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Something Extra COG

Old 08-25-2005, 11:04 AM
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ClarkFlyer
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Default Something Extra COG

Not experienced with changing the COG on planes to increase response. I have a SSE ARF on order and wish to play with the COG. If, for example, the plans call for 3" back, will I notice much difference if I move it 3.5" back? What kind of increments do I want to make each time I mess with it? Thanks, All!
Old 08-25-2005, 11:31 AM
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Charlie P.
 
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Default RE: Something Extra COG

Here's a useless rule of thumb for you.

Balance the plane (empty fuel tank, of course). Check COG again with a full tank. That range is how much your COG shifts in a long flight. Divide that range by four and that figure is how much you should incrementally change the COG by when making adjustments.

I just made that up, but it sounds good. I would recommend 1/4" increments. It really depends on a lot of things. Percent of chord, aerofoil shape, weight of plane (wing loading), your comfort level of instability. Some designs have a wide "sweet" range, others don't.
Old 08-25-2005, 11:33 AM
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bubbagates
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Default RE: Something Extra COG


ORIGINAL: dsk

Not experienced with changing the COG on planes to increase response. I have a SSE ARF on order and wish to play with the COG. If, for example, the plans call for 3" back, will I notice much difference if I move it 3.5" back? What kind of increments do I want to make each time I mess with it? Thanks, All!
DSK,

1/8 incrememnts is fine. It does not take much to change it.

However, it will become quite sensitive on the elevator at the back end of the CG. Hang for a while at the recommended point, trust me that's all you'll need. Also stay at the book rates for both high and low throws. On low rates it's still really good and a nice roll rate. Go to high rates, come across the field at half throttle using an OS46AX with an APC 11X6 prop and you will loose count as the roll rate is so high it becomes a blur, BUT, when you release the aileron's it stops right there, no over-rotation at all.

As far as the elevator difference with the CG back, it becomes quite easy to get into a sudden stall. Normally this thing just drops the nose in a stall but too much elevator at too far back on the CG and it will drop a wing quickly. So if you do move the CG back, increase expo if you have it and do not be fast when you jam in full elevator.

Otherwise, this is a great plane, you're gonna love it
Old 08-25-2005, 12:49 PM
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ClarkFlyer
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Default RE: Something Extra COG

I do appreciate the responses.....perhaps I'll go by the book for awhile and see how it flies......I AM putting an OS .46 AX on this plane and will check the roll rate you speak of. Thanks again.

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