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CG question on the HK Ugly Stik

Old 02-07-2015, 08:01 AM
  #1  
abborgogna
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Default CG question on the HK Ugly Stik

Recently I purchased the new foam Hobby King electric Ugly Stik. Loved the plane even talked about here on the forum. It's the one that come with the very realistic faux engine up front. Anyway to make a long story short a few weeks after getting it I had a mid-air with another plane. The wing was ripped off and the fuselage lawn-darted into the dirt. The wings and tail feather survived quite well as did the motor/electronics. I have since framed up a new fuselage from balsa and am almost ready to fly. For the life of me I can't find information as to where the CG should be located. If anybody out there has one of these could you please put a 3S 2200 battery in it and check where the CG is. I can always do the math and come up with a close enough approximation to do the trim work, but it's always easier to use a little empirical data.

Thanks in Advance
Andy
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Old 02-07-2015, 10:40 AM
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Panther
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Hmmm sounds too technical for me. I always use the wing main spar as my CG point initially. (or 1/3 of the chord back from the leading edge)
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Old 02-07-2015, 11:11 AM
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Siberianhusky
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Get it in the ball park then do a dive test.
Trim for level flight, put it into a dive, if it pulls out you are nose heavy if the dive steepens you are tail heavy.
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Old 02-07-2015, 12:57 PM
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Henry Sistrunk
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Default Hobby King Stick

I have two of them. The manual states 65mm back from the leading edge of the wing.
Henry
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Old 02-07-2015, 01:47 PM
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NJSwede
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Since that plane has standard, straight non-swept wings it's easy. Set the CG to 1/4 of the distance from the leading edge about 1" from the fuse and fly it. Put it into a 45 degree upline and flip over inverted. A nose heavy plane will pitch down quickly, a tail heavy plane will stay on course or even pitch up. A perfectly balanced plane should pitch down ever so slightly and require a light up-pressure on the elevator to stay on the upline.

Published CG number are dead wrong more often than not, even from the premium vendors, so I always prefer this method.
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Old 02-14-2015, 03:42 AM
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abborgogna
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I flew the rebuilt Ugly Stik and it flies great. The fuselage is has the exact dimensions as original foam unit and I set the CG to around 30% everything worked great. I still love this plane, it brings back great memories of when I first started flying R/C and the faux motor is beautiful,.
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Old 02-14-2015, 04:04 AM
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BroncoSquid
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Originally Posted by Siberianhusky View Post
Get it in the ball park then do a dive test.
Trim for level flight, put it into a dive, if it pulls out you are nose heavy if the dive steepens you are tail heavy.
Why dose this sound backwards to me?
I am NOT saying it is wrong but could someone direct me to a web page that explains this if it is correct. I spend alot of time on Wiki trying to understand the fundamentals of flight.
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Old 02-14-2015, 04:11 AM
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fhhuber
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http://www.wtp.net/DBEST/trimchrt.html

Note that the trim chart makes the assumption of a plane intended for precision aerobatics with minimal to no input needed to hold level inverted when trimmed for level upright.

The dive test method is going to fail for any flat bottom wing trainer. As these gain speed they will pull out of the dive with no input if set up correctly.
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Old 02-14-2015, 06:21 AM
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fhhuber thank you for the link, I have it saved now.

After furthur research, I feel that S-huskys statement is incorrect but I understand the confusion.
"Once established in the dive, return elevator to neutral and see what the plane does. If it pulls out of the dive sharply then the CG is too far forward, if the dive angle increases then the CG is too far back. Ideally you want the plane to gradually and naturally pull out of the dive."

With the CoG too far forward= tail heavy
With the CoG too fat Aft= Nose heavy

I can easily see myself getting that backwards while trying to explain it.

http://www.rc-airplane-world.com/tri...-airplane.html
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Old 02-14-2015, 03:35 PM
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fhhuber
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Originally Posted by BroncoSquid View Post
fhhuber thank you for the link, I have it saved now.

After furthur research, I feel that S-huskys statement is incorrect but I understand the confusion.
"Once established in the dive, return elevator to neutral and see what the plane does. If it pulls out of the dive sharply then the CG is too far forward, if the dive angle increases then the CG is too far back. Ideally you want the plane to gradually and naturally pull out of the dive."

With the CoG too far forward= tail heavy
With the CoG too fat Aft= Nose heavy

I can easily see myself getting that backwards while trying to explain it.

http://www.rc-airplane-world.com/tri...-airplane.html
Too far forward = nose heavy.
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Old 02-14-2015, 04:12 PM
  #11  
abborgogna
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I was always taught, and have followed, CG forward "nose heavy", CG aft "tail heavy". I cannot get my mind around the opposite, that doesn't mean I'm right it just means that's how I have viewed it for the last 40 years. By the way when the CG is wrong on one of my planes I shift or add weight to correct per my view of CG and it does seem to work.
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Old 02-14-2015, 04:36 PM
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BroncoSquid
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Again you are right, Why am I so Bass Ackwards on this?
I was reading CG and thinking Center of balance.

I guess I can't wrap my head around a tail heavy plane wanting to climb and stall in level flight, but in a dive, it will dive steeper?
Or am I wrong again
I need to start eating more fish.
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Old 02-14-2015, 05:32 PM
  #13  
fhhuber
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Tail heavy you add down trim to keep the tail up. As speed increases the effect of the trim increases thus lifting the tail, forcing the nose down.

****

Note that many 3D guys balance the planes very tailheavy as that aids the stability in hovering maneuvers. As they slow for landing they have to push the stick forward to keep the nose down.
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Old 02-14-2015, 11:06 PM
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How well did the fake nitro motor hold up in the crash?
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Old 02-15-2015, 05:46 AM
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abborgogna
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Actually the fake motor and the entire power system came through the "lawn dart" maneuver untouched except the fake carburetor flew off and was lost. I searched my old stuff and found a Perry Carb from decades ago that dropped right in. If anything it looks better now than before. You might also notice how close the paint I used matched the foam parts I saved from the crash. When the Stik when through the other plane the wings were ripped off, the rest went in straight in on the nose in soft dirt. The wing and tail feather were undamaged so all I had to do was scratch build a fuselage. I used what was left of original foam fuselage for templates, including ripping out the of the foam the mount for the tail feathers. It all worked out quite well, and for a weeks work (couple hours a day) I save $133 by not buying a new plane. I have quite a stash of balsa wood from my C/L and F/F days.
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