Sig 1/4 Scale Spacewalker Conversion to Electric

[Mark Winstanley]

Hi guys; I am fairly new to the giant scale electric arena but not to electrics or giant scale. I have built a couple of 1/4 scale Spacewalkers from Sig kits and have used a US 25 gas and a converted Robin 23cc gas engine for power. Both flew the respective models adequately in a scale manner and were capable of some basic aerobatics.

I like the Spacewalker and at this size it is easy to transport even with the one piece wing (provided you are not on a motorcycle!).

I am considering building another but this time I would like to have it electric powered. My question to you guys with the experience is - would you make any changes to the airframe to lighten it? As I recall the AUW was in the region of 12 lbs as built to the kit standard. I am thinking about powering it with a HXT 63-54-A-250 motor on either 6 or 8 LiPo cells - comments on this power set up would be appreciated as I have not yet bought the power train. I am aiming for similar performance levels as with the gas motors (so no 3D for this one). I will be building the model from the SIG plans as I now have 2 sets from the previous models.

Your comments and insight is appreciated

Mark.

[appleflyer]

i would use the e-flite power 110 motor, it cost more then the HXT but will be overall a better motor, the HXT motors are good but their have been some that have failed in the air casing the plane to crash, you can use batteries from hobby city like the Zippy but i would not use motors ore ESC's from them, hope this helps :)

[appleflyer]

here is a link to the power 110

http://www.horizonhobby.com/Products/Default.aspx?ProdID=EFLM4110A

[Mark Winstanley]

Thanks for the link - definitely something worth looking at. Would that be too powerful though able to turn a 20 inch prop. I think I need a 16x8 at between 7 and 8000 rpm (at least that is what the gas motors used to give).

Mark.

[Ron]

Eflite power 60 on 6S lithiums with a 16X10 prop gives me 6300 rpm, and pretty much stellar performance in an 8lb model

[appleflyer]

you could also check out the power 90

http://www.horizonhobby.com/Products/Default.aspx?ProdID=EFLM4090A

i have not had a power 110 so i am not shore about the prop/ RPM, do you have motocalc? if not go to this link and download the 30 day trial for free,

http://motocalc.com/motodown.htm

[Grant Lord]

I used to have one of the great planes spacewalkers converted. same basic size... all of the sig kits that i have seen came in above the box weight. Art used to fly one on a maxcim with 24 nicads, but it was a little underpowered. that being said, i used to fly mine on a actro 40-5 on 30 round cells. old technolagy, it was heavy :eek: Although the power 60 will fly it, the 90 would give it more authourity. of course anyone that knows me, knows i would go with the power 110 on 8-10s with a 18" to 20" prop :D . i am currently flying one of the old hanger 9 pt19's (same size) on a 5320, 10s 5000mah, 19x10 set up and it flies great!

fwiw

Grant

[Mark Winstanley]

would you make any changes to the airframe? The Sig model is obviously strong enough for a 25cc gasser I was wondering if some weight should be removed from the ply doublers for example, reduction in spruce spar size or general thicknesses of balsa wood to save weight. The Landing Gear plus wheels must have weighed at least a pound!

I will also look at the eflight 90.

Suggestions welcome

Mark.

[bigbobed]

Is there a way to add a hatch so you don't have to take the wing off to get at the batteries?

[Mark Winstanley]

Probably. I used to have a hatch on the top to access the engine bolts from the rear of the fire wall. I had the front cockpit removeable - so that should be OK.

Mark.

[Ron]

Grant...You power hungry Monster ! Yes your PT 19 flies well with the power system you have in it, but if you lighten the spacewalker down to about 8 pounds it flies well too...I agree their kits are HEAVY, but a good dose of diet will lighten them up :-)

[Grant Lord]

now if i could just build as light as Ron and Ivan ;)

[Grant Lord]

yes you can lighten it up many of the doublers are not needed, and in some cases you can trade out some of the wood. cut new pieces of plywood....

the trouble is, where do you stop? to get truly light like Ron builds, use the wood as templates and scratch the whole plane. :eek:

then sell the kit at the next swap meet!

to give you an idea of the difference, my dad had a midwest citabria with a os91 in it that the all up weight was 10 pounds. i have one scratch built from the plans with a 4130 axi and 6s that is 7 pounds.

what you have to decide is how far do you want to go. you can make minor modifications and build a nice plane that is reasonably light, and go fly!

Grant

[Mark Winstanley]

Thanks for all the tips guys. I will get the plans out again and see what I can delete. I would like to aim for 8lbs so I am thinking balsa spars with webbing. Balsa structure for the fuselage with the ply doublers full of lightning holes.

Mark.

[Ron]

The Spacewalker built at 8 lbs is no problem...had one in the later 90's with a Hacker B50/13S 6.7 to 1 I think 16 cells ( nicads) and it was just over 8 lbs.....so now with Lithium cells, it should be relatively easy to accomplish...it flies much better at 8 lbs than it does at 12 :-)

[pda4you]

So Mark - did you start this project? I was thinking about a big(ish) plane....

Mike

[Mark Winstanley]

Well I have done a lot of soul searching after a lot of research on the cost of batteries, chargers abd infrastructure etc. I have decided that, for me, large aircraft will be gas powered and small ones electric powered.

I was at the Rally of Giants in Arnprior, Ontario, Canada in late June and saw some large electrics. The large deep cycle batteries needed for charging the large LiPos seemed both bulky and too expensive for me. The performance was certainly there and they performed equally as well as the gas powered equivalents. It is just the investment needed is beyond me at present. Maybe as the battery technology and charging facilities get better I will change this view. But for now Large gas - small electric.

Mark.

[pda4you]

Yep no question the cost of batteries/ESC's and motors are pretty high for the large ships.

I fully understand!

Mike

[bob laine]

I have converted my Sig 33% Spacewalker over from an Zenoah G38, to Electric. I'm running an "ELE" 63/45 on 12S A123, and the Power is greatly improved from the G38. A little on the heavy side, but it fly's a little faster than Scale. Bob Laine

By the way..........This conversion took only about 4 hours to complete.

[pda4you]

Bob we need some pics...

[tai626]

I am converting a 50cc to electric. I studied the cost of the gas power and electric power and my conclusion is the price is really close. The numbers are rough estimative, btw:
DA 50 ~ over $500;
Canister ~ 100;
Gas Field equipment ~ $100;
6 metal gear servos ~ $300; (because of vibration)
Total for gas set up: ~ $1000.

Hacker A60 ~ $200;
CC-85 HV ~ $200;
15S A123 ~ $220;
Power supply ~ $200. (3 deep cycles or 1 mastech 3010 or 5020)
5 Hi-torque servos: ~ $150
Total for electric set up: ~ $970.

I went a little cheaper and wait patiently for deals...The result was:

New Hacker A60 22M: $95;
New Electrify SS-60 HV:~$100;
15S A123 from a seller in rcgroups: ~$90;
mean well 500-24 power supply: ~$70 for two;
7 Hi torque servos: $100;
The price come down to:~$455.

Plus, I got my Extrana 80" (extra + katana) for $110 from fleabay.

The built receiver really 80" giant will cost me a little over $550. Not bad for 1st giant :-)












Yep no question the cost of batteries/ESC's and motors are pretty high for the large ships.

I fully understand!

Mike

[propnut07]

I have a gas powered sig spacewalker but look at the featured article on a 1/4 scale cub from hanger 9 using a castle 80 with an elite 110.could be very similar in performance would love to see more when your done .good luck..

[dirtybird]

The key to holding down the cost of large models is to use A123's. With a good charger the batteries can be built in the aircraft. You don't need three or four packs.
I have a Scorpion 4025 with 8s1p A123's that flies a 62" converted Lazy Ace. That is about the same set up you would need for the Spacewalker.

[bob laine]

Bob we need some pics...
I'll post some in the next day or two. Bad weather right now. Bob Laine

[Mark Winstanley]

DirtyBird; can you give me some more info on your set up - model of motor, size of prop, ESC, duration of flights etc?

My interest has been piqued again!

Mark.

[Art Newland]

I built my Spacewalker in 1999!! I originally was going to use an OS Gemini twin, so it was built with IC power in mind and basically built it stock. I also had this planned for an entry level scale plane to compete in the US Scale Master program, so it is covered with fabric and then painted. It has a lot of scale detail added also... to make a long story short; it's heavy at nearly 13LBS. After a conversion to 6S lipo last year it lost 6-7 ounces, but I don't notice much difference in the way it flies. On the 24 round cells it made 750 watts, after converting to 6S it was only at 575 watts because of the lower voltage. I actually flew it a couple of time on 575 watts… way too scale of a power loading!! It amazed me that it would fly at all. I re-geared the old MAXCIM to get it back up to 750 watts, and since the lipos are 4000 mA’s and the old cells were 3000, it all kind-of evens out. One word of caution about building it lighter, you would really need to keep it light in the tail as you’ll run into CG trouble. I had to cut a hole through the firewall and move the battery forward as far as it would go to get the CG back to normal. Or you could put way to many batteries in it… like Grant! 8^)

If the weather is good for the Equinox fly-in at Washougal, I’ll have my Spacewalker out for a flight!