Converting Glow Glider to Electric - What to Use?

[sdabiker]

Hello All,
I am somewhat familiar with electric power systems thanks to the FT beginner series and research, but I am completely lost on what system to buy for this glider that I am working on. I was given an Ace High MkII. It is made of a balsa fuselage with a foam wing. It use to have a pod on the wing, where you mounted a .049 glow engine. I have since removed the pod and chopped off the front. I would like to convert it to electric with a folding prop. There is a video of a person who did this to his, but it doesn't list what setup he is using.
Can I get some help.
Also I would like to maybe like to get the motor and prop from Hobby King, but I don't know which to get and then match it up.

 

[Craftydan]

Well isn't that a nice looking bird!

not sure about conversions between glow sizes and electrics, and 0.049 is smaller than most motors designed for conversions, but if you know what size prop it threw and the RPM, we can go from there.

 

[lonewolf7717]

Couple questions:

1. What size prop can you swing without clearance issues?
2. What was the AUW of the craft with Cox and full fuel tank?

Basic rule of thumb for glow to electric conversion/ displacement x 2000= watts
So you would be looking for something 100-150 watts, prop clearance and application will determine KV best suited for job. The great thing about brushless is they are highly versatile and it may be a dozen different motors will fill the role nicely. May even be a good application for a plain 'ol brushed job so you don't have to jack around with an ESC.

 

[lonewolf7717]

Oh...I wasn't paying attention....see that you are opting to mount on nose....well in that case something like 800-1000watts on 4s should do nicely lol....at that point you have a hotliner that may fly to pieces mid-air....if on nose with no clearance issues...I would go lower kv/larger prop on perhaps a 2s setup. Keep in mind though this will create some CG issues that will need to be addressed.

 

[sdabiker]

Just a reminder, I am not trying to mount the motor on the pod. I am trying to mount it on the front. I realize that I will have to overcome some CG issues, but I need to know what size prop. Would a 8 x 6 folding be too big or too small. I actually had been given a Parkzone Radian Motor, but it was too large and had been cracked. Thats what you see on the front. I also plan on recovering it. I was thinking about keeping this 3s, maybe a 1300mah?

 

[pgerts]

First is to find a motor that fits well in the fuse.
It is always hard to pass the cables but with a square fuse it will do.
When you got your motor and battery you will get the biggest prop working on that motor/cell combination.
Have you any measures for the free area om the "firewall" where you can position the motor.
A lower KV will get you a bigger prop (but less watts). You will not need the maximum power but the best static pull on the glider.
>Perhaps some inspiration ? http://www.ripamfk.com/bilder/Patrik/index.html#Renovering


And why not make some holes in the stab, fin and fuse to make the plane lighter. Light span will also reduce the weight compared to "normal" oracover or similar that probably was used on the original.

Every fraction of an oz you can save makes the plane fly better.

 

[Ron B]

Check weight of the plane with any equiptment that you have for it then check on weight of equipment you still need to get. That will decide what size motor you will need and you can check on what size folding prop would be recomended. I agree with pgerts on using holes to lighten up the airframe, on the fuselage you can look inside to make sure you don't cut out any reinforcemnt and on the tail surfaces use pins to find out where the frame members are under the skin. Good luck

 

[sdabiker]

Ok All,
Thanks for the Helpful hints. I weighed the plane, and it comes to about 407grams or about 14.3oz. This does not include ESC, Battery, or Motor or being recovered.
Also, I have about a 1.5" x 1.25" firewall that I can mount it too. So what prop, motor and esc am I looking for?

 

[rcspaceflight]

This is the thrust calculator I use, but you can find others: http://personal.osi.hu/fuzesisz/strc_eng/

Using one can be helpful, but its only an estimate. I tried typing in an 8 x 6 prop on a 1100kv motor with a 3S battery, and you should get almost 30oz of thrust. Which is way too much. I think for a glider, even a 1:1 power ratio is too much. So trying to get a 1:1 off of your current weight should be good enough, maybe a little overpowered would be nice. The same set up but with a 2S battery would be 12oz of thrust. A 1300kv motor, 8 x 6 prop, and a 2S battery would be 16oz of thrust. Probably what you're looking for. But honestly, an 8 x 4 prop would probably be a lot better than an 8 x 6. The 8 x 4 theoretically has the exact same thrust, but would accelerate faster with a lower top speed. You don't need a high top speed for a glider. The 8 x 4 requires a lot less watts, and would have an estimated top speed of 36mph. Where as the 8 x 6 would have an estimated top speed of 55mph. Too fast for a glider.

Playing around with the math some more, a 9 x 5 prop, 1100kv motor, and a 2S battery might be one of the best set ups. That would be 18oz of thrust, top speed of 38mph, and require 88watts. (Which is less watts than an 8x4, 1300kv set up.)

 

[rcspaceflight]

Putting what I said inconsideration, and looking at the size of your firewall, I think this will be a good motor: http://www.hobbyking.com/hobbyking/...D2836_8_1100KV_Brushless_Outrunner_Motor.html Honestly, it's a little too big. It can handle a prop bigger than a 9 x 5. But the similar motor that is smaller is a little too small.

But that motor has a diameter of 28mm, or about 1.1". So it should fit right onto the nose of your plane. The mounting plate is going to stick out past the diameter of the motor, but it should fit fine. Actually, I have the smaller version of that motor I'm recommending (by smaller I mean that the motor isn't as deep but the diameter is exactly the same) and the mounting plate is a hair above 1.25". So if you mount it in an "X" fashion instead of a "+" fashion, it should fit perfectly onto your firewall.

 

[sdabiker]

Thanks Rcspaceflight. This is really helpful. I have 9.75 x 7.5, blades at home already. Maybe I can try those on this motor. Does spinner size matter? I saw folding prop sizes ranging from 30 and up in diameter. Also, would a 20A ESC be compatible with this setup. I already have an 18A at home. Would that work?

 

[pgerts]

The RCspaceflight motor will be fine.
Move the shaft to the other side of the motor and mount the motor inside the fuse.
I have some pictures of a similar motor half way down in this link
A folding prop spinner like this http://www.hobbyking.com/hobbyking/...opeller_9x5_W_Alloy_hub_40mm_4_0mm_shaft.html
and your blades on 3 cell LiPo will be fine.

 

[Craftydan]

an 18A ESC might work fine on that motor with a 10ishx7ish prop -- looks like it peaks at 11x7 on 2S, and dropping over an inch off the prop will dramatically cut the WOT current (I'd expect in the neighborood of 20%!). Just make sure it gets airflow over the smooth side -- that's the heatsink.

Spinner should be sized to smooth the airflow. If the motor is in a cowling, size it to the cowling. If it's in open space, size to to the bell diameter.

Also, don't forget to activate the break in the ESC's programming, or the prop won't fold correctly -- then you'll have an airbreak about the size of the prop disk.

 

[William A]

Ace High MkII.

This brings back memories, this was my very first RC plane back in the mid to late 70's.

About 5 years ago I seen another like new kit on fleabay and picked it up.

Still sitting in the box top shelf.

 

[rcspaceflight]

Thanks Rcspaceflight. This is really helpful. I have 9.75 x 7.5, blades at home already. Maybe I can try those on this motor. Does spinner size matter? I saw folding prop sizes ranging from 30 and up in diameter. Also, would a 20A ESC be compatible with this setup. I already have an 18A at home. Would that work?

I think that prop and a 20A ESC should be fine if you're going with a 2S battery. If you want to go with a 3S battery, the prop should still be fine, but you might want a bigger ESC just to be on the safe side.

The battery size is going to depend on what you want the glider to be. If you're just going to power up to height and then float around, 2S would be the way to go. If you want speed, then go with the 3S.

I admit that I didn't look around at motors too much. But I like the Turnigy I have and the one I recommended is just a bigger/more powerful version of what I have. There is just too many options to look at them all.

 

[rcspaceflight]

I got bored and typed in the Turnigy D2836/8 with a 2S battery and your 9.75" x 7.5" prop into the thrust calculator:


25oz of thrust is more than enough. The motor supposedly can handle an even bigger prop than that, so you don't have to worry about over working the motor. The calculator says it would require 182watts, divided by the 7.4volts equals 24.6Amps. Although, that's just an estimate and I may be using that part of the equation wrong. Especially since the motor has a max current of 18Amps and can handle a bigger prop with a 2S battery. But real world and estimates usually don't match. I still say that an 20, or even 18amp ESC would be fine, but it might be cutting it a little close.

 

[pgerts]

.. If you're just going to power up to height and then float around, 2S would be the way to go. If you want speed,..

That is not a plane for speed -¨it is to catch thermal. You use the motor only to get to heigt - in a few seconds.
You use the power relatively hard - much unlike with the old glow power pod. You normally push full down elevator not to get the plane NOT to loop getting up to height. There is no need for a big battery - BUT a lot of C as you normally only use the motor 5-10 seconds at a time. A small 3 cell 800 mAh battery will last about 8-10 "starts". The motor spec says max 18 Amps and a good 18A controller will give at least 25A in short bursts.

 

[sdabiker]

I appreciate your work! Thanks. I had been looking at that motor, and now when I got to order it, its on backorder. Oh Well, with a couple inches of snow today, its not like I am going to be out flying anyway.
I was originally told to get a 1300 3S, but I wonder if that would fit. It sounds like you did the numbers and know what you are talking about, so I will look for the 2S. Thanks again for all your help. I am still trying to understand those equations. I have learned a lot from your posts!