Can I conver the Giant Scale 83" CMPro Cessna in to Brushless?

[lrplin]

Hi guys,
here is the plane: http://www.raidentech.com/gisccmceskar.html
As the title said, is that doable?
Can this motor replace the suggested 2 stroke engine? http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idproduct=5144
Thanks.

[Lynxman]

No problem. A friend of mine flies a CMP Cessna with an Axi 5320. The motor you link to looks like it should be perfect for the plane with a 10S lipo and 16x8 or 16x10 prop if the specs are remotely accurate.

[SHELBY1]

Yep those are great motors for the money. I had em in both my NitroPlanes and VQ P38's. One's now residing in my Agri Duck, and one's going in my new Gee BeeR-3.

I spun 15x13x3 APC's on 6 cells in the 38's. The Duck's running a 20x8 MAS on 6.

I have the Cessna, but "Termite" thru in a Mega motor when I bought his, so I'll be using it.

Make sure you read up the builds on the Cessna, couple of things to look out for. Like don't trust the stock nose gear. Go with a Robart or similar strut set up.

[lrplin]

Thankyou both. It is my first time using more than 3cells lipo. Is that any thing I need to be aware of when connecting 6cells or 10cells together?
And I am going to use this 100A ESC plus a BEC for the Rx.
http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=7341&Product_Name=SuperSimple_100A_ESC

[SHELBY1]

You can use the 3 cell packs, if they are a sufficant capacity, by using a series connector, or wiring your own. (Voltage doubled, capacity same as a single pack)

If your 3 cell packs aren't big enough capacity, you would wire up 4 of them, in a series/parallel connection. (Double the voltage and capacity of a single pack)

or just get the correct cell count pack.

Hobby Lobby used to sell some really slick parallel/series connectors with the Deans plugs already on them. Was a quick easy way to rig up different combos. 17th and 18th items on this page.

http://www.hobby-lobby.com/connectors.htm

[lrplin]

Thanks Shelby1

[WreckRman2]

I've had one of these kits sitting on the shelf for about a year and decided I might change it up and go electric. Did that motor work out well for you?

[parkfly27]

Irplin, if you don't want to pay the $$$ for axi, check out the HXT 63-64-A over at hobbycity. I found a youtube vid of a guy flying a 11-pound 76-inch corsair on 6S lipo with that motor. Looks like it flies great! Should have no problem pulling your cessna.

Also, the supersimple 100A esc is only good to 8 series lipo cells. However, many users report it frying on 8S lipos, so i'd say 6 series is the safe maximum for that ESC.

Also, you can save the hassle of wiring packs together by just getting one of these 6-cell packs: http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=8582&Product_Name=ZIPPY_Flightmax_5000mAh_6S1P_20C_

http://www.youtube.com/watch?v=dTcbOMdSC0g

hope this helps...

[Andrew McGregor]

That's the BIG CMPro Cessna... they fly on 26cc petrol motors, so about 1900W should do it. 100A on 6s is over that, so you should be fine with 6s (of enough capacity of course) if you can find a suitable motor.

[parkfly27]

just to clarify, are we looking to make this cessna go vertical or just cruise around? If irplin wants his cessna to go vertical (and no,there's nothing wrong with that), then 1900 watts would be perfect. 20C on that 6S 5000mah pack is 100 amps. The airplane should weigh 11.5-pounds according to manufacturer, maybe a little less with a lightweight electric power system, so 1900 wats is about 165 watts per pound. I fly my 3D airplane with that same number. :D

Please don't think i'm trying to sound arrogant; I'm just taking what i know from previous e-conversions, and applying it to this airplane. I'm curious though, did the big cessna go vertical with the 26cc gasser? seems like it should with that much power.

There's also the problem of prop efficency... a bigger, slower prop is much more efficent than a small, fast spinning prop. And yes, i speak from experience here too :rolleyes: had a .60-size plane spinning a 10-inch prop on 6S, and it would barely stay up. Went down to 4S with a 14-inch prop, same watts (600) and the thing will torque roll now!

I electrified the smaller version of the cessna for a guy, and it flew fine on 100 watts/pound and 3S 5000mah lipo.

Please, power it up however you want. Sometimes it's good to have excess power to get you out of trouble. For me, excess power usually gets me into trouble :p

best of luck! :)

[Andrew McGregor]

Well, the small one seems about right with 1100 or so... mine's overpowered at almost 1300.

I don't know how it flies with 26cc, I've not seen that and only own the smaller version.

[jfetter]

Hi guys,
here is the plane: http://www.raidentech.com/gisccmceskar.html
As the title said, is that doable?
Can this motor replace the suggested 2 stroke engine? http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idproduct=5144
Thanks.

No problem to make this electric, I have 4 planes a little larger than this. My first opinion would be to go with an Axi 5330/18 (not the 5320/18 someone else recommended, max voltage is 6 cells and it has to high a kV rating for 10S) and 10S. You can turn a 3-blade 16" or a 2-blade 17" or 18" on that setup and have huge power. If you are looking for scale flight, go with an Axi 5320/18 on 6S, you'll save on the ESC since it won't have to be high voltage and you'll still have plenty of power for scale flight...

Jack

[parkfly27]

No problem to make this electric, I have 4 planes a little larger than this. My first opinion would be to go with an Axi 5330/18 (not the 5320/18 someone else recommended, max voltage is 6 cells and it has to high a kV rating for 10S) and 10S. You can turn a 3-blade 16" or a 2-blade 17" or 18" on that setup and have huge power. If you are looking for scale flight, go with an Axi 5320/18 on 6S, you'll save on the ESC since it won't have to be high voltage and you'll still have plenty of power for scale flight...

Jack

Yup, Those axi 5330-18's are very good motors. There's a vid on youtube of a guy flying a 50cc-size yak with one of those, and it goes vertical on 10S lipo. it goes 50 feet from take-off, then he does 3 rolls going vertical :D

but yes, the 5320-18 or HXT 63-64-A on 6S lipo would fly it just fine, and would be real cheap. Here's a test report of that motor on 8S and 6S lipo. He reports 5356 grams thrust with a 21X14 APC-E. Don't know about the prop clearance for that plane tho..

http://www.bungymania.com/imageshome/includes3/motorperf1.php?id=36

Jack, what large airplanes do you have? I'm going to do a 1/4 scale wagstaff extra e-powered soon, and would love to see what kind of power setups you have.

[jfetter]

Jack, what large airplanes do you have? I'm going to do a 1/4 scale wagstaff extra e-powered soon, and would love to see what kind of power setups you have.

I've had good luck with Axi, you'll note a common theme in my larger setups;

> Hanger 9 Sundowner F1, Axi 5330/F3A, 12S, Spin 99, Mejzlik 20 x 10
> C-ARF Impact F3A, Axi 5330/F3A, 12S, Spin 99, Mejzlik 18 x 10 3-Blade
> Sebart Sukhoi 29S 140E, Axi 5330/F3A, 12S, Spin 99, Mejzlik 20 x 10
> CAModel Genesis 3D, Neu 2115/2Y, 12S, Spin 99, Mejzlik 20 x 12 3-Blade
> KMP Pilatus PC-21, Axi 5330/F3A, 12S, Spin 99, Mejzlik 18 x 10 3-Blade

Some smaller stuff includes;

> Fliton Inspire 60, Hacker A50 12L, 6S, Spin 75, APC 17 x 10
> Fliton Inspire 90, Hacker A50 12L, 6S, Spin 75, APC 17 x 10
> Thunder Tiger Rare Bear, Axi 5320/18, 6S, Spin 75, APC 17 x 10
> Sebart AngelS EVO, Hacker A50 12L, Spin 75, APC 17 x 10

And some smaller stuff, my blog (http://www.rcgroups.com/forums/member.php?u=163497) has more details...

Jack

[Gopedasia]

Very interested in e-conversion for the CMP Cessna as well. Please keep me posted :)

[eye4wings]

Just a little trick I've learned on the forum is - if you don't want that big fat spark when connecting up a large cell count to your ESC, there is a cure!
Wire in a smaller connection through a 22ohm (or thereabouts) 1/2 watt resistor, then connect up in the sequence: Black wire first, then small hot wire through the resistor (this charges the capacitors in the ESC) then connect the red... Voila! No spark!
I use 4mm gold connectors for the main power lines and 2mm for the low power strap, but since it is low current you can use just about any connector you like.
It works!

I won't see your Cessna fly, but if you are going to fly it like a sport model and haul it off the deck into a vertical climb out, I don't want to! I'm one who thinks that to go to the trouble and expense of owning a scale model the full size of which is a sedate workhorse, it should be flown like one. Otherwise get yourself an aerobatic type.
FWIW from where I stand I would think 1100W would be MORE than adequate to fly in a scale-like manner and have plenty in hand for any brown-trouser moments. In fact I'd guess she'd take off on half throttle. Your Cessna is only 86" span. I have a DC-3 of 96" span with 400W motors flying on 3s and the Q6 in my avatar spans 112" and flies off grass at three quarters throttle with 3s Lipos and two 600W max motors that aren't even getting warm. She potters around sedately just like the full size will (when restoration is complete) - very rewarding.
Oh, and I use 40A ESCs on both of these models. Save yourself some money as well.

[jfetter]

Just a little trick I've learned on the forum is - if you don't want that big fat spark when connecting up a large cell count to your ESC, there is a cure!
Wire in a smaller connection through a 22ohm (or thereabouts) 1/2 watt resistor, then connect up in the sequence: Black wire first, then small hot wire through the resistor (this charges the capacitors in the ESC) then connect the red... Voila! No spark!
I use 4mm gold connectors for the main power lines and 2mm for the low power strap, but since it is low current you can use just about any connector you like.
It works!

I won't see your Cessna fly, but if you are going to fly it like a sport model and haul it off the deck into a vertical climb out, I don't want to! I'm one who thinks that to go to the trouble and expense of owning a scale model the full size of which is a sedate workhorse, it should be flown like one. Otherwise get yourself an aerobatic type.
FWIW from where I stand I would think 1100W would be MORE than adequate to fly in a scale-like manner and have plenty in hand for any brown-trouser moments. In fact I'd guess she'd take off on half throttle. Your Cessna is only 86" span. I have a DC-3 of 96" span with 400W motors flying on 3s and the Q6 in my avatar spans 112" and flies off grass at three quarters throttle with 3s Lipos and two 600W max motors that aren't even getting warm. She potters around sedately just like the full size will (when restoration is complete) - very rewarding.
Oh, and I use 40A ESCs on both of these models. Save yourself some money as well.

If you simply take the box at face value and plan on the electric equivalent of a 120 - 140, you are looking at a 2,250 to 2,750 watt e-setup. You may prefer scale flying and it is still possible with more power than you need but keep in mind a 15 MPH wind is perhaps 75 MPH scale and you'll need power to fly through it. An 11.25 pound electric is pretty much mid-sized nowadays but it will be quite boring and underpowered @ 1,100 watts in.

If you had to do it on a budget I'd say 2,000 watts on 8S (around 62 amps) and you lay save a little with a 75 amp ESC. Going smaller won't work as it has to support the voltage (8S) and the smaller ESC's (even high amp) are not high voltage. I'm not saying I am right only giving my opinion based on converting models from 6 through 15 pounds to electric. Scale isn't my thing but just because you have the power doesn't mean you have to take off vertically...

Jack

[eye4wings]

If you decide to go overpower this link may be of interest


http://www.giantcod.co.uk/100a-speed-controller-opto-p-402531.html?osCsid=jtcdpjskughs518b3egd1634f7

[jfetter]

If you decide to go overpower this link may be of interest


http://www.giantcod.co.uk/100a-speed-controller-opto-p-402531.html?osCsid=jtcdpjskughs518b3egd1634f7

As with almost all of the "high amp" ESC's, this one is only good to 7S (LiPo) and some of the folks are saying the cheap ones shouldn't be pushed too hard, so maybe 6S is the "safe" limit. Truth is if you go more than 6 or 7 LiPo's, you'll need to spring for a good (read, name brand) high voltage ESC. You don't have to go huge like the 99, 120, 170 or 200 amp "high voltage", even the Jeti Spin 75 will do 8S...

Jack

[JIMinKENTUCKY]

Here's mine.
http://www.rcgroups.com/forums/showthread.php?t=690433

Sorry no flight report.
No chance to fly yet, my field here is not large enough but hope to fly it in a few weeks.

James

[parkfly27]

"An 11.25 pound electric is pretty much mid-sized nowadays but it will be quite boring and underpowered @ 1,100 watts in."

Sorry, but that's just plain wrong. I fly a .60-size 6LB SF Eindecker at 100 watts per pound (600 watts) and it is not the least bit boring! It will go vertical from takeoff, then stop and hang on the prop. It's not a 3D plane (nor was it made to be one).

From my experience (and eye4wing's experiences) 1100 watts will be fine for sport aerobatics on the 84-inch cessena. You can NOT just go from the power out from the gas engine to watts in to the electric motor. those are two completely un-related things. 2200-2700watts on that cessena would be ridiculous and a waste of money (and weight). 2700 watts on a large outrunner would pull at least 22-pounds. I doubt the airframe would handle that. I could understand that much power on somethink like a 1/4 scale extra but a 83-inch cessena????

If you still think that there's no replacement for displacement in the electric world, you need to see this video... 11LBS, 1100-watts, $65 turnigy motor, 6S 5000mah lipo.

just my $.02.... take it for what it's worth.

http://www.youtube.com/watch?v=dTcbOMdSC0g

[jfetter]

From my experience (and eye4wing's experiences) 1100 watts will be fine for sport aerobatics on the 84-inch cessena. You can NOT just go from the power out from the gas engine to watts in to the electric motor. those are two completely un-related things. 2200-2700watts on that cessena would be ridiculous and a waste of money (and weight). 2700 watts on a large outrunner would pull at least 22-pounds. I doubt the airframe would handle that. I could understand that much power on somethink like a 1/4 scale extra but a 83-inch cessena????

I am exclusively electric, I've done many conversions as well as straight e-builds, I was giving a quick rule which many follow and my 120 to 140 equivalent is pretty darned close though doesn't take into account flying style. I wasn't trying to say xxx in glow equals yyy in electric, just stating what I know works for me and others and provides room to grow.

As for 2,200 to 2,700 watts on that Cesna, I disagree again that it is a waste. Most folks that go light on power miss it in windy conditions and end up with a floater. Recommend what you like, I am meerly doing the same and I'll bet after 6 months into it the person would thank me for recomending something with room to grow.

Also, the 8S setup is an attempt to get more power from less amps, going higher voltage is also what many are doing with larger setups. As for the airframe, it will certainly handle the power, it's the one thing that is not scale. When you talk about scale keep in mind your car is driven at 55 to 70 on a regular basis but only using about half of the available power, building a plane with that in mind (reserve) isn't a bad thing and leaves room for growth and re-using the power setup in more models...

Jack

[jfetter]

I fly a .60-size 6LB SF Eindecker at 100 watts per pound (600 watts) and it is not the least bit boring! It will go vertical from takeoff, then stop and hang on the prop. It's not a 3D plane (nor was it made to be one).

Not sure what the F4U video is showing (I might have missed the comparison though I re-read it twice) but if it's meant to show a plane flying on 1,100 watts, I'd say that's low power output for a 6S setup. My 6S setups are putting out 1,600 to 1,750 watts which would be serious sport performance for a .70 to .90 sized model IMO...

Jack

[Andrew McGregor]

The thing we need to remember is that CMP build planes for big-sky flying and SPEED. You don't want to set one up for huge thrust, there's no real point, but you do want to prop it for maybe 130 MPH in this scale, and it's going to take quite a bit of power for that.

It is NEVER going to be a floater, it's always going to fly like the real thing... which is a big, solid airplane that feels like a van. Capable of pretty short landings, true, but not a floater.

[parkfly27]

hi everyone,

sorry if i was a little rude yesterday... had a very long day. :o

What i was trying to show on that video is that a non-floater type plane will fly fine on 100 watts per pound. As far as i know, a corsair is not a floater, or at least no more than a CMP cessena. But yes, it is nice to have power in reserve; you just have to be willing to carry the slight increase in weight.

And no, there's really no problem getting 2000 watts out of a 6S lipo. For example, a 6S 5000MAH battery can easily do 2000 watts at 20C. That would really make the cessena go.

There's also prop efficency. A large, slow prop is more efficent than a small, fast prop (to a point anyways)

It's really up to the builder to make the choice. There's almost infinite combinations of motors, esc's, and batteries that can power this aircraft, so there's no real wrong power system. Some just suit different flying styles better. Theres also programs like p-calc and drive calculator that really help in situations like this.

[parkfly27]

Jim, nice job on your cessena! Looks really sharp. Good luck with the maiden... can't wait to see how it flies!

How does that HXT motor look? Pretty good quality? I'm thinking of that motor for a ultra-light 1/3 yak-54 (not looking for ridiculous power; just light weight because of my small field). That or the turnigy SK 3200-watt motor.

[eye4wings]

Before commenting further I think apologies are due to Irplin, who asked for advice and unwittingly sparked a clash of views.
Hope you are not too confused Irplin - or have given up in disgust!

Picking up on Parkfly27's comments about prop efficiency, I thought that might be a good jumping off point for an explanation of my philosophy as I design build and fly my own models.
The IC scale fraternity have a problem in that scale contests normally consist of a flying and a static phase. Over-propping an IC engine even by a small margin leads to problems with the motor so they change from a scale propeller to what appears to us electric boys almost a ridiculously small one for the flying. They are not apparently marked down for this despite the fact that the size of the prop is evident in flight.
This practice uses props at a less efficient speed and motors large enough to compensate for the huge inefficiency, making direct comparison difficult if not meaningless.
With electric power using outrunner motors we can fly with the same propeller that we use for static display, and what can be more pleasingly scale than to go from static to engine start, taxi out and take off in one easy sequence?
(And even include a sound system that supplies authentic sounds should we so wish.)
There seems to me to be only one reason to fly scale models and that is to simulate as closely as we can the way the full size counterpart flies and there is nothing that turns me off quicker than seeing a B-17 or Lancaster howling round the sky with the speed of an F-15 or similar or being displayed doing an inverted fly-by at 1 foot altitude! YUK!
Okay if you like doing that in private or at your club field where your buddies tollerate that sort of non-scale antic - but that is not for me.

So having decided what scale I want to design my aircraft and before I start drawing I work out what sized prop will be in scale (within a small tollerance margin determined by 'what deviation won't be noticeable?') and adjust the model size accordingly if necessary. I recently rejected a Fairey Firefly IV because the prop was too large, representing too large an experience jump at the time.
From the prop size and number of blades (I normally use x8 pitch) used on the full size comes the decision of what motor to use, with what rev/volt rating to achieve the thrust and with how many cells. Lastly comes the ESC to handle the amps.

The result of applying this philosophy is that my models use wooden propellers working at the most efficient I can achieve, fly like the 'real thing' and use very low cell counts with correspondingly lower wing loading - so that I can build light - lowering the wing loading - and so on. This means that I avoid non-scale manouevres and have time to enjoy the look of my model as it flies past.
I have - as a rather extreme example - a 4lb 72" span Miles Messenger which flies on a 14x10 prop and 2s LiPos. (Which I hasten to say in deference to jfetter's comments about wind, I prefer not to fly in weather that exceeds its forward airspeed!)
My Percival Q6 spans 112" weighs in at 12lb and carries two packs of 8ah cells that fly it for over half an hour. This I have flown in a 15 knott wind.

So my comments are based on what I would personally do to get Irplin's Cessna flying on electric and flying scale. And I am sure the full size Cessna pilots would take due care of how high a wind they would be prepared to fly in too.
And having said all that (sorry it had to be so lengthy) I have to further admit that we all - myself included - make our own decisions about how far we are willing or able to go in pursuit of the scale ideal.
Basically 'yer pays yer money an' takes yer choice'... and we're all learning as we go.

[Andrew McGregor]

I think what you just described is a great philosophy, if the model's wing loading allows you to do it. But this is a CMP plane, which implies pretty heavy; you can pass it off as scale if you think of flying at max weight. The small Cessna looks great and flies great too... but it's much more dynamic scale than linear scale, which means it cruises at about 70 mph. I'd be pretty sure from the weight that this one is similar, and at this scale that would make cruise speed around 90 mph. That's going to take a fair bit of power to do with a scale prop (which would be a big three blade with a very deep pitch... remembering that the fullsize plane has a constant speed prop, which we can't realistically do).

[parkfly27]

Irplin, sorry if this thread has gotten a bit out of hand. My apologies.

I just found the link to one of the most helpfull tools in electric flight; Drive Calculator. I use it for my setups, and it's surprisingly accurate and easy to use. They also have a huge database of real measurments that people have taken with real motors (which is probably the reason it is so accurate) Furthermore, this database gets updated regularly. It has all kinds of motors, inluding the AXI's, HXT's ect...

http://www.drivecalc.de/

[bfischer]

If anyone has this big CMPro kit that is sitting around... I am interested in buying it...