Balancing
12-18-2002, 01:16 PM
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Balancing
I am building the Avastar 40 and I have been told to make it a little nose heavy. Dose this mean to balance the plane perfect with out fuel in the tank or dose this mean to balance it a little nose heavy with a empty fuel tank.
12-18-2002, 03:25 PM
#2
Balancing
You should always balance with an empty tank. A lot of guys recomend a litle nose heavy , I don't.
A little nose heavy makes it more stable but also makes the elevator less effective. Plus a tail heavy airplane has to land faster as it will have a higher stall speed.
I think you should
balance it in the center of the recomended range as a good starting point. Then if it gets to sensative as it burns
fuel move the C.G.
later daveo
A little nose heavy makes it more stable but also makes the elevator less effective. Plus a tail heavy airplane has to land faster as it will have a higher stall speed.
I think you should
balance it in the center of the recomended range as a good starting point. Then if it gets to sensative as it burns
fuel move the C.G.
later daveo
12-19-2002, 01:01 PM
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Balancing
When balanced, with an empty fule tank, the nose should point down , slightly.. A few degrees. that's nose heavy.
No, unless they are drasticly over weighted, a tail or nose heavy plane will fly, just the results are different.. [img]i/expressions/face-icon-small-happy.gif[/img]
the tail heavy plane will be squirrely, and all over the sky be fore it decides to plant itself. the noze heavy plane will be a wet sponge, untill it finally lands itself.. [img]i/expressions/face-icon-small-happy.gif[/img]
No, unless they are drasticly over weighted, a tail or nose heavy plane will fly, just the results are different.. [img]i/expressions/face-icon-small-happy.gif[/img]
the tail heavy plane will be squirrely, and all over the sky be fore it decides to plant itself. the noze heavy plane will be a wet sponge, untill it finally lands itself.. [img]i/expressions/face-icon-small-happy.gif[/img]
12-21-2002, 09:43 AM
#5
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Balancing
To paraphrase 3D, a nose-heavy plane flies poorly, a tail-heavy plane flies once.
It might do you good to use an airplane balance jig instead of your fingertips. I used to use the 'fingertip' method (put your fingertips where you think that CG is supposed to be) but was much happier using the balancing jig.
You can make one using a piece of pine for the base, and a couple of 8" pieces of 1/4" aluminum rod. Drill a hole in the base for the rods (use a drill press if you can, so that the rods are nice and vertical). Space the rods about 6" apart. Round over the tops of the rods where they will contact the airplane(remove any burrs so that you don't damage the covering). Make sure that the tops of the rod are even, so that your plane will sit evenly on them.
On your plane, measure carefully and put some masking tape marks on the wing where the balance range is supposed to be. Rest the plane on the balancer so that the rod tips are on the masking tape (within the range) and balance it (with the empty tank, as mentioned previously by Daveo). Make sure that there is balsa sheeting where the balance range is supposed to be. You don't want to rest the plane on just the covering - it might poke a hole through the covering.
That jig only cost a couple of bucks to make, and has been a real nice addition to the tool shop. I've re-checked planes that I initially balanced with the 'fingertip method' and found that I still had to add weight here or there to bring the plane into balance. And the difference in flying was better too.
Just my $.02. Hope this helps,
Bob
It might do you good to use an airplane balance jig instead of your fingertips. I used to use the 'fingertip' method (put your fingertips where you think that CG is supposed to be) but was much happier using the balancing jig.
You can make one using a piece of pine for the base, and a couple of 8" pieces of 1/4" aluminum rod. Drill a hole in the base for the rods (use a drill press if you can, so that the rods are nice and vertical). Space the rods about 6" apart. Round over the tops of the rods where they will contact the airplane(remove any burrs so that you don't damage the covering). Make sure that the tops of the rod are even, so that your plane will sit evenly on them.
On your plane, measure carefully and put some masking tape marks on the wing where the balance range is supposed to be. Rest the plane on the balancer so that the rod tips are on the masking tape (within the range) and balance it (with the empty tank, as mentioned previously by Daveo). Make sure that there is balsa sheeting where the balance range is supposed to be. You don't want to rest the plane on just the covering - it might poke a hole through the covering.
That jig only cost a couple of bucks to make, and has been a real nice addition to the tool shop. I've re-checked planes that I initially balanced with the 'fingertip method' and found that I still had to add weight here or there to bring the plane into balance. And the difference in flying was better too.
Just my $.02. Hope this helps,
Bob
12-22-2002, 12:33 PM
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Another suggestion about balancing a new aircraft. I also balance wingtip to wingtip. I make sure the wing is on straight and with equal amounts of wing on each side of the aircraft. It the wing is attached with rubber bands that can vary each time you attach the wing so I make sure the wing is on correctly and make little marks on the wing so that each flying session I can put the wing on the same.
I then suspend the plane from the ceiling on string attached to the fin and the shaft of the motor. The plane should be level wingtip to wingtip. If not a little lead in the high wingtip will make the plane fly better and not require as much aileron trim. This kind of out of balance can usually be corrected with aileron trim (if its not too bad) but its nicer not to do that especially while doing maneuvers and aerobatics.
Roodester
I then suspend the plane from the ceiling on string attached to the fin and the shaft of the motor. The plane should be level wingtip to wingtip. If not a little lead in the high wingtip will make the plane fly better and not require as much aileron trim. This kind of out of balance can usually be corrected with aileron trim (if its not too bad) but its nicer not to do that especially while doing maneuvers and aerobatics.
Roodester
12-23-2002, 09:25 PM
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One note concerning the Avistar, don't rely on the skimpy metal tie to hold the wing halves together. Go ahead and epoxy the two halves at least and I would even recommend some glass cloth around the wing joint to make it even stronger.
01-05-2003, 09:49 PM
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I had an Avistar a few years back and I cant say a lot bad about them except if you get to wild with it the frame will be overstressed very easy... I thought I would get board with it because I was use to flying 25 size low wings with bb40's and bb46's but it wasnt to bad. I used an ASP 46 with an 11-5 apc prop and I had all the power I needed, until I bumped the control throws up a little to much and did a snap [img]i/expressions/face-icon-small-smile.gif[/img]
