Go Back  RCU Forums > RC Airplanes > Questions and Answers
Reload this Page >

hanger9 cap232 da50 fuel tank question

Notices
Questions and Answers If you have general RC questions or answers discuss it here.

hanger9 cap232 da50 fuel tank question

Old 03-04-2004, 07:15 PM
  #1  
Jeff396
Senior Member
Thread Starter
My Feedback: (1)
 
Join Date: Apr 2002
Location: Fort Mill, SC
Posts: 198
Likes: 0
Received 0 Likes on 0 Posts
Default hanger9 cap232 da50 fuel tank question

I am putting together an 80" Hanger 9 Cap 232 with a Da50 for power. This is my first gasser. I am at the point where I need to install the gas tank. The instruction show mounting the tank in the nose as on a .40 size plane. My question is.....would it be better to mount the gas tank (24oz) on the CG? Is there any problem running the gas lines that far? Do I need to change the cg any? I would appreciate any help you can give.

Jeff
Old 03-04-2004, 07:24 PM
  #2  
John Murdoch
Senior Member
My Feedback: (11)
 
John Murdoch's Avatar
 
Join Date: Jun 2002
Location: Las Vegas, NV
Posts: 1,713
Likes: 0
Received 0 Likes on 0 Posts
Default RE: hanger9 cap232 da50 fuel tank question

Jeff,
This is an explaination of the Great Planes Patty Wagstaff tank location. It will give you a good idea of what you're wanting to know

When we finish a model, ARF or kit, we carefully balance it at the recommended C.G. Maybe sometimes a little forward for a safe first flight or maybe a little aft because experience has told us that we like them that way. Then we fill the fuel tank and completely change that carefully selected balance point. When the tank is in the usual position right behind the firewall, filling it moves the C.G. forward. Sometimes a little, sometimes a lot. On the review airplane, filling the tank moved the C.G. forward 5/8".

The recommended C.G. on the Great Planes Extra 300S ARF is 3-13/16" behind the leading edge, measured at the wingtip, with the tank empty. In technical terms, that's 34.4% of the Mean Aerodynamic Chord. Then with the tank full, the airplane balances at 3-3/16" (30.5% MAC). So in effect you take off with the C.G. at 30-1/2% and then during the flight, as you burn off fuel, the C.G. moves to the rear. (Have you ever had a model that wouldn't snap roll until halfway through a flight? I have.) But unless you run out of fuel, the C.G. will never get back as far as the recommended 34-1/2%.

Moving the tank to the center of the fuselage (over or under the wing spar) is a good thing. Burning off fuel does not change the C.G. and the flight characteristics of the airplane. Of course with the tank that far from the engine, you will need a fuel pump, but fuel pumps have advantages of their own (consistent running at all attitudes and the ability to safely use a leaner needle setting for more power) and if you are using a gasoline engine it already has a pump built into the carburetor.

But what about the C.G.? With the tank moved to the center, do you still want to set the balance point at the factory recommended C.G.? NO! Remember, when the tank is at the C.G., filling it does not move the C.G. forward, as the factory expected. After considering the filling and draining of the tank, the factory recommended C.G. for the review airplane really amounts to 3-3/16" at take-off and somewhere around 3-5/8" at landing.

I felt that the factory's effective take-off (full tank) setting of approximately 30% of the MAC would be a safe place to start, so I balanced the airplane at 3-3/16" (5/8" in front of the recommended setting, but still within the recommended range). That turned out to be an excellent choice for the trim flights. My airplane flies inverted with just a hair of forward stick and landing approaches require only a light touch of back stick. Elevator sensitivity at the recommended throws is normal. I moved the C.G. back to about 3-5/16" after I got thoroughly comfortable with the airplane, and at that point it will fly hands-off inverted. It is clear that with a center mounted tank, setting the C.G. at the recommended point would result in a severely tail-heavy airplane.

NOTE: This analysis applies only to airplanes with the fuel tank mounted at the center of the fuselage. If you install the tank in its planned position behind the firewall, you should stick with the factory's recommended C.G. position.
Old 03-05-2004, 08:20 AM
  #3  
Jeff396
Senior Member
Thread Starter
My Feedback: (1)
 
Join Date: Apr 2002
Location: Fort Mill, SC
Posts: 198
Likes: 0
Received 0 Likes on 0 Posts
Default RE: hanger9 cap232 da50 fuel tank question

Thanks for the info! That's kinda what I was feeling.....but now understand why I was feeling it. I don't think the plane would be un flyable if I kept the cg where it is (especially if I keep it toward the front of the range) but I imagine it will be a whole lot more snappy there. That's not exactly what I'm looking for on my maiden flight. So, I will initially balance the plane at 6.5 inches per the instruction and what others have been saying here on rcu. Then I will fill the tank in the forward position and mark where the balance point has moved forward to. Then I will move the tank back and rebalance at that forward point. This will also make throttle and choke linkage installation easier as the tank was a bit in the way what with the rear carb on the DA50. Thanks again for the help!!!

Jeff

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 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.