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Old Dec 08, 2012, 09:20 AM
Ldm
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United States, PA, Conestoga
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110 or a 160 motor ??

Since starting in eletric I feel like I have over powered everything underestimating the power of eletric !!!
So now as I have to get more motors for my next set of planes that I want to convert I need some advice .
Three planes 71" CMP P40 , 70" CMP Spitfire and 70 CMP BF109 ,
these planes are not maxing over 14lbs when built with fuel , so I wanted to know if the 110 are adequate?
There glow suggestions were 180 4 strokes that is why I was thinking i need a 160 in epower but again the finished weight is not the high
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Old Dec 08, 2012, 11:00 AM
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Canada, ON, Owen Sound
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Since starting into electric RC, the first thing I realized was I had to totally ignore the original IC power requirements.
I pick a prop size FIRST, that includes diameter and pitch size. that will depend on plane type, but I generally the higher pitches, like 15/10 etc.
Now determine the power required going IN to the motor. On warbirds, I use 125-150 watts/lb. I haven't had one that didn't fly very well on 125w/lb.
Now, I decide on the battery cell count.
Then I look for a motor, using the cell count selected, turning the chosen prop, that give me the power level and airspeed I want. The cell count and mah determine flight times at power levels chosen.
So, a 14lb warbird, would require 125 x 14 = 1750watts In. Bragging rights is the only reason others would power over this level, its not a JET and shouldn't fly like one -hehe. These plane would fly easily on 6s if wished, but not with the 110, kv too low, but 8s should provide a scale sized prop, and more than enough power. jmho fwiw Doug B
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Old Dec 08, 2012, 05:15 PM
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Fort Collins, Colorado, USA
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LDM.....

You know I have the CMP ME-109. BTW..its 73" not 70 For this plane in particular...you'll want the 160. As an E conversion, this plane usually comes out at 16 pounds or higher. Ive built 3 of them and all of them came out over 16 pounds with the first one being the heaviest cuz I put in a scale full figure pilot.

Motor 160. Battery 10s 5000-6000. Ive done all 3 10s 5000, but would love a bit more reserve.
Prop 18x12(do not use an APC as they suck). You'll definitely want the 160 if you want to run a 3 blade prop. Zoar may have an 18x12, but I know Beila makes one. I run a 2 blade 18x12 turnigy type E cherry wood prop.

For the P-40, a 110 might be OK. it doesnt have flaps(that I recall) and isnt quite as heavy as the ME-109. For a 110, you'd run 8s with an 18x12 or 20x10. If you try to go 9s, then maybe a 16x10.

The Spitfire...Im not sure about. I havent visit the CMp Spit thread in quite some time.

I have several ESM or other 70-73" size planes using the 110 on 8s 5000 with 20x10(or 18x12).
ME-109E power 110 8s 18x12
P-51B power 110 8s 20x10
Graupner Fw-190 D9 power 110 8s 18x12
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Old Dec 08, 2012, 05:35 PM
Ldm
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Thanks Doug great explanation and I have quite a few 5000 4, that would make good 8s when combined
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Old Dec 08, 2012, 05:41 PM
Ldm
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Thanks Ka , I know the BF109 was one of your favorites !!
I do have one 160 turnegy left , was saving it for a fat nose P47, am I going to take your advice and use it in the BF109 .
As you stated the P40 is very light but ... I will add flaps and tons of detail so I may be pushing it .
The spit was one of the original CMPS , the flaps are included but not scale so that is a mod i have to make , also have sierra gear for that plane and a small interior kit .
I think the 110 would be ok for that one
Thanks for the advice
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Old Dec 08, 2012, 09:13 PM
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I'll second Doug's advice, particularly on the overall approach. I don't have anything glow or gas, so i always work from the airframe and prop back, and as my models get bigger (.60 size), I find the rules of thumb less useful

For example, bigger props are significantly more efficient so assuming comparable motor efficiency 100W/lb into an 18" prop is more like 125W/lb into a 14" prop. And bigger motors with thick wire and less internal resistance tend to be a bit more efficient, so 100W/lb in to a 110 sized electric is more like 110-115W/lb into a 32-40 sized motor. What I'm getting at is the rules of thumb were developed when motors were less efficient, and noone conceived the possibility of flying a 14lb warbird on 18-20" props with brushless motors weighing several pounds. That's probably why you feel you've overpowered everything

A specific example: 600W in / 540W out turning a 16x10 prop develops more thrust than 800W in/ 720W out turning a 12x6. Both have comparable pitch speed.

Sorry if this is suck eggs stuff, but one reason to overpower a bit (or a lot) may be just to get the weight where you need it, and you might as well use a bigger motor than lead.
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Old Dec 08, 2012, 09:54 PM
Ldm
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Sci , I have never been one to add weight with years on the glow side .
I would do everything possible to add functional weight ie move the servos , everything possible forward ect .
Your point and the rest along with Doug , Kahlog ect all make sence .
My challenge with some of the CMP planes is that the fiberglass is not really great so I need to also consider the worthness of the airframe . As Kahlogs knows the CMP BF109 was one of the last CMP planes released and the quality was much better over the original CMP planes .
As an example I am working on a willshobby seafury , same fiberglass as the CMPS and the fuse will tin can ect . I have a 160 in this plane because with a 4 stroke it needed a ton of nose weight . Partially because of poor design with the wing servos behind the CG !!!
Anyway back on subject, So if I am reading you guys correctly it would seem that 110 would be efficient but 160 would be more efficent use of functional weight if needed .
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Old Dec 08, 2012, 10:09 PM
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I built an old Midwest T-6 that weighed 14lbs, with a 160 on 6s. I used a 20x15 prop and only turned it about 4500 rpm. It actually only consumed about 800 watts but flew great, with lots of authority.
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Old Dec 09, 2012, 02:07 PM
An itch?. Scratch build.
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South Wales U.K.
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Can I just mention the other side of electric power for those that enjoy building, .... building a model specifically for electric power, not converting models designed for IC power.

The reason is I have a model in the above range, a 72" span Spitfire.

The model is based on a plan that was originally for a balsa build and a 1.20 four stroke. But, I built it using Depron foam, ( shock, horror, 'that foam stuff....', I hear from the, balsa or death modelers, '.....that's for toys'.).

Well this is one toy that flies great on less than 700watts,.....mainly because it weighs 7lbs - 2oz flying, less than half the weight of the balsa IC version, (15lbs).

Just a thought....

Spitfire 5 (5 min 11 sec)
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Old Dec 09, 2012, 05:04 PM
Ldm
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lol,
I have no issues with foam , check my blog out I have the 79" P40 , its a dream on a E flight 110 . To be honest epo in my humble opinion is better then the cheap low end side of fiberglass . ESM planes are the good examples of the upper end of glass , I have wills-hobby Seafury that I am converting to epower now .The reason why it will come in heavy is that the glass is so cheap that you cant grasp the fuse without it compressing in-between the formers and making creaking sounds .
I am adding light ply to the inside to make it up to par with standards .
The 79" epo P40 I have is solid , I did add carbon fiber rods for my own taste but its rock solid .
I have a red box P40 wood kit that was designed for a 60 size two stroke but I will be making it from the ground up eletric so it will be lighter then its fuel brother and I am sure it will perform better .
WHat your referring to in epo is one of the main reasons why I am drawn to epo --light wing loading .Its makes these planes a joy to fly !!!
I have a 66" Corsair coming to me from FMS , should be a cream puff to fly .
Lastly checkout the 1/5 scale P40 build from foam in the scratch building section , its a beauty and flys like a trainer !!
My conversion projects are in reality a result of me acquiring CMP kits at a good price otherwise I have moved much of my time to EPO
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Old Dec 09, 2012, 05:06 PM
Ldm
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I am at the airport on wifi , but could not get your video to play , perhaps its my connection .
WOuld love see the build !!!
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Old Dec 09, 2012, 06:36 PM
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Hey LDM... I've been mulling over getting another H9 spitfire and running a g60 Turnigy as I have one on hand. The only spitfire I have that's not a parkflier is the 90 size kyosho which is painted in captured German colors.
I'd love the ESM but doubt it would fly on a power 60 class motor.

However, I do have a monster 110 in a H9 fokker dvii that's only running
on 6s I could swap out. The problem with the monster 110 is the prop shaft is 10mm and no one makes a spinner adapter that would screw down on 10mm threads that I know of.

Would probably be just better to get another H9 and paint it like the ESM. Making a hatch on the H9 would be ten times easier also.

I'm also really eyeing a gee bee r3. Love the lines of the R3 and no one has one at my field.
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Old Dec 09, 2012, 11:56 PM
Ldm
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Kah , on my Dora I am useing the Monster 110 and have a prop adabter from True Turn .
I think its listed in my thread on the bash , if you cant find it let me know .
I just sold my Hanger 9 corsair with an OS 91 4 stroke but know that size and weight (like the spit ) has been flown very well on the 60 epower !!.
On another note I emailed Jose from flite -skin as the thin sheeting he sells is great for internal extreme strength with very little weight gain , but he I think he is out of that business
because I dont see the ads the way I use to.
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Old Dec 10, 2012, 04:40 AM
An itch?. Scratch build.
eflightray's Avatar
South Wales U.K.
Joined Mar 2003
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Quote:
Originally Posted by Ldm View Post
I am at the airport on wifi , but could not get your video to play , perhaps its my connection .
WOuld love see the build !!!
Your welcome -

Spitfire 72" Depron foam, she's flown, plus a video.
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Old Dec 10, 2012, 10:12 AM
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Fort Collins, Colorado, USA
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Quote:
Originally Posted by Ldm View Post
Kah , on my Dora I am useing the Monster 110 and have a prop adabter from True Turn .
I think its listed in my thread on the bash , if you cant find it let me know .
I just sold my Hanger 9 corsair with an OS 91 4 stroke but know that size and weight (like the spit ) has been flown very well on the 60 epower !!.
On another note I emailed Jose from flite -skin as the thin sheeting he sells is great for internal extreme strength with very little weight gain , but he I think he is out of that business
because I dont see the ads the way I use to.
Is it this?
http://www.truturn.com/cgi-bin/store...exact_match=on

for flitskin...website still up and some sizes are still available:
http://fliteskin.com/Sheeting.htm
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