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Old Sep 10, 2013, 11:09 PM
Registered User
United States, KS, Junction City
Joined Aug 2008
209 Posts
Question
Nose heavy and out of options

Hello, I have an old Large scale Champ (Bud Nosen I believe). It has a Zenoah G380 gas engine that came already installed in the airplane. My problem is that with everything I have in the plane (electronics, batts, servos, ect) moved as far back as I can the plane is still balancing out at the leading edge of the wing. It takes a little over a pound to get the balance point back to 1/3 from the leading edge. Any ideas on what can be done.
If I need to move the motor back its going to be a major structural change. The leading edge balance just seems to far forward to me but I have always flown smaller lighter airplanes.
I can take a Saito 100 fourstroke that I have lying around but I was really hoping to get into a gas model. The 100 may be underpowered also.
What do you guys think? Any ideas? Would adding a pound to that big plane even be a big deal?
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Old Sep 11, 2013, 01:12 AM
Scale Builder
United States, AZ, Litchfield Park
Joined Jul 2002
2,494 Posts
What is the wing span and the all up weight? Honestly, a pound is probably nothing. I often have to add three or four times that amount to the nose of my giant warbirds!
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Old Sep 11, 2013, 02:16 AM
Registered User
United States, KS, Junction City
Joined Aug 2008
209 Posts
I'm not at home now but wingspan is 120", I'm not sure on the weight. The wing area is massive so I doubt it will be overloaded.
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Old Sep 11, 2013, 08:33 AM
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United States, TX, Leander
Joined Sep 2003
2,579 Posts
I think my Nosen champ is around 108" give or take a little bit, I havent messed with it for awhile. I got mine from an estate sale a few years back and have been slowly working on it. It came with an OS BGX monster. Thats a 35cc glow engine. I'd suggest using a different engine with electronic ignition. Losing a little weight up front can help a fair amount. These champs have a lot of lumber in them from old school design and construction. My BUSA cubs are the same size and weigh a lot less and easily fly on 1.20 glow or 20cc gas. I would speculate that something in the 26cc range would fly it scale like. Thats the plans I have for mine.
Edwin
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Old Sep 11, 2013, 09:52 AM
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Traverse City, Michigan
Joined Dec 2005
11,383 Posts
I've seen\ these fly well on a G-38. If it were mine, I'd add the weight, and go flying.
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Last edited by TomCrump; Sep 11, 2013 at 10:23 AM.
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Old Sep 11, 2013, 03:14 PM
Registered User
United States, KS, Junction City
Joined Aug 2008
209 Posts
Thanks for the advice guys. I guess what I really need to do is add the weight and then do a wing loading calculation to see how much it has. I know there is a difference between what a little plane can fly well with for wing loading and what a larger one can. Anyone have an idea of what good wing loading would be for this plane.
Also, I was incorrect earlier. I mixed up a PT-19 that I have that is 120" wingspan, the champ is as edwin described, 108" wingspan.
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Old Sep 11, 2013, 04:14 PM
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ace4rc's Avatar
tampa,florida
Joined Nov 2007
1,833 Posts
The best formula for wing load is add the weight and go fly. How one flies has more of an effect on an airframe than the wing load. For example, I fly scale and my Waco is way heavy for its size, about 2-3lbs. And it is nose heavy, but I love the way she flies.
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Old Sep 11, 2013, 09:17 PM
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Nergall's Avatar
Joined Aug 2009
1,416 Posts
Wing loadings for large planes are nothing like what you would expect in a .40 sized plane. To get comparable numbers you have to use a wing cubed loading.
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Old Sep 12, 2013, 09:07 AM
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United States, MI, Waterford Charter Township
Joined Aug 2008
1,330 Posts
I built mine (BN Citabria) with a ST2500, so it had the opposite problem. I had to move everything forward!

I like light planes. Adding the extra pound would bug me as well. If you like the G38, maybe consider an EI conversion to lighten it a little? Or bight the bullet and modernize with a newer style gasser.
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Old Sep 12, 2013, 05:32 PM
I broke it
David Hogue's Avatar
USA, NC, Clayton
Joined Feb 2001
5,775 Posts
If you have to add a pound to the tail, then there's like 4lbs in the nose thats being offset...thats prob about the weight of the g38. I dont see how anyone could build the thing that nose heavy...you sure theres no lead, old battery pack, or anything up there you can remove?
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Old Sep 13, 2013, 11:11 PM
TexasFlyBoy13
United States, TX, Summerfield
Joined Sep 2013
1 Posts
These are great flying airplanes and you'll love it when you get it setup right. First off, get rid of the G38, its just a rock. Saito FG30 gas or 180 glow is perfect fit for the 105 inch champ or citabria. G26 is the choice for 2 stroke. As a rule of thumb, balance it right off of the main spar and then adjust to your liking. mine balances with a 3600 mah battery just below the rear window. The saito engine, with a 17X6 xoar, will barely hold a torque roll hover and knife edges very nice. Though mine are built a bit heavy as bush planes with flaps and 6 inch big wheels, weigh in at 17.5 lbs. float effortlessly and are a pure pleasure to fly.
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Old Sep 14, 2013, 10:12 AM
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United States, MD, Elkton
Joined Oct 2011
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Now, if you don't want to throw away an engine that's worth $150 used, and if you don't want to spend $300 for a newer lighter, engine, then just balance that baby at about 4" from the leading edge with whatever weight it takes, and go have yourself a ball.16 oz.s ain.'t nothing to an airplane that size

.Earl.
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Old Sep 14, 2013, 10:58 AM
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Athens, Greece
Joined Apr 2010
453 Posts
I agree with Earls reasoning.
That bird has acres of wing area, the ballast in the tail will make very little difference to the performance.

mike
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Old Sep 15, 2013, 06:29 AM
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United States, MD, Elkton
Joined Oct 2011
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I have a 1/3 scale model, with an 8' wingspan. I have two 32 oz tanks in it, one for fuel, and one for the smoke system. that's a total of four pounds I add to the model, each time I fly it.
When I have flown it with low fuel, and no smoke oil aboard, the only noticeable differences are better verticals ( it goes about 30' higher,), and a stall speed about 2 mph slower...
Weight on a 1/4 scale model has little effect on normal flight.....you're worried about 16 ozs ?? Yet you'll add over 400 lbs of pilot, passenger, and fuel to a Champ to go for a ride in the full sized one..
Keep things in perspective, and you'll do fine.
It simply must balance to fly-add what you need.
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Old Sep 15, 2013, 07:47 AM
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United States, MI, Waterford Charter Township
Joined Aug 2008
1,330 Posts
I don't think there's any question regarding whether the plane will fly with a G38 or not. There might be other considerations to be made though? Depending on the OP's flying style and intended purpose for this plane, that may make a big difference on whether or not he enjoys it?

Regarding the plane's all up weight, at SOME point, you need to step back and assess it's abilities to carry that weight safely, and maybe start drawing some lines regarding maneuvers you might want to try with it? Anyone that's built a Nosen kit (or flown full scale?), can appreciate this. I think, with the weights the OP is speaking of, that might be a consideration I'd be looking at here.....
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