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Old Jun 24, 2012, 05:51 PM
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out of stock's Avatar
United States, FL, Lehigh Acres
Joined Jan 2012
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Question
how much weight can i add on a 30cc plane?

ok. i completed my plane and i found that the CG is 119mm from the leading edge. as i balanced it, the results was pretty tail heavy. i placed my cell phone on the cowl and it balanced out without touching it.

my cell phone weighs 120 grams (4 oz) so whats the best method in adding weight to the nose? im aware that this airframe is intended for gas which is probably the reason why its tail heavy. ideally, i also know that getting a bigger battery is the efficient way in adding weight but lets exclude that for this topic.

additional information:

eg msxr 30cc (electric)
4400 mah 6s 30c lipo.
1100 mah liFe pack. (both are shifted all the way to the front i have nothing else to move)

any ideas?
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Old Jun 24, 2012, 06:23 PM
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Mark Wood's Avatar
United States, CA, Bear Valley Springs
Joined Feb 2000
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Get a bigger/heavier rx pack. It's much better to install useful battery capacity rather than just parasitic weight.

mw
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Old Jun 24, 2012, 06:35 PM
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C₄H₁₀'s Avatar
United States, AK, Fairbanks
Joined Aug 2009
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Mount your cell phone inside the cowl when you fly...

I think the obvious answer would be to add weight to balance it out. Four ounces isn't much for a plane of that size; you're not likely to notice it.

If there's a lot of heavy stuff in the back of the plane, see if you can remove it or lighten it.
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Old Jun 24, 2012, 07:25 PM
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Originally Posted by C₄H₁₀ View Post
Mount your cell phone inside the cowl when you fly...
That doesn't make sense. How can he take calls while he is flying? I know Bluetooth doesn't transmit very far.

The obvious answer is to research phone weights and purchase an inexpensive phone of the same weight for ballast. No sense in signing a two year contract for four ounces either; get a pay as you go phone.
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Old Jun 25, 2012, 07:17 AM
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South Wales U.K.
Joined Mar 2003
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Change your lightweight motor spaces to heavy ones ?
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Old Jun 25, 2012, 07:51 AM
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United States, FL, Lehigh Acres
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I just got my hands on the actual manual of this model. (Eg aircraft msxr 30cc). The disc manual states i should start at wing tube. Doing so now the plane is just slightly nose heavy. I moved the battery back a bit and its balanced out.

If your wondering where did i get 119mm from the leading edge, i got it from an online shop. Its all in spanish but i did read "center of gravity 119mm. Im not sure whose right but I'm going with what the manual states.

I've also heard that the wing tube is an ideal spot to start.
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Old Jun 25, 2012, 09:05 AM
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1/3 back from the leading edge is often a good rule of thumb for a starting point if the recommended CG is not known. Starting with the CG a bit too far forward is likely to be less catastrophic than a CG too far back, in my experience. A plane that is overly nose heavy will usually just have a higher stall speed, while a plane that is tail heavy will often nose up, then stall one whole wing first (often the left wing) and nose in, particularly on turns. Some people erroneously refer to this as a "tip stall."
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Old Jun 25, 2012, 11:39 AM
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Originally Posted by caseih View Post
1/3 back from the leading edge is often a good rule of thumb for a starting point if the recommended CG is not known. Starting with the CG a bit too far forward is likely to be less catastrophic than a CG too far back, in my experience. A plane that is overly nose heavy will usually just have a higher stall speed, while a plane that is tail heavy will often nose up, then stall one whole wing first (often the left wing) and nose in, particularly on turns. Some people erroneously refer to this as a "tip stall."
Forgive me im not inclined in measuring. When you say 1/3 does that mean 1/3 of the wing from leading edge? .thank you for your input.
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Old Jun 25, 2012, 01:12 PM
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South Wales U.K.
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Try this CG calculator - http://www.geistware.com/rcmodeling/cg_super_calc.htm - just enter the dimensions in the 'MAC And Neutral Point' section, then set the 'Desired Static Margin' to how you want the plane to fly.

Personally I feel the 1/3 may be too far back for a first flight. I have always worked the 25% to 30% CG range, at least until I have flown the model a few times.
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Old Jun 25, 2012, 01:41 PM
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United States, VA, Virginia Beach
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I always guestimate where a wing spar would be placed and try to balance withing a 1/2 inch fore or aft of that. If your wing tube is about where a wing spar should be I'd roll with that.
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Old Jun 25, 2012, 03:20 PM
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Originally Posted by dedStik View Post
I always guestimate where a wing spar would be placed and try to balance withing a 1/2 inch fore or aft of that. If your wing tube is about where a wing spar should be I'd roll with that.
Wait, so wing tube & wing spar are two different things?
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Old Jun 25, 2012, 09:47 PM
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Originally Posted by out of stock View Post
Forgive me im not inclined in measuring. When you say 1/3 does that mean 1/3 of the wing from leading edge? .thank you for your input.
Yes. I agree with the other poster that often 25-30% is good too. And like the poster who talked about measuring from the wing spar, I do that as well.
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