rhodenga500 Show full post »
solentlife
The comment about larger motors and lower kv as models get bigger - is due to various factors ... a) can accommodate larger prop, b) larger battery / more cells, c) greater wing area .. 

The 1300kv motors - I was surprised you spent money on them, its generally the case with 5" ... 6" props you need more than 2000kv unless you can hit with a high cell count battery to compensate. Small props as those rely on RPM unlike larger props.

Comparing scratchbuild to store bought often leads to heartbreak I'm afraid. There are various factors in play ... aerofoil section, distribution of construction materials in the build, placement of gear etc.  

The biggest factor that is causing limitations here - is the requirement for grass take-off. I have many well powered models in similar size that would struggle to lift off grass runway. 
I'll fly anything if I can launch it ! Youtube : solentlifeuk
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rhodenga500
Test Flight with the Brotherhobby 2806.5_1300 KV Motors

Solentlife,
I ordered the 1300KV because the 1700KV was not in stock at http://www.getfpv.com. 

Flight test (Using 6S-3000_30C Battery with 6X4X3 dual props):
Got everything ready on the ground for take-off (grass runway), noticed that the F-15 began taxing with very little throttle. The jet was able to take-off without flaps and using half throttle. The jet kept pitching upward (I think due to the 6S 3000 battery being 4 ounces lighter than the 4S 5000), I quickly look down at transmitter and trim down elevator, 2-3 clicks), looked up and noticed that the jet was very high and was moving fast, and was getting too far away from sight, so I made a hard left turn and heard something hit the prop. I noticed something came loose and was flying in the air. I thought it was only the battery door cover, so I decreased the throttle (little below half way), leveled the jet and circled the air field at a high altitude. Everything looked good, the jet was very stable and I decided to drop landing gear, flaps and land the aircraft. 
 
I reduced the speed, noticed that something is wrong and the jet became very unstable. Managed to land a distance away and stopping with the aircraft tilting on the left wing. Noticed that the rear right vertical stabilizer/rudder was missing with a piece of the rudder and control horn still attached to the control rod. No major damage to the aircraft. Hand touch the motors and they were slightly warm.

The Brotherhobby 2806.5_1300 KV flew the F-15_38"WS with very little effort with 6X4X3 props. I estimate about 65-70 ounces of thrust per motor. This is a good motor for this size scratch built jet. I believe that the 1700KV with 6X4X3 prop will give me at-least 75-80 ounces of thrust per motor.
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solentlife
Your 'success' was based on what we had advised earlier ... more powerful battery.

Have you ever considered using a calculator such as eCalc ?? saves a lot of heartache .... and of course the best tool of all is the WATTMETER ... 

A wattmeter would most likely have saved you burning out the first motors.
I'll fly anything if I can launch it ! Youtube : solentlifeuk
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rhodenga500
solentlife wrote:
   Your 'success' was based on what we had advised earlier ... more powerful battery.

Have you ever considered using a calculator such as eCalc ?? saves a lot of heartache .... and of course the best tool of all is the WATTMETER ... 

A wattmeter would most likely have saved you burning out the first motors.


Thanks Solentlife,
 
I will also build me a test stand and test my prop motors and EDF's with the wattmeter. 
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Wildthing
rhodenga500 wrote:
Test Flight with the Brotherhobby 2806.5_1300 KV Motors

Solentlife,
I ordered the 1300KV because the 1700KV was not in stock at http://www.getfpv.com. 

Flight test (Using 6S-3000_30C Battery with 6X4X3 dual props):
Got everything ready on the ground for take-off (grass runway), noticed that the F-15 began taxing with very little throttle. The jet was able to take-off without flaps and using half throttle. The jet kept pitching upward (I think due to the 6S 3000 battery being 4 ounces lighter than the 4S 5000), I quickly look down at transmitter and trim down elevator, 2-3 clicks), looked up and noticed that the jet was very high and was moving fast, and was getting too far away from sight, so I made a hard left turn and heard something hit the prop. I noticed something came loose and was flying in the air. I thought it was only the battery door cover, so I decreased the throttle (little below half way), leveled the jet and circled the air field at a high altitude. Everything looked good, the jet was very stable and I decided to drop landing gear, flaps and land the aircraft. 
 
I reduced the speed, noticed that something is wrong and the jet became very unstable. Managed to land a distance away and stopping with the aircraft tilting on the left wing. Noticed that the rear right vertical stabilizer/rudder was missing with a piece of the rudder and control horn still attached to the control rod. No major damage to the aircraft. Hand touch the motors and they were slightly warm.

The Brotherhobby 2806.5_1300 KV flew the F-15_38"WS with very little effort with 6X4X3 props. I estimate about 65-70 ounces of thrust per motor. This is a good motor for this size scratch built jet. I believe that the 1700KV with 6X4X3 prop will give me at-least 75-80 ounces of thrust per motor.


WHOOPS ðŸ™†ðŸ™†ðŸ™†ðŸ™†ðŸ™†ðŸ™†ðŸ™†
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