airofoil
03-05-2004, 07:57 PM
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airofoil
What do you guys think of this airofoil. I use it for my ww2 paper-project jets. Is it a good one because I got is from another ww2 jet (Me-262) plan.
03-05-2004, 11:35 PM
#2
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RE: airofoil
How large is the plane?
Small light low-speed planes can get along with practically any shape.
The blunt leading edge on your drawing wouldn't be good. It could be rounded off.
Also depening on the model size the shape can be quite simple... a curved single surface, or a curve on top, flat on the bottom.
The fancy high-speed airfoils work poorly for most models, they're just too small to do much more than nudge the air out of the way and the models fly much slower than full-scales. Simple curves work quite well, until you get into high performance.
Small light low-speed planes can get along with practically any shape.
The blunt leading edge on your drawing wouldn't be good. It could be rounded off.
Also depening on the model size the shape can be quite simple... a curved single surface, or a curve on top, flat on the bottom.
The fancy high-speed airfoils work poorly for most models, they're just too small to do much more than nudge the air out of the way and the models fly much slower than full-scales. Simple curves work quite well, until you get into high performance.
03-06-2004, 04:21 AM
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RE: airofoil
If that is just a rib and the leading edge is missing then it's still a bit rough along the upper forward surface of the leading edge. It's very flat there. Or as Paul suggests you need to round it properley. Fixed up this looks like a higher lift type airfoil suitable more for gliders or slower power models that won't spend much time upside down. If that's what you want then fine... with mods as suggested.
Paper jets? Got pics?
As for the question about the airfoil how about some more specs on what sort of flying you want to do with this airfoil and we could then offer a better opinion of this airfoil or recomend better ones for you application.
Paper jets? Got pics?
As for the question about the airfoil how about some more specs on what sort of flying you want to do with this airfoil and we could then offer a better opinion of this airfoil or recomend better ones for you application.
03-06-2004, 02:07 PM
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RE: airofoil
Well as you said its a airofoil with out the leading edge. I use it for jets like the one I posted. What do you mean I have to round it off more at the leading edge (I will scan one of the real rib sections and then post it). The plane specs are 38" wingspan 68" length with two wemotec 480 motors. I also used this airofoil for many other planes as well. And thanks for all the info.
03-06-2004, 02:20 PM
#5
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RE: airofoil
That looks fine.
There's an old expression that fits model airplanes...
"If it ain't broke, don't fix it!"
Your shape works on the others, it will work on almost anything else.
There's an old expression that fits model airplanes...
"If it ain't broke, don't fix it!"
Your shape works on the others, it will work on almost anything else.
03-06-2004, 02:36 PM
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RE: airofoil
That's a great looking and unique model design. I LIKE IT ! ! ! !
The airfoil, on the other hand, is very badly shaped. If it's working well for this model I suspect it's more because of the power and light weight of the model. If this was a thermal glider I'd say you would gain a LOT by switching to a better brand named airfoil from one of the more recognized sources.
In the case of this one the leading edge shape is quite blunt and does not transition smoothly into the upper leading edge curve. This sort of abruptness can often result in a premature stall and higher drag at all speeds. Compare the one in your expample to this one. A Selig 6062 airfoil......
The airfoil, on the other hand, is very badly shaped. If it's working well for this model I suspect it's more because of the power and light weight of the model. If this was a thermal glider I'd say you would gain a LOT by switching to a better brand named airfoil from one of the more recognized sources.
In the case of this one the leading edge shape is quite blunt and does not transition smoothly into the upper leading edge curve. This sort of abruptness can often result in a premature stall and higher drag at all speeds. Compare the one in your expample to this one. A Selig 6062 airfoil......
03-06-2004, 04:15 PM
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RE: airofoil
ORIGINAL: BMatthews
That's a great looking and unique model design. I LIKE IT ! ! ! !
The airfoil, on the other hand, is very badly shaped. If it's working well for this model I suspect it's more because of the power and light weight of the model. If this was a thermal glider I'd say you would gain a LOT by switching to a better brand named airfoil from one of the more recognized sources.
In the case of this one the leading edge shape is quite blunt and does not transition smoothly into the upper leading edge curve. This sort of abruptness can often result in a premature stall and higher drag at all speeds. Compare the one in your expample to this one. A Selig 6062 airfoil.......
That's a great looking and unique model design. I LIKE IT ! ! ! !
The airfoil, on the other hand, is very badly shaped. If it's working well for this model I suspect it's more because of the power and light weight of the model. If this was a thermal glider I'd say you would gain a LOT by switching to a better brand named airfoil from one of the more recognized sources.
In the case of this one the leading edge shape is quite blunt and does not transition smoothly into the upper leading edge curve. This sort of abruptness can often result in a premature stall and higher drag at all speeds. Compare the one in your expample to this one. A Selig 6062 airfoil.......
03-06-2004, 08:40 PM
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RE: airofoil
Um, I thought I DID put a picture in there. Can you not see the airfoil graphic in my last post? Your quote has it as well.
Here's a sketch of what I'm reffering to for your airfoil shape. In the first part is a copy of your graphic file with a couple of lines showing how the upper portion just behind the leading edge is very close to flat rather than having a nice blended curve down to the leading edge shape. This kind of shape can help lead to an early stall. Now also look at the leading edge curve. Your's is very close in size to the Clark Y but then the Clark Y is a thicker aifoil that is meant for slower speeds and higher lift. Now compare it to the Selig 6061. The Selig has a much smaller nose radius than your shape. This shape combined with the curve behind it on the upper side will provide a lower drag at high speeds but still "ease" the air over the curve behind the leading edge in a way that does not strain it's ability to stick to the surface and thus avoid a stall even at lower speeds.
The last three parts show a tracing I made of your airfoil along with a Clark Y and a Selig 6061 (those are what I had CAD files for already so I used them). Note how I've added station lines and a middle line that splits the distance between the upper and lower curves. This middle line is what is called the camber line and determines a lot about how an airfoil works. Note how in the lower two cases the camber line is a curve that arcs smoothly from the leading edge to the trailing edge. Now look at your aifoil. It may not be apparent from the small size here but in my CAD screen I was able to zoom in on the leading edge area to see that the camber curve actually arcs downwards before it comes back up and over to finish it's run to the trailing edge. In effect the way you have shaped your airfoil so that the first 1/4 of it is upside down according to standard modeling practice. In full sized aviation there are a few real odd balls that defy this logic but at our model airspeeds and other factors this shape is nothing but trouble.
So what airfoil would I suggest for your model design? Assuming you did see the S6062 in my previous post but didn't realize what it was I would suggest using that one but modified very slightly to make the lower surface from the 50% mark back to the trailing edge flat. There's supposed to be a slight pinching at the trailing edge but for power model work you'll never notice the difference. This airfoil is a low camber slippery racer like shape that will produce a wing that will a happy blend of upright and inverted flight with a definite advantage when upright. It'll also be slippery and a fast flier that gains speed in the dives quickly. Speed that can be turned back into altitude or fast rolls on command in a stunning way. If your design is meant for electric power then this may be the best of both worlds. To get the best from this or any thin performance airfoil shape I would suggest thin sheeting back to the 35% chord position on the lower side and the 50% position on the upper side so the covering is better supported from sagging over the most highly curve portions of the wing's shape. Otherwise you get a lot of covering sag between the ribs and end up with diamond shapes between the rib stations where the air wants to see curves.
Go to www.profili2.com and download the airfoil plotting program Profili 2. It'll give you more airfoils than you ever realized existed at your fingertips and you can browse to your heart's content to develop a feel for what they should look like.
Now many, many modelers have had luck drawing airfoils around their french curves or shoe insole in the past but they all did it with an eye to certain rules about the camber line, leading edge radius and overall thickness. For the most part you can get away with a lot as long as the basics are followed. In your case if you modified the forward leading edge area to re-shape the camber curve you could save this airfoil. The leading edge could either be reduced in it's radius or the upper line could be reshaped to blend into it better. But either way the leading edge has to come down to let the camber line be reshaped into an arc. But doing that would produce an airfoil with lots of camber similar to the ClarkY. That much camber would hinder the model's happiness about flying upside down or otherwise pulling negative G loads. The amount of camber is tied in to how much time you intend to fly inverted. That's why hotdog aerobatic models use symetrical airfoils.... because they can't make up their minds about which way is up...
That model you designed deserves the best. I really do like the shape of it and if my little offering here can help you ensure that it flies like you intend then I'll be happy. It's almost got a science fiction look to it and that really apeals to me. Best of luck with it and I hope you get to build it soon.
Here's a sketch of what I'm reffering to for your airfoil shape. In the first part is a copy of your graphic file with a couple of lines showing how the upper portion just behind the leading edge is very close to flat rather than having a nice blended curve down to the leading edge shape. This kind of shape can help lead to an early stall. Now also look at the leading edge curve. Your's is very close in size to the Clark Y but then the Clark Y is a thicker aifoil that is meant for slower speeds and higher lift. Now compare it to the Selig 6061. The Selig has a much smaller nose radius than your shape. This shape combined with the curve behind it on the upper side will provide a lower drag at high speeds but still "ease" the air over the curve behind the leading edge in a way that does not strain it's ability to stick to the surface and thus avoid a stall even at lower speeds.
The last three parts show a tracing I made of your airfoil along with a Clark Y and a Selig 6061 (those are what I had CAD files for already so I used them). Note how I've added station lines and a middle line that splits the distance between the upper and lower curves. This middle line is what is called the camber line and determines a lot about how an airfoil works. Note how in the lower two cases the camber line is a curve that arcs smoothly from the leading edge to the trailing edge. Now look at your aifoil. It may not be apparent from the small size here but in my CAD screen I was able to zoom in on the leading edge area to see that the camber curve actually arcs downwards before it comes back up and over to finish it's run to the trailing edge. In effect the way you have shaped your airfoil so that the first 1/4 of it is upside down according to standard modeling practice. In full sized aviation there are a few real odd balls that defy this logic but at our model airspeeds and other factors this shape is nothing but trouble.
So what airfoil would I suggest for your model design? Assuming you did see the S6062 in my previous post but didn't realize what it was I would suggest using that one but modified very slightly to make the lower surface from the 50% mark back to the trailing edge flat. There's supposed to be a slight pinching at the trailing edge but for power model work you'll never notice the difference. This airfoil is a low camber slippery racer like shape that will produce a wing that will a happy blend of upright and inverted flight with a definite advantage when upright. It'll also be slippery and a fast flier that gains speed in the dives quickly. Speed that can be turned back into altitude or fast rolls on command in a stunning way. If your design is meant for electric power then this may be the best of both worlds. To get the best from this or any thin performance airfoil shape I would suggest thin sheeting back to the 35% chord position on the lower side and the 50% position on the upper side so the covering is better supported from sagging over the most highly curve portions of the wing's shape. Otherwise you get a lot of covering sag between the ribs and end up with diamond shapes between the rib stations where the air wants to see curves.
Go to www.profili2.com and download the airfoil plotting program Profili 2. It'll give you more airfoils than you ever realized existed at your fingertips and you can browse to your heart's content to develop a feel for what they should look like.
Now many, many modelers have had luck drawing airfoils around their french curves or shoe insole in the past but they all did it with an eye to certain rules about the camber line, leading edge radius and overall thickness. For the most part you can get away with a lot as long as the basics are followed. In your case if you modified the forward leading edge area to re-shape the camber curve you could save this airfoil. The leading edge could either be reduced in it's radius or the upper line could be reshaped to blend into it better. But either way the leading edge has to come down to let the camber line be reshaped into an arc. But doing that would produce an airfoil with lots of camber similar to the ClarkY. That much camber would hinder the model's happiness about flying upside down or otherwise pulling negative G loads. The amount of camber is tied in to how much time you intend to fly inverted. That's why hotdog aerobatic models use symetrical airfoils.... because they can't make up their minds about which way is up...
That model you designed deserves the best. I really do like the shape of it and if my little offering here can help you ensure that it flies like you intend then I'll be happy. It's almost got a science fiction look to it and that really apeals to me. Best of luck with it and I hope you get to build it soon.
03-07-2004, 03:16 PM
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RE: airofoil
Well thanks allot for all the info but I think I am now so comfused that I dont know witch way is up[sm=confused.gif] . I have downloaded the profili program and I am trying to figure out how it works, but thanks for all your help.
03-07-2004, 03:33 PM
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RE: airofoil
Well I have NO IDEA how this programe works? And I did not see the Selig 6062 rib it did not show up on my computer. But again thanks for all your help!!!
