Jul 28, 2012, 03:39 PM Registered User Joined Sep 2011 128 Posts Discussion good quality motor takes 5kg 3D?? I'll make a a big 3D scratch built airplane . What good quality motor that can take 5kg 3D airplane?'
 Jul 28, 2012, 06:04 PM The 6 P principle works for me Ventura CA Joined Aug 2007 980 Posts So, you are asking for help and there are a lot of people on this forum that love to help! Bad news is, we need more input! 5 kilo plane that you want to 3D so..... What is the wing area? What does the 5 kilo weight include? Does that weight include the motor esc and batteries? Another words is it 5 kilos RTF or.....?????Assuming LiPo's, how many cells do you want to use or how many does the mfg recommend? Also important, how much ground clearence do you have or how big a prop can fit on the plane? 5 kilos is about 11 pounds. At 175 watts per pound in thats 1,925 watts in at full power static. At 200 watts per pound the power required is now up to 2200 watts in. If your plane has a light wing loading then you might be looking for 40-50 mph top speed (64-80 kph). At full power static you might want to see a prop pitch speed of your estimated flying speed + 30% - 40% (54-75 mph). More cells (in series) = more power AND more weight! Also for a given motor, more cells in series = more rpm and then you need to use a smaller prop! Also important, how long a flight do you want? Just need more info from you! Michael
Jul 28, 2012, 06:30 PM
Registered User
Joined Sep 2011
128 Posts
Quote:
 Originally Posted by elecfryer So, you are asking for help and there are a lot of people on this forum that love to help! Bad news is, we need more input! 5 kilo plane that you want to 3D so..... What is the wing area? What does the 5 kilo weight include? Does that weight include the motor esc and batteries? Another words is it 5 kilos RTF or.....?????Assuming LiPo's, how many cells do you want to use or how many does the mfg recommend? Also important, how much ground clearence do you have or how big a prop can fit on the plane? 5 kilos is about 11 pounds. At 175 watts per pound in thats 1,925 watts in at full power static. At 200 watts per pound the power required is now up to 2200 watts in. If your plane has a light wing loading then you might be looking for 40-50 mph top speed (64-80 kph). At full power static you might want to see a prop pitch speed of your estimated flying speed + 30% - 40% (54-75 mph). More cells (in series) = more power AND more weight! Also for a given motor, more cells in series = more rpm and then you need to use a smaller prop! Also important, how long a flight do you want? Just need more info from you! Michael
what do you think of this ? http://www.scorpionsystem.com/catalo.../s-4035-250KV/

and yes it will be 1m-1.30m wing with batteries and servos and esc.
atleast 10 minutes
Last edited by Wa7sh; Jul 28, 2012 at 06:59 PM.
 Jul 28, 2012, 09:22 PM Registered User Australia, ACT, Kambah Joined Feb 2001 3,271 Posts Any half decent commerically available 1.2m 3D model weighs less than 3lb. 5kg seems way way off
 Jul 28, 2012, 10:38 PM The 6 P principle works for me Ventura CA Joined Aug 2007 980 Posts Hey Sciroco, your reading my mind! I had better think nice thoughts! Being on the "foot/inch/pound" side of the pond.....1- 1.3 meter = 39" - 51". Borrowing numbers from the Gary Wright E3D (48" wingspan, 600 sq inches and 3.4 pounds RTF.) This gives a wing loading of around .82 pounds per sq foot. 5 kilos is about equal to 11 pounds which at 600 sq inches of wing area will be about 2.6 pounds per sq foot...... just a little high for 3D....yes?? I will be the first to admit that the E3D has a very light wing loading however, 2.6 pounds per sq foot is IMHO way to far over on the dark side! At around 50" wing span and around 600 sqs, I would think that 2.2 - 2.5 kilos would work for a 3D plane of that size. At 175 watts in per pound, that would be around 900 watts in. Compared to my first post, about 1/2 the power so, smaller/lighter motor and less weight in batteries as well! What are your thoughts Sciroco? Michael Last edited by elecfryer; Jul 28, 2012 at 10:39 PM. Reason: corrected mfgr name
Jul 29, 2012, 12:05 AM
Registered User
Australia, ACT, Kambah
Joined Feb 2001
3,271 Posts
Quote:
 Originally Posted by elecfryer Hey Sciroco, your reading my mind! I had better think nice thoughts! Being on the "foot/inch/pound" side of the pond.....1- 1.3 meter = 39" - 51". Borrowing numbers from the Gary Wright E3D (48" wingspan, 600 sq inches and 3.4 pounds RTF.) This gives a wing loading of around .82 pounds per sq foot. 5 kilos is about equal to 11 pounds which at 600 sq inches of wing area will be about 2.6 pounds per sq foot...... just a little high for 3D....yes?? I will be the first to admit that the E3D has a very light wing loading however, 2.6 pounds per sq foot is IMHO way to far over on the dark side! At around 50" wing span and around 600 sqs, I would think that 2.2 - 2.5 kilos would work for a 3D plane of that size. At 175 watts in per pound, that would be around 900 watts in. Compared to my first post, about 1/2 the power so, smaller/lighter motor and less weight in batteries as well! What are your thoughts Sciroco? Michael
Even 2 kg=4.4lb=70oz is way high for 1.3m/51". The PA Bandit is a 50" model around 45oz with wing loading about 12oz/sqft.
3DHS 47" Extra 44oz about 13.7oz/sqft Extreme Flight 48" MXS about the same.

For a benchmark 3D wing loading that doesn't push you into overly heavy power systems and thus even higher wing loading, a 600 sq in model shouldn't weigh more than about 54oz/1.5kg

ps my kit built E3D is about 48oz - happy on around 350W
 Jul 29, 2012, 08:43 AM I like the violent stuff! Costa Mesa, CA Joined Oct 2004 1,220 Posts I fly with 3DHS team pilots. The field has just recently removed the size restriction. Two weeks ago Kevin brought out a 104" 3DHS Slick and yesterday he brought out a 87" Extra both well over 5 kilos and both flying Hacker. Hacker, Scorpion and Motrolfly are at the top of the motors list. Good luck with you project!
Jul 29, 2012, 09:37 AM
Registered User
Australia, ACT, Kambah
Joined Feb 2001
3,271 Posts
Quote:
 Originally Posted by Wingin' Wayne I fly with 3DHS team pilots. The field has just recently removed the size restriction. Two weeks ago Kevin brought out a 104" 3DHS Slick and yesterday he brought out a 87" Extra both well over 5 kilos and both flying Hacker. Hacker, Scorpion and Motrolfly are at the top of the motors list. Good luck with you project!
104"=2.64m

3dhs 7" Extra ~ 8kg 1475 sq in motor ~ 900g 12S 5000 battery weighs ~ 1.7kg
3dhs 47" Extra ~ 1.2kg 460 sq in motor ~ 130g 3S 2500 battery weighs ~ 0.2kg

Hopefully some reference targets for design, but definitely not 5kg for 1 to 1.3m span
 Jul 29, 2012, 12:05 PM Registered User Joined Sep 2011 128 Posts i know its a bet overpowered motor. i choose this because i will move this motor to other airplanes and will fly perfect its better than buying several motor.
 Jul 30, 2012, 02:02 PM Product Manager at Hobbico United States Joined May 2000 5,163 Posts The plane in my avatar is just under that weight. It's a 90" span version of the E3D, at 10 lbs, so roughly 4.5kilo. 1660 square inches of wing (I think the math works out to about 14 ounce per sq ft), and I fly it with a Hacker A60M motor. Don't remember the wind and not at home right now to look, but it's the lowest KV version of the A60M. I fly it on 10S of various capacities, and a 22X10 prop. This setup would easily pull another kilo for 3D, maybe even 2. I'm sure around6.5~7kilos it would fly one well and hover, not sure how much authority on the pullout.