How Do I Figure Out This Airfoil? Please Help!
07-24-2004, 09:12 PM
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How Do I Figure Out This Airfoil? Please Help!
Hi Everyone,
I have an airplane here that I've found a problem with the stab on. It's not enough to keep it from flying, but it will present a trim problem. I need to figure out what the airfoil is so i can send this information to the foam cutter to get one cut. If you had a model that you needed to figure out what the airfoil was, how would you go about doing this? Is there a way to plot and compare it? I have profili software, but there are thousands of airfoils, ands I must be sure I get the same one that was on the plane as this is a competition aircraft. I also need to keep this airplane flying until I get new stabs for it. Please help! It will be GREATLY appreciated.
I have an airplane here that I've found a problem with the stab on. It's not enough to keep it from flying, but it will present a trim problem. I need to figure out what the airfoil is so i can send this information to the foam cutter to get one cut. If you had a model that you needed to figure out what the airfoil was, how would you go about doing this? Is there a way to plot and compare it? I have profili software, but there are thousands of airfoils, ands I must be sure I get the same one that was on the plane as this is a competition aircraft. I also need to keep this airplane flying until I get new stabs for it. Please help! It will be GREATLY appreciated.
07-24-2004, 10:11 PM
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RE: How Do I Figure Out This Airfoil? Please Help!
You just named the top question as to airfoils raised by CAD users today. It was discussed at length about a year ago here, but no answer was evident. Some of the glider designers will state on the plans which airfoil number was used, but not too often on powered models. Some times, in a magazine model review the airfoil number may come up. Normally this is seldom noted on the plans either.
Compufoil has a bit of software referred to as CONVERT which can come up with an airfoil based on a drawing. It involves tracing the lines, converting into Autocad DXF format, then using the software to come up with one, to which you name. It does not go through a big list and make a comparison of coordinates to give you the Best Fit answer. I once plotted out all the airfoils by number I had on the hard drive, and bound into a book. I then tried comparing a model airfoil to those in the book. Seldom came up with an exact match. Many airfoils differ from another by only a few thousanths back there in the 60-80 percentile area, or up around the nose. I copied an airfoil sent to me from the Czech Republic via the internet a few years back. It was in TIFF format, plus had a few additional dimensions given. We laser cut about 500 of them and had in the mail by Friday. Mail was so slow it took about two months to get into their hands unfortunately.
It is much simplier to just come up with your own new airfoil name based upon measurements, and use that for replications purposes.
I have friends on the automotive market who copy profiles to camshaft lobes. Just giving the lift and duration in numbers is only part of the solving. They spend a whole day trying to copy and record the coordinates of all the ramps for a sucessful cam lobe. Then they try and reproduce it on theirown Landis cam grinder. Ther is good money in copys.
When you figure out a simple way, let all of us know. We have tried many methods and are quick to critisize or point out the errors in the method used.
Wm.
Compufoil has a bit of software referred to as CONVERT which can come up with an airfoil based on a drawing. It involves tracing the lines, converting into Autocad DXF format, then using the software to come up with one, to which you name. It does not go through a big list and make a comparison of coordinates to give you the Best Fit answer. I once plotted out all the airfoils by number I had on the hard drive, and bound into a book. I then tried comparing a model airfoil to those in the book. Seldom came up with an exact match. Many airfoils differ from another by only a few thousanths back there in the 60-80 percentile area, or up around the nose. I copied an airfoil sent to me from the Czech Republic via the internet a few years back. It was in TIFF format, plus had a few additional dimensions given. We laser cut about 500 of them and had in the mail by Friday. Mail was so slow it took about two months to get into their hands unfortunately.
It is much simplier to just come up with your own new airfoil name based upon measurements, and use that for replications purposes.
I have friends on the automotive market who copy profiles to camshaft lobes. Just giving the lift and duration in numbers is only part of the solving. They spend a whole day trying to copy and record the coordinates of all the ramps for a sucessful cam lobe. Then they try and reproduce it on theirown Landis cam grinder. Ther is good money in copys.
When you figure out a simple way, let all of us know. We have tried many methods and are quick to critisize or point out the errors in the method used.
Wm.
07-27-2004, 12:47 AM
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RE: How Do I Figure Out This Airfoil? Please Help!
ORIGINAL: SharksTooth
Hi Everyone,
....I have profili software, but there are thousands of airfoils....
Hi Everyone,
....I have profili software, but there are thousands of airfoils....
Which software is that ? Is it free ? is so - where can I download it ? Is it easy to use ?
Thanks
10-01-2004, 10:41 PM
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RE: How Do I Figure Out This Airfoil? Please Help!
Shark,
Profili is capable of comparing airfoils.
If you have access to a flatbed scanner, you could scan your airfoil, then import it into Profili. You can then go back to "airfoil Management" and then select the airfoil that you just imported, click on "Show airfoils similar to the selected one", and Profili will give you a list of airfoils that closely match the one that you scanned in.
That's what I did in this screenshot... I made up an airfoil of my own design, and then had Profili see what other airfoils were similar to it.
If any of you don't have Profili2, I HIGHLY suggest that you get it, and register it too!! For about $13, it is an incredible incredible bargain when you look at what it can do! Registering unlocks some pretty slick features.[sm=thumbup.gif]
Profili is capable of comparing airfoils.
If you have access to a flatbed scanner, you could scan your airfoil, then import it into Profili. You can then go back to "airfoil Management" and then select the airfoil that you just imported, click on "Show airfoils similar to the selected one", and Profili will give you a list of airfoils that closely match the one that you scanned in.
That's what I did in this screenshot... I made up an airfoil of my own design, and then had Profili see what other airfoils were similar to it.
If any of you don't have Profili2, I HIGHLY suggest that you get it, and register it too!! For about $13, it is an incredible incredible bargain when you look at what it can do! Registering unlocks some pretty slick features.[sm=thumbup.gif]
10-01-2004, 11:59 PM
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RE: How Do I Figure Out This Airfoil? Please Help!
SharksTooth
This may sound silly, but most sailplanes use one of two airfoils on stabs, NACA 0009, or SD 8020. Pattern planes used the 0009, last time I looked at a set of planes. The 8020 was developed to have very little deadband, I've never seen someone that could tell the differance between it and the 0009.
If you measure the chord, then measure the thickness and get a thickness that's 9% it's most likely 0009, if it's 10.1% thick it's probably a 8020. If you get something else you're on you own, but my guess would be it'll be one of the two.
The NACA airfoils the last number is how thick it is, so if it comes out 6%, try NACA 0006.
This may sound silly, but most sailplanes use one of two airfoils on stabs, NACA 0009, or SD 8020. Pattern planes used the 0009, last time I looked at a set of planes. The 8020 was developed to have very little deadband, I've never seen someone that could tell the differance between it and the 0009.
If you measure the chord, then measure the thickness and get a thickness that's 9% it's most likely 0009, if it's 10.1% thick it's probably a 8020. If you get something else you're on you own, but my guess would be it'll be one of the two.
The NACA airfoils the last number is how thick it is, so if it comes out 6%, try NACA 0006.
