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Old Aug 27, 2012, 03:52 AM
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Nutball CG

Wingman: you're quite right to be concerned about the Nutball's CG. This design seems extra sensitive to CG, and if it's tail heavy you have a sort of backflipping machine on your hands.

When I started scratch building foamies a year ago the Nutball was my first, and I didn't know what I was doing. I destroyed one right off the bat, figuring it was pilot error (which it may well have been, but now I know that it was wildly tail heavy). I got another one flying really well by moving the battery forward, but by then it was pretty well trashed and came apart after a hard bit of aerobatics. You do NOT want to get the CG wrong on this little thing.

25% of root chord works great. On my 20 inch Nutball (see above, the Irish one) the CG is 4 inches aft of the leading edge of the circular wing. Note that I extended the motor beyond the circle about two inches. It's just easier that way.
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Old Aug 27, 2012, 07:59 AM
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a 25% cog for all circles is good... dont forget the down thrust and slight right thrust.. and for beginers low rates and low power make the first flight easy...
position your servos etc all forward if you have problems with a rearward cog..extending the nose or adding an under carriage up front will also help
going larger makes it even more docile... and easier in the wind. 26-32 is a good big size
going bigger and adding a KF step adds even more stability
However you like yours it always makes for a fun model
..
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Old Aug 27, 2012, 08:30 AM
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Quote:
Originally Posted by Wingman26 View Post
So does this thing have a recommended CG or is it exempt from the laws of nature that govern everything else? Why isn't this in the original post AND on the plans?

I read the first 100 posts, and the only reference to CG was in post 37 which read: "and the CG well back.", well back of WHAT? Its not on the plans either...

I'm sorry, I'm not going to read all 8,262 posts, as I said, I did read the first 100.
Here is a quote from Goldguy from the first page "Balance at 25% of the root cord to start, them adjust rear ward to suite your flying style."
20"=5" cg
17"=4.25"cg
24"=6"cg
Take some time and read through the thread. You will learn a lot from what people have already tried that did and didn't work for them. I have read the whole thread. Took me about a month reading lil bits here and there when I found time.
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Old Aug 27, 2012, 10:32 AM
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or...................there is a 'search this thread' function.

The problem with some designs that get posted is that the R &D is done as the thread progresses, so changes are constant and that often includes the CG location.

I post only after it's a proven success, so post #1 is always all you really need to know for success.
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Old Aug 27, 2012, 10:40 AM
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Quote:
Originally Posted by phil_g View Post
A manned Nutball!
Thanks for that Phil..... funny.
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Old Aug 27, 2012, 10:53 AM
flyin' fool
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Like Dave sez....................DON'T FORGET THE MOTOR THRUST ANGLES.

Without them the CG will seems sensitive. I'm at between 25 and 33% for outdoor depending on wind conditions and waaaaaaaay back around 40% for indoor.

Then there's my sloper NB with no motor angles. I compensated with nose heavy for the plus 30 knot winds. Worked great, flew on rails.
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Old Aug 27, 2012, 11:31 AM
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I did miss the balance at 25% of the root chord, so I apologize for that. It is fairly buried in the text, so its easy to miss, and when I searched for the term CG or Center of Gravity, it doesn't come up.

Personal comments about being lazy or lame are out of line.
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Old Aug 27, 2012, 11:55 AM
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I agree, some of you guys were just a little harsh, especially when you don't know who your talking too. I happen to know that Wingman26 is a 6' 6" tall 250 lb boxer with a deadly right.

Better apologize................
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Old Aug 27, 2012, 11:58 AM
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Quote:
Originally Posted by Wingman26 View Post
I did miss the balance at 25% of the root chord, so I apologize for that. It is fairly buried in the text, so its easy to miss, and when I searched for the term CG or Center of Gravity, it doesn't come up.

Personal comments about being lazy or lame are out of line.
I too have searched cg, cog and center of gravity. My search of cog returned this. http://www.rcgroups.com/forums/searc...6602&query=cog
No worries, some people take things a little too far. BUT, you said you READ about 100 pages and did a search. I think it may have been more of a SCAN than a READ if you think it's jumbled in the text. I am guilty of scanning a lot of things myself. But, when trying to comprehend what is being said I slow down and really read.
Regardless of any previous comments we would all like to see you build one and join the unofficial nutball club so get to work. If you have any questions just ask but if you don't search first someone undoubtedly is going to point it out. It's the same on every forum.
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Old Aug 27, 2012, 12:19 PM
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I should clarify that I searched the first page, for me that includes the first 100 posts (100 posts per page). I searched for the terms I most expected to see, CG or Center of Gravity, the term I forgot to search for was "balance" which would have turned up the sentence in the first post, and it is correct, I was scanning, and mostly looking for CG or Center of Gravity.

I'm definitely building one, I've got a motor and speed control coming from Heads Up RC, I've got servos running out my ears.

As a former Chief Pilot for the Sheriffs Dept Aviation Division, and now a volunteer helping teach aviation at the local Vo Tech, I thought this might be a good one for a demo for the students.
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Old Aug 27, 2012, 01:35 PM
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Yes, this would be a great plane for demonstration. It can haul butt and it can fly really slow and even hover right in front of you. You can drag the tail across the ground or do flips and rolls with it. I even think that with tame control expos that this could be used even as a trainer plane. I wouldn't recommend using dollar tree foamboard for a trainer though. A few nose dives and a lot of hot glue and the leading edge of the wing won't look so pretty anymore.
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Old Aug 27, 2012, 02:29 PM
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I've seen at least five locals teach THEMSELVES to fly with the NB.
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Old Aug 27, 2012, 02:45 PM
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Quote:
Originally Posted by Wingman26 View Post
I did miss the balance at 25% of the root chord, so I apologize for that. It is fairly buried in the text, so its easy to miss, and when I searched for the term CG or Center of Gravity, it doesn't come up.

Personal comments about being lazy or lame are out of line.
You are right, I am sorry for that. Sounds like I could use Wingman here, Shooting yesterday, gang activity, and the house two lots away robbed. I have resorted to keeping a weapon near the door.
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Old Aug 27, 2012, 04:32 PM
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This will be the 4th year helping them learn about flight in general, and teaching them to fly RC, we set up a Real Flight on one of their computers when we first started, and try to make it out to the field at least once during the year. I was thinking I might be able to build one of these small enough to fly inside one of the hangers at the aviation campus where I volunteer. I help out High School Seniors who are starting on their road to be A&P certified aircraft mechanics, I'm not qualified to help them on the mechanics part, but I can help them understand better how airplanes work.
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Old Aug 27, 2012, 07:19 PM
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Something that looks and flies more like a real airplane and has ailerons might be better to show them how real airplanes work.

The first msg covers quite a bit of ground. Might be useful though to have a .pdf manual with step by step building directions, hints, list of materials, lessons learned; etc ...or perhaps in the first msg, add links to notable messages.

The video (on how to build it) is good...don't see a link to it though:
http://flitetest.com/articles/nutball-scratch-build/
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