CG - RCCanada - Canada Radio Controlled Hobby Forum
RCCanada - Canada's Radio Control Hobby Forum
General RC Aircraft Discussion Discuss anything RC related

Thread Tools Display Modes
Old 10-10-2015, 08:24 PM   #1
RCC Apprentice
essi's Avatar
I am: ehsan.a
Join Date: Jul 2015
Location: toronto ontario
Radio of choice:

Feedback: 2 / 100%
Posts: 46
Total Props: 0

       Remove this ad - become a site supporter!
Is that true that as you move the CG towards the back,plane would be more aerobatic!
i did it on 300 extra, flew ok but such a hard landing almost crash...
essi is offline   Quick reply to this message.

Sponsored Links - Subscribe to remove this ad.
Old 10-10-2015, 09:22 PM   #2
★ Site Supporter ★★ Administrator ★
chuebner's Avatar
I am: Curtis H
Join Date: Mar 2007
Location: Imperial & Regina, Sask.
Radio of choice:

Feedback: 31 / 100%
Posts: 8,220
Total Props: 53
Re: CG

Yup it does but moving it back to far will make certain airframes almost uncontrollable. Highly aerobatic, fun fly etc etc planes handle it planes like warbirds it would be disasterous.

There is a saying..... Forward CG planes fly, tail heavy planes fly once.

You can fly Hitec or use the other "low tech" stuff!!

Forum Rules Link
chuebner is online now   Quick reply to this message.
Old 10-10-2015, 09:24 PM   #3
RCC Expert Contributor
JoeT's Avatar
I am: JoeT
Join Date: Mar 2004
Location: Maple, Ontario, Canada
Radio of choice:
Was a Futaba, Now a Tyrant with Taranis.
# of RCs: 5

Feedback: 11 / 100%
Posts: 812
Total Props: 8
Re: CG

Generally 30% back from the MAC is a good starting point. The farther rearward you put the CG the more unstable the plane gets. The elevator sensitivity goes way up, and depending on the size of the horizontal stab / elevator, may stall first during slow flight.

There's a correct CG "RANGE" where it's safe to move to get the appropriate response, anything out of that range = major compremise.

The old saying goes: A nose heavy plane flies poorly, a tail heavy plane flies ONCE!!
Not just any old Joe.. LOL
Almost ancient MAAC Number 28296
R/C 400 Club, Toronto RCFC
JoeT is offline   Quick reply to this message.
Old 10-10-2015, 09:57 PM   #4
Mike Sebastien
RCC Supreme Contributor
Mike Sebastien's Avatar
I am: Mike s
Join Date: Sep 2005
Location: Moncton, NB

Feedback: 11 / 100%
Posts: 2,069
Total Props: 9
Re: CG

Why did you move the CG to the rear? Bad landing isn't indicative of a rearward CG it's more about the pilot.
Mike Sebastien is offline   Quick reply to this message.
Old 10-11-2015, 06:46 AM   #5
Level 3 Supporter
★ Site Supporter ★
Cougar429's Avatar
I am: Gary L
Join Date: Aug 2008
Location: Tecumseh, Ontario

Feedback: 72 / 100%
Posts: 5,253
Total Props: 30
Re: CG

The reason there is the saying a tail heavy plane flies only once is that most aircraft are designed to be stable and controllable within a defined CofG range. Move it outside that and unless changes are made to the control system you will run out of authority. In most cases this occurs when slowed down for aeros or landing. As speed lessens so does airflow over the tail and if the plane departs from controlled flight and cannot recover the end is pretty well guaranteed very quickly, usually from the wing stalling and remaining that way.

Design can play a part, as well, as some aircraft can hide the tails behind the wing at high alpha, meaning the tail moves into the airflow shadow of the main wing and therefore loses complete control. In tail heavy conditions it remains that way and unrecoverable.

Ducted fans, pushers and turbines can suffer the same effects since they have no way to accelerate airflow over the controls with propwash and unless the CofG is forward enough to pull the nose down or they have enough thrust to accelerate away they don't live long either.

Having said that there are systems that now mimic what has been available in full size military aviation for quite a while. As said, tail heavy can make the plane more maneuverable, a condition you would want in a fighter aircraft. Unfortunately, the closer to the ragged edge, (and beyond) you push this condition the more you rely on external stabilization and limitation systems. The F-16 is a perfect example of this, if not the first to require external systems to the pilot to remain controllable in flight. The plane is so tail heavy that without those systems it simply will not remain airborne.

These systems work by recognizing and correcting changes too small and quick to be noticed by us mere humans and inputting control corrections before these changes can grow too large to be reigned back. Lately the same can be said of stab systems available to modellers in the form of Futaba and Demon multi-axis gyros.
I know there's money in aviation........I put it there!
Cougar429 is online now   Quick reply to this message.
Old 10-11-2015, 12:23 PM   #6
RCC Pro Contributor
Flypaper's Avatar
I am: Gord C
Join Date: Sep 2002
Location: kingston Ont.

Feedback: 1 / 100%
Posts: 1,803
Total Props: 7
Re: CG

One good way of finding the rearward limit on an aerobatic plane is to use the inverted flight method. Keep moving the CG back a bit at a time and retrimming for level flight each time you go upright. When you go inverted, it will normally drop the nose when going inverted. Keep moving the CG back until you find the magic spot, the plane will fly level inverted or upright with no trim change and no elev. stick movement.
Another point. As you move the cg back, you need to lessen the control throws to keep the same loop rate as with the CG further ahead.
Tried for my kamikazi pilots licence. Flunked the test.
MAAC 5276
Flypaper is offline   Quick reply to this message.
Old 10-12-2015, 09:27 PM   #7
RCC Apprentice
essi's Avatar
I am: ehsan.a
Join Date: Jul 2015
Location: toronto ontario
Radio of choice:

Feedback: 2 / 100%
Posts: 46
Total Props: 0
Re: CG

thanks Gord
you've been help full thanks for your info...
essi is offline   Quick reply to this message.
Old 10-12-2015, 09:44 PM   #8
RCC Supreme Contributor
I am: eric q
Join Date: Jun 2005
Location: Crawford Lake, Ontario
Radio of choice:
# of RCs: too

Feedback: 9 / 100%
Posts: 7,159
Total Props: 26
Re: CG

Originally Posted by Cougar429 View Post
Lately the same can be said of stab systems available to modellers in the form of Futaba and Demon multi-axis gyros.
If you want something really fast, stable, and bleeding edge get yourself over to cleanflight running on a Naze32

about $30

Just switch it on for take-off and landing
You can also use it to run your string of RGB LEDs

P.S. they are not gyros, Naze32 uses a 10 degree-of-freedom accelerometer and air pressure sensor. You can use a compass and GPS (another $25)

A Naze32 mini is under 10 grams

Much older board (three years ago):
but you will get the idea
desiderantes meliorem patriam
To err is human, to moo is bovine
moo is offline   Quick reply to this message.

Quick Reply

Register Now

In order to be able to post messages on the RCCanada - Canada Radio Controlled Hobby Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

Member names may only be composed of alpha-numeric characters. (A-Z and 0-9)

!!ATTENTION ADVERTISERS!! If you intend on advertising anything on this forum, whatsoever, you are required to first contact us here . Additionally, we do NOT allow BUSINESS NAMES unless you are an Authorized Vendor. If you own a business, and want to do sales on this site via posting or private message, you will need to follow the rules. Shops, Stores, Distributors, Group Buys without being authorized will see your account terminated.
User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Your Name
Your first name and last initial is required if you plan on using the forum.
Which city & province you live in. This is mandatory for classified listings.
Radio of choice?
Which radio is your current favorite to use?
Number of RC Vehicles?
How many boats, cars, planes do you own?


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
vBulletin Message

Thread Tools
Display Modes

Forum Jump

All times are GMT -5. The time now is 08:01 PM.

vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2016 DragonByte Technologies Ltd.