balance
#1
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balance
I'm sure it is here some place, I just cant find it. how do you calculate the balance point on a scratch built symmetrical, tapered wing aircraft? Is it balanced at the fuselage sides?
Roger
Roger
#2
Senior Member
RE: balance
This site ought to give you some idea of "how", and then it'll do the computation for you: http://www.geistware.com/rcmodeling/cg_super_calc.htm
Then you'll know how far back the CG should be, and then...
If your a/c is low wing, it's easiest to turn it upside down to balance it. If it's mid wing, try it right side up and upside down and see which way is easiest to hold the a/c. If it's a high wing, just sit it on the wheels and have at it. And how do you "have at it"?
A good thing to do is place some masking tape on the a/c on the wing on each side, against the fuselage where the CG should be. A piece on the left wing, a piece on the right wing works good. Mark the tape where the suggested CG is for reference. Then pick the a/c up with a hand near each piece of tape. Try to balance it with one finger of each hand. Try to keep those two fingers about the same distance back from the LE of the wing. Once you have the a/c balancing on those two fingers, look to see where they are in relationship to the marks on the two pieces of tape.
Nothing says you have to use your fingers. I cut a piece of 3/4" insulation foam to make a saddle that holds the fuselage as I build the model steady for me. It's quite useful all during the building and especially so when installing things inside the fuselage. And then when it's time to work the CG on the almost completed model, it's also useful with this task. It becomes my "two fingers". It's wide enough at 3/4" to safely balance the wing on, and narrow enough that you get a good feel for when it's exactly balancing the a/c front to back. Of course, I also make a saddle for the rear of the fuselage because two are far more useful than one, but that rear saddle isn't needed for this balancing act.
That's it.
Then you'll know how far back the CG should be, and then...
If your a/c is low wing, it's easiest to turn it upside down to balance it. If it's mid wing, try it right side up and upside down and see which way is easiest to hold the a/c. If it's a high wing, just sit it on the wheels and have at it. And how do you "have at it"?
A good thing to do is place some masking tape on the a/c on the wing on each side, against the fuselage where the CG should be. A piece on the left wing, a piece on the right wing works good. Mark the tape where the suggested CG is for reference. Then pick the a/c up with a hand near each piece of tape. Try to balance it with one finger of each hand. Try to keep those two fingers about the same distance back from the LE of the wing. Once you have the a/c balancing on those two fingers, look to see where they are in relationship to the marks on the two pieces of tape.
Nothing says you have to use your fingers. I cut a piece of 3/4" insulation foam to make a saddle that holds the fuselage as I build the model steady for me. It's quite useful all during the building and especially so when installing things inside the fuselage. And then when it's time to work the CG on the almost completed model, it's also useful with this task. It becomes my "two fingers". It's wide enough at 3/4" to safely balance the wing on, and narrow enough that you get a good feel for when it's exactly balancing the a/c front to back. Of course, I also make a saddle for the rear of the fuselage because two are far more useful than one, but that rear saddle isn't needed for this balancing act.
That's it.
#3
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RE: balance
darock, Thats it! Thank you.---It is a 49" low wing that I built in the early 80s that flew well back then. After a 25yr layoff I'm back. I gave her a NOS engine that I had in storage, K&B 3.5.I'm also replacing all my old Kraft radio systems. Kraft was pretty good in its day.
Note: A permanent CG mark is going on all my planes from now on.
Note: A permanent CG mark is going on all my planes from now on.