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Author Topic: What to include in wing loading calcs?  (Read 774 times)
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Saabotage
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« on: April 23, 2018, 06:20:27 AM »

Guys,
I'm new to design so am feeling my way around.

When you work out the wing loading on your designs do you include the area hidden between the fuselage? To me there seems to be a lot of measuring and confirmation of it only to negate a fair percentage which contributes nothing to lift but adds to weight?

Am I being too anal? Grin
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ironmike
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« Reply #1 on: April 23, 2018, 07:48:07 AM »

Yep
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piecost
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« Reply #2 on: April 23, 2018, 07:55:22 AM »

It does not matter that the area within the fuselage is not contributing to lift. It is more important that we all use standard assumptions so we can compare different models.
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lincoln
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« Reply #3 on: April 23, 2018, 01:28:58 PM »

It's quite an assumption that the "area within the fuselage" provides no lift. I suppose it's technically correct, since if you supported the wing in some other way, you could cut out the enclosed part, but the fuselage and its interaction with the wing are complicated. The results I've seen indicate that the fuselage itself contributes some lift, although that depends on the details of the design. Look up "spanwise lift distribution" and you'll see what I mean.

Anyway, piecost is correct that the usual assumption, for wing area calculations, is that the wing carries through. Unless you're talking the rules for old Wakefields*, but that's another story.


*I  don't know what they say now, but at one point the rules didn't count the part of the wing enclosed by the fuselage.
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USch
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« Reply #4 on: April 23, 2018, 02:25:04 PM »

*I  don't know what they say now.........

I can only speak for what the Fédération Aéronautique Internationale (FAI) says in the rulebook. The part crossing the fuselage does count as wing/tailplane aerea. The wing cord taken into account is the cord at the intersection between wing (tail) and fuselage.

FAI does the wing loading count adding wing and tailplane aerea, but thats for the sake of ruling, not for an aerodynamic reason.

Urs

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lincoln
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« Reply #5 on: June 16, 2018, 11:49:52 PM »

That's what the rule says now, but it has gone through some revisions over the years. I've found some references to the rule change regarding the area passing through the fuselage, but nothing truly authoritative. It would have been 70 or 80 years ago, I think.
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