About four months ago I started selling off all my glow power systems and switched over to exclusive electric flying. About three months back I said I wouldn't convert one of my 40% planes to electric until I could use two or less batteries. A month later I decided, the hell with it, I would do it anyway.

Originally my plan was to do things gradually. Choose a motor and start putting together a power system funded by selling off my DA150's. In the mean time I would finish the re-cover job on my 120" sukhoi and set it up for electric power at the same time. As is pretty much standard for me in such undertakings, things got out of hand quickly. First of all I tracked down a hacker A150-8 with a spin 300 controller new in box for a good price. The seller agreed to a trade for my DA150 straight up and we sealed the deal.

So now I'm sitting looking at the PM telling me I'm about to own a new motor and controller, and realizing that my power system is going to be ready far before my plane is. With that in mind I decided to change my plans and start converting the big planes with my 40% cap which is in flying condition.

The cap is almost a new plane with less than 50 flights on it. It was built by my friend and professional builder Jack here in Austin. I fell in love with it after flying a couple of its very early flights under Jack's ownership and traded him another plane for it. I since put another 5 flights on it at an event (I fly my big planes mostly at events) and had since parked it in my trailer.

The cap as it was before conversion weighed in with a full tank of fuel at about 39lbs give or take a few oz. It currently is set up using hitec HS5955TG servos everywhere. Two per aileron, one per elevator half and two in a push-pull arrangement on the rudder. The throttle and choke were handled by a 5645 and 5625 respectively. Power was previously provided by a DA150 on standard mufflers. I use a pair of li-ions through a turboreg for servo power.

First a couple pics this morning before I started the tear-down:





Not going to be messing with this anymore!



Now on to seeing how things are going to come out weight wise.

Everything that came off the plane related to the engine that will not be going back on at the end:





Total weight: 10lbs 11.1oz

Also being removed is this:



Yes, sadly that IS 1lb 10.3 oz of lead used on the nose for ballast. I had plans to move things around and get rid of that and I will be taking care of that now as I convert the plane over.

Also to be added to the total is the weight of a full tank (50oz) of gasoline which comes in at near as makes no difference 2lbs 8 oz.

Total weight coming out: 14lbs 13.4oz

The motor and controller:



Weight 5lbs 6.2oz

I don't have my battery weights yet but a bit of match based off the weight of a 5S 3000 yielded an equivalent weight for a 14S 13200 of somewhere just over 5lbs. This should obviously not be taken for anything resembling a final weight but it does bode well for a reduction in all up weight.

Now by now some of you may be going "an A150 and 13200 packs... this thing is going to be underpowered". By the numbers, it does look that way but the catch is this: I fly almost exclusively 3D. By the research I've done so far, the A150 should be good for more than hacker rates it for. In fact the one person I was able to track down with actual use of the motor said that it remained completely cold at rated power output. If that is the case, the controller (which is de-rated to 220 cont. amps) becomes the weak point in the system. My expectation is that I should be able to prop the plane for somewhere between 10,000 and 12,000 watts without pushing the system too far. The final number will be determined by doing a lot of test flying up high and seeing how hot the system gets. I hope to hit 300 watts/lb but I will be satisfied with anything north of 225/lb.

No actual progress has been made yet for the conversion - I spent most of today deciding how to proceed with mounting the motor. Now that I have that figured out things should move quickly as soon as I get my hands on a set of DA50 2.5" standoffs and find someone to machine me an aluminum adapter plate. Both should happen tomorrow and I'll post updates as soon as the motor goes on the front of the plane.

a 17s6p A123 battery pack would weigh 15 lb.
6x 2.3 = 13.8ah
That is only 4 lb more than lipolys and you only need 1 pack. You might need that extra weight.

I am looking forward to the rest of this story. I have not seen a thread before where the gas components were removed and weighed at the start. I somehow doubt that this will be underpowered when you are done. In my 35% conversion I am going to use 4 x Zippy FlightMax 6S 5800s 30C (12S2P 11600mAh). Total weight of batteries will be 7.39 lbs (3352 g).

Dirty Bird:

I weighed my 2300 A123 cells and they are 85 g each. 17S6P = 102 cells x 85 g = 8670 g (19 lbs)

Originally Posted by Geoff Dryer

I am looking forward to the rest of this story. I have not seen a thread before where the gas components were removed and weighed at the start. I somehow doubt that this will be underpowered when you are done. In my 35% conversion I am going to use 4 x Zippy FlightMax 6S 5800s 30C (12S2P 11600mAh). Total weight of batteries will be 7.39 lbs (3352 g).

Thank you for the battery weight. A little math off that total gives me 9.8lbs projected weight for my packs which ought to be a LOT closer to the real number.

Unfortunately I can't just go to the web for the weights on my battery yet. Kevin at spyder batteries has graciously agreed to be a sponsor for this aircraft and is getting me a custom made set of four 7S2P 6600mah packs. He is getting me the weight from the factory right now so I expect to have a better idea of my real AUW soon.

I haven't really considered A123's for this project just because even though they are close, they will be heavier than the same voltage and MAH of lipo cells. I'm a performance junkie and anywhere I can cut some weight out I will.

Yes, A123's will be heavier but it looks as though you will be adding ballast any way. But then if you will get the lipolys free thats another consideration

Not free, just at a very nice price. I don't plan on adding ballast.

A few nice things about electric that ought to help with balance: I can shove the batteries the whole way to the firewall where the fuel tank had to be put on the CG. The motor is also a lot further out since the back of the A150 starts at the front of the cylinders were for the DA when you put the drive hubs at the same point.

If I do that as well as move the rudder servos forward and lighten the rudder a little it ought to put the CG near where it needs to be. If I DO have to opt for ballast I would go for more a larger lipo pack in order to get more flight time instead of going to a heaver battery technology.

Considering that you already run this plane on a DA-150 and you probably already have all the accessories to run gas, what is your motivation to convert this plane to electric?

I think you should extend the motor box out instead of using stand offs, this way you can move the batteries that much more forward if you need it.

Update:

I spent some time on the phone today locating a shop to water-jet out a nice motor mount plate for me. I found one and took my own cad file out and got it cut. Came out looking great.

This mount uses the SWB right thrust mount that was used with the DA150 and a set of 2.5" spacers from a DA50 to put the adapter plate I had cut today about where it needs to go. I'll shim it out with some spacers to the perfect distance.

I only mocked it up since I don't have the right bolts yet but it still looks really cool mounted this way.

The new CNC plate:



..with the motor on there



That is just too cool



This is a big enough motor... right?

Originally Posted by Geoff Dryer

Considering that you already run this plane on a DA-150 and you probably already have all the accessories to run gas, what is your motivation to convert this plane to electric?

A little bit of a lot of things. First of all was my move to convert everything else I own to electric and how much I like all of them afterward. The other part is the hassle factor. I don't fly my big planes as often as my little ones so they spend a lot of time in the trailer sitting. inevitably this means that I have to worry about the carbs gunking up, the gas going bad, charging my electric fuel pump, etc. The beauty of an electric setup is once the batteries are put to a storage voltage, they will store for months without issue. There is also the reliability factor to consider. The way I fly my big planes, my primary concern isn't dumb thumbs, its system failure. That means electronics and engines. No matter how good they run, gasoline engines DO and WILL flame out.

All that plus a desire to see what it would be like led me to convert.

Originally Posted by lazyboyflyer

I think you should extend the motor box out instead of using stand offs, this way you can move the batteries that much more forward if you need it.

That is a great point but anything I do woodwork-wise at this point will never be as pretty as it is now so I'll take the chance and leave the box alone.

Nevermind, what you did looks great, very good motor mount design.

I really like your mounting plate. That would be a great item to sell as a little kit with standoffs that the enduser could cut to length.

I went to the hardware store and bought some more bolts so I could mount things correctly and determine the right length for the spacers. Here's some pictures with the cowl on and the prop/spinner mocked up.

Ignore the odd looking spacers I have on there right now. Those were just to determine how much spacer I needed. They will be replaced with some custom length aluminum spacers cut on a lathe. I should have those later this week along with the last four bolts I need.

Originally Posted by Geoff Dryer

I am looking forward to the rest of this story. I have not seen a thread before where the gas components were removed and weighed at the start. I somehow doubt that this will be underpowered when you are done. In my 35% conversion I am going to use 4 x Zippy FlightMax 6S 5800s 30C (12S2P 11600mAh). Total weight of batteries will be 7.39 lbs (3352 g).

Dirty Bird:

I weighed my 2300 A123 cells and they are 85 g each. 17S6P = 102 cells x 85 g = 8670 g (19 lbs)

I just went out and weighed two batteries taped together.
They weighed 5 oz or 2.5 oz each. This agrees with the figures given in Motocalc. 2.5 x 102 = 255 oz =15.9 lb

It looks like balance may work itself out pretty well. I took a little tool box I use for hauling batteries and weighed it out to 9lbs. I threw that on top of the motor box where I plan to mount the batteries and did a REALLY rough no-wings, no cowling, no hatch balance and its somewhere about 1-2" forward of the wing tube with that on there.

As usual that only works out as an extremely rough estimate of real end balance but its in the neighborhood of the proper CG so at least I'm not way out of the ball park.