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Nov 07, 2017, 03:22 PM
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slow flight


How slow can a wing fly? I know there are many variables, I would just like a general answer
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Nov 07, 2017, 03:37 PM
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Quote:
Originally Posted by Oklahoma Crude
How slow can a wing fly? I know there are many variables, I would just like a general answer
Airspeed, as slow as the wing loading and control authority will allow. Ground speed, less than zero if the pilot up to the task.

Here's a link to a nice slow flying wing with a video in post 12: https://www.rcgroups.com/forums/show...05-250-Weezzle
Nov 07, 2017, 04:03 PM
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mike3976's Avatar
SuperFly Mid Motor EPP Wing (2 min 41 sec)
Nov 10, 2017, 03:34 PM
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You can fly a wing very slow, just like any other model. It all depends on wing loading. Here is my styker built to 8.3 ounces. It flies pretty slow.

8.3 ounce Stryker (0 min 27 sec)
Nov 12, 2017, 07:24 PM
We don't need no stinkin' tail
RPM314's Avatar
Quote:
Originally Posted by Oklahoma Crude
How slow can a wing fly? I know there are many variables, I would just like a general answer
Yes there are many variables. Here's what they are:

Bernoulli's equation tells us:
Lift = 0.5 * air density * airspeed^2 * wing area * lift coefficient

The lift is your weight, in newtons or pounds; air density is 1.225kg/m^3 or 0.00238slug/ft^3; airspeed is in m/s or ft/s; wing area is in m^2 or ft^2; and the lift coefficient depends on the model. I've been able to get lift coefficients of ~1.0 out of wings with inboard flaps like the SWIFT glider has, but you should probably use 0.7 or 0.8 for an average wing. Solve for airspeed.

RC conventional planes, for comparison, can have lift coefficients maybe up to 1.2 with high lift flaps. But they also have the weight of a fuselage to contend with. With these figures, we can say that if an average plane of a given wing area could have about 35% *COUGH COUGH extremely rough COUGH number I pulled COUGH COUGH out my arse COUGH* of its weight removed (compared to a conventional configuration) by going with a tailless configuration it can fly slower.

So then the slowest a wing could go is as slow as any conventional ultra micro could go, give or take some factor depending on whatever. I suppose that's the general answer.
Nov 17, 2017, 06:34 AM
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I would be surprised if any flying wing can produce a C_L of more than 0.7-0.75-ish. I'd be keen to see real data on something that is near 1.0!
Nov 17, 2017, 09:03 AM
We don't need no stinkin' tail
RPM314's Avatar
The SWIFT glider claims either about 1.0 (not completely clear from the document) with its inboard flaps, so it's the right ballpark.
My XFLR5 predicts that my 1250mm wing in the flaps down configuration can go up to ~1.0 before sections start stalling. XFLR5 is sometimes overly optimistic about lift coefficients, but at the same time planes can be flown with parts of the wing beginning to stall, where XFLR5 gives up.
Anecdotally, I can tell you that my wing with inboard flaps feels wayyy floatier than wings of similar size I've built before, but I'd need a wind tunnel to check any numbers. Or maybe with a windless day and a radar gun I could back-calculate the lift coefficient, but that's not happening either.
In short, I'd love to see test data too! Hate making these claims based only on back of napkin math.


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