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ESC advice - EDF HAwk (Sapac?)

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Tony Kenny26/08/2017 19:05:20
282 forum posts
62 photos

Hi All,

I picked up a lovely EDF Hawk at the Wragley Hall show, much easier to fly than I imagined and performed a perfect landing

But, the motor cut out. On the advice of the club instructor testing it with me, I let it cool a few seconds then throttled up and it was OK, He had the same problem with his former EDF Hawk.

Testing it on the bench, full throttle was drawing about 35A on a 3S Lipo and the ESC was very hot, and only rated at 25A! The fan is about 65/70mm.

So, 2 questions, if I may.

1. Does that current draw of 35A sound about right for a 65/70mm fan on a 3S lipo?

2. Do I have to buy a special ESC for an EDF or just any that's rated high enough?

Many thanks in advance!


pete taylor26/08/2017 19:30:39
349 forum posts
164 photos

Hi Tony,

I'm glad you like your Hawk and are getting the EDF bug!

35A on 3 cells sounds about right for a relatively tame EDF setup. As for the ESC, I would be inclined to go for at least 40A and preferably a 60A one, so that if you feel inclined to put a hotter fan unit in the model at a later date you have a bit of wiggle room with regard to the ESC. 60A will also give you plenty of "headroom" in your existing setup.

ESC's can get a hard time in EDF models and I generally go for at least 20A more than required.


Tony Kenny26/08/2017 19:45:25
282 forum posts
62 photos

Yes, got the bug, even after only a 60 second flight before I decided to land due to the cutting out. A slightly different style of flying and I had to be more careful in turns, but loved it.

Thanks for the advice, I've got a 60A ESC 2nd hand that I earmarked for a renovation project so I can sling that in and see how it goes!

Just waiting for some new cable to arrive so I can extent the power connection, the one in it was way too think to handle 35Amps and was also pretty warm!

Simon Chaddock27/08/2017 01:56:02
5621 forum posts
2987 photos


Drawing 35A through a 25A ESC will cause it to over heat and trip the thermal cut out.

You were lucky that is all that happened as run like that it will 'die' sooner rather than later resulting in at best a dead stick or worse no control at all.

A 60A ESC is indeed sensible but remember it too will still generate a significant amount of heat so needs an adequate cooling airflow .

Tony Kenny02/09/2017 20:34:24
282 forum posts
62 photos

Thanks guys

With a 60A ESC, I got the hawk back in the air today and had a flight but it felt like it needed more throttle than before. Something didn't feel right so I decided to land, but on the approach I went dead stick and ended up landing short which ripped off the wheels, easy fix thankfully.

But, I tried the throttle to see if there was anything left in the battery and got a nice stream of blue smoke!!

In the pits I discovered that the Rx had fallen off and was in the air flow, could that be enough to cause a loss of power and eventually melt the motor?

Trying now to get the motor out, but looks like it was put in before the fuz was glued together, so probably a it of surgery required.

onetenor02/09/2017 23:34:58
1901 forum posts

Sounds like the 2nd hand esc is duff .

Piers Bowlan03/09/2017 05:39:46
2055 forum posts
53 photos

As you are enjoying the model Tony and hopefully it didn't cost too much, perhaps you could consider investing in a good quality motor and ESC upgrade? That might avoid further dead sticks, damage and frustration. It could transform the model.

Tony Kenny03/09/2017 09:35:10
282 forum posts
62 photos

Thanks, can a faulty ESC cause a motor burn out? Is there any way to test an ESC other than "the motor spins"?

Piers, I will indeed invest in a new motor and ESC, I'll probably upgrade to a 12 blade which I understand can also be a bit quieter. Can you suggest a good source? My usual supplier doesn't do much in the way of ESC motors.

Piers Bowlan03/09/2017 14:11:07
2055 forum posts
53 photos

Tony, my best advice is to contact George Worley at 4-Max here. He will advise you of the best set up to get the most out of your model and save you messing about experimenting with different Fans/Motors/ESCs etc. Just tell him what the model is and he will do the rest hopefully. I am not qualified to advise you on what to try but good luck with your project.

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