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Information on CG for Vern Zundel design -1911 Deperdussin

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Old 04-20-2017, 06:25 PM
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ektpuah
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Default Information on CG for Vern Zundel design -1911 Deperdussin

Dear builders, I am currently scratch building the 1911 Deperdussin designed by Vern Zundel in 1970. The CG position was not indicated in the plans. Does anyone know where is the recommended CG position?

I tried to email Vern but his email address is no longer valid.

Many thanks and best regards
James Puah
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Old 04-20-2017, 06:46 PM
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That plane has a constant chord wing which means that the Mean Aerodynamic Chord of the wing is the chord. Put the CG at 30% of the chord measured from the leading edge of the wing for a safe first flight. Dan.
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Old 04-27-2017, 08:43 AM
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Funny he didn't mark it on the plan; he probably stated it in the text. I know he needed a lot of weight up front; there is practically no nose at all.

I think a lot of Deperdussin aircraft had constant chord wings, but this one didn't; the leading edge is straight but the trailing edge is not.

The usual rules of thumb don't always apply to early aircraft because many of them had large tail volumes, so a suitable CG could often be further back than you would expect. It's important to know because the plane is so hard to balance anyway, you don't want to use even more weight than necessary.

Maybe someone with the original article will show up with the answer. If not, I would use a calculator... Aircraft Center of Gravity Calculator

You need the kind that takes into account the wing area, the mean aerodynamic chord (MAC), the stab area and the tail arm. Just finding the MAC and using a rule of thumb might not do the job in this case.

Jim

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Old 04-27-2017, 09:01 AM
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Good point Jim. That calculator is one of the best. Dan.
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Old 04-27-2017, 06:29 PM
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Thanks Dan; I agree, that calculator is a good one. Jim
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