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Dec 04, 2008, 10:14 PM
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Great Planes 60 size Extra 300s Conversion


Hi all,

Iím going to convert my Great Planes 60 size Extra 300s from an OS .91 4-stroke to electric. I have on hand a Suppo 4130 510 KV motor, 60 amp esc, bec, props, and 6 cell lipo 4600 mAh batteries ready for this airplane. The motor turns an APC 14x10 at about 9,000 rpms, pulling 50 amps and producing somewhere in the area of 1160 watts. This setup should be plenty for the airframe.

Attached are a few pictures of the airplane with the OS attached and then pulled off. My main concerns are how to get the backplate out 6 ľ inches from the firewall and how to cut the hatch in the top of the fuse in order to access the batteries.

Looking for any ideas and help along the way.

I work kind of slow so it may be a long time between posts.

Scott.
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Dec 05, 2008, 10:47 PM
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I kept the plans for the airplane and was able to draw up a former that will be used as one of the ends of the hatch Iím going to cut out. I traced the drawn former onto 5/32nds inch lite ply. It should be strong and light enough to act as an additional former. Glued in place with epoxy it is meant to keep the ridgedness (is that a word?) in the top turtle deck when I cut into the turtle deck for the battery hatch.

Scott.
Dec 06, 2008, 11:09 AM
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I went ahead and cut the battery hatch opening. I should have plenty of room to get my hand in there to access the battery!

Now I need to figure out how to beef up the hatch top and a way to attach it. I donít think I want to go with magnets because of the chance of it flying off while in the air. Iíll probably go with screws somehow. Iíll post more pictures as I get that far.

Scott.
Dec 06, 2008, 03:18 PM
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Great conversion. Good luck.

Joe
Dec 06, 2008, 05:01 PM
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Thanks for the encouragement Joe,

The airplane flew great with the IC engine but I got really mad when it deadsticked on me and I tore out the landing gear (in which the wheel pants busted up the underside of the wing) as I tried to land short of the field I fly at.

My hope is that deadsticks are a thing of the past with the new electric power system I'm going to convert to.

I'll keep posting pictures and asking questions as I move along.

Scott.
Dec 14, 2008, 04:34 PM
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Iíve finally finished the hatch. I made formers for both the front and back to keep the shape the same as the deck. It will be attached with a couple of screws. On the inside of the fuse I created a couple simple attachment points with light ply which allow the screws to bite into. I then reinforced the underside of the hatch with hardwood and applied CA to the area around the screw holes to make the balsa much harder. Then I recovered the hatch with matching Monokote.

Iíve also included a picture of all the Ďstuffí needed to convert this airplane.

Iíll post more pictures as I figure out how to install the motor.

Scott.
Dec 14, 2008, 11:08 PM
ab amicis auxilio parvulo
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Scott,

I was going to mention at the WFRC meeting when you said you were using screws to hold down the hatch what I've used on some of my hatches. Maybe you have seen mine or you just had the same good idea of using the hex socket-head screws (from Dubro I believe). That way you don't chance slipping off them and gouging the hatch as with a typical screwdriver.
Dec 15, 2008, 08:03 PM
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Aerospacer,

You can kind of see in the first picture (I know it's somewhat blurry) in the above post that I am using socket head screws on the hatch. I originally used philips head screws but was worried about the screwdriver slipping (just like you state in your post) so I changed them out. They are actually servo mounting screws I purchased from Bad Brad Graphics. I need to change the hatch screws in my Hog Bipe for the same reason.

I think I've figured out how to mount the motor to the box firewall. Instead of building out the box further, I'm going to use a couple of layers of lite ply as a spacer combined with stand offs.

I'll post pictures as it is easier to see than explain.

Scott.
Dec 15, 2008, 09:35 PM
ab amicis auxilio parvulo
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Scott,

I thought those socket head screws looked like the servo screws that are commonly available. I have also gone to button head socket screws that don't stick up nearly as much as those servo mounting screws. Great Planes has them in #2, 4 & 6 sizes. I like them especially for attaching cowlings.
Dec 19, 2008, 11:04 PM
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I figured out how Iím going to mount the motor Ė Iím going with the simple method.

I started by measuring out how far the thrust washer needs to be from the firewall (to clear the cowl), then simply measured the stand offís I had on hand, and came up with how thick a spacer was needed. The spacer is made up of a few layers of light ply glued together with 5 minute epoxy. I will mount this contraption to the existing firewall with bolts and blind nuts and hope it works out.

Here are a couple of pictures of the motor mount.

Scott.
Jan 01, 2009, 10:08 AM
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I've got the cooling holes drilled in the motor mount and everything is mounted to the firewall.

Attached are a couple of pictures of the motor mount.

Scott.
Jan 01, 2009, 01:03 PM
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I made a outlet in the bottom of the fuse in order to allow the cooling airflow to exit. I built up the area around the exit to give the Monokote a structure to adhere to.

Scott.
Jan 01, 2009, 10:29 PM
ab amicis auxilio parvulo
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Scott,

Looks good! Hope we might see this at the meeting on the 12th? If you get it hooked up, maybe you can even demo it by blowing over some chairs with the prop wash.
Jan 02, 2009, 03:14 PM
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This is a nice conversion....

I was browsing for yet another kit to build, and saw this plane. And even luckier to see this thread.

I wish I had seen it earlier.

For the hatch, a thought I've been meaning to try is a rubber band hook, setup. A rubber band is in the fuselage, and a hook extends from the bottom of the hatch. When putting the hatch on, simply reach in with a finger, pull the rubber band out and put it on the hook. Viola! the hatch is held on, and won't come off.

For the motor mount.. I've been using a two-step motor mount system. A single piece of ply is half way between the motor and the firewall. Two sets of stand-offs are used. The intermediate firewall can then be swapped out, if you have to change motors. (See my Ultra Sport 60, conversion). If space allows, one could use the intermediate mount as a place for the ESC.

Of course, all of this is easier to build into a plane, then retro into already built IC powered bird.

Good luck...
Jan 02, 2009, 04:10 PM
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Before/after weight???


Oh.. A quick question...

Did you by chance get an all-up-weight before you started the conversion?

Could you weigh it after the conversion is complete???

Thanks....


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