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wing chord

Old 07-31-2021, 01:34 PM
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hawkman-RCU
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Question wing chord

does anybody know the wing chord/ minus ailerons of a sig 4 star 120 or simular low wing sport plane with around 80 inch span. i need to figure out how long to make the ribs. thank you.

Last edited by hawkman-RCU; 07-31-2021 at 01:37 PM.
Old 07-31-2021, 06:53 PM
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I just checked the Sig web site and found the 120 has a wing area of 1205 square inches. By dividing that by the 81" span, I got 14.876 so I'd round it up to 15". That should get you into the ballpark. Now, you just need to figure out how much chord you want for your ailerons and you should be good to go
Old 07-31-2021, 07:03 PM
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thanks hydro, is that not counting the ailerons ? so the simple process is dividing wing area by span = chord ?

Last edited by hawkman-RCU; 07-31-2021 at 07:06 PM.
Old 07-31-2021, 07:24 PM
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Pretty much. Area has always been length multiplied by width so it just makes sense to divide area by span to get chord. Now, you subtract the depth needed for the desired chord of the ailerons and that will give you the outer location for the rear spar and the forward edge of the aileron leading edge. From there, it's just a matter of building as desired. I rounded up to 15" for two reasons:
1) to make calculations easier
2) to compensate for the width of the fuselage since the wing area enclosed under the fuse isn't going to have any lift so I compensated for it by rounding up.

Last edited by Hydro Junkie; 07-31-2021 at 07:27 PM.
Old 07-31-2021, 08:57 PM
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thanks again hydro. so im looking at 15" from leading edge of wing to trailing edge of ailerons, is that about right ? thank again for your reply.
Old 07-31-2021, 10:59 PM
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That's what the numbers say. With that said, there is a little room for error. If you want to double check the numbers, you could always contact Sig directly. They are closed until Monday but, come 7:00 central time Monday morning, you could call and ask them. Their phone number is 641-623-3922
Old 08-01-2021, 09:07 AM
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once again, thanks hydro for your input.

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