HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Jan 13, 2011, 07:01 PM
Registered User
Yuma, AZ
Joined Oct 2003
363 Posts
Discussion
Flight Performance of 1400mm FMS BF-109

I finally got my 1400mm FMS BF109 into the air today. To make a long story short, I was somewhat disappointed in the flight performance. I flew it twice and on both flights I spent the whole flight at full throttle to get anything approaching enjoyable performance. I am not a speed demon, but I would like to fly and enjoy the speed at less than full throttle except for vertical maneuvers. Now I'm new to these electric foamies and maybe I am expecting too much, but here goes...

4c 2650/3000 mah batteries, the motor says it's a 520kv motor, the ESC instructions cover three different models (20A, 30A & 50A), I'm thinking it's the 50A versions. the plane is flying on a 13x9 3-blade prop that I know hurts a little.

So I'm not that up on the technical part of this electric stuff, not even sure what is interchangable. the plane is stuck with a 3-blade prop because of ground clearance.

Could someone help me out here with what I would have to do to increase performance a bit.
splais is offline Find More Posts by splais
Reply With Quote
Sign up now
to remove ads between posts
Old Jan 13, 2011, 07:07 PM
Registered User
Yuma, AZ
Joined Oct 2003
363 Posts
PS: I notice the FMS P-51 uses a 600KV motor and has a 2-blade spinner available. Wonder if I could solve my problem with the P-51 motor and say a 13x10 or 12 prop?
splais is offline Find More Posts by splais
Reply With Quote
Old Jan 13, 2011, 07:55 PM
Registered User
kahloq's Avatar
Fort Collins, Colorado, USA
Joined Dec 2005
7,821 Posts
Here's the problem....the kv of the motor is too low for the pitch of the prop for the given voltage(4s)

A 520 kv motor using a 9 pitch prop on only a 4s lipo.
Here's the rundown....
4s lipo = 16.8 volts charged (minus a few tenths for battery condition....we'll use 16.5. A decent lipo will push out the amperage similar to a fully charged battery till about 3.85 volts per cell so you dont see much of a drop off in power output till then)

16.5 volts x 520kv = 8580 unloaded rpm

8580 x 9 pitch of prop = 77220

77220 x 60 minutes = 4633200

4633200 / 63360(inches in a mile) = 73 miles per hour(no drag or prop load, efficiency factored in)

So take 75% of 73 mph and you get 54mph. So..yeah...not exactly screaming fast.

if you change to the 600kv motor, you'll get 84mph unloaded, 63mph real world. A nice improvement.

If you get a spinner with a 2 blade cutout, use a 13x10 and you should see 60mph real world on the 520kv motor or 70mph real world with the 600kv motor.

In all honesty, a 520-600kv motor is suited for a 5cell setup, not a 4s.
I have a 500kv turnigy motor possibly going in my bash of this me-109(whatever...E/F/something) and Id be using a 5s lipo with it
5s = 20.5 volts
500x20.5x9x60= 5535000
5535000 / 63360 = 87mph unloaded or 65mph real world with the stock prop

Or using an e-flite power 25 with a 870kv motor on 4s
870x16.5x9x60= 7751700
7751700 / 63360 = 122mph unloaded or 91mph real world

I was using the power 25 with a 12x6 APC E prop on an E-flite Erratix 3D 55" wingspan balsa plane and had unlimited vertical.
The 3 blade 13x9x3 from FMS might be a bit much for that motor, but as long as you dont go full throttle often..it'd be fine
kahloq is offline Find More Posts by kahloq
Last edited by kahloq; Jan 14, 2011 at 04:16 PM.
Reply With Quote
Old Jan 13, 2011, 08:07 PM
Registered User
kahloq's Avatar
Fort Collins, Colorado, USA
Joined Dec 2005
7,821 Posts
btw i used that power 25 with 12x10 in a parkzone me-109

speed u ask?

101mph on 4s! yes...I had to reinforce the plane.
kahloq is offline Find More Posts by kahloq
Reply With Quote
Old Jan 13, 2011, 08:09 PM
Registered User
Yuma, AZ
Joined Oct 2003
363 Posts
So it sounds like you are saying my idea will work and work even better with a 5c battery. I can't spend the money for a couple of 5c's, even from China right now; but a new motor/ESC is possible.
splais is offline Find More Posts by splais
Reply With Quote
Old Jan 13, 2011, 08:59 PM
GLF4-SP Driver
rgd1065's Avatar
USA, TX, North Richland Hills
Joined Dec 2009
331 Posts
isn't a 4s 14.8 volts, nominal charged?
rgd1065 is offline Find More Posts by rgd1065
Reply With Quote
Old Jan 14, 2011, 04:13 PM
Registered User
kahloq's Avatar
Fort Collins, Colorado, USA
Joined Dec 2005
7,821 Posts
Quote:
Originally Posted by rgd1065 View Post
isn't a 4s 14.8 volts, nominal charged?
14.8 at safe discharged/storage status yes. 3.7 volts per cell. But a fully charged 4s is 16.8 volts or 4.2 volts per cell.
kahloq is offline Find More Posts by kahloq
Reply With Quote
Old Jan 14, 2011, 04:20 PM
Old, New Guy
Tubo's Avatar
USA, FL, Fort Walton Beach
Joined May 2010
211 Posts
Interested in selling the 520kv motor??
PM if ya want to plz.

Tubo
Tubo is offline Find More Posts by Tubo
Reply With Quote
Old Jan 14, 2011, 07:31 PM
Registered User
Dennis Everett's Avatar
United States, CA, Ontario
Joined Mar 2002
7,765 Posts
A very nice cheap upgrade is the monster power 32 from hobby partz(22.00) (out of stock) i put a hyperion 3025-990 in mine , on 4s were guessing 80 mph , was 39.99 at aircraft world , 2.50 shipping , just going to a 2 blade prop will help a bunch , 13x10 ish
Dennis Everett is online now Find More Posts by Dennis Everett
Reply With Quote
Old Jan 14, 2011, 11:35 PM
GLF4-SP Driver
rgd1065's Avatar
USA, TX, North Richland Hills
Joined Dec 2009
331 Posts
Quote:
Originally Posted by kahloq View Post
14.8 at safe discharged/storage status yes. 3.7 volts per cell. But a fully charged 4s is 16.8 volts or 4.2 volts per cell.
It was tongue in cheek. You got it though.
rgd1065 is offline Find More Posts by rgd1065
Reply With Quote
Old Apr 21, 2011, 08:35 AM
Team Wack-a-Mole
Melnic's Avatar
Maryland
Joined Oct 2008
8,439 Posts
Looks like the Airfield BF109 is on sale. The Rx ready version is only $149 http://www.nitroplanes.com/specials.html
Melnic is offline Find More Posts by Melnic
Last edited by Melnic; Oct 17, 2011 at 03:23 PM.
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion FMS FW-190a 1400mm Tommy D Electric Warbirds 1811 Feb 02, 2012 08:54 PM
New Product New Giant FMS EPO BF 109 fletchace Electric Warbirds 20 Nov 23, 2010 08:53 PM
For Sale SIG Messerschmitt bf 109 RxR ARTF Never Flown bobschultz Aircraft - Electric - Airplanes (FS/W) 2 Oct 26, 2010 02:55 AM
Discussion Just a Glimpse- FMS BF-109 ozzi supercub Electric Warbirds 38 Sep 28, 2010 12:58 AM
Poll PZ BF-109 or P-51 BL ElIntocable Parkflyers 16 Sep 04, 2010 05:04 PM