Goldberg Super Chipmunk from Glow to Electric
 

I am building a Goldberg Super Chipmunk and have decided rather late in the project that I would like to try electric power. The problem is how do I make it easy to swap out the batteries ?
If I were starting fresh on building the fuselage then it would be very easy to build a removable hatch. The only way I can see to do it, without butchering the plane, is by removing the
wing each time.
Any suggestions?

thanks rv9-a

RE: Goldberg Super Chipmunk from Glow to Electric
 

rv9-a,
I am finishing construction of my Super Chipmunk and also did an electric conversion. I attempted to figure out a way to creat a hatch for simple battery removal but after looking closely at it and this being my first kit build I settled on the fact that I would just remove the wings. I didn't feel I yet had the building experience to make that large of a modification.

RE: Goldberg Super Chipmunk from Glow to Electric
 

Can you cut the hatch into the lower part of the cowl? If you have not painted it yet, it should not be to hard. You could have the battery holder in the area where the fuel tank used to be.

Buzz

RE: Goldberg Super Chipmunk from Glow to Electric
 

zflyz

I have attached a photo of what I think may work for a hatch. The red outlines the new part that would form the removable hatch. The green is the existing fuse parts. There is a new former located between "TA" and "TB" the yellow is fixed and the red removable. One drawback to this is that the canopy aft of former TC would not be attached to the aft turtle-deck. It should be ok in the installed position but would be rather fragile when it is removed for access to the batteries. A possible solution would be to add formers just aft of the canopy, as was done in the front , then everything should be a lot stronger. In any case these mods would need to be done during the original construction.

keep the ideas coming!

rv9-a

RE: Goldberg Super Chipmunk from Glow to Electric
 

I do like you idea. I would extend the "HATCH" to include the whole canopy. Make a new former about 1/2 inch behind the canopy. That way you would not have to worry about the canopy being fragile.

Sort of like the picture of this plane

http://www.nitroplanes.com/cmp-ep-pa28-kit.html

Buzz.

RE: Goldberg Super Chipmunk from Glow to Electric
 

I had thought of that also. It doesn't give you any more room to reach in but does give more strength for the canopy. The new formers in the rear should be slanted aft to make removal easier, a 1/4" dowel secures the front and magnets in the rear. The fuselage top should be opened up a little for more access but I would not go any further aft than the forward edge of the servos.

Now if I can force myself to build another Chipmunk

rv9-a

RE: Goldberg Super Chipmunk from Glow to Electric
 

I would say that is the way to go. One BIG canopy hatch.

I have a World Models Chipmunk. I was tempted to go E power on it but had a .91Fs sitting on the shelf. If I ever do another Chipmunk it will be electric.

Buzz.

RE: Goldberg Super Chipmunk from Glow to Electric
 

rv9-a,
Great idea on the plans, thanks for passing it along. I'll review and decided if I will attempt to modify.
I am just about ready to start covering. I want to get everything trial fitted and an approximate CG figured out This is my first time ever covering an aircarft, not sure wether to use Monocote or Ultracoat. Seems to be pretty much a 50/50 split on the forums regarding the subject.

RE: Goldberg Super Chipmunk from Glow to Electric
 

It is a Ford, Chevy, Dodge debate on the covering. I will add one thing to debate on covering. I used Balsarite for every covering job I could. That is until the state of Kalifornia said it had bad stuff in it and they said I could not use it any more. Some say it is not needed, other say it is a must. I have found it works better with this on plywood. Sticks like crazy with no bubbles under the covering.


http://www3.towerhobbies.com/cgi-bin...?&I=LXB356&P=7


Buzz.

RE: Goldberg Super Chipmunk from Glow to Electric
 

zflyz

Monokote/ultracote ? I don't think either one is as good as they used to be. One advantage to ultracote is it has a paper backing that is easier to remove than monokote.
I used 3 rolls monokote on this plane. The wings took one roll.

rv9-a

just about done

RE: Goldberg Super Chipmunk from Glow to Electric
 

Well the Electric Chipmunk is finished :D Since this was my first electric it was more costly than I expected not having the support equipment that electric requires.

The motor is a Tacon Big Foot 60, ESC is a Phoenix ICE 75, BEC is a CC BEC Pro. Battery is a 6s1p 3300 mah. The flying weight came in at just under 8 pounds. I am going to try an APC 13" x 6.5 prop as a starting point.


rv9-a

RE: Goldberg Super Chipmunk from Glow to Electric
 

So happy you are showing this.  I got a Bigfoot 60 for Xmas and will put it into a 46-60 size Stampe biplane.  The plane is almost framed up but still leaves me some wiggle room for kit mods.  I see you used standoffs for the motor mount rather than building a box.  Did you evaluate a box as to whether or not it would lessen any twisting caused by the electric motor torque?  What size standoffs did you use (length, width and thread)?  And did you provide offset thrust?   I also saw you did not provide any cooling holes through the firewall for the motor.  Do you think you will have enough airflow without them?  And why did you choose a 13x6.5 prop?  I have seen some people say they use up to a 16x8 on this motor.

Sorry for all the questions - I'm behind you in my build so I am eager to lear from your mistakes, er successes :D

Thanks,
Bob

RE: Goldberg Super Chipmunk from Glow to Electric
 

rv9, I do not think that prop is going to work. I just ran the numbers on the calc program and it said it would make about 83 ounces of thrust. That is only just over 5 pounds. On my Monster power 60 I run a 18X6 APC prop.

I use the 13x6.5 on my Monster Power 46 with a 5s 5000 pack.

Do you have a watt meter? If not this one works pretty well

http://www.hobbypartz.com/aeo-p0-watt-meter.html

Buzz.

RE: Goldberg Super Chipmunk from Glow to Electric
 

Bob
The standoffs are a Hanger Nine product. The number is HAN 4773 and they are almost two inches long and are 1/2 " across the flats. They are clearance drilled for an 8-32 machine screw and come with 4, 8-32 x 2 1/2 in. Phillips head machine screws. The screws were too short and I don't care for phillips so I ordered some 8-32 x 3" Allen head cap screws from Fastenal (part number 23126). I was not worried about twist as these mounts are used in a couple of Hanger 9 electric powered planes. I used two #8 flat washers for a little right thrust.

I didn't put any cooling holes in the firewall because I didn't have any exit holes in the fuselage so there is no where for the air to go. Something to think about while framing up the Fuse. I have made holes in the bottom of the cowl and may need to make more.

Buzz and Bob
The 13"prop was a suggestion I got from a hobby shop and it appears to be a wrong choice ! I have since learned that I will need a 15 to 16 inch prop. I do have a watt meter coming and will do some prop testing when I get it. Buzz can you tell me what the numbers look like with a 16/8 thin APC ?


rv9-a

RE: Goldberg Super Chipmunk from Glow to Electric
 

Even a 16X8 might be to small.

Program says it will pull 44.6 amps and give 154 ounces, 9.6 pounds of thrust with about 12 minutes of flight time.

upping the prop to a 16x10 brings the amps up to 51 amps, thrust up to 180 ounces, 11.25 pounds of thrust 10 minutes of flight time.


Buzz.

RE: Goldberg Super Chipmunk from Glow to Electric
 

Buzz,

What program are you using? Will it work on a Mac?

rv9-a

RE: Goldberg Super Chipmunk from Glow to Electric
 

Great information so far.  I also would like to know the program, but for Windows XP.

rv9-a, can you post a vidoe when you get flying.  I will start back on mine today and try to get some pictures.  I think I should start a new thread, though, so I don't hijack yours.

RE: Goldberg Super Chipmunk from Glow to Electric
 

rv9-a did you add any right thrust in the engine mount/standoffs? If so, how did you accomplish this? I am doing a full mock-up before I start covering. Don't want any last minute suprises.

RE: Goldberg Super Chipmunk from Glow to Electric
 

zflyz

I used two #8 washers between the left standoffs and the fire wall to give a little right thrust. rgburrill mentioned twist using the standoffs, I think I am going to get 4 #8 fender washers and add them between each the standoffs and the firewall. This should prevent any twist by allowing even tightening of the bolts without crushing the plywood mount. The smaller #8 washers would still be used to give the right thrust.

rv9-a

RE: Goldberg Super Chipmunk from Glow to Electric
 

Rv9 thank you for the information. I was planning on using washers also, I just wasn't sure about size.

RE: Goldberg Super Chipmunk from Glow to Electric
 

I found a cool on-line thrust calculator at http://personal.osi.hu/fuzesisz/strc_eng/index.htm.  Be very careful if you do a search - I found one that led to a known bad web site.  But the link above was determined to be OK by Norton and it did give me some decent results including thrust and power.

RE: Goldberg Super Chipmunk from Glow to Electric
 

Here is the online motor calc program.

http://www.s4a.ch/eflight/motorcalc_e.htm

The Eflite motor is the one I picked.


Buzz.

RE: Goldberg Super Chipmunk from Glow to Electric
 

Thanks for the links......got them bookmarked.

rv9-a

RE: Goldberg Super Chipmunk from Glow to Electric
 

Buzz

Which particular e-flight motor did you use, or did you use custom and plug in your own numbers? When I try to plug in what numbers I have from Tacon the box light up red and says my figures are unrealistic.....go figure eh!!

rv9-a

Anybody,
Would the Rimfire 1.20 be comparable to the Tacon Bigfoot 60. The weight, physical size and Kv are just about the same?
The input wattage is off 1800 watts verses 1200 for the Tacon

RE: Goldberg Super Chipmunk from Glow to Electric
 

Well the Tacon sort of replaced the Monster Power series and the MP motors were a direct copy of the Eflite, so I just the Eflite 60 motor.

The Tacoon has a tad bit more power. I have the Monster Power 60, brother has the Tacon 60. Same batteries, same ESC and his has just a touch more power. I would say about 2 or 3%, not much, but in the vertical climb you can see it ever so slightly.

From what I have had with the RImfires and read about them, they are over estimated on watts and power. I could be wrong.


Buzz.