Thread Tools
Jun 13, 2016, 11:35 AM
Registered User
Thread OP
Question

How to: flight time of 1 hour - which motor/prop/batt


Hi all,

Firstly, I hope I'm posting this in the right place.

I'm designing and building a plane for an ecology project (http://projecterebus.weebly.com/blog) and am trying to find the right motor/prop/battery (and I guess ESC) combo for this.

I spoke to a chap at my local hobby store who recommended a 1050 KV motor / 12x5 prop / 40A ESC and 3S battery. I've plugged this into WebOcalc (http://flbeagle.rchomepage.com/softw.../webocalc.html) and it does seem like it'll work but I have heard that using a higher voltage battery (eg 6S) and larger prop on a lower KV motor can be more efficient?

Also, the LHS chap thought that this motor will generate a power of about 440W (giving me over my target of 100W/lb) but WebOcalc is saying it's more like 215W out of the motor which has confused me a bit. The motor is this one: http://www.overlander.co.uk/motors/b...est-model.html

I wanted to ask for some advice from you guys as well. Here's the info I think you'll need about the plane:

Weight: 2100 g / 74 oz
Wingspan: 2000 mm / 79 in
Wing area: 60 dm2 / 930 in2
Flight mission: I chose gentle scale flight as I want to fly slowly (for the purpose of the project)

My goal is to achieve a flight time of 1 hour and to easily have enough power for take off. Am I going down the wrong route using 3S and should be looking at a higher voltage system or is this the way to go?

Also, a larger prop turning slower would be advantageous for the project as I think this will generate less noise which is important. I'd be interested in anything up to a 15 inch prop (it'll be folding so ground clearance isn't of the utmost importance).

Thanks for reading this and any advice would be much appreciated.

Cheers, Tom
Sign up now
to remove ads between posts
Jun 13, 2016, 12:29 PM
Laughs at un-boxing videos...
basicguy's Avatar
How heavy of motor are you planning? 1050 kv 3s and 15" prop is going to take a motor which weighs 200 grams I would think. Not that having a large motor is bad, large usually gets more output for the input power.

I have a plane flying with a 150 gram 450kv motor on 4s with a 15.5 prop. It runs quiet. Weight is about 2.4 pounds with a 5ah battery. It flies well at 8-10 amps.
Jun 13, 2016, 12:59 PM
gpw
gpw
“There’s no place like Foam”
gpw's Avatar
They used to call it Duration ... All up last down ... Usually with powered gliders ...
Latest blog entry: Lost plans
Jun 13, 2016, 01:55 PM
Registered User
Thread OP
Quote:
Originally Posted by basicguy
How heavy of motor are you planning? 1050 kv 3s and 15" prop is going to take a motor which weighs 200 grams I would think. Not that having a large motor is bad, large usually gets more output for the input power.
The LHS recommended motor is just shy of 100g so perhaps it's not large enough?
Jun 13, 2016, 02:01 PM
Registered User
Ken Myers's Avatar
Perhaps not, for sure.

From a pure hobby point of view, getting to fly an electric plane, with the power on, for one hour is almost unattainable. Even glow powered aircraft must be specially built and designed for the large fuel tank and with absolute duration in mind.

With no experience in the field, the chances of achieving a successful duration design with an electric power system, to fly for one hour, is unachievable.
Jun 13, 2016, 02:05 PM
An itch?. Scratch build.
eflightray's Avatar
Sorry, but I think you are maybe asking about the wrong thing, the power system, unless you have the design fully sorted to achieve the best possible flight performance.

is the design finalized ?

As the airframe is likely to be the more important part of a 1 hour flight over the power system.

A good design should cruise on about 20 watts / Lb.

Weight, (wing loading), is the critical side of slow flight.

I assume it will be mostly autonomous, (pre-programmed).

Maybe the best place to ask, or look for long flight/long distance designs etc is the -- UAV - Unmanned Aerial Vehicles forum -- they have achieved long flights, and have been developing that type of plane for quite some time.

Basically a high efficient glider design with electric power.

Ray.
Jun 13, 2016, 02:11 PM
Closed Account
Yeah that was my first thought when I saw the post. In terms of models one hour out of an electric aircraft is a lofty goal. You'll have to carry a lot of weight in batteries and then you'd be right on the edge of minimal thrust to weight. Still that would probably not get you close to an hour. Powered gliders are the only electric motored models that can attain flight times approaching an hour and that's with with periods of unpowered flight. Sail planes can get flight times like that regularly, but that's slope soaring not powered flight. I had to qualify that with the term "model" because there actually is a commercially built electric manned plane that can fly for over an hour. Saw a video clip on it the other day, really interesting actually.
Last edited by CraigHB; Jun 13, 2016 at 02:18 PM.
Jun 13, 2016, 11:06 PM
Registered User
An hour is definitely possible. I'm not sure about with a bix 3 though. Best place to look for endurance is probably the FPV section of this forum. Lot's of long range flights, and generally long range means long duration.

Here's an example of a scratchbuilt high endurance plane: https://www.rcgroups.com/forums/show....php?t=1774660

That has more than half its weight in battery though
Jun 14, 2016, 05:47 AM
Registered User
Thread OP
Thanks for the replies, much appreciated. I'll check out the other forums and see what I can find!

I've been aiming for an hour as I read a couple of posts on conservation drones in which they achieved 2 and 3 hours and over 100 km during the flight. Check them out:

https://conservationdrones.org/2016/...ervationdrone/

http://diydrones.com/profiles/blogs/100km-challenge

I would say that the design is not set as yet but I have a few restrictions that I'm working with (namely, it has to be something I'm capable of building, the motor must be at the front and the fuselage must be 2 m or longer, ideally I would use a large slow turning prop).

Cheers, Tom
Jun 14, 2016, 08:25 AM
Registered User
Thread OP
Just following up on this, I've started another thread in the UAV forum so thank you for the recommendation of that (the thread is here: https://www.rcgroups.com/forums/show....php?t=2682977).

After reviewing the conservation drones effort on diydrones (http://diydrones.com/profiles/blogs/100km-challenge) I think that the following 400 KV Tiger motor (http://www.rctigermotor.com/html/201...r_0910/40.html) and a 15 x 5 prop along with a 6S ~ 12,000mAh battery would allow me to fly for circa 1 hour given the thrust that the motor would generate and the current draw (1250g, 5.7A).

I guess the important thing is, do you think this would work?

Cheers, Tom
Jun 14, 2016, 09:11 AM
Registered User
Ken Myers's Avatar
Quote:
Originally Posted by Tom_
and a 15 x 5 prop along with a 6S ~ 12,000mAh battery would allow me to fly for circa 1 hour given the thrust that the motor would generate and the current draw (1250g, 5.7A).
Motors do not create thrust. They convert energy.
Jun 14, 2016, 02:06 PM
Registered User
Thread OP
Quote:
Originally Posted by Ken Myers
Motors do not create thrust. They convert energy.
Great.

What do you think about the setup?
Jun 14, 2016, 04:52 PM
Closed Account
If you go to 12S you'll get better efficiency. When going for endurance every little bit helps. Longer slower turning props are more efficient, but it's important to match the Kv of the motor to the rpms you'll be running. Synchronous motors (the kind we use in models) can get highly inefficient when running rpm very far below nominal voltage times Kv. Ideally you want rpms in the range of 70 to 90% at full throttle.
Jun 14, 2016, 09:50 PM
Bind n' Crash
this plane built by rctestflight runs for 1 hour and 8 minutes:
RC Plane Long Duration Flight (5 min 21 sec)


you would have to switch up your design a bit to meet the weight specs of this plane, but you're looking at intensely long flights. Just wondering, what is the application? By the way you describe it (long, quiet flights) makes it sounds like you're about to go over area 51!(let me know if you find aliens or some awesome aircraft)
Jun 15, 2016, 04:38 PM
serial scratchbuilder
Granted's Avatar
Check out some of Quornengs' work, one hour duration is on the low side for his builds: https://www.rcgroups.com/forums/show....php?t=2468269
https://www.rcgroups.com/forums/show....php?t=1774660


Quick Reply
Message:

Thread Tools