Building a GT Wing
Jan 21, 2009, 08:01 PM
#5
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I still haven't figured out the details like support height, and spacing. But I'd like to keep the supports inboard of the basic silhouette to decrease drag, as opposed to ones on the edge of the trunk. I'm planning on having it at roughly the height of the roof. I am still researching airfoil profiles, which I know very little about at the moment. So I plan on doing some research and talking with a local aero engineer who works for Boeing.
I don't really know what sort of force I need to create. I know that my current configuration nets roughly zero lift at around 80 mph, but I don't know the amount the stock wing is really doing. For that matter nobody has ever shared the amount of force a typical after market wing creates either. EVOlutionary was going to go to a wind tunnel this winter - not sure if that happened.
The construction will be based on an aluminum frame, with a foam core shaped in the airfoil profile that surrounds the frame. Then I'll lay it up with 5 or so layers of carbon and vacuum bag it. I'm pretty sure this is how most racing wings are built as well. I've never worked with composites before, but have always wanted to. I missed the grad level composites class I wanted to take my senior year of college because I procrastinated a required electrical engineering class which conflicted. I'm still bitter about that. I'll probably plasma cut the uprights. I could have them machined, but I just bought a plasma cutter and want to do work with it. Probably build a tow hook as well with it.
In the last year I've taught myself to TIG weld, built my first motor, and now will be doing composites - good stuff.
I don't really know what sort of force I need to create. I know that my current configuration nets roughly zero lift at around 80 mph, but I don't know the amount the stock wing is really doing. For that matter nobody has ever shared the amount of force a typical after market wing creates either. EVOlutionary was going to go to a wind tunnel this winter - not sure if that happened.
The construction will be based on an aluminum frame, with a foam core shaped in the airfoil profile that surrounds the frame. Then I'll lay it up with 5 or so layers of carbon and vacuum bag it. I'm pretty sure this is how most racing wings are built as well. I've never worked with composites before, but have always wanted to. I missed the grad level composites class I wanted to take my senior year of college because I procrastinated a required electrical engineering class which conflicted. I'm still bitter about that. I'll probably plasma cut the uprights. I could have them machined, but I just bought a plasma cutter and want to do work with it. Probably build a tow hook as well with it.
In the last year I've taught myself to TIG weld, built my first motor, and now will be doing composites - good stuff.
Last edited by jid2; Jan 21, 2009 at 08:05 PM.
Jan 21, 2009, 08:12 PM
#7
jid2,
system three- PHASE TWO epoxy.
http://www.systemthree.com/p_phase_two.asp
I prolly got the foam for you too. And the stuff to cut the core.
system three- PHASE TWO epoxy.
http://www.systemthree.com/p_phase_two.asp
I prolly got the foam for you too. And the stuff to cut the core.
Last edited by nothere; Jan 21, 2009 at 08:18 PM.
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Jan 21, 2009, 08:28 PM
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jid2,
system three- PHASE TWO epoxy.
http://www.systemthree.com/p_phase_two.asp
I prolly got the foam for you too. And the stuff to cut the core.
system three- PHASE TWO epoxy.
http://www.systemthree.com/p_phase_two.asp
I prolly got the foam for you too. And the stuff to cut the core.
Where did you get your materials, I'm looking at these two places they have better prices than some of the other stores.
http://www.avtcomposites.com/
http://www.jamestowndistributors.com...c)&match_type=
I'd go to Tap Plastic locally, but they are twice as expensive.
Last edited by jid2; Jan 21, 2009 at 08:45 PM.
Jan 21, 2009, 08:55 PM
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I'm still gathering data, planning, and looking around. I'll start to buy some of the material in the next few weeks. First I need to get my car back on the road.
Jan 21, 2009, 11:25 PM
#13
Would like to hit the tunnel in the spring, but I don't think this years race budget will allow. We'll see how good Uncle Sam is to me with my tax return. . .
The wing structure looks very similar to the DHP wing on my car - aluminum skeleton with carbon skin - except mine's hollow without the foam core. . .
I'm sure you'll have fun with this project! Looks good!
EVOlutionary
The wing structure looks very similar to the DHP wing on my car - aluminum skeleton with carbon skin - except mine's hollow without the foam core. . .
I'm sure you'll have fun with this project! Looks good!
EVOlutionary
Jan 22, 2009, 10:21 AM
#14
Ever consider attaching it to the rear, lower cross member rather than the trunk?
d
EDIT: Or at least some lower part of the of the chassis, although I think the rear crossmember might be best (short of the uprights themselves
)
EDIT: Actually, after thinking about it for a minute, maybe that's a bad idea...Although the aero load would still be sprung...
d
EDIT: Or at least some lower part of the of the chassis, although I think the rear crossmember might be best (short of the uprights themselves
)EDIT: Actually, after thinking about it for a minute, maybe that's a bad idea...Although the aero load would still be sprung...
Last edited by donour; Jan 22, 2009 at 10:27 AM.
Jan 23, 2009, 10:21 AM
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A few quick notes about wings.. There are a number of different types of airfoil designs that can be used depending on the appliction or result. for example..
But these wings, in this orientation, will producde lift. Since we want downforce, you simply invert the airfoil.
If you look carefully, you'll notice that the top "low camber" airfoil design in the picure above is very similar to the wing that comes with the Evo - only upside down. You'll notice it's rounded at the front then tapers off to thin at the back of the wing. Also notice on the Evo Wing it's curved on the bottom and flat on the top. So it's basically an upside down airplane wing.
Also, you'll notice that the top of the evo wing is esentially flat. So any downforce provided by the wing is fully dependant upon the curvature or "camber" of the airfoil. In short, you would say the Evo wing has a "zero angle of attack."
With increased angle of attack, lift (or downforce) increases in a roughly linear relation, called the slope of the lift curve. In other words, the more you tilt the wing, the more downforce you get (and more drag at the same time) up to the point of "stall" where the lift or downforce begins to sharply roll off once again.
The angle versus downforce versus drag chart would look something like this...
If you look at the chart above, you'll see that even at zero angle of attack (such as the Evo wing) there is a lift co-efficient of .30 so ther's some downforce but the good thing is there isn't much drag on the car. But now look what happens if you tilt the exact same wing to 10 degrees. Now the lift coefficient is around 1.00 which is more than 3 times the lift coefficient of the same wing with a zero angle of attack. Unfortunately, the drag coeffieicnt more than quadruples. So it's always a trade-off.
My points in all this are that simply changing the angle of the existing Evo wing by a few degrees will increase downforce. The other point is, if you're building a wing from scratch, be mindful of the airfoil design above all and maybe consider a "high lift - low speed" design and stay away from "low lift - high drag" design or you may not end up with the results you're looking for.
Good luck.
But these wings, in this orientation, will producde lift. Since we want downforce, you simply invert the airfoil.
If you look carefully, you'll notice that the top "low camber" airfoil design in the picure above is very similar to the wing that comes with the Evo - only upside down. You'll notice it's rounded at the front then tapers off to thin at the back of the wing. Also notice on the Evo Wing it's curved on the bottom and flat on the top. So it's basically an upside down airplane wing.
Also, you'll notice that the top of the evo wing is esentially flat. So any downforce provided by the wing is fully dependant upon the curvature or "camber" of the airfoil. In short, you would say the Evo wing has a "zero angle of attack."
With increased angle of attack, lift (or downforce) increases in a roughly linear relation, called the slope of the lift curve. In other words, the more you tilt the wing, the more downforce you get (and more drag at the same time) up to the point of "stall" where the lift or downforce begins to sharply roll off once again.
The angle versus downforce versus drag chart would look something like this...
If you look at the chart above, you'll see that even at zero angle of attack (such as the Evo wing) there is a lift co-efficient of .30 so ther's some downforce but the good thing is there isn't much drag on the car. But now look what happens if you tilt the exact same wing to 10 degrees. Now the lift coefficient is around 1.00 which is more than 3 times the lift coefficient of the same wing with a zero angle of attack. Unfortunately, the drag coeffieicnt more than quadruples. So it's always a trade-off.
My points in all this are that simply changing the angle of the existing Evo wing by a few degrees will increase downforce. The other point is, if you're building a wing from scratch, be mindful of the airfoil design above all and maybe consider a "high lift - low speed" design and stay away from "low lift - high drag" design or you may not end up with the results you're looking for.
Good luck.
Last edited by Evo_Someday; Jan 23, 2009 at 10:23 AM.
