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JimStanmore
06-18-2006, 10:26 PM
Hello All,
For my first post, I am asking for advice/suggestions/help. I am finally going to start on a Super Chipmunk after years of considering the project; of course, it will be electric. I know there are other kits available now, but there is this comittment thing involved... I used MotorCalc to run some numbers and they are a far cry from my little park flyer figures! I have chosen direct over geared because of preference and weight. The prop size does concern me because the "stock" prop is a 10 and MotorCalc is prefering 14. Weight is also supposed to be 6-8 lbs. MotorCalc seems to prefer the Neu 1912/1Y, although an Aveox 1817-4Y and a Model Motors AXI 5320-28 were mentioned.

What I would like to do is use the Chipmunk for aerobatics in RC Standoff Scale and Sportsman Class. With dynamic braking and one of the sound systems I've seen discussed on WattFlyer, I think this would be a good combination. BTW, I am also thinking in terms of demonstration flights with smoke, etc.

Has anyone done this conversion? My internet searches haven't turned up anything on this.

ADDED: What I've just been reading seems to say that I should pay more attention to 100W to 150W/lb than to MotoCalc. I've read about MotoCalc for years and this is the first time I have tried to use it.

Motor Calc:

14x7
MotOpinion - CG Super Chipmunk Aerobatic 9 Minute Duration
50ft above Sea Level, 29.92inHg, 59°F

Motor: Neu 1912/1Y; 810rpm/V; 1.6A no-load; 0.011 Ohms.
Battery: Kokam 3200SHD (20C); 5 series x 3 parallel cells; 3200mAh @ 3.7V; 0.008 Ohms/cell.
Speed Control: Generic Brushless ESC; 0.006 Ohms; High rate.
Drive System: Generic 14x7in Prop; 14x7 (Pconst=1.25; Tconst=0.956) direct drive.
Airframe: Goldberg Super Chipmunk; 688sq.in; 152oz RTF; 31.8oz/sq.ft; Cd=0.038; Cl=0.21; Clopt=0.45; Clmax=0.89.
Stats: 220 W/lb in; 187 W/lb out; 31mph stall; 43mph opt @ 65% (50:57, 73°F); 64mph level @ 95% (21:48, 82°F); 3316ft/min @ 60.6°; -461ft/min @ -7°.

Power System Notes:

The full-throttle motor current at the best lift-to-drag ratio airspeed (107.5A) falls approximately between the motor's maximum efficiency current (48.9A) and its current at theoretical maximum output (747.2A), thus making effective use of the motor.
The voltage (16V) exceeds 12V. Be sure the speed control is rated for at least the number of cells specified above.

Aerodynamic Notes:

The static pitch speed (74mph) is within the range of approximately 2.5 to 3 times the model's stall speed (31mph), which is considered ideal for good performance. With a wing loading of 31.8oz/sq.ft, a model of this size will have flying characteristics suited to an experienced pilot. The plane will fly fast, and be readily able to handle fairly strong winds.
The static thrust (233.9oz) to weight (152oz) ratio is 1.54:1, 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 (125.3oz) to weight (152oz) ratio is 0.82:1, 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.

12x7
MotOpinion - CG Super Chipmunk Aerobatic 9 Minute Duration
50ft above Sea Level, 29.92inHg, 59°F

Motor: Neu 1912/1Y; 810rpm/V; 1.6A no-load; 0.011 Ohms.
Battery: Kokam 3200SHD (20C); 6 series x 3 parallel cells; 3200mAh @ 3.7V; 0.008 Ohms/cell.
Speed Control: Generic Brushless ESC; 0.006 Ohms; High rate.
Drive System: Generic 12x7in Prop; 12x7 (Pconst=1.25; Tconst=0.956) direct drive.
Airframe: Goldberg Super Chipmunk; 688sq.in; 160.4oz RTF; 33.6oz/sq.ft; Cd=0.038; Cl=0.21; Clopt=0.45; Clmax=0.89.
Stats: 232 W/lb in; 207 W/lb out; 32mph stall; 44mph opt @ 53% (56:09, 73°F); 65mph level @ 76% (25:12, 82°F); 3784ft/min @ 75.5°; -473ft/min @ -7°.

Power System Notes:

The full-throttle motor current at the best lift-to-drag ratio airspeed (114A) falls approximately between the motor's maximum efficiency current (53.5A) and its current at theoretical maximum output (895.9A), thus making effective use of the motor.
The voltage (19.6V) exceeds 12V. Be sure the speed control is rated for at least the number of cells specified above.

Aerodynamic Notes:

The static pitch speed (95mph) is within the range of approximately 2.5 to 3 times the model's stall speed (32mph), which is considered ideal for good performance.
With a wing loading of 33.6oz/sq.ft, a model of this size will have flying characteristics suited to an experienced pilot. The plane will fly fast, and be readily able to handle fairly strong winds.
The static thrust (216oz) to weight (160.4oz) ratio is 1.35:1, 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 (145.1oz) to weight (160.4oz) ratio is 0.9:1, 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.

Thanks for reading!

spiders96
07-27-2006, 12:21 AM
Hi,

I've been considering this plane also. Have you started building it yet? Any updates?

-Joe

JimStanmore
09-03-2006, 08:07 PM
I received this info in an email from Justin Smith at Hobby-Lobby:

Hello,

Thank you for the opportunity to convert your Glow plane to Electric power. We at Hobby Lobby feel confident that anyone who pilots an airplane that has a well thought out, brushless setup such as this one will fall in love with electric power. Following many advances in recent years, it will truly out perform glow in many ways. You will notice that more and more professional pilots are using brushless electric for it's numerous performance advantages. Electric pilots say they have serious trouble going back to their glow... Just charge and fly, pack up and go home when done with no cleanup.

Here's everything you'll need to complete your Glow to Electric Conversion of the Super Chipmunk.

PM413016 AXI 4130/16 External Rotor Brushless Motor ..... $ 127.00

Radial Motor Mount:
PM41002 Radial Mount Set for AXI 41 Series Motors ..... $ 18.50

Brushless Controller:
JESAP77PW Jeti Advance PLUS 77 Amp Opto Brushless Controller with
Program Card ..... $ 157.90

BEC:
KFS003 Ultimate BEC with 6V Output ..... $ 43.90

Battery Pack:
Two -- TP420032 3S2P 4200 mAh 11.1V Lithium Polymer
Pack @ $ 159.90 ea., ..... $ 319.80

Series Module:
FMAC03S Series Module w/Deans Ultra Connectors ..... $ 15.90

Charger:
AST109 Astro Flight 109 Lithium Charger ..... $ 119.90

Charger Lead:
FMAC709 Charger Lead with Deans Ultra Connector ..... $ 4.90

Prop:
PE15010E 15x10 APC Electric Prop ..... $ 6.50

maddawg
04-03-2008, 08:06 PM
Hey I was wondering if you ever got this bird in the Air. I getting ready to finish mine.

Trent