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Question on Knife Balancing

Old 08-05-2004, 07:02 AM
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Default Question on Knife Balancing

I am getting ready to balance my Knife kit and the instructions says to balance with a full tank, all the planes I balanced I usually balance with the tank empty. How should I do it, full or empty?

I am mounting my tank on the outside of the wing behind the engine if this makes a difference. Also this is my first 3D profile plane so I would like to set it up to be nice and docile and slowly work my way to wild.

Also any recommendations on throws to be docile.

Thanks
NB
Old 08-05-2004, 07:26 AM
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Default RE: Question on Knife Balancing

I dont know why they would tell you to balence this plane with a full tank, once you burn most or half of your fuel that could turn your plane tail heavy which if you havent flown a tail heavy plane before could be a scary learning experience. If this is your first profile I would suggest to make sure you are right on CG or a little nose heavy at first. Once you get the feel for its flight characteristics, then if you want move the CG aft little by little. As for the throws I have triple rates on my TX and there is no more then 15 degree deflection on low low rate on alerons and elevator rudder maybe 25 degree that will make it pretty docile. They go up from there to prob 25 degrees on the middle rates and finally on 3D rates 45 to 50 degree with expos and set ups for flaperons and spoilerons. By the way my profile is a Morris the Knife. I am a little tail heavy with it but am extremly comfortable flying it and my tank i built in the wing not by choice I bought it RTF. I also installed carbon fiber flying rods to the tail from vert stab to horiz stab for support. With the axial loops and rolls it is capable of I have cracked the horz stab twice before I realized what was causing it. I havent had an issue since. Hope this helps. Good Luck.
Old 08-05-2004, 12:58 PM
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Default RE: Question on Knife Balancing

Balance the Knife with an empty tank.

Set your throws at about 1/2 for docile, but, you won't want to stay there long. Use some expo to take the overcorrections out of the high throw rates.

For props, use a 11x4 to a 12x4 if your using a 40/46 size 2 cycle. You'll have to experiment to see which works the best.

I think the 14 x 4W is the prop of choice for either the Saito 72 or YS63 (Double check, I'm not sure on the 4 cycles)


Have Fun!
Old 08-06-2004, 10:50 PM
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Default RE: Question on Knife Balancing

Personally I found the Knife almost unflyable at the sugested CG. The nose heavy is almost as bad as tail heavy. In the case of flame out you'll have a falling rock, and landing speed and harrier speed are way higher. But that's my opinion. If you are a competint pilot on any sport plane the Knife will be a piece of cake, I'd start at 1/2 behind recomended. If you want to be conservative with your CG at first, just be sure you plan ahead to be able to adjust it back a lot. If memory serves I was about 1 1/4" back when I got happy.
Old 08-08-2004, 11:02 PM
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Default RE: Question on Knife Balancing

Mine has the tank in the wing which places it close to the center of gravity. I balanced empty and have no problems. The plane actually requires a little tail weight even with a half/pipe on the MVVS. This is a very light scratch built and flies very well....I also balance laterally with half a tank of fuel.
Old 08-09-2004, 05:16 AM
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Default RE: Question on Knife Balancing

I have a Morris the Knife which here in Australia are very rare.Everybody who sees them loves the way they fly,we have a ball with them.Mine was built from a plan and I have a6oz tank mounted in the wing,it is powered by a Enya53 fourstroke turning a 12x4 prop.Hovers beautifully and does what its name suggests Knife edges.To balance all my planes I start a little on the nose heavy side ,then fly it and turn inverted,if i find I need alot of pressure on the elevator to remain levell I start moving the cg back.I like to be able to fly Hands Off inverted.This setting seems to make all the controls function smoothly and accurately.Things like landings are ever so soft with this type of cg setting.Have fun..Oh p.s balance with an empty tank sorry nearly forgot.
Old 08-09-2004, 11:48 AM
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Default RE: Question on Knife Balancing

Thanks guys for the responce. I have it balanced with the battery as far forward as I can. After it's maiden flight I may move it back.

Thanks Again
NB

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