Electric Flight Experts! Your Assistance Is Sought Again!

[David Davis]

I am currently doing a fair bit of instructing using a Seagull Boomerang 2 powered by an Enya 50SS. Actually it's currently powered by an Enya 45 while a stripped thread is sorted out but that's by the by. I have recently bought a Protronik DM2839 660kv motor and a Protronik BFu 95A speed controller for another project which I abandoned by fitting an i/c engine to the model. I have had a 5350 mAh 5S LiPo for some time and the thought occured to me that I could buy another Boomerang, after all they're cheap enough, and have an electric powered trainer as a reserve model. According to the information in the catalogue the electric motor is capable of flying trainers which weigh up to 6kgs, (over 13lbs) and I doubt that the the Boomerang weighs half of that. Given all of the above, I have a number of questions for the electricians.

1. The nominal voltage of the LiPo is 18.5 volts.

Do I need a seperate receiver battery or can I simply plug the cable from the speed controller into the throttle channel of the receiver as I would with a Foam-E WOT 4 and a 3S LiPo?

 

2. What is a ubec and do I need one for this installation? If I need one where can I buy one?

 

3. There is a label on the speed controller which reads as follows: "Pro-Tronik BFu 95A. U.B.E.C 4A."

Does this mean that the speed controller contains its own UBEC whatever one of those is?

 

4. The Boomerang 2 comes complete with all of the parts and instructions for the installation of an electric motor and it recommends a 4S or 5S LiPo. However, in the photograph accompanying the instructions a 3200 mAh 4S LiPo is clearly shown. This battery would be much lighter than the one I have in stock.

Is my 5350 mAh 5S battery too big and heavy for the airframe and if I fitted it would it ruin the flight characteristics of the model?

 

Edited By David Davis on 03/07/2018 05:53:04

[andyh]

1/2/3: your ESC has a built-in BEC (Battery Elimination Circuit) which provides a 5V power supply for your Rx. you don't need a separate BEC or Rx battery.

4. it will make the plane a little heavier - at a guess by 1/2 lb - but it's unlikely to ruin the flight characteristics on a plane weighing 5-6lb in total. I doubt the leccy conversion would be any heavier than the IC version it's based upon.

[David Davis]

Thank you Andy.

[Biggles' Elder Brother - Moderator]

Yeap, Andy has nailed it.
One thing I would add, your higher capacity battery won't make any significant difference to the aircraft's flight characteristics, but it will enable you to fly for longer!
BEB

[David Davis]

Ideal for training then! Thanks BEB!

[MattyB]

All the above advise is on point, but I personally don't use the ESC BEC for any model that needs a battery with more than 4 cells - I have had failures of ESC BECs in the past, and prefer to fit a separate unit that will run much cooler or a separate RX pack. Many will tell you this is unnecessarily conservative given most ESCs now have switching BECs that are more reliable, but it works for me

Edited By MattyB on 03/07/2018 11:01:55

[Philflyer]

My Boomerang 2 has an NGH 9cc petrol engine, weighs 3.1 Kg and does everything a 'hack' flyer should providing you manage its energy when doing aeros! Very forgiving when landing in windy conditions. I very much doubt if your set up will weigh more than mine so should not be a problem.

Edited By Philflyer on 03/07/2018 11:04:36

[eflightray]

Had to look up the Pro Tronic 2839 660kv. -- **LINK** -- French web site ?

If you are going to use the 5s pack you will need to use the smaller prop quoted, 12" x 8" prop.

A very useful tool to get, if you don't already have one, is a wattmeter. It will allow you to see what amps the system is drawing. Can save the 'magic smoke' from escaping.

Ray.