CMP Me 109 - RC Groups
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Jul 20, 2008, 06:26 AM
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CMP Me 109

We have a had a little bit of discussion about this plane in the "Fuel Warbirds" forum but I have decided that I am going to make mine electric so I thought I'd better start a new thread. Please feel free to chime in even if yours will be fuel powered...

Here are some pics to show the overall layout and some detail.

I have emailed a few places for retracts but for some weird reason Melbourne, Australia seems to have been the only place these are available yet.

I am thinking of using this engine on lipo or A123:

Any thoughts?

I have some ideas for motor fitment and cooling but I will have to draw a sketch or two to explain. The front of the engine bay is a substantial piece of ply so could be used for motor mounting I think.

I have never converted or owned an aircraft of this size before so I am really interested in different approaches to the job.

I should point out that I cannot fly this aircraft until January next year because I have no local field that I'm a member of but once I move at Christmas time I will be only 2km away from a massive field/club so this will be a slow build for me.

I plan to make a cockpit tub, hinge the canopy and attempt some weathering. I am considering respraying a winter scheme but am not sure yet. The only reason for considering a new scheme is the wing. The fuselage paint job is excellent but the wing doesn't match the quality.
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Jul 20, 2008, 08:12 AM
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Coastwatcher's Avatar

Maybe an x-bracket and thrust angle

They got the crosses pretty close on the prototype pics. So this would led me to believe it to be an early production line goof up . Maybe they will realize it , maybe already have and fix this minor problem as more show up.

* It appears the thrust angles are build into the flat-ply center section where one would mount the glow engine. I WONDER ??? does the front ply cowling wall "ALSO" have the correct thrust angles too?

* I ask this I initially plan on using a front mounted "X" bracket on my outrunner screwed to this heavy cowling wall using about 3/8- 1/2 inch nylon standoff.
Last edited by Coastwatcher; Jul 20, 2008 at 08:22 AM.
Jul 20, 2008, 09:46 AM
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kahloq's Avatar
I also ordered a motor for the CMP Me-109 from hobby-city. I got the 230 kv version:

I got this one because CorsairNut has used it in a TT Bearcat with very good results on various lipo cell count. I figured if Im gonna order a motor from overseas, might as well get one I can match to what someone has already tested. I am sure the 280kv version will work just as well.....might be higher amp draw with the higher kv though.

Both of the motors are not HXT as listed on hobbycitys site though. They are actually turnigy brand. I've already got a turnigy 50-65c in my kyosho corsair and it flies it very well on a 6s Im happy so far with turnigy motors.

I'd like to do A123 batts, but getting the correct setup is pretty costly(including a charger that can do higher cell count then what i have and is good for a123 batts).
As it stands now, I have the battery packs to run a 9s, 10s, or 11s 4400mah setup using smaller 2200 size 3s and 4s batteries in series/parallel. As such I wouldnt have to buy anything else, but only one flight per day doesnt sound so grand either.
Jul 20, 2008, 07:15 PM
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Here is my current thoughts on motor mounting in sketch form. Essentially, I have to believe that the front face that mates against the spinner has the correct thrust angles - otherwise you would have to have an uneven gap which would be rubbish.

So I would mount my motor to this on four bolts going to either the normal bolting points or more likely to a custom heatsink. I have been thinking quite seriously about mounting a small fan on the section of shaft protuding inside the aircraft for further cooling. This could either blow onto the motor or be ducted rearwards and out.

The mounting bolts would allow the angle and placement of the motor to move infinitely within a certain range.

Kahloq - if the motor you ordered has been proven to work then I am getting that one too!
Jul 21, 2008, 08:29 AM
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Coastwatcher's Avatar
Steve, thats close to what I'm thinking . Be interested in seeing what fan parts you come up with. I'm sure my mind and installation will be close to what you drew. Its hard to get a scale pic of inside area to work with without it being in front of me.

I 've decided to use the supplied spinner .......till someone like Gaint Sierra , builds a custom one for the CMP. They have a 6" 109G spinner already available, I HOPE they can produce a 5" Alum or whatever the size is for this CMP109 . IN A THREE BLADE........A 109 JUST "NEEDS" a three blade prop to look the part.

I wondering HOW MUCH surgery I'm going to have to do to get "NEAR SCALE" or decent sized retracts under her. I'm prepared for the worst. This plane needs something like 4" wheels to be scale. I'm sure "THEY" thought minature 2" wheels would be fine with a unscale glow set up with its dinky little two blade prop. Oh well, thats why its the conversion thread
Jul 21, 2008, 09:58 AM
Done it all
I'm not doing any planning yet on the 109 until it arrives and can be inspected in person.

The biggest problem regarding the conversion to electric, is the length of the motor shaft or adaptor shaft on the electric motor. Electric motors have short shafts and the adaptors have short shafts. So, it doesn't matter which way the motor is facing. The short shaft is suited to E-Props, but, it is difficult to get a larger size prop on these shafts, along with a spinner. There are no threads left for the prop bolt and washer. This is not the problem with Nitro motors.

The problem gets worse if the spinner is aluminum with a center bolt. There is no room for the adaptor to spin on the shaft, not enough threads left, even if the washer and bolt fit.

I think E-flite motors have the shaft drilled out for a spinner bolt, so the adaptor is not needed, we just have to change the bolt that comes with the spinner to match the threads in the motor shaft.

If you guys want to plan ahead, I'll give you something to worry about? LOL It's called "hurricane" Freddie, keep your feet dry.
Jul 21, 2008, 10:10 AM
Done it all
As an afterthought, it doesn't look like mounting the typcial electric outrunner through the nose piece directly behind the spinner will work, not enough motor shaft will protrude out the front. We might have to cut out the nose piece, depending on how strong the front of the fiberglass fuse is. Another option is to drill out the center hole quite a bit so that the electric motor can protrude slightly out, that way it will give more room for the spinner and bolts to be attached. But still, electric motors have short shafts, so, the spinner becomes a problem.

Anyhow, that is what my thinking is.
Jul 21, 2008, 11:56 AM
I fly for Beer
Jagzilla's Avatar
I did an electric conversion on the cmp .50 size mustang with the same sort of motor mount arrangement. I found it to be a real headache to deal with. I felt to do it properly, there needed to be major reworking of the whole nose section. To just mount the motor directly to the front ply/fibreglass nose was awkward to do, and not overly strong. In the end, I told myself to never buy that style of plane again to do an e-conversion on. I'll take a plain old flat firewall to mount a motor to any day of the week. Having said that, I love the 109, and I hope this project goes well for the owner.
Jul 21, 2008, 01:10 PM
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Joespeeder's Avatar
Hey Guys,

I don't know a thing about inrunners and gear boxes but I found this review that shows various setups for this type of mount. Would something like this work for the 109? Does using an inrunner and gear box mean you can get away with a smaller motor, less amps, and longer flight times? Or doesn't it really work out that way in the real world?

Jul 21, 2008, 03:20 PM
drksyd's Avatar
Glad you posted the pics, looks like I won't be getting one after all. For a less troublesome setup, I would go with a geared inrunner but that's a whole lot more costly than an outrunner.
Jul 21, 2008, 03:42 PM
Registered User
The biggest problem regarding the conversion to electric, is the length of the motor shaft or adaptor shaft on the electric motor. Electric motors have short shafts and the adaptors have short shafts. So, it doesn't matter which way the motor is facing.
I usually end up with the reverse problem of having to cut the motor shaft shorter!

Jul 21, 2008, 03:49 PM
Done it all

Here in the states we all seem to end up with short shafts. However, that might be lots better than having the shaft cut to make it shorter. To each his or her own.

I am a number one proponent of not having a shaft cut short.

Jul 21, 2008, 05:37 PM
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Coastwatcher's Avatar
I think there probally some Inrunner solutions , known by people who have used them exclusively . I also prefer not to use them as they are big bucks. I called HAcker , their geared inrunner units actually have a SHORTER shaft than their outrunner equal. The problem is the same with either , we loose the shaft lenght exiting the thick ply.

Eventually , somebody who has BOUGHT a system that willwork may speakup and come to our rescue.......I know there are people with machine shops , and all that that have built their own gear box and such......but that s not practical for 99% of us. Thats why we are building arfs
Jul 21, 2008, 10:54 PM
drksyd's Avatar
I'm sure this Hacker setup would be perfect for the 109.
Jul 21, 2008, 11:50 PM
Done it all
That geared Hacker, $400 plus bucks new, for sale for $250.00 or whaterver.

I just called a vote of my assembly crew, me, myself and I and we came up with a conclusion to that choice.


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