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RE: CMP 120 Zero ARF Build thread - 9/1/2011 4:25 PM   
L16pilot


 

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From: Hurlock, MD, USA
Status: offline 		Thanks Chad...for the comments and noticing it's a Hamp! Well, it was roughly a 9 month build, but there were a lot of mods made, so I guess that's not too bad. Looking back, there are some details I think I should have added...such as a scale tailwheel, but overall I'm really pleased and it's a robust bird that should be very reliable with minimal maintenance. I've completed the set up based on my Zero #1, so i do not expect anything unusual and the initial flights should be almost routine with no surprises. Will post a Pirep after the first flights...and hopefully some in-air photos.

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RE: CMP 120 Zero ARF Build thread - 9/1/2011 4:36 PM   
77chickenhawk



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quote:

ORIGINAL: tomandjan@live.co.uk

just glove and fuel is there any other out there that will take the wieght








Glove? lol

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RE: CMP 120 Zero ARF Build thread - 9/2/2011 2:29 AM   
frets24


 

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ORIGINAL: tomandjan@live.co.uk

add these? i dont fancy the HK ones and the eflight are to much money may try the HK in another model but not this one im looking at electric retracts because im going petrol and dont wont to take pump and battery to the field as well just glove and fuel is there any other out there that will take the wieght



Sorry about that, mate. I forgot to add the link Here it is:

http://www.wingspanretracts.com/Actuators

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RE: CMP 120 Zero ARF Build thread - 9/2/2011 2:32 AM   
frets24


 

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Status: offline 		L16pilot,
Nice Zero. It's really a treat to see one that isn't the same solid IJA green or IJN white as so many are. Nice paint job.

I thought these colors would be an interesting departure from the norm for mine. I've also decided to break from my habit of not doing two in a row from the same country and starting on my zero even though I just finished a KI-61 Tony.



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RE: CMP 120 Zero ARF Build thread - 9/2/2011 3:15 AM   
L16pilot


 

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Status: offline 		Frets - Thanks for the compliments. A fellow member here, (Tofly), did a CMP Zero in a similar scheme to your views posted....but he did a two tone green. I like the green/tan scheme in your views....Go for it!



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RE: CMP 120 Zero ARF Build thread - 9/2/2011 7:44 AM   
frets24


 

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Status: offline 		Nice!

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RE: CMP 120 Zero ARF Build thread - 9/4/2011 1:56 AM   
misha034



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From: KragujevacSerbia, YUGOSLAVIA
Status: offline 		Hi to all of you. New and old Zero builders.

After a few months of break, making Zero's is coming to an end. By some plans, the model had already supposed to fly, but private and
also, business probems came on way. Some time and we can not affect everything that happens in the life.
I have decided to test several propellers today, and chose one of them for a maiden flight.





In competition were propellers

1. Master Airscrew K Series (plastic) 16 x 8

2. Pelikan (wooden) 16 x 8

3. Menz Props (wooden) 17 x 10

4. Graupner Sonic (plastic) 18 x 8





Instruments for Measuring revs and pulling power where these



Tachometer is from tower hobbies, and scale was bought in the Chinese shop in my town for 5$.
It can measure up to 40 kg.

And here are the results

1. Master Airscrew K Series (plastic) 16 x 8
max speed 8750
thrust 5.9 kg

2. Pelikan (wood) 16 x 8
max speed 7700
thrust 4.2 kg

3. Menz Props (wood) 17 x 10
max speed 6600
thrust 4.4 kg

4. Graupner Sonic (plastic) 18 x 8
max speed 7800
thrust 6.4 kg


So, the result is somewhat expected. Menz immediately scrapped, and the difference between Pelican and Master (same dimensions)
is amazing.
Graupner Sonic is my favorite after this. 80% of thrust comparing the total weight will, hopefully, be enough.

Factory recommendations are:

prop 18 x 7 - 12, or 16 x 10-14
and speed does not exceed 7500-8500 (in air)

So, it would be great to find some propeller which will give a little more speed and maybe even few grams of thrust.

Every help and feedback is welcome.

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RE: CMP 120 Zero ARF Build thread - 9/5/2011 5:33 PM   
shuglu


 

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Status: offline 		I started with Master Airscrew K 16x10 and before i'd even flown it i'd gone to a Master Airscrew Classic (rounded tips) 18x8 and due to the noise it was producing i went up to master Airscrew Classic 18x10. The CRRC 26R produces a quoted 3.1hp so check your hp out before you go up to this size but i have to say the performance was great and the noise much reduced........then i crashed it.......but it was not the props fault.


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RE: CMP 120 Zero ARF Build thread - 9/6/2011 4:31 PM   
L16pilot


 

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Status: offline 		Zero #2 flew for the first time on Sunday, 4 September with "Tofly" on the sticks. Winds were 5-10 and a bit gusty with a quartering crosswind. I chose an APC 17x6 prop and the static RPM peaked at 8910. Take off was smooth adn the DLE-20 provides plenty of power....but I may try a 17x8 just to get the RPMs down a bit. Flaps generated considerable pitch up...so I may mix in some down elevator to counter the effects. Now for the bad....the approach was smooth, but in retrospect, probably too slow and it dropped a wing at about 1' height and cartwheeled. Now for the good...no structural damage. One of the Robart trunions oblonged and two cowl mounts are cracked....that's it. Called and ordered a pair of trunions from Robart this morning, so can't wait to get it fixed and back in the air. Overall, flight wise....very, very nice and in my opinion, the DLE 20 with this airframe is a great combination.

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RE: CMP 120 Zero ARF Build thread - 9/6/2011 10:05 PM   
RBean


 

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Congrads on the test flight. Sorry about the mishaps on landing. Glad damage was minor. I added scale split flaps to mine also. With the flaps down it slows real quick with the power off (which I guess you know now). I usually carry just a little power all the way to the ground and land on the mains. It gets too slow for me to try to three point with flaps, unless the air is dead calm. Regarding engines, I have a McCoughal 25cc conversion, because that is what I had and I needed the weight forward anyway. It turns a Master Airscrew 16-8 three blade 7,900-8,000 rpm. Flys scale, not over powered. By comparison, I have a DLE 20 in an H-9 Hellcat. It turns the same 3 blade Master Airscrew 16-8 prop 8,450 rpm. Go to a bigger prop and slow down the engine. You really don't want it going much over 9,000 rpm in the air, or so I've heard. Here is mine. Over a hundred flights on her.

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RE: CMP 120 Zero ARF Build thread - 9/6/2011 10:11 PM   
L16pilot


 

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Status: offline 		Rbean - Thanks. I agree about keeping the RPMS lower and will be going to a larger prop. I only had a small amount of time on hte Zero while in the air...first flight is to trim it....get a feel...then land and check everything over, but yeah, it appeared to slow really quick with the flaps. Once fixed and I get some more slilghts on it...I'll report more.

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RE: CMP 120 Zero ARF Build thread - 9/7/2011 12:15 AM   
misha034



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Status: offline 		@L16pilot, congratulations on your maiden. Hope mine maiden will be soon.
where did you set up CG?

@rbean, can you tell me your CG

As for all others, I have decided wich prop to use. As a matter of fact wich two props.
Today I have measured one more and here are results:

Graupner sonic 18 - 6,- 9000 revs and 15.5 lb of thrust.

So I will be using first two from table


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RE: CMP 120 Zero ARF Build thread - 9/7/2011 2:44 AM   
L16pilot


 

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Status: offline 		Hi Misha - I balanced at 135mm...going back over old posts, that seemed to be a good measurement.

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RE: CMP 120 Zero ARF Build thread - 9/7/2011 5:13 PM   
tomandjan@live.co.uk


 

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Status: offline 		wingspan offered me big discount if i try them and review them for him ive also spoken to lado they recomend there r333 which is also rated to 60-120size! but looking at ther gallery there used on bigger planes than that like the ems stuff which is ruffly the size were talking . so why not the wingspan models i may give them ago and hope? one qestion though what deg's do i use on this zero have a look at the pic i added do i need 85deg or95degs which way is it meseared?

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RE: CMP 120 Zero ARF Build thread - 9/8/2011 3:18 AM   
RBean


 

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Status: offline 		Misha034,

The cg was at 135mm for the maiden. At that cg my plane was tail heavy. Ran out of down trim and flew at reduced power, but was able to land. Moved cg forward to 120mm and that works for me. Still have about about 5mm down deflection of elevator at trailing edge when trimmed, but flys good. As RC warbirds go, this Zero is about the best flying I have seen. Stalls, dirty or clean are fairly gentile and straight with little wing drop, landing speed is fairly slow, the flaps keep it from floating.

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RE: CMP 120 Zero ARF Build thread - 9/8/2011 7:15 AM   
misha034



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quote:

ORIGINAL: L16pilot
I balanced at 135mm...going back over old posts, that seemed to be a good measurement.

ORIGINAL: RBean
The cg was at 135mm for the maiden. At that cg my plane was tail heavy. Ran out of down trim and flew at reduced power, but was able to land. Moved cg forward to 120mm and that works for me.


That is my problem for now. I do not want to loose plane because of wrong CG.
In user manual, recommendation is 140 mm, and you guys are in from 120 to 140 (related to old posts).
Maybe I will go with 130 (some middle point) and start from there.

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RE: CMP 120 Zero ARF Build thread - 9/8/2011 2:46 PM   
frets24


 

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Status: offline 		I have never lost a plane due to a nose heavy condition/forward CG. As the old saying goes; " a nose heavy plane flies poorly, but a tail heavy plane flies once..." Better to have the CG a bit too far forward and remove some weight over progressive flights than to chance a tail heavy condition and a loss of your masterpiece.

By the way Misha, Your plane looks great!

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RE: CMP 120 Zero ARF Build thread - 9/8/2011 3:33 PM   
misha034



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Status: offline 		thank you frets24.

Well my dilemma get's bigger every minute. if you can see picture cg1, you can see original
CMP manual with balancing point at 140-145mm from cord. people are flying this plane from 120 to 140 mm.
My CG at the moment is 135 without lead under the cowl. I have used two different calculators
and results are 141-142 mm.

What should I do?
If I have to make it some 120 mm then it will have about 350 g (0.8 pound) of lead in the nose of plane.

have made balancing with empty tank, model upside down, gear retracted.

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RE: CMP 120 Zero ARF Build thread - 9/9/2011 2:45 AM   
RBean


 

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Status: offline 		Misha034,

I mounted both batteries and the ignition modual on platforms inside the cowling, as far forward as possible and added a heavy hub. Total weight 15 lbs 15 oz. It was flyable at cg of 135mm but touchy. Could have adjusted controls for more down trim and flown it that way with more negative expo. I just don't like them that touchy in pitch. At 120mm cg it flys good for me and has plenty of elevator authority to three point at slow speed, but does not snap out of tight turns etc. I completely rebuilt gear mounts and angled forward a little, but not noticable. I fly off a grass field and no tendency to nose over. A cg of 130mm should work for the maiden then adjust later to suit yourself. It will fly at 130mm.

DO NOT ATTEMPT TO FLY AT 140MM OR FURTHER BACK ON MAIDEN. Please. I'd hate to see you loose the plane.

Mine was balanced upside down, gear up, gas tank empty.

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RE: CMP 120 Zero ARF Build thread - 9/9/2011 4:20 AM   
frets24


 

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Status: offline 		IMHO, use the average of the CG location that people who are already flying this model have found to be ideal. Forget about the plans, CG calculators and any other voodoo....go with what has been found to work in real application and adjust from there. That's my plan anyway. Here is why;

I have used that same CG calculator on several projects with some nearly disasterous results. It doesn't seem to work very well for me on a wing such as on a warbird. It has always given me a seriously tail heavy recomendation when the wing has a double taper...like on the Zero or messerschmitt or P-51...where the trailing edge tapers forward and the leading edge tapers back. On slab wings, such as on a trainer, a Cessna 182, or a Corsair, where there is very little taper, it seems to be perfect and almost exactly what the plans recommend.

Just from curiosity, I ran the numbers on a friend's pattern plane that has a swept wing shape just like the outline picture on the CG calculator and it put the CG just 2mm behind where he has his set up at.

I also ran the numbers on my recent KI-61 build. This wing has a serious forward taper on the trailing edge(132mm/5.25") and very little on the leading edge(40mm/1.5"). The CG calculator had the CG 12mm behind the plan's CG. My experience with Chinese ARFs has taught me that the Chinese usually have the recommended CG a bit to far back and wind up tail heavy, so I set my CG 7mm ahead of the plan's location. After 3 flights the CG is now at 15mm ahead of the plan CG. If I had used the Calculator's CG I'm pretty sure I would have lost the plane on maiden as It had the CG 27mm/1.25" behind where it now flies well. Even with a 5 cell sub-c battery pack and a standard servo mounted under the cowl it still took 1.2lbs/544g of lead to get it there. What ever it takes!! Better a bit more weight and happy flying than tail heavy and a box of balsa and fiberglass shreads.

Ponavljam. Uporabite CG lokacija, ki so ljudje, ki plujejo pod ta model ugotovljeno, da je idealen. Pozabite na načrtih, CG kalkulatorji, in katerikoli drugi čarobno. iti s tem, kar je bilo ugotovljeno, da delo v realnem uporabi in prilagodi od tam. To je tisto, kar bom storil z mojo.

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RE: CMP 120 Zero ARF Build thread - 9/9/2011 6:48 AM   
misha034



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From: KragujevacSerbia, YUGOSLAVIA
Status: offline 		Thanks for your time and advises. I will do so. The battery is lithium and as far front as I can mount it safely,
engine is very heavy, but ....
I will put some lead, and if needed, take out little by little.

As one of our fellow modeler said, nose heavy plane flies poorly, but with tail heavy only once.


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RE: CMP 120 Zero ARF Build thread - 9/28/2011 10:44 PM   
misha034



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From: KragujevacSerbia, YUGOSLAVIA
Status: offline 		Well, I' am happy to announce that my Zero has learned to fly.

Maiden flight was yesterday. Weather was beautiful for flying, and only two models on field.
After days and days of checking and again checking, we went on the field, did range test,
tune up a little bit low and high needle, and my friend and test pilot Coka (Predrag Pantic)
took plane to sky. Very short run before take of, and in flight it was sharp on turns, but
flies beautiful with 50-60% throttle. Prop was 18/6 and it was not good in air as at ground level.
For second flight I have change it for 18/8 and it was much better. Motor has 7500-7600 revs (1500 less
than with 18/6) but flies phenomenal. Enough power for take of and for warbird style flying.
After second take off, i was able to fly my biggest and most challenging plane that I had.
Feeling was beautiful.

As we were too much excited, none of us took photos of plane in the air, so you can see it on the ground.
Hope I will post video of maiden tomorrow, and all setup changes that I have made so you can have
some valuable starting data for your maiden flights.

Best regards to all

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RE: CMP 120 Zero ARF Build thread - 9/29/2011 2:47 AM   
RBean


 

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Status: offline 		Congradulations on the sucessful maiden. Glad it went well. What cg did you finally use?

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RE: CMP 120 Zero ARF Build thread - 9/29/2011 3:10 AM   
Whistling Death



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Status: offline 		These are the retracts I got to use in my Zero.E-Flite 85 degree electric retracts. They will support up to a 15lbs airplane. I haven't built the plane yet BTW.



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RE: CMP 120 Zero ARF Build thread - 9/29/2011 6:24 AM   
frets24


 

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ORIGINAL: misha034

Well, I' am happy to announce that my Zero has learned to fly.



Very happy for you!!

Now I'm just waiting for the video!!


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