Is my CG off, need little help  
View related threads: (in this forum | in all forums)

Tower Hobbies
Enter up to 4 keywords or Tower stock numbers
Logged in as Guest



Users viewing this topic: none
  Printable Version
       

All Forums >> RC Airplanes >> ARF or RTF >> NitroModels Support >> Is my CG off, need little help
Page: [1]

Login
Message << Older Topic   Newer Topic >>
Is my CG off, need little help - 8/17/2007 2:42:19 AM   
jnewington


 

Posts: 1
Joined: 8/9/2007
From: Plainwell, MI, USA
Status: offline 		The airplane is a supersport 40 with a .46 towerhobbies engine. the CG is a little forward even after weight added to tail and moving the battery to the aft. Here's the problem, I am always adjusting the elevator subtrim when I change throttle input. the plane goes faster it climbs like crazy. I trim it down and when I throttle down it dives like crazy. I can't take much more of this. Can anyone help and shed some light on my problem?
Thanks
Justin Newington
       Post #: 1

RE: Is my CG off, need little help - 8/17/2007 3:18:06 AM   
Mr67Stang



Posts: 2339
Joined: 4/26/2006
From: Raeford, NC, USA
Status: offline 		Try adding some down thrust. Your simptoms describe a thrust alignment problem, not a CG problem. Put, I would guess, two washers behind the engine mounts top two bolts between the mount and the fire wall to tilt the engine slightly down.

_____________________________

He who dies with the most toys wins!

(in reply to jnewington)
       Post #: 2

RE: Is my CG off, need little help - 8/17/2007 3:36:28 AM   
opjose



Posts: 6166
Joined: 11/26/2005
From: Poolesville, MD, USA
Status: offline 		Yup a thrust angle problem.

As he said add the washers.

I've also have resorted to sanding the engine mounts down using a band sander or circular sander, so that I add the required downthrust to the mount itself.

While you DO want a bit of climb at higher throttle you want this to be within reason.

The down thrust will counteract the tendancy to climb at full throttle. You will then need to retrim your plane so that if flies level at mid throttle.

The plane should just hold level flight down to about 40% throttle, at that point and below it should start nosing down if it does not have an airspeed reserve.


Note the Supersport should have the required thrust angle built in. However often when one is aligning the engine, especially with side mounts, the angle of the engine may change a couple of degrees while mounting it, causing the down thrust to be off.

I did this a couple of times when I tackled my first ARF's.




_____________________________

-
Build em'', fly em'', crash em'' and build more.

(in reply to Mr67Stang)
       Post #: 3

Page:   [1]
All Forums >> RC Airplanes >> ARF or RTF >> NitroModels Support >> Is my CG off, need little help
Page: [1]





Jump to:


Google 



Search | Marketplace | Event Calendar | Local Clubs | Magazine | Product Ratings | New Products | Discussion Forums

Photo Gallery | Member Video Posts | RCU Video Gallery | Instructor Search | Field|Track|Marina Search

Advertisers | Hobby Vendor Resources | Rate Manufacturers | Sign In/Sign Up

SITE MAP!   : :   FORUM RULES

© 2001 - 2007 24-7 RC, LLC, all rights reserved.

Charities we support that also need your help
Yorkie Rescue | Humane Society | ASPCA | Crohn's-Colitis America

Kaango.com Classifieds

0.313RCU5