Electrifying a great planes extra300 .46 size
 

Hi,

I have an extra 300 that I had powered before with a thrunder tiger .46. It was fine, but I wanted more power. it was a kit and it has not flown in 12 years but everything looks fine.
It has a 58 inch wingspan.

I started electrics with an apprentice this spring and so far love it. I have a good charger.

If I want to electrify it, I found that an Eflite 46BL would do the trick with a 5s pack (or maybe a slighly more powerful motor). The Plane weighed about 6 lb with the glow engine, and would be about the same or slightly heavier with electrics.
The battery would likely be a 5s 4000 or 5000 mah pack.

What motor / power pack would you suggest?

DO you suggest I buy an ARF or another Kit instead? If so for what reason?

I want to try an aerobatic electric plane but will only electrify the extra300 if it is appropriate.

Thanks!

RE: Electrifying a great planes extra300 .46 size
 

You're going to want at least 125 watts/lb for an Extra. So you need a motor/esc/batt combo that puts out 750 watts. Next, I'm assuming you want power not speed for this type of bird, so you want a lower Kv motor that will give good vertical performance. Download DriveCalc (freeware) and have fun playing with the numbers. With EP there's always more than one way to achieve a desired end.
Walt

RE: Electrifying a great planes extra300 .46 size
 

Thanks.

Basically I was wondering if the bird was a bit too heavy? Its an extra 300 kit from great planes .46 sized, built about 12 years ago. Discontinued now.

I will check out DriveCalc and see.

I also read the electric forum threads a while back and they have recommendations for different types of aircraft and the power needed. I will try for more than 125 w/ lb.

Focus is on power in this case indeed. I guess I have some learning to do to get the right motor / prop combo. I assume here a bigger prop with a lower pitch is desirable. I am not an expert at sizing props :) Any suggestions on how to approach this?

RE: Electrifying a great planes extra300 .46 size
 

DriveCalc is a great tool for seeing what happens when you change one parameter, like pitch. since you are new to EP learning how to use it will be a great help.

I'm not sure why you think a 6lb airplane is too heavy for EP, unless the wing loading is very high. Even so, if it can be flown IC it can be flown EP. I have been flying electric exclusively since '92 and have never let the intended power source stop me from flying a plane with EP. Ex: top flight P-47, Nosen 1/4 scale Citabria, Platt Waco, Sig Astro Hog, GP Kaos 40.

As for props, the VERY rough rule of thumb is "inch for inch." Increase the dia. 1", decrease the pitch 1".

Hope this helps. Keep asking questions. The only dumb one is the one you don't ask.
Walt

RE: Electrifying a great planes extra300 .46 size
 

PS 125 watts per pound is more than enough for sport flying. Another rule of thumb: 65 watts per pound for hand launch; 75 for ROG and training; 85 - 100 general sport flying; 100 plus for aerobatics; 125 plus for 3D.
WT

RE: Electrifying a great planes extra300 .46 size
 

What do people do to adapt the motor when doing a conversion? Build their own mount? Buy one?

RE: Electrifying a great planes extra300 .46 size
 

I did an elecric conversion on a World Models Rambler 45 a few years ago and used the E-flight Power 46, 5S 3700 battery and APC 13 x 8 E prop.  It pulled around 1300 watts and gave great performance.

As far as notor mounts go, you can buy a commercial mount or mount the X-mount to the fiewall using  long bolts passing through nylon stand-offs (from Ace Hardware).  Tower sells aluminum mounts if you prefer that route.


Rob

RE: Electrifying a great planes extra300 .46 size
 

I converted my old kit built GP Extra last year. I used a Hacker A40, Hacker 70amp esc, Hacker motor mount mounted right to the firewall, Apc 14-10 prop, 4000mah 5cell lipo. Fly's better than ever. To get the CG right had to cut the bottom of the firewall out to slide the battery up under the motor.

RE: Electrifying a great planes extra300 .46 size
 

Is it the same as mine?

Can you send pics so I can see your setup?

RE: Electrifying a great planes extra300 .46 size
 

I usually build a plywood box to extend the firewall and mount the motor to that.

RE: Electrifying a great planes extra300 .46 size
 

Here are a couple pictures

RE: Electrifying a great planes extra300 .46 size
 

Nice setup, thanks!

How long does it last on that battery on an average flight?

RE: Electrifying a great planes extra300 .46 size
 

12 to 15 minutes

RE: Electrifying a great planes extra300 .46 size
 

Wow that sounds very good!

I guess I will do some reading and try a setup soon!