E-power F3B set-ups - RC Groups
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Oct 16, 2012, 01:37 PM
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Shedofdread's Avatar

E-power F3B set-ups

Hi Everyone,

A few questions for those who've invested in an 'e-power' fuselage for their F3B models -
What set-up did you go for? Geared inrunner or outrunner? (I suppose the geared inrunner would fit better into the nose...?)
What size LiPo? How many climbs to winch launch type height do you get from this size pack?

If you'd be so kind as to share your experience, it would be most appreciated. As would a piccy or two.

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Oct 16, 2012, 02:22 PM
In F3J size does matter!
roydor's Avatar
What sort of flying are you looking for?
I ask because it makes a big difference on the available power you want.
For low speed climbs you could go 200 watt/kg and get 3 launched on a light and cheep setup.
If you want a 30+ m/sec climbs you should be looking for 2kW which means bigger, more expensive motors and big batteries to provide the current for these monsters.

In any case, fitting an outrunner in the very narrow fuses is usually not possible unless you are going for really underpowered climbs.
You will probably need a geared motor and you can look at the Hacker B40 and B-50, Neu, Kira combinations and micro edition setups:

If you tell me what you are looking for, maybe I can help you with something a little more focused

Oct 16, 2012, 03:12 PM
Deniable plausibility
Shedofdread's Avatar

Many thanks for the swift reply and the links. At this stage, it's really an intell gathering excercise. The basis for which is that I wish to fly more often and it seems that when the wind is on my preferred slope (which is 40mins drive away...), I'm at work etc. Living in the countryside, it shouldn't be that difficult to find a field from which to fly from - hence my interest in e-power (less set-up time and space than with a winch or bungee).

Once I've got an idea of the sort of set-up typically used to successfully launch a 3ish m, 2.5ish kg, fairly fast sailplane, I can then decide whether I can fit the required kit into one of my existing fuselages or whether I need to make new fuz moulds. Or indeed, if an elegant 'power pod' (Schambeck-style http://www.klapptriebwerk.de/produkt...power/?lang=en ) has merit.

As to the desired climb rate, I think something between the two is probably the way to go. I have a number of 80A ESCs not currently (every pun intended ) in use and would like to use them to keep costs down. This clearly limits climb rate. On 4s, using 65A (to give the ESC a little safety margin) that's about 1KW. About twice your min rate of 200W/Kg so at least they'll be usable.

Thanks again.

PS Tom - thanks for the link
Last edited by Shedofdread; Oct 16, 2012 at 03:16 PM. Reason: Other posts posted while typing mine
Oct 16, 2012, 06:33 PM
Registered User
Hey Shred

Perhaps a Vid of what approx 1.4kw static, translates to in the air (approx 1.1kw dropping to 1kw after a few climbs and approx 80a on 4s) might give you a better idea!

Set up now is B50 12s geared, 16x13, CC100 lite on TP 65c 1800mah 4s, AUW 2.45kg

We also run TP 65c 1300mah 4s at AUW 2.4kg but this is approx 30s total motor run time which is about 6x 5s climbs.

Oct 16, 2012, 06:56 PM
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Shedofdread's Avatar
Mmmmm... That would appear 'sufficient' Many thanks for the info.
Oct 17, 2012, 04:32 AM
In F3J size does matter!
roydor's Avatar
I would recommend that if weight is not an issue, you choose yourself a motor with gearbox with a thick shaft, 5 or 6 mm. That would mean not choosing a B-40 with a Maxon 4.4:1 gear box as they are only 4 mm in dia.
I have a motor with a Maxon gear box but I'm not very confident about its survivability in a hard landing with a heavy model.

I think that the B-50 and Kira motors would be a good option it they fit in your fuse.
Try building a mockup motor, and see what diameter motor you can put in the nose.
CG is a problem and you shouldn’t worry about it too much at the moment as you can put the servos in the tail if needed to get the CG you want. I plan for CG only after getting all the equipment for the model if weight is not an issue.

You would probably need a battery of 200 to 250 grams in weight to get +1 kW of power without stressing it to hard so you better check some of the available batteries and make a mockup of them as well.

Use an external BEC. Castle creation has a good one at ~10 grams. Hyperion has a good one as well but it's bigger and heavier (~20 grams).

Oct 17, 2012, 12:52 PM
Registered User
Roy, good advice.

We have recently done a lot of testing with skinny clean 3m F3X electric models in mind and previously converted a lot of 3m gliders to electric power mainly because manufacturer’s electric versions of 3m F3X ships are just not as good for the purposes we wanted.

That is; light and not too much difference in weight to the glider version, clean so lower drag and finally ability to take a fully loaded F3B plane to height safely so approx 4kg +.

This basically led us to 1 Kw out put power trains, which of course is a very nice amount of power for sports flying a 3m F3X.

At this power level we discovered some interesting things about what works keeping the system as light as possible. You would think that a Hacker B40 or Kontronik Kira 480, basically off the shelf 28mm can geared motors, would work well. They didn’t, yes whilst these motors can be pushed to 1kw in the air, they are not efficient and so need bigger batteries than you would expect. The climb is slower, so you need longer motor runs. Around 750w is good but not 1kw.

A better solution was when we ran 36mm can motors, where the efficiency is much higher at the 1kw level. (We used a Hacker B50 12s geared after a few changes). Then you are looking at 5-6s motor runs for 250m and so high C rating small capacity cells can be used. We have tested TP, 65c 1300mah 4s which with a safety margin can provide 30s at around 80a so about 5-6 climbs. Motor weighs 250g and lipos 165g so 415g in total. This is marginally lighter than a B40 geared set up with larger capacity lipos weighing 250g and motor 180g (=430g). But because of reduced efficiency you would be on the road to ever decreasing returns pushing a B40 to climb in the same way even though you might measure the same 1kw.

The problem of course that there are not many skinny F3X fuses that will accommodate a 36mm can motor. Those that do like the New Air One allow a really lightweight set up. Ours using TP1300mah weighs just 2.4kg. As you might imagine it can thermal very well at this weight.

Incidentally, we settled on 4s as the minimum lipo cells to support a UBec at reasonable currents. 3s was just too much for comfort and 5s excessive. Remember we wanted to optimise for lightness and 1kw.

Another route is to use long case 28/29 can motors and marry to a Kontronik gear box, a custom motor then. Neu motors 1115 will do and also one of the Mega 28mm cans. These are basically longer than stock B40L and Kira 480s and will handle 1kw efficiently. They are also over an ounce lighter than say a Hacker B5012s geared.

So for a skinny F3X- E glider there is a bit of difference in what 1kw can do, not all power systems deliver in the same way and also you really you need a 16-17 inch prop to make use of it in a 3m. Our results in flying look like much more power as the previous video posting shows. It’s definitely no slouch!

The results on the flat without a slope were also much better than we expected.
Oct 17, 2012, 05:37 PM
Registered User
Some motor sizes and winds simply have too high an internal resistance to be used at high power levels. This results in low efficiency and high power loss. This is frustrating because what seems to be the perfect motor just doesn't work at 700-1000 watts.
Oct 17, 2012, 06:26 PM
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Shedofdread's Avatar
Just want to say 'thanks' again for all the info - it's really appreciated. I need to spend a little while carefully measuring and planning now.
Already, I'm thinking the servos will HAVE to go in the tail as the LiPo will only go in the nose and the area under the wing will only just take the Rx.
Oct 18, 2012, 02:45 AM
Tragic case
davidleitch's Avatar
A neu, kontonik or more exotic plettenberg geared in runner are the way to go. Of the hackers the b40 f5b with 6.7 gearbox also works well. The 4.4 gearbox will not handle power levels in excess of 1kw reliably.

In f5b we run power levels of 5-7kw but for f3b with narrow fuselage the choice is mostly limited by the battery that will fit. A 3s 2200 battery can produce around 1300-1500 watts in 10 second bursts.

A neu 1506-1509 would be a nice choice
Oct 18, 2012, 03:36 AM
Registered User
David you are right, for converting F3x fuses you are generally looking at 3s maximum in a stacked pack. So then 3s+3s can work, joining 2 packs in series.. But to get the CG you might need to go under the joiner so then you are probably looking at 2s+2s. This is another good reason for using a system based on 4s. (But we have also done 3s+2s with the 3s ahead and 2s under the joiner).

Under 1kw though 3s would be fine if you also want to run a Ubec but pulling over a 1kw and running 6 power hungry MKS servos for instance was just too much for comfort though pretty certain it would work. I guess you would be looking at each cell under load dropping below 2v before it didn't! So probably better to use a separate RX battery for this system. This didn't work for us because it adds more weight and needs more space etc.

Our thinking for a light set up at this power level was even if the motor demand was so high to drop each cell to 2v with 4s there is still 8v for the radio. Anyway, a simple cost consideration also played a part. 3s systems based on 1kw + needs a high amp ESC which is more expensive. 4s systems need a 75-100a ESC which are far less expensive and freely available.
Oct 18, 2012, 05:42 AM
Registered User
Harri Pihl's Avatar
Regarding the use of the Kira 480 with more than 4S lipos. Yes, it's indeed limited due to current limit and the efficiency drops too much (and there is big risk to burn it). However, it would be still very good had they made a higher ratio reduction gear for it; Drive calc gives about 1,2 kW with 85% efficiency at about 70A with 6.7:1 gear assuming 6S lipo and 16x13 AeroCAM.
Oct 18, 2012, 08:05 AM
Registered User

i´m going to cut off the nose my crossfire classic this winter going for this setup:
- Scorpion 2221-8
- Reisenauer Micro Edition 5:1
- 16x10
- 3s (if i 'find'enough space maybe 4s)

won´t be vertical, but about 70°
Oct 18, 2012, 01:09 PM
Sure it'll work
Flyextreme's Avatar
Originally Posted by Shedofdread
Mmmmm... That would appear 'sufficient' Many thanks for the info.
Do you want sufficient, or a little more on the High Performance side of fun? I'm in the middle of my build, which is going very slow BTW, and my ship is somewhat porky. AUW estimated to be approx 2800-2900gms, 1650gms. empty.

RFM 17x13-40mm spinner
Ice Lite 200 (I could use smaller)
2x2S Nanotech 65 3850
Est. 200 amps 3000w or so....40-45 m/s or so.

I have to remove the pod, and slide the motor in from the back (barely). Also, my RX and RX pack are in the boom. Nothing can go under the wing joiner, so the motor, esc, and lipos (end to end) fit in the nose (again, barely).

I don't know if my fuse is any bigger or smaller than other F3B fuses or not.

I'm guessing you only want to get to altitude, but you said you plane was fairly fast, so I posted this possible option.

EDIT: Here are some other Neu options (at least that work in the Viking). Some are considerably smaller than my system.

Motor Propeller Batt watts in Airspeed AUW
SNeu 1110/1Y/6.7 Aeronaut16x8 3S 2200mAh 700 W 3 Kg 5-10m/s 2550 g
SNeu 1110/1Y/6.7 Aeronaut15x13 3S 2200mAh 900 W 2 Kg 7-12m/s 2550 g
SNeu 1115/2.5D/6.7 RF 17x13 6S 2200mAh 1,4 kW 3,7 Kg
SNeu 1115/2.5D/6.7 RF 17x13 7S 2200mAh 2,4 kW 4,8 Kg 38-40 m/s 2900 g
SNeu 1512/1.5Y/6.7 RF 20x13 7S 2200mAh 2 kW 7,2 Kg 28-30 m/s 2980 g

It sounds like your's may be lighter than these, so performance should be even better.

Last edited by Flyextreme; Oct 18, 2012 at 02:11 PM.

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