Go Back  RCU Forums > RC Airplanes > Giant Scale Aircraft - General
Reload this Page >

Balancing heavy aircraft

Notices
Giant Scale Aircraft - General Discuss all other giant scale aircraft here.

Balancing heavy aircraft

Old 11-12-2020, 07:44 AM
  #1  
sweinhart
Junior Member
Thread Starter
 
Join Date: Oct 2020
Posts: 12
Likes: 0
Received 0 Likes on 0 Posts
Default Balancing heavy aircraft

My large scale aircraft is nearly complete. I've never had problems balancing a model before, but this one presents a little challenge, its heavy. I'm estimating in the neighborhood of 30-35lbs flying weight. The balancing point on the wing does not have any support for say, attaching dowels for string to attach, and balsa sheeting isn't strong enough to support that much weight with out using a strong point. How do people generally balance a heavy model?
Old 11-16-2020, 06:10 AM
  #2  
Tony Hallo
 
Join Date: Jan 2003
Location: Springdale, PA
Posts: 1,622
Received 3 Likes on 3 Posts
Default

If your plane has a wing tube, 1/8" plywood drilled for the wing tube inserted between the wing and fuselage works well. If the cg is off from the wing tube the plywood \ can be drilled for the alignment dowel as well. Then a small 1/8" at the location of the CG will get it done. On my current 33% Champ build I am using a bathroom scale under the mains and a food scale under the tailwheel then calculating the CG from weights and measurements, looks like it will come it at about 40 pounds.
Old 11-16-2020, 07:45 AM
  #3  
sweinhart
Junior Member
Thread Starter
 
Join Date: Oct 2020
Posts: 12
Likes: 0
Received 0 Likes on 0 Posts
Default

Thnx for input. No wing tube in this plane. Hopefully the wing joiner holds lol. I'm thinking about making a couple dummy ply wing ribs that will hold a dowel at the CG location and bolting them to the wing ends. The actual ribs just have a big lightening hole there
Old 11-16-2020, 08:27 AM
  #4  
tedsander
 
Join Date: Jul 2004
Location: White Bear lake, MN
Posts: 397
Likes: 0
Received 25 Likes on 25 Posts
Default

Google how to do weight/balance/cg for real aircraft. The FAA has a comprehensive (and very understandable to us non-engineers) booklet available on line detailing how-to. Essentially block the plane up so it is level, weigh all the wheels, then using the distances do the math to find the current CG. Also details how to figure out how much to add where to get the cg where you want it. Very accurate.
Old 11-16-2020, 12:35 PM
  #5  
sweinhart
Junior Member
Thread Starter
 
Join Date: Oct 2020
Posts: 12
Likes: 0
Received 0 Likes on 0 Posts
Default

I looked and it seemed quite complicated with things called arms and datum I've never heard of before in reference to aircraft. One pictured showed a calculus formula after weighing the three wheels. Plans already indicate location of CG. I was interested in finding out how people usually do this. The scale idea would work if I understood the concept, though I only have one scale. The other option would be easier, but I'm a little concerned about 1/8 plywood holding full weight of the aircraft.
Old 11-16-2020, 02:03 PM
  #6  
tedsander
 
Join Date: Jul 2004
Location: White Bear lake, MN
Posts: 397
Likes: 0
Received 25 Likes on 25 Posts
Default

Here's a well written article about how to do it, step-by-step for a large scale RC aircraft....and the math is very easy.....

c-of-g-v2.pdf
Old 11-16-2020, 02:32 PM
  #7  
sweinhart
Junior Member
Thread Starter
 
Join Date: Oct 2020
Posts: 12
Likes: 0
Received 0 Likes on 0 Posts
Default

thnx. Assuming the math/science confirms those calculations, it'll probably be the best method to apply given the size/weight of my model.
Old 11-17-2020, 07:44 AM
  #8  
sweinhart
Junior Member
Thread Starter
 
Join Date: Oct 2020
Posts: 12
Likes: 0
Received 0 Likes on 0 Posts
Default

One other question regarding this. My plane is a c-130 which has 2 mains on each side. When taking measurements from front to wheels, would you assume the center point between the wheels as the measuring point, and would you measure perpendicular length or diagonal length (that is from a front center point) from front to mains as these will be different
Old 11-17-2020, 10:24 AM
  #9  
tedsander
 
Join Date: Jul 2004
Location: White Bear lake, MN
Posts: 397
Likes: 0
Received 25 Likes on 25 Posts
Default

It has two wheels (fore and aft) on either side, not really completely separate sets of main gear. I would weight each set at the same time (fore and aft wheels on the scale at once). Maybe using a board to rest them on, just subtracting the weight of the board from the weight measured. Measure from the "datum" (the wall noted in the article) straight back (perpendicular) to the midpoint between the two wheels.

If using the board to weigh both, don't forget to put one on the other side to jack it up to the same level as the set on the scale. It's important to take the weights on all points with the plane level both front to back and side to side.
Old 11-17-2020, 08:51 PM
  #10  
ForcesR
 
Join Date: Dec 2009
Location: Ottawa, ON, CANADA
Posts: 810
Likes: 0
Received 2 Likes on 2 Posts
Default

This is what I use for balancing heavy model aircraft, works like a charm. Sold by Legend Hobby https://www.legendhobby.com/product/vic-rc-cger-stand/


Old 11-18-2020, 08:29 AM
  #11  
tedsander
 
Join Date: Jul 2004
Location: White Bear lake, MN
Posts: 397
Likes: 0
Received 25 Likes on 25 Posts
Default

Or...you could buy this: https://www.chiefaircraft.com/xcy-cgcombo.html
Old 11-20-2020, 10:12 AM
  #12  
DGrant
My Feedback: (4)
 
DGrant's Avatar
 
Join Date: Dec 2001
Location: Clovis, CA
Posts: 2,120
Received 24 Likes on 23 Posts
Default

Study up on the the "Vanessa rig"... Simple, cheap, and very effective..

Old 11-20-2020, 02:51 PM
  #13  
Britflier
 
Join Date: Nov 2015
Location: Boynton Beach, FL
Posts: 20
Received 3 Likes on 2 Posts
Default

+1 for DGrant. I have a Vanessa rig permanently set up in my garage.

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.