Ok I am embarrassed to ask this but something is wrong here.What is level on a cub. What I mean is when I lift the cub at the cg how does it sit. On other models I would prop up the tail until the horizontal stab was level. Then I would lift it at the CG. If the tail or nose didn't drop it was level. On this cub if I prop the tail in the air until the horizontal stab was level it would be really really high. (the wing would have a negative incidence). To get it to stay there I would need a HUGE amount of nose weight (like 12oz). Am I missing something ? Does the horizontal stab have positive incidence on a cub ?Its an old 1/5 scale hanger 9 1st generation ARF cub that I'm rebuilding. The CG is supposed to be at 3 1/4" from the leading edge.


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If it were flying thru the air Id say that's looks about right.
The horizontal should be level when the CG is correct.
What motor are you using vs. what the manual recommends.

Im using an old OS .72 Fs Surpass II. It is very heavy (.20 Oz).

A Cub is not necessarily Cub, unlike the contemporary similar cub models of the period such as the Goldberg and the Great Planes versions the answer to your quest is YES that one does and no the others do not. I am intimately familiar with that airplane had fun with mine for years before giving it away to someone that just loved the way it flew. Had a K&B Screaming .48 and also obtained it from a dumpster but covered all black with a yellow lightning strip.

You airplane uses an entirely different decaledge arraingement than the others, Its a great flyer. Do not attempt to level it by leveling the stab, if you do that will pretty well clean out your local hobby shops supply of lead.

No rocket science here just level the fuselage from an imaginary line through the fuse forget the stab.

John

This is not my first plane but the first one where I cared about the details. I suppose because it was an unknown, I got to learn about a lot of stuff I just never paid much attention to. The cub had a 6oz heavy nose, a heavy engine (about 4oz more than normal), 2 Oz of lead on the firewall and still "tail heavy" at the 3 1/4" mark. That is what freaked me out. I gleaned a lot of information from this board but I got time to visit with a friend who has building for many years to help lock it in. I got a good lesson on CG "ranges" and how they were going to effect flight. I was too worried about if it is tail heavy it would snap roll or be uncontrollable just after takeoff. I was quite happy to learn if it is in the range its just going behave a little different but it should fly (we went into more detail of course). The cub balanced on my imaginary line (I used the bottom of the windows) at about 3 3/4" - 4" back from the leading edge. I was also worried about the weight and got another good lesson on wing loading and how even at 9 lbs this cub is very comfortably in the zone.One thing he did notice is the engine was tight back against the firewall and I had a room to move it forward (the cowl could move forward as well). I elected to do that (about 3/4" ) and wouldn't you know it, it cleanly balances at 3 1/4 with the heavy nose. Thanks for the help

CG is much easier to locate when dealing with a kit or plans built plane because they show a datum line where measurements are taken from. When dealing with an ARF this line isn't often shown so you are given a spot that they tell you that you should balance at this point. That's fine except you are left to wonder how the plane is to sit when in balance. When given a datum line it is easy to tell when the plane is at the correct level. I have built several Cubs but as john pointed out, they are not all the same. You can usually tell by the stab but I have only had to CG the kits, an ARF can be a mystery due to the lack of information given on there instructions.