Electric Decathlon Black Horse set up

[Stuart Marsden]

I have acquired 65 inch span Decathlon Bellanca Axi 2826/10 with Ripmax Dragon 60 amp sec and 4 cell lipo 2500math 25c. The model has a 11/7apce and flies ok but appears a little revy. My watts metre tells me 380watts and showing 34 amps flat out and I am getting about 4 minutes leaving each cell about 3.75 per cell. Has anyone out there have one of these models are has experience of an ideal setup. I do expect to try larger capacity cells but this will bring g the c of g forward. Help please.

[Trevor Crook]

My son has one. It flies on a 4s setup but I'm afraid I can't remember all the details. It weighs about 6lb, and the batteries are 3000mAh 4s. The power was measured as about 600W. I'm guessing that with only 380W it's a bit marginal and is at full throttle for most of the flight. I think his prop is bigger, too.

I'll try to get more details, but suggest trying to fit higher capacity lipos and a bigger prop, provided the esc and motor can handle the extra current. I would also suggest your lipos are sagging under load if you are only getting 380W from 34A. A 40c 3000 4s pack should give a vast improvement, and allow the model to be throttled back for much of the flight envelope - my son gets 7 minute flights with his, with a bit to spare.

As I say, I'll report back when I find out more.

[Stuart Marsden]

Many thanks, I look forward to that

[Trevor Crook]

Stuart, I've re-read your thread heading and see you are using a 920kV motor. That's a bit high for 4s. I've had a quick look around and something like the Turnigy G32, which is 600kV, would be better. This would turn a 13 inch prop, and I'd estimate a 13x6 or 13x8 would pull around 40A, which would be fine for your 60A esc, and give you the 500 - 600W to fly the model well. A larger prop with lower rpm is more effecient than a smaller one spinning fast, and will sound less "buzzy".

The motor I mentioned is available from Hobbyking or Rapid RC for about £30. As I suggested above, getting some bigger batteries will also help. A bit of outlay I'm afraid, but worth it as the model is a good flier, no real vices but aerobatic like the real one.

[Stuart Marsden]

Thank you for this. It has also been suggested that a 3 cell pack of say 3300 upto 4000 at 30C would probably swing a larger prop and be more efficient for the 920KV motor, would others comment before I go down this route, I believe I need larger cell capacity and c rating as my tests this morning read on a 11x7apce 475watts at 36amps but the voltage dropped to 12volts quickly, all help much appreciated. Best regards, all.

[Frank Skilbeck]

I just ran your set up through Ecalc, setting the battery charge state to low, I got 37Amps, 470W and 2.26kg static thrust at 9500 rpm, based on this it sounds as though your batteries may be a bit weak.

If you change to a 3s set up, using the same motor then a 14 x 7 prop on a 3300 mah 25c battery gives 2.1 kg at 45A, 420w, 6400 rpm (with charge state set to low), with a new battery fully charged that goes up to 53A and 2.5kg thrust

[Stuart Marsden]

I will try 3 cells tomorrow with a 13by7 as I have this in stock, although my 3 cell pack is 2700 but it is new condition. Thank you so much, I expect I will end up hanging everything but want to get it right if I do.

[Frank Skilbeck]

With a good battery, Ecalc says you should get 2.3kg thrust at 7,400rpm and 44amps on a fully charged battery dropping off to 1.9kg, 6,750rpm and 1.9kg when the battery is run down.

Don't forget to let the battery warm up before you do any tests as cold batteries don't perform too their full potential

[Stuart Marsden]

many thanks, I will test tomorrow or at latest Friday and post results. On cell again many thanks

[Stuart Marsden]

many thanks, I will test tomorrow or at latest Friday and post results. On cell again many thanks

[Stuart Marsden]

many thanks, I will test tomorrow or at latest Friday and post results. On cell again many thanks

[Trevor Crook]

Stuart, sticking with 3 cells may well be the most pragmatic solution. If your experiments are encouraging, you could consider getting some higher capacity packs if you can fit them in. This would obviously increase duration, but would probably also improve performance - a 4000 pack with the same C rating as your 2800 will suffer less voltage drop under load. I discovered this benefit recently when I tried replacing a 3000 with a 4000 in my Ballerina.

[Stuart Marsden]

Thank you for this I am thinking along the same lines as a 3 cell pack 4000mah will probably weigh little more than the 2500mm 4 cell packs I have and this will not affect the c of G to much. I tested this morning as I said and with a 3 cell 3200 pack with storage charge of 3.9volts per cell I used a apce 13x6.5 and had readings of 350watts, 34amps but volts down to 9.9v. the battery I am using is a nearly new Dynamic 30c 96a rating but I am not convinced of the quality of these cells. As many comments as possible please as this is a great way for me in making progress.

[Frank Skilbeck]

A resting voltage of 3.9v per cell means that it's got about 40% capacity left, the volts down to 9.9v at 34 amps at this state of discharge isn't too bad, try it again with the battery full charged.

[Stuart Marsden]

Will do. A great friend has leaned me 4000 30c 4 cell pack to try as well, so will post the results once tested. Thanks l