Flying time for Pattern competition
11-04-2010 | 12:29 PM
#26
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From: Fenton,
MI
RE: Flying time for Pattern competition
You can run the Hacker A50-16L on 10S as long as you don't over prop it. I run mine on 8S with an APC 18x12. You might get it to work with 10S and a 17x10 or 17x8. You have to give it a try.
11-04-2010 | 07:32 PM
#27
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From: Fenton,
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RE: Flying time for Pattern competition
OK Tim,
I plugged you numbers into Motocalc. I tweeked on the prop P constant and the battery voltage under load to get approximately the same RPM at the prop and same current draw as you stated above. The wattage is down around 1600 however which is more in line with what I would have expected. I wonder if you have bum watt meter?
I plugged you numbers into Motocalc. I tweeked on the prop P constant and the battery voltage under load to get approximately the same RPM at the prop and same current draw as you stated above. The wattage is down around 1600 however which is more in line with what I would have expected. I wonder if you have bum watt meter?
MotOpinion - Venus II
850ft above Sea Level, 29.92inHg, 56°F
Motor: Great Planes Rimfire 50-65-450 (#4770); 450rpm/V; 2.2A no-load; 0.024 Ohms.
Battery: Thunder Power TP3850 (G4 ProPower 30C) (30C); 6 cells; 3850mAh @ 3.7V; 0.0056 Ohms/cell.
Speed Control: Castle Creations Phoenix 80; 0.001 Ohms; High rate.
Drive System: APC 17x8 Electric; 17x8 (Pconst=1.21; Tconst=1) direct drive.
Airframe: Venus II; 866sq.in; 139.1oz RTF; 23.1oz/sq.ft; Cd=0.043; Cl=0.07; Clopt=0.46; Clmax=0.81.
Stats: 188 W/lb in; 164 W/lb out; 28mph stall; 37mph opt @ 76% (24:11); 98mph level; 2376ft/min @ 47.1°; -474ft/min @ -8.4°.
Warning:
MotoCalc was unable to determine a throttle setting for hands-off cruise airspeed, so the best lift-to-drag ratio airspeed and throttle setting will be used instead.
Inability to determine a throttle setting for an airspeed usually means the model is not capable of reaching the required speed with the given power system, or the airfoil information has not been specified correctly.
Power System Notes:
The full-throttle motor current at the best lift-to-drag ratio airspeed (55.7A) falls approximately between the motor's maximum efficiency current (43.1A) and its current at theoretical maximum output (423.5A), thus making effective use of the motor.
The voltage (19.3V) exceeds 12V. Be sure the speed control is rated for at least the number of cells specified above.
Possible Aerodynamic Problems:
The static pitch speed (58.7mph) is less than 2.5 times the stall speed (27.7mph), which may result in reduced performance at typical flying speeds and a low maximum speed. This situation is usually acceptable for an electric sailplane or other slow-flying model.
Pitch speed can be increased by using a higher pitched and/or smaller diameter propeller, a higher cell count, or some combination of these methods.
The diameter (17.0in) to pitch (8.00in) ratio is greater than 2:1, which will result in reduced propeller efficiency at flying speeds. An appropriate smaller diameter, higher pitched propeller would improve this.
Aerodynamic Notes:
With a wing loading of 23.1oz/sq.ft, a model of this size will have trainer-like flying characteristics. It would make an ideal trainer, for use in calm to light wind conditions.
The static thrust (249.2oz) to weight (139.1oz) ratio is 1.79:1, which will result in extremely short take-off runs, no difficulty taking off from grass surfaces (assuming sufficiently large wheels), and vertical climb-outs. This model will probably be able to perform a hover or torque roll.
At the best lift-to-drag ratio airspeed, the excess-thrust (101.6oz) to weight (139.1oz) ratio is 0.731:1, which will give very steep climbs and incredible acceleration. This model can easily do consecutive loops, and has sufficient in-flight thrust for any aerobatic maneuver.
General Notes:
This analysis is based on calculations that do NOT take motor heating effects into account. This also means that no calculations were done to determine if the motor might overheat.
These calculations are based on mathematical models that may not account for all limitations of the components used. Always consult the power system component manufacturers to ensure that no limits (current, rpm, etc.) are being exceeded.
850ft above Sea Level, 29.92inHg, 56°F
Motor: Great Planes Rimfire 50-65-450 (#4770); 450rpm/V; 2.2A no-load; 0.024 Ohms.
Battery: Thunder Power TP3850 (G4 ProPower 30C) (30C); 6 cells; 3850mAh @ 3.7V; 0.0056 Ohms/cell.
Speed Control: Castle Creations Phoenix 80; 0.001 Ohms; High rate.
Drive System: APC 17x8 Electric; 17x8 (Pconst=1.21; Tconst=1) direct drive.
Airframe: Venus II; 866sq.in; 139.1oz RTF; 23.1oz/sq.ft; Cd=0.043; Cl=0.07; Clopt=0.46; Clmax=0.81.
Stats: 188 W/lb in; 164 W/lb out; 28mph stall; 37mph opt @ 76% (24:11); 98mph level; 2376ft/min @ 47.1°; -474ft/min @ -8.4°.
Warning:
MotoCalc was unable to determine a throttle setting for hands-off cruise airspeed, so the best lift-to-drag ratio airspeed and throttle setting will be used instead.
Inability to determine a throttle setting for an airspeed usually means the model is not capable of reaching the required speed with the given power system, or the airfoil information has not been specified correctly.
Power System Notes:
The full-throttle motor current at the best lift-to-drag ratio airspeed (55.7A) falls approximately between the motor's maximum efficiency current (43.1A) and its current at theoretical maximum output (423.5A), thus making effective use of the motor.
The voltage (19.3V) exceeds 12V. Be sure the speed control is rated for at least the number of cells specified above.
Possible Aerodynamic Problems:
The static pitch speed (58.7mph) is less than 2.5 times the stall speed (27.7mph), which may result in reduced performance at typical flying speeds and a low maximum speed. This situation is usually acceptable for an electric sailplane or other slow-flying model.
Pitch speed can be increased by using a higher pitched and/or smaller diameter propeller, a higher cell count, or some combination of these methods.
The diameter (17.0in) to pitch (8.00in) ratio is greater than 2:1, which will result in reduced propeller efficiency at flying speeds. An appropriate smaller diameter, higher pitched propeller would improve this.
Aerodynamic Notes:
With a wing loading of 23.1oz/sq.ft, a model of this size will have trainer-like flying characteristics. It would make an ideal trainer, for use in calm to light wind conditions.
The static thrust (249.2oz) to weight (139.1oz) ratio is 1.79:1, which will result in extremely short take-off runs, no difficulty taking off from grass surfaces (assuming sufficiently large wheels), and vertical climb-outs. This model will probably be able to perform a hover or torque roll.
At the best lift-to-drag ratio airspeed, the excess-thrust (101.6oz) to weight (139.1oz) ratio is 0.731:1, which will give very steep climbs and incredible acceleration. This model can easily do consecutive loops, and has sufficient in-flight thrust for any aerobatic maneuver.
General Notes:
This analysis is based on calculations that do NOT take motor heating effects into account. This also means that no calculations were done to determine if the motor might overheat.
These calculations are based on mathematical models that may not account for all limitations of the components used. Always consult the power system component manufacturers to ensure that no limits (current, rpm, etc.) are being exceeded.
11-04-2010 | 07:55 PM
#28
My Feedback: (8)
RE: Flying time for Pattern competition
ORIGINAL: greg_m
Hi Guys - motor manufacturers!
For years we flew pattern with an OS 140. Now the motor manufacturers come up with equivalent outrunners motors of size 120 or 160 = refer to post #7 above. WHY WHY WHY?
I recently converted to the dark side - Otop. The 160 outrunner is to big, too powerfull and way to heavy . The 120 outrunner is not powerfull enough although size and weight are good. Most guys here in SA using the power160 outrunner love it but say they only using half throttle most of the time.
Why is there no 250kV 140 equivalent size outrunner out there that can take a 10S battery setup?????????????
I am current weighing in at 5.2kg in my Otop with a 120 size equivalent motor (63x56 can), 10S 4400 15C lipos and 100A HV speed controller all from a cheap source because it was purely experimental for me. Averaging about 2800 mAh per intermediate flight ... max amps of about 60A and average around 35 - 45 Amps for the flight. running a 17x10 APC-E prop.
the cheap motor is heavy - if there was an equivalent 140 size outrunner from a reputable manufacturer that weighed the same or less I would go for it like a shot...
Hi Guys - motor manufacturers!
For years we flew pattern with an OS 140. Now the motor manufacturers come up with equivalent outrunners motors of size 120 or 160 = refer to post #7 above. WHY WHY WHY?
I recently converted to the dark side - Otop. The 160 outrunner is to big, too powerfull and way to heavy . The 120 outrunner is not powerfull enough although size and weight are good. Most guys here in SA using the power160 outrunner love it but say they only using half throttle most of the time.
Why is there no 250kV 140 equivalent size outrunner out there that can take a 10S battery setup?????????????
I am current weighing in at 5.2kg in my Otop with a 120 size equivalent motor (63x56 can), 10S 4400 15C lipos and 100A HV speed controller all from a cheap source because it was purely experimental for me. Averaging about 2800 mAh per intermediate flight ... max amps of about 60A and average around 35 - 45 Amps for the flight. running a 17x10 APC-E prop.
the cheap motor is heavy - if there was an equivalent 140 size outrunner from a reputable manufacturer that weighed the same or less I would go for it like a shot...
They are the 1900 series motors, 1917 and 1920 I think.
I'm running a Scorpion 210kV on 10S and really liking it. Max current is low though. 19x12 would be the most it could handle. 18x12 is pretty easy for it. They make a 250kV motor too, but over rated. 17x12 was OK, 17x10 is probably better.
11-04-2010 | 07:55 PM
#29
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From: Fenton,
MI
RE: Flying time for Pattern competition
Tim,
After fiddling with the setup awhile it seems difficult to do much better (with the power system) than you have. The Venus II is a bit of an odd duck. It seems to be between a .60 size plane and a .90 size plane. For that reason, I keep ending up with a 7S power system. That's not ideal, IMHO. I suppose it would be OK if you had smaller planes that could fly on 3S and other ones on 4S packs but usually 3S planes wouldn't be using 4000 mAh or higher packs.
If you are ever asked your opinion at work about the development of a new pattern plane of similar size. Get them to design it around an 8S power system and get them to make a Rimfire 140 that has a KV around 250-270. Then get some of your high profile pilots to show up at some local contests with it. I think there is a market for a good quality pattern setup that is less expensive than today's 2m planes. Especially in light of the economy.
After fiddling with the setup awhile it seems difficult to do much better (with the power system) than you have. The Venus II is a bit of an odd duck. It seems to be between a .60 size plane and a .90 size plane. For that reason, I keep ending up with a 7S power system. That's not ideal, IMHO. I suppose it would be OK if you had smaller planes that could fly on 3S and other ones on 4S packs but usually 3S planes wouldn't be using 4000 mAh or higher packs.
If you are ever asked your opinion at work about the development of a new pattern plane of similar size. Get them to design it around an 8S power system and get them to make a Rimfire 140 that has a KV around 250-270. Then get some of your high profile pilots to show up at some local contests with it. I think there is a market for a good quality pattern setup that is less expensive than today's 2m planes. Especially in light of the economy.
