcome of flight duration, do look at other bits of information these motor/flight performance calculators generate, such as performance indicators such as thrust, pitch/stall speed, thrust/weight ratio, wing loading as well as safety factors such as motor temperature, max amp/watts, etc.

Again, do pick up a wattmeter as way of ensuring you are not pushing a motor or esc below their capacities.

good luck,

Thanks Michaely, that was helpful info. I'll keep playing with the calculator for now. I have the 46 already, so maybe I should live with it..will be a decision I will have to make eventually..use the 46 or buy a 25 or 32.

[williame3590]

I love threads like this......great info from everyone!!

Bill

[OLD PRAIRIE RED NECK]

Originally Posted by rcav8r71

Welcome back!
Unless you want to fly your Cub like a 3D acro, the Power 46 is WAY too much power for the Sig 1/6 J-3. I've got the same plane, clipped wing, with a Power 25, 60A ESC, on a 4S 3600 battery, and get almost unlimited vertical at full power. Most takeoffs are done at 1/2 throttle. Flight times at 1/2 throttle are 12-15 minutes without totally draining the pack.
Those Sig Cubs are great, light weight models that fly on the wing. They don't need a gross amount of power to perform well.
Jon

I'm with Jon on the motor size. I have a trainer with a 63" WS that I put an E Flight 25 on. I took it off before I destroyed the plane and went with the E Flight 15. It still goes vertical for a long way and has no problem with floats and towing gliders up to 3 meters.

Of course you could just undersize the prop on the 46 to keep the power output at a reasonable level. No harm in that!

Also I have been running two 2 cell 2000mAh packs in series on this plane for several years with no problems at all. I now have a couple of 4 cell packs and they are more convenient for sure.

[Hover]

Originally Posted by OLD PRAIRIE RED NECK

I'm with Jon on the motor size. I have a trainer with a 63" WS that I put an E Flight 25 on. I took it off before I destroyed the plane and went with the E Flight 15. It still goes vertical for a long way and has no problem with floats and towing gliders up to 3 meters.

Of course you could just undersize the prop on the 46 to keep the power output at a reasonable level. No harm in that!

Also I have been running two 2 cell 2000mAh packs in series on this plane for several years with no problems at all. I now have a couple of 4 cell packs and they are more convenient for sure.

Mervin, what is your all up weight, length of flight times and flying style?