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Need CG confirmation on Yak 85"

 
Old 06-04-2006, 12:59 PM
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bart-rennes
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Default Need CG confirmation on Yak 85"

Hello,

I'm from europe and have a problem to understand well the QQ documentation on CG.
So, do you take the CG (7 5/8" = 19,36cm) from the end of the wing or from start of the wing, like in the picture show below (orange or green ?).

thank you.
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Old 06-04-2006, 01:05 PM
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Default RE: Need CG confirmation

Hi There,

Download the new manual at http://www.qqaircraft.com/downloads/...5yakmanual.pdf
Look at page 43.

It's from trainling edge. Basically your green line but from the trailing edge(at Wing Tip). Look at the pic in the manual.

Thank you,
Reza
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Old 06-06-2006, 04:38 AM
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bart-rennes
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Default RE: Need CG confirmation

Found the solution, thank you resa.
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Old 06-06-2006, 04:59 AM
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Default RE: Need CG confirmation

WARNING

The C of G on the 85" is measured at the wing tip not the root its taken from the TE of the aileron forward to the LE of the wing, but at the TIP of the wing.

Mike
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Old 06-06-2006, 09:18 AM
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Default RE: Need CG confirmation

Mike,

Page 43 clearly shows where the CG is measured from. Thank you for your conern.

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Old 06-06-2006, 11:22 AM
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Default RE: Need CG confirmation

Rezagh

Barts pic shows he is measuring from the Root not the tip, I do not think the pic in the manual or the words of explanation are clear and obviously Bart thought the same.

Mike
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Old 06-07-2006, 02:24 AM
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Default RE: Need CG confirmation

I found the CG, but my problem is that it is centered at the back. Very hard to center it correctly, my motor is a ZDZ50 NG, and the motor weight is more heavy than a DA50 !! I set all batteries just behind the motor...
Normally with a DA50, is it well centered by default ?
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Old 06-07-2006, 02:30 AM
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Default RE: Need CG confirmation

Bart

Most guys with a 3lb or under motor have not had a problem with the C of G location, all the batteries are normally on the motor box, you may need to move your batteries rearwards to compensate for your heavier engine.

Mike
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Old 06-07-2006, 02:47 AM
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Default RE: Need CG confirmation

The problem is that it is not enough heavier on the motor !
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Old 06-07-2006, 03:20 AM
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Default RE: Need CG confirmation

Bart

If I understand you correctly, you are saying your battery is not heavy enough to compensate for the weight of the motor, if that is the case I can only suggest you buy two larger capacity batteries, what have you got at the moment?

Mike
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Old 06-07-2006, 09:24 AM
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Default RE: Need CG confirmation

Bart,

It depends on howmuch your motor sticks out. What size stand off are you using? What's the clearance between back of your prop or spinner plate to the cowl? I'm guessing you might have the motor too close to cowl.

If you can email me more detailed info and I will be more than happy to walk you through it. Some pics also would help.

Thank you,
Reza
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Old 06-07-2006, 09:30 AM
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Default RE: Need CG confirmation

Thank you, i will post tomorrow when i will get my new muffler which is a little bit more heavy than the one i have now.
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Old 06-09-2006, 06:51 AM
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Default RE: Need CG confirmation

So i received my new muffle today and test the CG, i put all batteries and all weight i can in the motor box but i need more weight: 0.77 lb at least.
Here a photo of the motor installation with all batteries (not fixed yet).

Thank you for your support.
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Old 06-09-2006, 07:21 AM
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Default RE: Need CG confirmation

are you measureing the CG without the prop, prop bolts and spinner?? they will make a big difference
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Old 06-09-2006, 07:35 AM
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Default RE: Need CG confirmation

i'm measuring the CG with everything (prop, bolts, spinner,...) the picture is for resa to see motor installation.
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Old 06-09-2006, 07:59 AM
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Default RE: Need CG confirmation

Hi Bart,

I had the same problem than you and I use the idea on the picture below and work for me. The picture is from a extreme flight Yak, but I did it in my Yak 85 QQ, no photo yet.

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Old 06-09-2006, 11:06 AM
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Default RE: Need CG confirmation

Bart

make sure your prop driver is approximatly 165mm in front of the engine mounting bulkhead, this will give you the required 37mm clearance between the prop and cowl, I no its a big clearance but it seems its required for prop airflow efficiency.

Mike
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Old 06-09-2006, 11:29 AM
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Default RE: Need CG confirmation

Thank you mike for precision, i just checked and i have exactly (lucky) 165mm as you say. I think i will do 'jdavera' idea but if someone has another idea ?
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Old 06-09-2006, 11:56 AM
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Default RE: Need CG confirmation

Bart

Looks like you need a heavier engine? Ho Ho, the new 86" I understand will have a longer nose to eleviate this problem, as more and more manufactures compete for our buisness they will come out with lighter and lighter and hopefully better engines, good luck with moving the batteries.

Mike
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Old 06-09-2006, 12:29 PM
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Default RE: Need CG confirmation

Yes, the 86 could be a solution but i've just received the plane 2 weeks ago [] and shipping is very extensive to France ! Anyway when solution will be found i'll post here picture.
(What i can't understand is that it is recommended for DA50 and my ZDZ50 is more heavy!!!).
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Old 06-09-2006, 12:42 PM
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Default RE: Need CG confirmation

Bart

I also have only just received mine it was a personnal inport from the US which worked out over ÂŁ100.00 cheaper than buying in the UK, I must admit I would have prefered the new 86" version if only because it has a canister silencer provision, still may just have to get both.

It seems that most people have had a C of G issue getting it in the correct postition with the new lightweight engines is a problem, why yours is like it is can only be the weight behind the C of G, I am assuming that you are measuring the C of G at the wing tip and not at the root.
Sorry to repeat this but: At the WING TIP measure 7 3/8" from the trailing edge of the aileron towards the Leading edge, this will give you the centre of the C of G range.

Hope this helps

Mike
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Old 06-09-2006, 03:55 PM
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Default RE: Need CG confirmation

Hi Bart,

Do me a favor, tell me where your CG would be with the same set up you have with cowl,prop and everything installed. This will give me a better idea, how far you are off. What size and type batteries are you using? or if you can tell me the weight of your batteries(separately) would be great too. We'll get it worked out, just feed me more info.

Thank you,
Reza
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Old 06-14-2006, 11:10 AM
  #23  
bart-rennes
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Default RE: Need CG confirmation

Rezagh, can you confirm the space between prop and cowl has to be 37mm (1.25oz) ? is from the most advanced cowl or the black section cowl ?
Also i convert 7 3/8" into 18,73cm, can someone confirm ?
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Old 06-14-2006, 11:18 AM
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Default RE: Need CG confirmation

Hi Bart,

1.25" to the yellow section most forward part of the cowl would be better, especially for you that have balance problem. Did you solve your balance issue yet?

Thank you,
Reza
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Old 06-14-2006, 11:30 AM
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Default RE: Need CG confirmation

Not solve the problem yet (not enough time).
For information some weights:
battery for motor : 0.44lb
Battery 1 for Rx: 0.40lb
Battery 2 for Rx: 0.31lb
Here a picture of the installation with the most advanced battery, and it missing 0.33lb !!
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