Building Enforcer - curious about mods
06-08-2012, 06:45 AM
#1
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Building Enforcer - curious about mods
Good morning everybody,
I have wanted to build a Balsa USA Enforcer for some time now (have three kits in my collection). I have seen the enforcers that have been converted to ducted fans. Mods on these include extending the nose by 6 inches and moving the CG 1 to 1.5 inches forward. I have also seen some of these ducted fans with canards. I really like the look of the Enforcer with the longer nose and canards. i would like to do this to my Enforcer build but I do not plan on using a ducted fan, but an OS 75ax with a pusher prop. If I were to use the 75ax and extended the nose 6 inches and add canards, do I need to still move the CG 1 to 1.5 inches forward? I do not know if the CG is moved forward because of the weight of the ducted fan in the back or if it is do to aerodynamic forces and increased surface area (more lifting body) due to the six additional inches of fuselage and canards? I would greatly appreciate any suggestions or comments on this.
Happy flying and soft landings!
I have wanted to build a Balsa USA Enforcer for some time now (have three kits in my collection). I have seen the enforcers that have been converted to ducted fans. Mods on these include extending the nose by 6 inches and moving the CG 1 to 1.5 inches forward. I have also seen some of these ducted fans with canards. I really like the look of the Enforcer with the longer nose and canards. i would like to do this to my Enforcer build but I do not plan on using a ducted fan, but an OS 75ax with a pusher prop. If I were to use the 75ax and extended the nose 6 inches and add canards, do I need to still move the CG 1 to 1.5 inches forward? I do not know if the CG is moved forward because of the weight of the ducted fan in the back or if it is do to aerodynamic forces and increased surface area (more lifting body) due to the six additional inches of fuselage and canards? I would greatly appreciate any suggestions or comments on this.
Happy flying and soft landings!
06-09-2012, 11:01 PM
#2
Join Date: Jun 2008
Location: Christchurch, NEW ZEALAND
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RE: Building Enforcer - curious about mods
Yes, if you add aerodynamic surfaces forward then the balance point will have to move forward too. Use one of the on line calculators to confirm the new position, a blanket 1 to 1.5 inches might be about right, but it might be wrong also. Depends how big your canard is.
Another method is to build a sheet miniature version of your model (12 inch span should do) and test glide and adjust balance with clay ( you will need some 'up' elevator built in, either in the canard or trailing edge of the wing).
Try posting in the aerodynamics forum for further advice.
Good luck,
Dave H
Another method is to build a sheet miniature version of your model (12 inch span should do) and test glide and adjust balance with clay ( you will need some 'up' elevator built in, either in the canard or trailing edge of the wing).
Try posting in the aerodynamics forum for further advice.
Good luck,
Dave H
06-10-2012, 06:10 AM
#3
RE: Building Enforcer - curious about mods
ORIGINAL: ser00
I do not know if the CG is moved forward because of the weight of the ducted fan in the back or if it is do to aerodynamic forces and increased surface area (more lifting body) due to the six additional inches of fuselage and canards?
I do not know if the CG is moved forward because of the weight of the ducted fan in the back or if it is do to aerodynamic forces and increased surface area (more lifting body) due to the six additional inches of fuselage and canards?
The location of the CG depends on the lifting surfaces (including the canard wing) and their areas and distances between them.
The weight of the ducted fan or your tail engine has no effect over that CG location, only on how much counter weight you will need to add or remove from the nose.
In the sticky forum of the Aerodynamics section you can find an on-line calculator that is specific for canards.
I copy it here as well:
http://adamone.rchomepage.com/cg_canard.htm
