Project RATTLESNAKE: Building A Better Swing / Gurney

[erolivas]

To start with one would need to know the amount of down force that is generated with the OEM base wing/swing to get started. Generally speaking you start seeing measurable down force around 50mph; however anything over 70mph is when the vehicle handling increases due to the benefits of the wing. There is a fine line of adding too much surface area that gives you more down force, but then you pay the piper with added drag (more on that). Drag can be broken down to frictional drag and pressure drag. If there is no flow separation in the flow field then frictional drag (stresses acting on the surface of the vehicle) is the main drag component. If there is a ton of flow separation in the rear of the vehicle this leads to a pretty drastic pressure gradient, i.e. pressure drag. Ideally to design a wing one would need a scaled model to use in a wind tunnel along with particle injection to measure and map the velocity profile and pressure contour via PIV (particle induced velocimetry). These results along with CFD and 2-way FSI (fluid structure interaction) to do verification and validation. If experimentation is out of reach CFD is a must.

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[Houston Kid]

I’m pulling my gunnery flap off for Friday night legal street racing this week and the wickers. I need one with less drag and good looks for the strip. Trying to get the base 100% stock car in the 10s. Then I would need another “better” one for the track.

 

[protraxduner]

Terrance i will send you my thoughts and sketches ...they are rough.

I would like to know your audience because that will likely drive your design. As other have mentioned FORM and FUNCTION can be hard to accomplish in a single piece.

I am after FORM something that looks cool, gives that little extra edge that the base model is missing. The stock gurney flap and the others i have seen are literally nothing more than a 1/4 piece plastic/lexan with ZERO style. The OEM peice i assume performs as it should, the other bolt on ones i have seen look like something i could cut from Lowes hardware, some like that look some don't.

I don't care if what you created creates XYZ more downforce or XYZ less downforce. I think those are good things to know but would not drive my decision to buy one. If it don't look cool....count me out and from the offerings i have seen from other places...there just tacky....

I want a form fitting, curvy, extension of the wing, something that looks like it could have been part of the original plan for the spoiler/swing.

I would assume the market for 'cosmetic' gurney would outweigh the market for 'track' gurney. Surely if you are that concerned about tracking and downforce you would go with CFTP wing or GT4, etc.

I have literally thought about this since the 1st day I saw the standard wing/spoiler.

As for a new Wing/spoiler/swing completely...i have no ideas, just have ideas for the gurney.

Very interested in how this plays out.

Things to NOTE:

The stock spoiler is a TOTAL PITA to get off...i am experienced at doing this and this one is STUCK on. Every square inch of the contact space of spoiler is double sided tape...they didn't skimp.

The stock gurney even with the gasket and rubber pads, if left on , likely will damage the paint of the spoiler/wing. Mine was on only a few months and had already etched the paint.

 

[Epiphany]

Although I'm headed in a different direction I am indeed interested in this discussion. I was impressed with the aesthetic improvement via the Gurney Flap over that of a bare "Swing" from the moment I first saw one piggybacked off the rear. There is certainly a visual wickedness to it that simply isn't there without the Flap on there. I always wanted just a little more on there though. Go too far and the proportions go out of wack so I say this with some semblance of caution that proportions don't become overly grotesque.

From a data perspective, I'd kill to see the testing done and the numbers they saw with different height Flaps bolted in place. If I pick a random number, say 2" of additional vertical Flap height, I ponder about how much additional drag is introduced? If so, what would be the real world fuel economy decrease (keeping it simple here)? And how much additional downforce? I'd love to see the graphs that Ford has buried with development such that we will never see it.

Because I could give a shit about any decrease in fuel economy here, I'm all for more downforce - even with additional drag. And I'm aware of a potentially commensurate increase necessary up front to maintain a similar or more optimized fore/aft aero balance. So I'd love to see a simple, bolt on Flap that has a taller vertical wall than stock that can be added to the Swing as it sits - that's it out back.

This guy's video can be a bit dry and there is much to grasp if you can watch it but here's the relevant portion that relates to what I'm getting at.

 

[50 Deep]

Terrance i will send you my thoughts and sketches ...they are rough.

I would like to know your audience because that will likely drive your design. As other have mentioned FORM and FUNCTION can be hard to accomplish in a single piece.

I am after FORM something that looks cool, gives that little extra edge that the base model is missing. The stock gurney flap and the others i have seen are literally nothing more than a 1/4 piece plastic/lexan with ZERO style. The OEM peice i assume performs as it should, the other bolt on ones i have seen look like something i could cut from Lowes hardware, some like that look some don't.

I don't care if what you created creates XYZ more downforce or XYZ less downforce. I think those are good things to know but would not drive my decision to buy one. If it don't look cool....count me out and from the offerings i have seen from other places...there just tacky....

I want a form fitting, curvy, extension of the wing, something that looks like it could have been part of the original plan for the spoiler/swing.

I would assume the market for 'cosmetic' gurney would outweigh the market for 'track' gurney. Surely if you are that concerned about tracking and downforce you would go with CFTP wing or GT4, etc.

I have literally thought about this since the 1st day I saw the standard wing/spoiler.

As for a new Wing/spoiler/swing completely...i have no ideas, just have ideas for the gurney.

Very interested in how this plays out.

Things to NOTE:

The stock spoiler is a TOTAL PITA to get off...i am experienced at doing this and this one is STUCK on. Every square inch of the contact space of spoiler is double sided tape...they didn't skimp.

The stock gurney even with the gasket and rubber pads, if left on , likely will damage the paint of the spoiler/wing. Mine was on only a few months and had already etched the paint.

Great points you hit. The oem unit is on there like a bear

Although I'm headed in a different direction I am indeed interested in this discussion. I was impressed with the aesthetic improvement via the Gurney Flap over that of a bare "Swing" from the moment I first saw one piggybacked off the rear. There is certainly a visual wickedness to it that simply isn't there without the Flap on there. I always wanted just a little more on there though. Go too far and the proportions go out of wack so I say this with some semblance of caution that proportions don't become overly grotesque.

From a data perspective, I'd kill to see the testing done and the numbers they saw with different height Flaps bolted in place. If I pick a random number, say 2" of additional vertical Flap height, I ponder about how much additional drag is introduced? If so, what would be the real world fuel economy decrease (keeping it simple here)? And how much additional downforce? I'd love to see the graphs that Ford has buried with development such that we will never see it.

Because I could give a shit about any decrease in fuel economy here, I'm all for more downforce - even with additional drag. And I'm aware of a potentially commensurate increase necessary up front to maintain a similar or more optimized fore/aft aero balance. So I'd love to see a simple, bolt on Flap that has a taller vertical wall than stock that can be added to the Swing as it sits - that's it out back.

This guy's video can be a bit dry and there is much to grasp if you can watch it but here's the relevant portion that relates to what I'm getting at.

Great data points. I think you will like what follows

 

[protraxduner]

I know you are tied up with hood vents but you have a rough idea when we might see gurney flap?

 

[50 Deep]

I know you are tied up with hood vents but you have a rough idea when we might see gurney flap?

Hopefully releasing some info next week

 

[50 Deep]

Some initial work coming together

 

[protraxduner]

Some initial work coming together

Why the notch? That is probably my biggest complaint of the current GF. I personally think it would look better if it flowed to the edge as pictured in red.....

 

[50 Deep]

Why the notch? That is probably my biggest complaint of the current GF. I personally think it would look better if it flowed to the edge as pictured in red.....

The gurney has to step down and come under the wing. You would end up with a gap if you radius that edge

 

[protraxduner]

The gurney has to step down and come under the wing. You would end up with a gap if you radius that edge

I guess i don't follow, there is only a gap if you create gap it could still step down further outboard. The only difference being the curvature becomes greater and maybe little more complex. Just thinking outloud. The width of the current GF makes it looked added on.....which it is. Pulling it out further to the edge with a gentler curve looks better to me.......

 

[protraxduner]

Again this is my opinion, but i would like to see the additional lip go across the full width or even inversed so that the ends have additional lip but not the center. And with the GF extending further outward and curving naturally with the swing not notched.

Just giving you my thoughts. rough sketch below

I can't tell from your render but is the GF the same dimensionally outside of the raised center section and ends extending further under swing?

 

[50 Deep]

Again this is my opinion, but i would like to see the additional lip go across the full width or even inversed so that the ends have additional lip but not the center. And with the GF extending further outward and curving naturally with the swing not notched.

Just giving you my thoughts. rough sketch below

I can't tell from your render but is the GF the same dimensionally outside of the raised center section and ends extending further under swing?

I will have some more data and visuals for you guys soon. One thing to keep in mind is the ability of that outside fastener to handle the added load at 100, 130, 150 mph. Adding more surface area to the outside will create some additional drag and potentially cause that outside edge the flex. Picking and choosing where to add material is definitely a consideration.

Good ideas though. I’m excited about this one

 

[50 Deep]

Been working on this RATTLESNAKE a bit behind the scenes. Lets discuss a little of what you are seeing.

Overall the RATTLESNAKE will have an increased height over OEM. The center "A-Cup" as I have named it will add another layer of aggression to the swing. It is designed to be the same width as the aeordynamic valley that is located on the roofline. Air will naturally flow over the car into it.

The rear profile is about where I want it. At certain angles the front view looked too thick. Going to make some small changes and bring down the height a tad on the edges. Then going to make the "A-Cup" a little taller. Overall the height will decrease, but the lower edges will make the center section more pronounced.

Also incorporated broader coverage on the back of the OEM swing at the outer edges. This will allow for more carbon fiber presence from the rear view.

"OEM plus" is the concept here. It will stand far enough apart from the OEM piece to be noticeable, but no so far different it loses the original level of sexiness the car had. I may do a CFD pull, but the changes here are not so drastic that it should unbalance the car. I would view this as an aesthetic upgrade over a performance modification.

Once those few revisions are done I will share some pics and start with preparations to build the mold and carbon production piece. Let me know if you guys like where this is going

 

[Cgouzoulis]

Been working on this RATTLESNAKE a bit behind the scenes. Lets discuss a little of what you are seeing.

Overall the RATTLESNAKE will have an increased height over OEM. The center "A-Cup" as I have named it will add another layer of aggression to the swing. It is designed to be the same width as the aeordynamic valley that is located on the roofline. Air will naturally flow over the car into it.

The rear profile is about where I want it. At certain angles the front view looked too thick. Going to make some small changes and bring down the height a tad on the edges. Then going to make the "A-Cup" a little taller. Overall the height will decrease, but the lower edges will make the center section more pronounced.

Also incorporated broader coverage on the back of the OEM swing at the outer edges. This will allow for more carbon fiber presence from the rear view.

"OEM plus" is the concept here. It will stand far enough apart from the OEM piece to be noticeable, but no so far different it loses the original level of sexiness the car had. I may do a CFD pull, but the changes here are not so drastic that it should unbalance the car. I would view this as an aesthetic upgrade over a performance modification.

Once those few revisions are done I will share some pics and start with preparations to build the mold and carbon production piece. Let me know if you guys like where this is going

When I get back Im calling you btw. Should be leaving end of next week. I'll call you over the weekend. Love it

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