ACHIEVING THE BEST REFLEXED AIRFOILS FOR FLYING WING USE IN THE SMALL PLANE CATEGORIES

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WINGITIS

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Wonderous Mountain has very kindly submitted a rather COOL looking idea of an airfoil for us to look at:

WONDEROUS AIRFOIL DESIGN.jpg

Using XFLR5 I have made a spline across it as accurately as possible and created a DAT file.

This was then analyzed.

As drawn it was 15% thick but that did not resolve well, neither did it at 14% so I had to change the shape somewhat to get it in the ballpark whilst keeping Wonderous's relative shape and his requirement to be around 13% or so.

I also made some changes to the nose to improve things, but as you can see from the slightly wobbly mean camber line near the nose some more work there would likely improve things a bit.

I then did a 5 Degree flaps up and down analysis for comparison.

You can see from the two different analysis lines that the airfoil has some potential flow separation issues(the two lines are FAR apart)

It does show some interesting trends though and is a GREAT indication of what we can learn if we just explore shapes from our MINDS.

There must be others with ARTISTIC/CREATIVE minds out there that can contribute an image!!!!

Hopefully...

Attached are the DAT files(as TXT) and Analysis Polars.

Thanks again Wonderous.

Kevin

WONDEROUS MOUNTAIN 3 AIRFOIL TEST.jpg
 

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Aesquire

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Just on "see the spray" first impressions, I'd flatten the bottom surface a bit. Lovely curve, I like the rearward "cusp"? on the bottom surface. I do wonder what the pitching moments are, the combinations of rear undercamber, & the slope of the curve?

Upon further inspection I see the hinge point with the long chord flaps, & that's clever. The wing's thickness at the hinge point looks about right. The flaps are harder to make, a good candidate for composites.

Nice.
 

WINGITIS

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The pitching moment "CM graph" is in the PDF, it slopes down to the right, goes negative with increasing alpha, that could be worked on somewhat.

Taking some of the "S" shape amplitude out is another idea, as it has a lot of camber and the maximum lift is not reflected in that.

The nose is not ideal as I have created it, that needs to be adjusted first before other changes as it is likely affecting the Polars in more than one way!

The DAT file is there as a TXT so someone could have a go at the nose and re-post.

Or change anything, the more inputs the better!

K
 

WINGITIS

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A while ago I ordered Jim Marskes book "THE WING AND I"

It arrived last week and I read it straight away, IT IS VERY GOOD.

Jim holds back nothing and gives a wealth of detail on his Reflex wing glider designs.

I CONSIDER IT AN ESSENTIAL MUST READ!

As a bonus Jim includes the detailed co-ordinates of a fair few airfoils he has used, some of which the co-ordinates of have not been shared with many before.

One which previously featured here but I had copied from a spline.

So I took the time to type 3 of them into a spreadsheet!!! then created the DAT files, its not all bad, they are listed in Selig format in the book.

One has 280 six digit numbers, decimal-ed and signed. I did not complete that one in a single session.......

NACA 33012-Hybrid
M-35A
HQ-34N

Here are the comparative results of the three I chose, ENJOY and thank you Jim:
 

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Voidhawk9

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14.1% thick racing airfoil. Very much a go-fast-at-all-costs design. Laminar flow over 75%+ of chord.
Works well in simulation, not yet tested in the real world. Separate OpenFOAM CFD of wing appears favourable.
Not suited to slow flight.
M13_race_foil.jpg
 

WINGITIS

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14.1% thick racing airfoil. Very much a go-fast-at-all-costs design. Laminar flow over 75%+ of chord.
Works well in simulation, not yet tested in the real world. Separate OpenFOAM CFD of wing appears favourable.
Not suited to slow flight.
View attachment 114142
Its too small!

Try

 

Voidhawk9

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Hmm, nope, not my fault, the forum is downscaling to destruction. I'll find a solution.

Try this:
 

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WINGITIS

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YES, its not your fault, a known problem, mentioned back in 2020 in this thread.

Many thanks for that, the quality is fine, you can zoom in with the PDF and see the values.

COME ON YOU OTHERS, dont let a couple of chaps from New Zealand outdo you!

SUBMIT SUBMIT, so to speak....
 

WINGITIS

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Some PDF's depending on how they are prepared will allow you to GRAB the co-ordinates with the TEXT tool.

I do have a DXF to DAT tool somewhere as well.

Cheers
 

Voidhawk9

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For that I usually just use an image as a background reference in XFLR5, line up the curves accordingly, and export if necessary.
If done carefully, it's within the margins of drawing accuracy and homebuilt construction accuracy!
 

rotax618

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I wanted the dxf > dat to create experimental wings with my cnc foam cutter, most free software only allows.dat airfoil files which limits me to existing published airfoils.
 

rtfm

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I use Sketchup. Piece of cake. But it has to be the 2018 (or later version). If you don't want to pay for it, you can use it (fully featured) for a 1 month trial period.
 

Norman

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I wanted the dxf > dat to create experimental wings with my cnc foam cutter, most free software only allows.dat airfoil files which limits me to existing published airfoils.
You can use a .DAT file as the base to create a script file for your CAD program. I only know how to do this in Autocad but other programs also have a scripting language for automating repetitive tasks. I haven't done it in quite a while but here's what I recall:

This can be done in any text editor that saves as flat ASCII such as windows notepad.
First of all the top line with the airfoil name is replaced with the command to use. That would be either <pline> or <spline>.

Then since the .DAT is a space delimited file you'll need to change that to a comma delimited file. Search and replace makes it a quick job if the .DAT file only has one space per ordinate pair, the .DAT format allows multiple spaces so watch for that. You have to make sure there are no blank spaces in the file except for the last line because the space bar is the end command in ACAD.

When you're finished it should look like this:

spline
1,0
.9,y
.8,y
.7,y
.6,y
.5,y
0,0
.5,y
1,0
<space>

Now SAVE AS with a .SCR extension.

Now that the spline is in CAD you can save it as a .DXF
 
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Norman

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YES, its not your fault, a known problem, mentioned back in 2020 in this thread.
I brought the loss of resolution problem up to the administrator a few months ago but got no help. Basically he just told me that it's my fault.

COME ON YOU OTHERS, don't let a couple of chaps from New Zealand outdo you!

SUBMIT SUBMIT, so to speak....
OK I've been working on a real oddball problem off and on for a while. It's a drop-in replacement airfoil for the Mitchell U-2. The spar is right up against the pilot's back so the replacement airfoil must have the thickest point in the same place. The problem is that the max thickness is at 40% and reflexed airfoils tend to have low CLmax with the thickness that far aft and his modified Wortmann didn't turn out very well so the plane doesn't live up to the hype. So here's my latest attempt to make a better airfoil that can fit onto the spar of that plane without any structural modifications. I'm not recommending that anybody actually use it without further testing because panel code software doesn't provide data about stall or hysteresis but a large scale model would validate it.
 

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rotax618

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I can use Freecad to import .dat airfoil files and scale, extrude, loft etc. the problem I have is if I want to cut an experimental shape on my cnc hotwire cutter, the ’free’ software that generates xyuz gcode requites a .dat file, I can generate dxf files of my shape but not .dat. Clearly there is paid software out ther that will do it but I was asking if anyone had knowledge of ‘freeware’. Because of the exchange rate, what appears to be cheap to the rest of the world is around double the cost here in OZ. A French free program Jedicut can cut dxf files If only someone could tell me how to get it to do that.
 

WINGITIS

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I brought the loss of resolution problem up to the administrator a few months ago but got no help. Basically he just told me that it's my fault.


OK I've been working on a real oddball problem off and on for a while. It's a drop-in replacement airfoil for the Mitchell U-2. The spar is right up against the pilot's back so the replacement airfoil must have the thickest point in the same place. The problem is that the max thickness is at 40% and reflexed airfoils tend to have low CLmax with the thickness that far aft and his modified Wortmann didn't turn out very well so the plane doesn't live up to the hype. So here's my latest attempt to make a better airfoil that can fit onto the spar of that plane without any structural modifications. I'm not recommending that anybody actually use it without further testing because panel code software doesn't provide data about stall or hysteresis but a large scale model would validate it.
Hi Norman thanks for that, I will run the airfoil through XFLR5 and post it later on.

In terms of the CRAPPY(To say the least) JPG file importer/display capability of the HBA I totally support you in that it is a BUG or INTENTIONAL limitation of the HBA feature set.

I have never seen such a poor import function of an image file ANYWHERE on the INTERNET before!

You can pass my comments on to the Administrator if you like and we should BATTLE to get this fixed.

THEY CANNOT BLAME THIS ON THE USERS BECAUSE WE ARE ALL EXPERIENCING THE SAME THING USING NATIVE MICROSOFT PRODUCTS WITH A WORLDWIDE COMMON STANDARD IMAGE FORMAT MOSTLY RUNNING ON MS WINDOWS PLATFORMS.

ITS NOT OUR FAULT IN ANY WAY SHAPE OR FORM.

Cheers
Kevin
 
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