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correct CG for mini telemaster

Old 02-07-2011, 01:24 AM
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2manyhobbies
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Default correct CG for mini telemaster

Instructions say 65-70 mm, the wing is 178mm wide, 30% of 178 is 53.4mm from the leading edge. Anyone have any experience with the mini Telemaster? Where should I start?
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Old 02-07-2011, 01:29 AM
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On the spar. Where is that in MM?
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Old 02-07-2011, 01:38 AM
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55mm
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Old 02-07-2011, 01:41 AM
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I had one and loved it... http://www.wattflyer.com/forums/showthread.php?t=48361

Because the model is originally nitro/gas plane you will need a big ol lipo to CG it, but I found from LE of wing measure back 1 3/4 inches and she will fly just right. This is 25% not 30% because I found the manual made her to nose heavy at 30. Hope this helps.
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Old 02-07-2011, 01:51 AM
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Thank you! That will help me. I will have to add weight to the nose, hopefully not a lot. It is balancing behind the recommended CG in the manual 65-70mm now. Thanks again!
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Old 02-07-2011, 07:58 AM
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Why not go with the manual?.. Do you have any reason to think that the manual is wrong?

The 25-30% 'rule' is a massively over-simplified generalisation that is very often misleading, sometimes dangerous.
If you want to check what is in the manual then at least use a valid CG calculation method. The online calculators that are available these days make it very easy: http://adamone.rchomepage.com/cg_calc.htm

If I were to guess I'd say that the calculator will confirm what the instructions already tell you (65-70% with about 10% static margin). The Telemaster has a large tail and long tail moment arm both of which tend to make for a rearward CG location. Certainly those advising setting CG at 25% have it badly wrong.. this will make a very nose heavy plane. While it will still fly it will be too stable and quite unpleasant. Also you increase weight by adding unnecessary ballast in the nose.

Steve
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Old 02-07-2011, 01:09 PM
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I have a Senior Telemaster which has a "lifting stabilizer". The airfoil on the stab moves the CG backwards to a point where it is almost halfway back on the wing. Doesn't look right, but is.

...The Bum
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Old 02-07-2011, 02:23 PM
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JetPlaneFlyer
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Originally Posted by Saddlebum View Post
I have a Senior Telemaster which has a "lifting stabilizer". The airfoil on the stab moves the CG backwards to a point where it is almost halfway back on the wing. Doesn't look right, but is.

...The Bum
The airfoil on the stab actually makes almost no difference to the CG location. The main driver for how back the CG can go is 'tail volume' which is a function of tail area and tail moment arm. The tail on the telemaster will 'lift' if the model ballanced as the designer intended, the airfoil used is a result of the tail lifting, not the cause of it. Ignore the plan and put the CG anywhere near 25% and the stab will produce downforce, which on the telemaster would be very inefficient.

Anyway.. whatever the cause the telemaster will have an optimal CG location that is well behind where some people might expect. This is confirmed by the instructions, which I've little doubt are correct.
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Old 02-08-2011, 03:43 AM
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Steve, thanks for the info! I was doubting the instructions because it was not even close to balancing at the recommended CG. I plugged in the numbers to the calculator link you gave me, and it puts the CG real close to the instructions. A previous poster said his flew well at 25%. I will balance it a little closer to the instructions and see how it reacts. I just don't want to have to add to much weight to the nose!

Tim
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Old 02-08-2011, 07:22 AM
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The further forward you try to balance the more nose weight you will have to add. Just balance as per the manual and you will save lots of unnecessary and counter productive nose weight. Trying to balance at 25% chord as someone said previously will need MUCH more noseweight than the recommended position.

Steve
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Old 02-09-2011, 04:03 AM
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I have it balanced as the manual states. had to add 1oz of weight. I am using a lighter motor than specified, so that does not help. When all the snow finally melts from our runway, I will maiden her! Thanks again for the help.
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Old 02-19-2011, 11:20 PM
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Hi 2Many;

I have a flying buddy with a Mini-Tele that flys GREAT! His is balanced 65mm back from the leading edge.

...The Bum
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Old 02-20-2011, 01:09 AM
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Bum, Thanks a lot for the info. I feel more confident for the maiden now!! 14 degress with winter storm warning. Can't wait for spring!!

Tim
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