Al's 125% PunkinII

June 13, 2001

Took 'the brick' out of the PunkinII and trashed it. I need to compress my planes for moving. This one had to go. Once I set up my new shop I'll put the brick into something new, possibly a lighter PunkinII built with contest balsa.

Update June 8, 2002

Flying indoors a little tail hevy, I bounced the PunkinII into a wall and destroyed the motor, ruining the bearings. I also smashed in the noseblock a little. This poor plane has seen some wear and tear. I'm not sure if another repair is in order, or if I should retire it.

Update Feb 25, 2002

Flew the PunkinII at the CRRC indoor fly at Sudbury High School last Friday night. It performed great. Here are some AVI movies:

Update Jan 22, 2002

Flew at lunch and my friend Robert took some movies with my digital camera. These actually make the plane look much faster than it is since we were outside and the camera is zoomed in on the plane. All movies are in quicktime format.

Update Jan 21, 2002

OK, I ditched the damaged DJ aerotech gear drive and dropped in a GWS IPS direct drive. The plane flys great! I'm now sure that a properly functioning DJ Aero drive system would have been plenty of power, the GWS IPS flys the 125% PunkinII at indoor speeds on 1/3 throttle. At full throttle it's quite quick and will loop fine.

Trimmed it out after dark at the local school under the streetlights in the parking lot. I'm glad I did. Trimming it out inside would have been very difficult.

When the plane is a little tail heavy I had some nasty tip stalls, but once the CG was put more forward this was mostly eliminated. I twisted a little washout in the upper wingtips to help more.

Update Jan 18, 2002

Tried maiden flights today indoors. My DJ Aerotec motor/gearbox wasn't getting good gear mesh and wouldn't provide enough power. I may have to give up with geared and go with direct drive IPS and 3"x2" prop and just admit that this needs to fly outdoors.

Update Jan 15, 2002 - 125% PunkinII ready for maiden flight

Somehow while testing the dual KP-00 motor the gearbox got out of mesh and started running rough. I toasted both motors before I figured out what was wrong - DOH! The only other acceptable motor I had on hand was the DJ Aerotech 'Roadkill' motor. This will force me to use my 9-volt rayovac batteries and pushes the total AUW to 109 grams or 3.7 oz. and pushes the wing loading just over 4 ounces/ft2

Update Jan 11, 2002 - The Motor, Gearbox and Battery

I printed out plans for the PunkinII in two variations, 112.5% and 125%. I need more wing area to carry my heaver RC gear. The DJ aerotech motor I have works great on 6 or 7 cells, but that's a lot of weight - too much I thought. The lightest packs I had were Rayovac 9-volt NiMh which weighed in at 39g. They work good on the DJ powerplant but I didn't want that much weight.

I had an idea to split one of my Qualacom LiOn 2-cell packs in half. Each cell is 4.2v, or a little less than 4 cells. The packs have a small PC board on them to balance the cells voltage during charge, and the charger can only charge the cells in pairs, so I made up a wiring harness to attach the two single cells to the board while charging. Cells charge and work well now. Weight of one cell is 28g, and they're 830 mAh!

With only 3.5-4.2 volts to work with the D.J. Aerotech powerplant is out. It's a high-voltage motor, no good at 4 volts. I had an E-chargers motor and gearbox but the gear ratio on them is too low for the thrust I needed so I busted the gearbox apart and extracted the motor (which I think is a KP-00?) Low and behold the pinion on it matches up to the main gear on a GWS-A gearbox and I happened to have plenty extras on hand. I also used the bearings from the GWS-A, but substituted a CF rod for the steel shaft. The bearings rest inside a small piece of a CF arrowshaft, and a second piece glued to the first supports the motor. Bingo, instant 6.75:1 gearbox. Weight with motor: 6.5g and with GWS 5.5"x4" prop is 8g.

The last step will be disabling the low voltage cutoff on the GWS ESC.

Update Jan 9, 2002 - The Brick

After some encouragement from Gordon Johnson on the RC Microflight discussion boards, I went ahead and made a brick from a GWS R-4P, ICS50, 2xPico servos and an Azarr antenna. I'll have to build something to put this into for the indoor fly next week..... Well maybe by the one in February.

Total weight as shown with 8" of wire to go to the motor is 20 grams. With DJ aerotech Roadkill motor (geared N-20) 28 grams. I plan to use 4x280 mAh NiMh pack or Rayovac 9-Volt 150 mAh NiMh with this.

The first picture is the final version, I mounted the ESC on top of the servos because I was afraid with it mounted under the receiver as in the second photo I'd get too much glitching.

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