How does a scale up affect airfoil center of lift?

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pjphilli

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I got excited and did the first phase for you, someone can please check my numbers, before I go on to create the DAT file.

A few issues I found:

1: The LE is not on the reference line, this can be rectified in XFLR5 with the Normalize and De-rotate features later in the process.

2: Where the tape is at the TE the station lengths are not the same, so it has been taped incorrectly.

3: The tape covers some of the measurements, I used a bit of math to solve for those missing points, using the slopes and intercept method(Overkill for this example, its more useful when the X axis values are to 6 decimal places and not equidistant, but I use it for all straight line interpolations as a rule)

Most of the other numbers are fairly readable, but it does not mean I have misread or mistyped 1 or 2, SO PLEASE CHECK!

Kevin
Thanks Again! Used my office with big computer monitors so I could blow up my plans copy to "really-really large" and scroll across inch-by inch, bottom and top. There was only (4) cells I highlighted in yellow and re-typed to what I think it said. I believe the "x.xx" last digit was only thing I saw different... really comparing how were 6's, 8's, "9 vs. 4's" etc. written elsewhere for comparison... those coordinated were tough to read even blown up. Hopefully this attaches right :)
 

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Norman

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Guys as long as the leading edge pressure distribution is reasonably smooth at some small positive AoA and Cm0 matches the Cm0 of the airfoil described in NACA report 537 it's close enough. Any error caused by misinterpreting the fuzzy numbers on your plans can be smoothed over with inverse design if they seem to be causing problems. The variation seen in the polars of the several versions we have are most likely to be small enough to be lost in the noise.
 

Jimstix

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While the old NACA 23112 has a good lift coefficient and a nearly zero pitching moment it has nasty stall characteristics. Increasing the Reynolds number by making it bigger will not change the poor stall characteristics. It is likely that any airfoil derived from the 23000 family will likewise have the same poor stall behavior. Many better choices are available.
 

BJC

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It is likely that any airfoil derived from the 23000 family will likewise have the same poor stall behavior. Many better choices are available.
What aircraft, with 23000 series airfoils, have you flown that have “poor stall behavior”?


BJC
 

WINGITIS

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OK here is the SPRATT 23112 version I have just finished the nose on and compared to the airfoil tools 23112.

The SPRATT version has no advantages and appears to have some issues at the nose, as Norman has suggested, that may be the way it is lofted, although it also has a flatter lower forward surface.

As Phil has just listed a few changes above I will check those, but here is the polar comparison and the DAT file in TXT format.

SPRATT CNTRL WING PLANS 23112 VERSUS AIRFOIL TOOLS FORMULA 23112.png
 

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WINGITIS

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Those 4 updates were very small but I have made them anyway and included the revised spreadsheet(SO YOU CAN SEE HOW I GOT THE NOSE DIMENSIONS FROM THE DRAWING)

That creates the input columns for the SELIG FORMAT in the spreadsheet as per EXACTLY what the drawing states.

I have then gone through the process of NORMALISING, DEROTATING and making it 299 panels and output the final DAT file attached here as a TXT.

I WAS HOPING IT WOULD BE BETTER OR WITH THE ODD BETTER FEATURE THAN THE ORIGINAL FROM THE AIRFOIL TOOLS FORMULA, as I am always on the lookout for better Reflex airfoils, but ALAS it was not the case this time.
 

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BJC

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Beech Bonanza. That's why they put those goofy looking stall wedges on the later models.
I’ve not flown a Bonanza, but friends who have say that they stall just fine if the pilot knows what the rudder pedals are for.


BJC
 

TFF

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Oh ye of little knowledge. Those little wedges are where the owners sign the checks on.

I believe the wedges part if a package that ups the gross.
 

pjphilli

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I love and appreciate all these responses. Remember the control wing as long as control deflection is limited to about 18 degrees or less is incapable of stall or spin. If memory recalls, about 22 degrees is where this airfoil breaks. If one does not use a collective lever plus a left/right control differential to a total of greater than 22 degrees, stall is impossible, as is spins or stunts of any kind. If one did not use a collective lever it would be a mono-speed airplane. When I learned to fly in late 70’s, power was altitude control, elevator was speed control. With a control wing with no elevator, rudder, or anything beyond differential wing deflection at slight angles that weather-cocking overcomes essentially non existent adverse yaw, it’s simply power for altitude, collective up for a flare at landing or to bungee down for increased cruise. Otherwise it’s one airspeed take off, steady state cruise and land.
PS: loved rudder comment, learned to fly in what’s now a family legacy J5A.., can’t get around the pattern without more than a passing familiarity with the rudder:) again, thank you wingitus, what you are doing is a few levels over my #2 wood pencil, but may provide inspiration for more than me to build one when I retire!!! Will check out attachments from PC tomorrow. Thanks:)
 

pjphilli

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Guys as long as the leading edge pressure distribution is reasonably smooth at some small positive AoA and Cm0 matches the Cm0 of the airfoil described in NACA report 537 it's close enough. Any error caused by misinterpreting the fuzzy numbers on your plans can be smoothed over with inverse design if they seem to be causing problems. The variation seen in the polars of the several versions we have are most likely to be small enough to be lost in the noise.
Norman, I interpret this to mean that the differences in the grand scheme of things is within the resolution of what I can actually plot out on a fiber board to make a wing rib jig/template from… this is reassuring, thank you very much!
 

Norman

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OK here is the SPRATT 23112 version I have just finished the nose on and compared to the airfoil tools 23112.

The SPRATT version has no advantages and appears to have some issues at the nose, as Norman has suggested, that may be the way it is lofted, although it also has a flatter lower forward surface.
It looks like Mr Spratt modified the 23112 ordinates to get rid of the leading edge cusp by decreasing the camber until it disappeared. Several designers (eg Marske Monarch, Schweizer 1-26, Corby Starlet) modified the 43012 similarly to produce the 43012a but they simply filled in the cusp, leaving the top surface unchanged. This was to simplify construction not for aerodynamic reasons. From your data curves it looks like the Spratt mod wasn't very successful.
 

Norman

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Norman, I interpret this to mean that the differences in the grand scheme of things is within the resolution of what I can actually plot out on a fiber board to make a wing rib jig/template from… this is reassuring, thank you very much!
I'm saying that it's not a terribly sensitive airfoil but as you can see in the polars that Wingitis posted small deviations from the nominal shape can degrade performance or even turn a marginal airfoil into a dangerous one.
 
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