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CG - What am I Doing Wrong?

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CG - What am I Doing Wrong?

Old 08-03-2022, 11:02 AM
  #26  
GorillaToast
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Originally Posted by speedracerntrixie View Post
To really get it fine tuned you also need to know where your wing and stab incidences are as they will influence CG position too.
Wing = 0*
Stab = +1*

Quote from edmond22 on the Team daddyHobby forum

"Cons:
- Some inaccuracies in Manual (Rudder Pull Pull installation)
- Elevator incidence off neutral (Seems to affect a lot of planes this size and above, search for EFC yak54 etc)"
Old 08-03-2022, 01:00 PM
  #27  
speedracerntrixie
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The big question now is how do you intend to fly it? Most 3D guys tend to like 0-0 and run the CG aft enough so that itís neutral both right side up and upside down. That setup however is absolutely crap for IMAC type flying.

My typical starting point is zero on the engine up or down but 2 degrees right. Positive .75 on the wing and zero on the stab. 30% on CG.

During testing, note what elevator trim is required for level 1/2 throttle flight. If it takes up trim, check CG for nose heavy. Once you are happy with CG and if it still has up trim, add more positive to the wing. The end result is you want the stab at zero with no trim, this will give you close to straight knife edge and up lines as possible. In those attitudes the wing is unloaded and any stab/elevator trim will be pronounced.
Old 08-03-2022, 02:27 PM
  #28  
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Unfortunately, the wing is not adjustable w/o some major reworking. It's an extremely tight fit into the fuse sides just to get ti to the bolt plates. I had to do some elongating of hole for the stab anti rotation pin on the starbooard half just to get it to +1 and match the port side.

I'm not into 3D, so I want it to be nice and stable. I actually prefer Pattern, but my 2M plane flew thru a hole in the woods and onto a busy street where it became splinters! I found the motor buried in the dirt on the shoulder today.

Think I can fix it?


This plane is just something I picked up dirt cheap so that I can have something to fly for the rest of the year. I'll get a new pattern plane when I can save up for one.
Old 08-03-2022, 02:33 PM
  #29  
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With the cost of pattern planes I just went and designed my own. Iíve sold 6 so far.
Old 08-03-2022, 04:45 PM
  #30  
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Ah.... I was waiting for the ad. lol

The most cost effective thing for me will probably be to rebuild the "Lightning" that I crashed when I stupidly forgot to check the receiver batteries before the 2nd flight. As I found out with the Yak build, the rudder servo was draining them because I had the pull-pull wires too tight.

Of course, if you'd like to send me a Divergent for crash testing purposes I'd be happy to oblige.
Old 08-03-2022, 06:04 PM
  #31  
Joseph Frost
 
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Originally Posted by GorillaToast View Post
Wing = 0*
Stab = +1*

Quote from edmond22 on the Team daddyHobby forum

"Cons:
- Some inaccuracies in Manual (Rudder Pull Pull installation)
- Elevator incidence off neutral (Seems to affect a lot of planes this size and above, search for EFC yak54 etc)"
Putting too much theory into it is only asking for a trouble, KIS is the key to a success!
Old 08-06-2022, 03:05 PM
  #32  
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Ok!

I maidened the rebuilt Yak this morning. CG was workable, but I had other issues. First was the tendency for it to roll right constantly. Even adding 10 clicks of L Aileron didn't help. I had to keep inputting L Ail to fly level. I'll recheck the wing / stab incidences and adjust if necessary before next flight. I'll also check the lateral balance.

Second issue was the tendency to continue rising at cruise throttle. Could be related to the 1* of stab incidence or I need to add 1* of down thrust. I'll try adjusting the stabs first, although they don't have adjusters. I'll have to elongate the anti-rotation pin holes to do that.

Thirdly was a motor case temp issue. In ground testing, I had to limit the throttle to 75% to keep the case temp below the recommend 65*C max. Ok, doable, but on a 20.5 x 12W APC prop I wasn't able to get much vertical. I switched to a 20 x 15 (which is the Himax 6330 Pro recommended prop), let the throttle go to 90% and was able to do a half reverse cuban at full throttle, but I'm guessing the case temp had to be over the max at that point. I landed and taxied over to my station and immediately checked the temp with an infrared gun and it read 47*C. Knowing how quickly the temp returns to 47* from 60* in bench testing, I'm guessing I was near the max.

Both of those props show overlimits on wattage and temp in propCalc, but a 20 x 10 does not. Just wondering if it would have enough thrust for precision aerobatics. I'll have to order one and see. I know that propCalc gives all kinds of thrust data, but I haven't studied about that enough to have it mean anything practical to me. Like how do I know what static thrust, stall thrust, specific thrust numbers are necessary for my Yak to do a decent vertical for a hammerhead?

Anyway, any opinions welcomed.
Thanks

Edited for: spelling / puncuation

Last edited by GorillaToast; 08-06-2022 at 03:08 PM.
Old 08-06-2022, 08:59 PM
  #33  
speedracerntrixie
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I found with my 6330 when I ran the CC 80HV ESC as plug and play it had horrible performance. It wasn’t until someone programmed the ESC with the correct timing that it made good power. Unfortunately that was when they first came out and I had very little knowledge about electrics. Since that airplane I have used Dualsky motors. I think with the large Round cowl you would be happier with a 22x10 Falcon CF prop. Anything over 14” an APC is just too heavy. Also what is your airplane weight? Anything over 12 lbs May have you considering 12S.
Old 08-07-2022, 01:40 AM
  #34  
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Originally Posted by GorillaToast View Post
Ok!

I maidened the rebuilt Yak this morning. CG was workable, but I had other issues. First was the tendency for it to roll right constantly. Even adding 10 clicks of L Aileron didn't help. I had to keep inputting L Ail to fly level. I'll recheck the wing / stab incidences and adjust if necessary before next flight. I'll also check the lateral balance.

Second issue was the tendency to continue rising at cruise throttle. Could be related to the 1* of stab incidence or I need to add 1* of down thrust. I'll try adjusting the stabs first, although they don't have adjusters. I'll have to elongate the anti-rotation pin holes to do that.

Thirdly was a motor case temp issue. In ground testing, I had to limit the throttle to 75% to keep the case temp below the recommend 65*C max. Ok, doable, but on a 20.5 x 12W APC prop I wasn't able to get much vertical. I switched to a 20 x 15 (which is the Himax 6330 Pro recommended prop), let the throttle go to 90% and was able to do a half reverse cuban at full throttle, but I'm guessing the case temp had to be over the max at that point. I landed and taxied over to my station and immediately checked the temp with an infrared gun and it read 47*C. Knowing how quickly the temp returns to 47* from 60* in bench testing, I'm guessing I was near the max.

Both of those props show overlimits on wattage and temp in propCalc, but a 20 x 10 does not. Just wondering if it would have enough thrust for precision aerobatics. I'll have to order one and see. I know that propCalc gives all kinds of thrust data, but I haven't studied about that enough to have it mean anything practical to me. Like how do I know what static thrust, stall thrust, specific thrust numbers are necessary for my Yak to do a decent vertical for a hammerhead?

Anyway, any opinions welcomed.
Thanks

Edited for: spelling / puncuation
Wrong set up, if you are running it on only 8S, too large prop, loading the motor especially after increasing the pitch!
You must go up to 10S, use also larger speedy. I run similar size model, EXTRA, with Extreme 5020 motor, that had avery bad repute, because people were simply overloading it with large props!
After reducing the prop size down to mod.


Extra on 10S/160ESC/19&3/8x8

19&3/8x8, it runs immaculate on 10S off 160A/ D/Lux speedy.
Old 08-07-2022, 05:13 AM
  #35  
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The Himax 6330 is a 10S-12S motor. I didn’t see anywhere where he said he was running 8S.
Old 08-07-2022, 05:48 AM
  #36  
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I'm running the Himax on 10s 5000mah 50c. Controller is a Jeti Spin 99 Opto. Manual set-up. Timing is 24.

I'm thinking of shimming the motor out 1/2". Might give me better cooling plus I could eliminate some of the 4oz of added lead to balance.
Old 08-07-2022, 06:18 PM
  #37  
Joseph Frost
 
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My assumption was based on post#7, - Q - First of all, the airplane weighs 11# with 2# of 8s batteries.
Old 08-07-2022, 07:25 PM
  #38  
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That was the blue Rearwin Speedster.
Old 08-07-2022, 09:25 PM
  #39  
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Yes, Joseph. Sorry for the confusion. The thread was originally about an 11# plane that I was planning to use 8s batteries in. But, when I did the calculations on wing loading and found it would be very unfriendly to fly with that wing, I switched over to talking about the Yak 54 I was working on.

Nice Extra, btw. Is that your everyday flying field? Cool!
Old 08-07-2022, 09:50 PM
  #40  
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Well, surely it was confusing, I thought the topic you started with was "Yak" and you never mentioned 10S set up in any posts.

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