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Best long range power setup for FT spear

duckduckgoose

Well-known member
#1
Hi all, so I'm about half way through my second FT SPEAR build and I was wondering if anyone had any suggestions for a long range power setup. In my last build I had a sunnysky 2216 1250kv motor spinning a 9x4.5 inch prop powered by a 3200mah 4s. This setup did get me around 20 minutes of flight time which could get me a 13-14km round trip with the vector. I was wondering if 3s and a larger prop /lower kV motor would be more efficient. Any suggestions would be great!
 

duckduckgoose

Well-known member
#3
Yes, a lower KV motor spinning a larger prop will be more efficient. I'm sure @Hai-Lee could give you a great explanation of why that is, and what a good setup would be.
Yeah thanks, I still struggle to get my head around the relationship between motor kV, prop size/pitch and battery capacity/voltage. Just picked a combination and stuck with it haha
 

Hai-Lee

Old and Bold RC PILOT
#4
Hi all, so I'm about half way through my second FT SPEAR build and I was wondering if anyone had any suggestions for a long range power setup. In my last build I had a sunnysky 2216 1250kv motor spinning a 9x4.5 inch prop powered by a 3200mah 4s. This setup did get me around 20 minutes of flight time which could get me a 13-14km round trip with the vector. I was wondering if 3s and a larger prop /lower kV motor would be more efficient. Any suggestions would be great!
The answer to range is simply the power used and the amount of power on board! If you are able to double the battery capacity then you would almost double the range, (actually it will be slightly more than twice the time due to the battery voltage recovery/sag with current draw with the extra weight adding slightly more drag and therefore a reduction.

The power Vs time Vs drag is the real issue. with drag if you double the speed you increase the drag 4 fold so slower is more efficient but there is a quiescent current draw in the ESC which means the ESC has a minimum current draw even with the motor cut. This means that the power is being used at all times. A smaller and closely matched ESC can add flight time as can less motor power being used.

To extend the range you need to find the economic cruise speed and stick to it. Fly in an energy conservation mode so that climbs are done slowly and the dives are done with the motor power off.

I hope that gives you some clues or insight!

have fun!
 

duckduckgoose

Well-known member
#5
The answer to range is simply the power used and the amount of power on board! If you are able to double the battery capacity then you would almost double the range, (actually it will be slightly more than twice the time due to the battery voltage recovery/sag with current draw with the extra weight adding slightly more drag and therefore a reduction.

The power Vs time Vs drag is the real issue. with drag if you double the speed you increase the drag 4 fold so slower is more efficient but there is a quiescent current draw in the ESC which means the ESC has a minimum current draw even with the motor cut. This means that the power is being used at all times. A smaller and closely matched ESC can add flight time as can less motor power being used.

To extend the range you need to find the economic cruise speed and stick to it. Fly in an energy conservation mode so that climbs are done slowly and the dives are done with the motor power off.

I hope that gives you some clues or insight!

have fun!
That makes a lot of sense, thanks.
 
#8
Hey dude,

I've converted my scratch FT spear mainly installing 5000mah 4s2p Li-Ion battery, Otherwise it flies with Radiolink MiniPix- Arduplane, Dragonlink V3 with telemetry 1W and gopro Hero 5 Black. I dont use FPV, because it feels too much hustle, I fly on telemetry when out of sight, or mostly doing missions. For flight times it flies around 50-60 minutes and covers around 50-60 km cruising.

Last mission I tested was 34 km and I flew like 20 minutes after that lowering my altitude gradually.

I've put all batteries in the back on both sides of the thrust section in order to balance the GorPro. Motor is NTM PropDrive V2 1200 with 30A ESC, 8x4.7 or 8x6 APC.

Total weight (AUW) is 1160g.

FT Spear is super capable platform, it's smooth.

Best,
 
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duckduckgoose

Well-known member
#9
Hey dude,

I've converted my scratch FT spear mainly installing 5000mah 4s2p Li-Ion battery, Otherwise it flies with Radiolink MiniPix- Arduplane, Dragonlink V3 with telemetry 1W and gopro Hero 5 Black. I dont use FPV, because it feels too much hustle, I fly on telemetry when out of sight, or mostly doing missions. For flight times it flies around 50-60 minutes and covers around 50-60 km cruising.

Last mission I tested was 34 km and I flew like 20 minutes after that lowering my altitude gradually.

I've put all batteries in the back on both sides of the thrust section in order to balance the GorPro. Motor is NTM PropDrive V2 1200 with 30A ESC, 8x4.7 or 8x6 APC.

Total weight (AUW) is 1160g.

FT Spear is super capable platform, it's smooth.

Best,
Wow, that's sounds great! I'm amazed you don't use fpv, I'd be terrified, but I guess telemetry should tell you all you need to know. The lion packs would be great for packing into tight spaces at the back of the plane. How do you find lion as opposed to lipo? Does it have enough thrust for takeoffs?
 
#10
Hey man,

Thanks for being interested, I wrote that because spear let you decide what king of plane it is.
Once you see that machine is robust, capable and stable, flying on telemetry is a breeze, sure you must check the terrain first and you have to have very well set autopilot. I flew it today in 3-8m/s wind, 300-400m over the terrain, checking the new baudrate for DL mavlink and it did 12 km against the wind on 11-13 amps all the time (usual cruise is 6A). Battery didn't sagged badly or was hot at landing, motor and esc were. Battery is Samsung R25 18650 x 8 in 4s2p config giving me solid 4750 mAh usable energy and up to 40A continuous draw (I Max at 24A).
I don't feel the need of extra punch with LiIon, even when cells are on 3.2v I still have enough trust to climb with around 5ms2, not stalling, on takeoff with fresh batteries It can go vertical.

LiIon in 3s is totally different and it makes spear definately underpowered. My initial setup was 3200 mAh 3s LiIon in the front and it's bad.

I've tried initially with FPV and it's bad, didn't liked it, quality is bad, range is sh on 1.3 or 5.8, its desorienting, then transmitters and power for them, additional weight, antennae management, temp management and ground station with tracker antenna, batteries, goggles... olalala. For nearly nothing...

The gold for me is Dragonlink v3 with Bluetooth connection to the PC sending mavlink telemetry to mission planner from pixhawk with arduplane.

Super simple and robust.
If you don't have DL, and use other LR radio, you can use 3dr radio for mavlink telemetry but your range is going to be 2km Max. Try to go beyond range for 5-6min and then rtl, feeling is fantastic when you hear it coming back.

Go ahead, it's satisfying to see how spear becomes from white foam to shiny piece of engineering.

Best,