GliderIreland - Ireland RC Forum - Flying Model forum in Ireland
Gliders => Slope Soaring => Topic started by: johnfireball on October 03, 2011, 00:22:53 AM
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(http://www.gliderireland.net/forum/images/uploads/johnfireball/canary1.JPG)
Hi all,
Another china glider, a simple 2 channel control 1200mm span, weight with ballast 340grms. It came without instructions so wondering where to setup CG. At present I have added noseweight to put it 1/4" forward of wingspar at root. Hoping it will be a nice relaxing model for those nice balmy days.
John.
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Hello
I think 33% is good for balance
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I believed that the theoretical CG point is 33% of the Average Mean Chord. Given that the wing has a slight front to back taper at the outer regions I’d have said that ¼ inch behind the spar was the best spot. If she’s too nose heavy then you’ll need lots of up/down movement of the elevator to change the pitch attitude of the plane. If she’s tail heavy, the model will react to the slightest elevator movement.
If I were you John, I’d try the CoG where Erwan suggests and see how she flys. It’s always best to error on the side of caution and keep her a bit nose heavy to start, then move the CG back slowly until she flys the way you want her to.
The way to really check is to fly the model up to a good height. Put her into a 45 degree dive, take your hands off the sticks and watch what she does.
Contrary to logic & common sense, if the model pulls up, out of the dive, then she is too nose heavy…..CG needs to go back.
If she increases the steepness of the dive then she’s tail heavy, CG needs to come forward.
If she stays on the same trajectory, the CG is correct.
Alas, with winter approaching I fear you might have to wait some time before you see any Balmy Days. :!:
They tell me that patience is a virtue. So the question is,………just how virtuous are you? :roll:
Keith
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(http://www.gliderireland.net/forum/images/uploads/johnfireball/canary1.JPG)
Hi all,
Another china glider, a simple 2 channel control 1200mm span, weight with ballast 340grms. It came without instructions so wondering where to setup CG. At present I have added noseweight to put it 1/4" forward of wingspar at root. Hoping it will be a nice relaxing model for those nice balmy days.
John.
Nice looking glider...
Where did you get the Glider from ?? R2Hobbies... ?
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Go check the Great planes fling for the CG, models are nearly identical
Ralph
p.s. it is a lovely flyer off a hi statrt bungee
Enjoy
The balance point is
located 2-3/4" [70mm]
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Hi John,
I have a spreadsheet that I have found to work very well for calculating the theoretical C of G. It is based on calculations set out in Model Aircraft Aerodynamics by Martin Simons. You need some measurements of the wing and tail, and their spacing. The output is a graph of C of G against static margin. Typically, the static margin should be between 5% and 15%. 15% should give a docile model that is easy to fly, while 5% will be very lively, ideal for aerobatics.
I could e-mail you the spreadsheet if you think it might be of help.
Best regards,
Fergal
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Hi John,
I have a spreadsheet that I have found to work very well for calculating the theoretical C of G. It is based on calculations set out in Model Aircraft Aerodynamics by Martin Simons. You need some measurements of the wing and tail, and their spacing. The output is a graph of C of G against static margin. Typically, the static margin should be between 5% and 15%. 15% should give a docile model that is easy to fly, while 5% will be very lively, ideal for aerobatics.
I could e-mail you the spreadsheet if you think it might be of help.
Best regards,
Fergal
Got a link ...
Think I could use something like that on some of my gliders..
Sean
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Hi,
Got this from Hobby King. I'm hoping my 7 & 8 year old son & daughter might be interested in flying it (get them off those game machines). Love to see spreadsheet Fergal.
jjd385@gmail.com
John.