|Oct 28, 2012, 08:38 PM|
Eflite UMX Sbach 3D on 3s - 2300Kv/5043 vs. 2500Kv/5030
Here's some 3s testing I did today with the Eflite UMX Sbach 3D. Sbach #1 is running the 2300Kv motor/GWS 5043 prop combo, while Sbach #2 is running the 2500Kv/GWS 5030 prop combo. Both have a 1mm rod under the horizontal stab to prevent high-speed aerodynamic flutter. I used a Hyperion 180 mAh 25c 3s Babbelbatt on both flights. It appears that I got the stab halves reasonably straight on S3D #1, as it flew about the same as it did before the aerodynamic flutter incident.
This thing really moves on 3s! Thanks to AS3X, the plane remains smooth & precise - even @ WOT. The 2300Kv/5043 combo is the faster of the two by a considerable margin. I noticed a bit of gain-induced elevator oscillation during the first two WOT passes with the 2300/5043, but it appeared to smooth-out after that. I could hold either plane @ WOT for as long as I wished without hitting OTP. But it was only 44 F during the flights. When flying in warmer wx, I may need to improve the cooling like some have had to do.
Here's some static RPM data on 3s.
Interestingly, there is little difference in static thrust between the two combos, however the 2300/5043 combo's pitch-speed is nearly 20% higher. It's also interesting that the 2500/5030 actually outperforms the 2300/5043 in terms of thrust, considering that the 2300/5043 produces more thrust on 2s than the 2500 with either prop.
RPM taken under natural light with a calibrated optical tach, 30 sec into each run on a freshly-charged pack:
Sbach 3D on 3s
Pack: Hyp 180 25c 3s
Elevation: 910 ft AMSL
Temp: 70 F
Motor/prop ---- RPM -- Thrust (g)* -- Speed (MPH)**
2300Kv/5043 - 10,700 ---- 159 ------------ 43.6
2500Kv/5030 - 12,870 ---- 164 ------------ 36.6
For reference, here's my stock Sbach data:
Elevation: 910 ft AMSL
Temp: 70 F
------------- Hyp 240 - TP 325 65c - Hyp 500 35c - Thrust (g)* ---- Speed (MPH)**
Stock prop - 10,550 ---- 10,770 -------- 11,100 ----- 99/103/110 --- 27.5/28/28.9
GWS 5030 - 11,010 ---- 11,160 -------- 11,340 --- 118/121/125 -- 31.3/31.7/32.2
GWS 5043 -- 8,910 ------ 9,040 --------- 9,210 ---- 108/112/116 -- 36.2/36.8/37.5
*Calculated using the GWS prop spreadsheet
**Calculated pitch-speed. Prop slippage and in-flight unloading not taken into account.
Also, I solved the high speed tail oscillation problem on 3s. Here's the test-flight. WOT laps at 2:00:
DISCLAIMER: UMX PLANES ARE NOT DESIGNED FOR 3s. TRY AT YOUR OWN RISK!
|Aug 22, 2013, 07:56 AM|
The 2s UMX planes are not designed for 3s. Try at your own risk. That said - most of the 2s AS3X bricks will handle 3s if you use the appropriate motor/prop combos - aside from possible OTP issues that can usually be solved by improving cooling. But the bricks rarely get damaged from 3s operation. See the Beast/Beast 3D & Sbach/Sbach 3D threads for more info & 3s reports.
|Jan 07, 2014, 02:45 AM|
Joined Dec 2010
Or even the 5.75 with a 1/8'th inch diced off both ends ?
Would that be more thrust , less speed ?
|Jan 07, 2014, 01:52 PM|
The E-flite 5" x 2.75" prop is less efficient than the GWS 5030 or 5043. You'll get more bottom-end grunt and longer flight-times with the 5030. Regarding the Yak prop - it's the clear winner for best low-end performance on 2s with either the 2300Kv or 3000Kv motor. However, it is too much load on 3s. You could cut it down, but doing so will eliminate its advantage over the others (the larger thrust-disk is why it is so efficient & has so much low-end grunt). Might as well go with the 5030 at that point. The Gee Bee's 5.25" x 3.5" prop is a horrible match for the UMX airframes & motors. The Gee Bee is considerably faster, has much better vertical, draws a lot less current, and flies a lot longer with the 5030. The only UMX-sized 2-blade E-flite prop I haven't tried yet is the Hyper Taxi's 5.5" x 2" prop. That might be a good choice on the 2300Kv for low-end grunt in a 3s app. Might be too much load for the 2500 & 3000Kv motors on 3s, though.
We've learned over the years that it's pretty tough to beat the efficiency & performance of the GWS 5030 & 5043 props on the UMX planes. The Yak is the first UM to come with a well-matched prop, but it's only a good match for slower airframes. For instance - the Yak prop is just about perfect on a 2300Kv-equipped CC, but it would be a poor match for the Sbach on 2s, even with a 3000Kv motor. The 3000Kv/5030 or 2300Kv/5043 combos provide much better overall performance on 2s in that airframe.
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