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CG for SIG MID-STAR 40

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Old 10-02-2017, 05:26 PM
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Timewarpped
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Question CG for SIG MID-STAR 40

I recently purchased a used SIG MID-STAR 40 (SIGRC56). I have it balanced on the spare, but it flies quit nose heavy. I would like to know where the CG is supposed to be. I have the build manual which says: “The balance range shown on the plans is a "safe" area to use for test flights”. The CG is not stated in the build manual. I do not have the plans nor can I find them on-line. Can anyone tell me where the “balance range” is located? Hopefully off the plans.
Thanks for any help.
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Old 10-02-2017, 09:10 PM
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Hydro Junkie
 
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I was "poking around" in some other aircraft forums and found several references to the Mid Star being the same, other than wing height, as the Four Star. I was able to find some plan shots of the Four Star that showed the CG to be at the forward spar with ends slightly fore and aft there of. Since many Sig planes appear to have that in common, it's as good of place to start as any.
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Old 10-02-2017, 09:53 PM
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Timewarpped
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I have also read the Mid-Star is basically the same as he Four-Star with the CG at the spar. I'll just have to move the balance point back a little at a time.
Thanks for your input.
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Old 10-03-2017, 03:57 AM
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TomCrump
 
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Just slowly move weight (battery pack ) towards the tail. until you are happy with the way she flies.
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Old 10-03-2017, 04:31 AM
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Top_Gunn
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I have a somewhat modified Mid-Star (no dihedral, clipped wing, bigger ailerons and rudder). With the CG in the range Sig suggested it flew very comfortably but wouldn't snap roll or spin. I moved the CG back a bit and it flies like it should. I did have to reduce the elevator throw some to keep it from being too much fun. I've found that some other Sig kits (Kadet Senior and LT-40) also have recommended CG locations farther forward than I like.
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Old 10-03-2017, 06:16 AM
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Timewarpped
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Everyone is saying start at the Main Spar and adjust from there.
Thanks all.
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Old 10-03-2017, 07:03 AM
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All Day Dan
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That plane has a constant chord wing. That means that the Mean Aerodynamic Chord is the chord. The correct location of the CG is 25 to 30% of the chord. Use this website to help out. Dan.

Center of Gravity Calculator
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Old 10-03-2017, 05:49 PM
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Got it! I'll see how the calculator stacks up.
Thanks.
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