Found this wing on ebay. It is a cheapo, but they show the profile of this extrusion. I was going to run some numbers on it and if someone's got a good way to trace the profile and then somehow plot that into say 30 points across the top and 30 along the bottom I would be grateful.
I can sorta do a "side by side" but it takes forever and isn't very exact. I could also print it out and take physical measurements, but I'm sure someone out there has software to do that for me.
What say you?
If you can do it easily it would be sick if you could do this one as well (not as great a pic because of the angle).
Also, I will totally have this moved to the aero forum, but I wanted more eyes out here to see if it can be translated. I will post the ebay links and my findings in the aero forum.
MS Paint shows the cursor position of images, you might be able to use that?
Im confused.. what does your x/y plot look like? If X is on the X and Y is on the Y, its just called a 2d profile :)
Those are fairly easy to translate into CAD if your profile shot is rather square (the second would be questionable)
I can paste something into javafoil like this. Yes, 2d profile sounds right.
Good call on MS paint coordinates!! I think I can use that.
Ah, I see what you are after.
Thats fairly easy in most CAD software. Let us know if MS paint doesn't work out.
Robbie, those profiles are likely to be "typical" profiles, so the coordinates should exist. Javafoil allows you to import based on NACA designations. I would suggest starting with NACA 5 series to match the first profile.
I have an add-on for my CAD that interpolates shapes from images, but you have to do some work to crop out all the background from images first, so about the same work as bringing the image in and then spline fitting to the shape.
Let me know if you still need this sorted and I can help out.
Like this?
Print the 2nd one out on 8.5x11 with 0 margin and it should come out to scale. I'm not sure what your plan with these is. I would cut both shapes out of wood to scale and hotwire foam cut them.. If you need all the dimensions you can measure or I can work up a grid and make a drawing with dimensions.
so, you can use JavaFoil to suck in an image and have it spit out some coordinates, although, they'll need some messaging. I went through this back around February with a wing from Amazon.
The trick is, that I first pulled the images into paint.net, and added layers... and then used it's line/spline curve to draw an outline over the one in the image, which can then be exported out onto a white background in png to then be pulled into JavaFoil. Png is better than jpg in this case, because it won't have compression artifacts.
edit:
also, I ran an analysis in JavaFoil... and you want at least 140points in your coordinate file to get "good"/"consistent" results.
In reply to nocones :
um, that's amazing! I was just hoping to take the outline and turn it into a series of points with x and y distance values. I'm not looking to build it, since it's a cheapo wing on ebay I was just thinking of buying it. But I wanted to run some numbers on it first before buying so that I can see if it would be effective at all.
sleepyhead the buffalo said:
so, you can use JavaFoil to suck in an image and have it spit out some coordinates, although, they'll need some messaging. I went through this back around February with a wing from Amazon.
The trick is, that I first pulled the images into paint.net, and added layers... and then used it's line/spline curve to draw an outline over the one in the image, which can then be exported out onto a white background in png to then be pulled into JavaFoil. Png is better than jpg in this case, because it won't have compression artifacts.
edit:
also, I ran an analysis in JavaFoil... and you want at least 140points in your coordinate file to get "good"/"consistent" results.
How did you do the "suck in an image and spit out coordinates" thing?
stafford1500 said:
Robbie, those profiles are likely to be "typical" profiles, so the coordinates should exist. Javafoil allows you to import based on NACA designations. I would suggest starting with NACA 5 series to match the first profile.
I have an add-on for my CAD that interpolates shapes from images, but you have to do some work to crop out all the background from images first, so about the same work as bringing the image in and then spline fitting to the shape.
Let me know if you still need this sorted and I can help out.
I figured they would be standard too but after casual browsing in airfoiltools and playing around with javafoil I haven't been able to find something super close to the first profile. I'm also thinking the rounded trailing edge has a pretty bad effect on the characteristics so I don't want to model from something with a sharp trailing edge. (Of course I could modify the model to match if I found something close).
In reply to Robbie (Forum Supporter) :
in the geometry tab, when you click the "open" button, you can select an image file, and it will pull coordinates from the outline. Those coordinates may require tweaking afterwards.
nocones image, after removing the dimensioning lines, and having it export to png instead of jpg (DM?) would probably the best place to start. But, leaving in the dimension lines will probably make getting a good "nose" shape... difficult. I've also sometimes "saved" the resulting coordinates and then loaded them into xfoil to tweak, and use it's "pane" algorithm which loads points at the front and back... which can sometimes help the transition algorithms, sine the front and back have the most 'curvature' change.
edit:
I'm assuming they're based on some kind of eppler coordinate... or another "high L/D" foil shape... but I haven't been real successful in identifying it yet, either. And, in a number of ways, it's actually easier/faster to pull them from the photo... even after acquisition, since they're usually in the $50-150 range.
Here they are with no leader lines as a PNG
ah, berkley, I forgot... JavaFoil wants a "filled" image...
Thanks guys! That import to javafoil worked incredibly well.
Sleepy, I actually just did thick black lines on top of nocones images and it worked. Thanks for the tip!
I'm still working on a final write-up, but let's just say the results are promising.
In stock config the wing isn't that great (perhaps on purpose), but if you follow the great Stafford advice and crank the angle on the smaller airfoil, you can achieve a very respectable coefficient of lift.
so the wing I was playing with was a single element... and was short on area for what we were aiming for. Thus, I was playing around with extensions to increase area, and add AoA.max/Clmax improvements.
assuming you're not limited to area, for some reason, you might play around with adding to the wing's trailing edge. or, maybe I should?
Here's the "stock profile" this is at a slightly high reynolds number, but still you can see the Coefficient of lift is pretty good and the drag is very low.
If we increase the angle of attack on the stock profile the coefficient of lift goes up, but the drag goes up a lot.
Here's the two profiles with the 2nd element angle cranked up - if the wing even makes half of this Coefficient of lift that would be 60+ lbs of downforce at 60 mph and nearly 200 lbs at 100 mph. That's useable in the autox zones. Drag is not great, but hey - ebay wing.
What is the defined area of the wing? Wondering how the drag of the wing compares to the overall vehicle drag
call it 56 inches wide and in the 3rd position it would be 7-8 inches "tall" (perpendicular to the airflow).
Since its about the same width as the car but only say 1/8th as tall, and since it has a similar Cd to a normal vehicle, it would have about 1/8th the drag. Or increase the drag of the vehicle 12.5%
In the first position, the calculated Cd is very low so it would have a much smaller impact.
I almost forgot, here's a link to the wing. For $120 with free shipping, this might be the easy button to add downforce on a challenge budget. Could you develop your own better and cheaper wing? Absolutely. But I don't think it's necessarily as useless as you might think.
https://www.ebay.com/itm/MEGAN-UNIVERSAL-GT-TYPE-ALUMINUM-SPOILER-WING-BLACK-56-WX10-H/111787566719?epid=6017015480&hash=item1a070ee67f:g:1R0AAOSwPcVVy~ks
"Megan Racing MR-AS-GT56BL"
Robbie (Forum Supporter) said:
I almost forgot, here's a link to the wing. For $120 with free shipping, this might be the easy button to add downforce on a challenge budget. Could you develop your own better and cheaper wing? Absolutely. But I don't think it's necessarily as useless as you might think.
https://www.ebay.com/itm/MEGAN-UNIVERSAL-GT-TYPE-ALUMINUM-SPOILER-WING-BLACK-56-WX10-H/111787566719?epid=6017015480&hash=item1a070ee67f:g:1R0AAOSwPcVVy~ks
"Megan Racing MR-AS-GT56BL"
I don't think that's the same wing as the profile of wing at the top of the page. I think it ends up looking like this:
although, it only looks that good because there's a bit of pine board attached to the "bottom" (in car wing parlance):
^ those via miataturbo
another thing to try, would be closing the gap between the two sections. It'd guess it should be 50-25% of what it is in your example. And you can play around with moving it forward and back to optimize performance.
I can only go by the pics shown in the ebay ad - if I buy it and end up with something completely different, then that would be lame.
But the ebay ad definitely lists the photos I pasted in the first post.
ideal conditions: rho = .002377, wing area = 56*(7.5+3.75) / 144 = 4.375, and Cd = 0.413
v = 60mph = 88fps ... Drag ~16.5#s
v = 100mph = 147fps ... Drag ~46.4#s
Robbie (Forum Supporter) said:
I can only go by the pics shown in the ebay ad - if I buy it and end up with something completely different, then that would be lame.
But the ebay ad definitely lists the photos I pasted in the first post.
gotcha, I didn't dig all the way down into the listing... and seeing that picture, I can now see the 'tabs' that stick down from the upper surface; and that seems to match the line drawing also listed.
