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Ask AJ Hartman - Aero Questions

Hey AJ, got a question for you I can't find the answer for:

What are the considerations for the width of the uprights/risers for a GT wing? I would assume wider is better for stability, but I must be wrong because I see your S550 specific wing kits (ones I was looking at, dunno about others) have the risers much narrower than the full width of the trunk. Why is this?
 
Hey AJ, got a question for you I can't find the answer for:

What are the considerations for the width of the uprights/risers for a GT wing? I would assume wider is better for stability, but I must be wrong because I see your S550 specific wing kits (ones I was looking at, dunno about others) have the risers much narrower than the full width of the trunk. Why is this?
Ive never seen any tests that prove or disprove a skinnier mount or wider mount spacing to be better in terms of performance. So we primarily look at how we can attach, and tie our uprights into the trunk in a way where its plenty strong. On the S550 that was at 18" where the uprights go not only through the trunks thin outer skin, but also the inner rib structure of the trunk. On the S197's that was 24". It all depend on the the trunk is constructed really. I also gotta note that there is a limit. Our Apex 15 dual element wing can make close to 2000lbs of Df at 150 so that has no trunk mount offerings. But anything from our Apex12 Df level and down have very sucessfully been trunk mounted. Hope that all helps.
 

Ron McCall

Pantera1889
AJ,

Curious to get your take on the different versions of the swan neck wing mount shown here.
It would seem that the rear mount version would disrupt the airflow over the wing less than
the front mount version? Any idea if this is the case?

Ron

258481_10150206193132011_545162_o.jpg

95849295_3092588884112774_4538305694721376256_o.jpg

NEQyQ0EyOTIyMEZBMjM5MUJENDk6NjcxYjQxNTZlMDhmMDFkMGViMmI5OTU5NWY1ZjI2Mjc6Ojo6OjA_large.jpg
 
Does this pp1 wing looking thing do anything good? Or is car better with it off?View attachment 64085
The question is a little vague. Define "good".
Does it make downforce? maybe a little bit. So thats good. Is it anywhere near a proper wing? No. Thats not good.


AJ,

Curious to get your take on the different versions of the swan neck wing mount shown here.
It would seem that the rear mount version would disrupt the airflow over the wing less than
the front mount version? Any idea if this is the case?

Ron

View attachment 64098

View attachment 64099

View attachment 64100
I've seen CFD where a front mounted swan neck can have an ever infinitesimally small disturbance on the wing where a rear mounted wouldn't. But the issue is that most classes allow some amount a wing setback, so a rear swan would just be extremely weird and have unnecessarily long and heavier mounts. It works well on the Ford GT in the pictures tho.
 
4,621
4,533
Exp. Type
W2W Racing
Exp. Level
20+ Years
Pleasanton: 1/2 way between Sonoma and Laguna Seca
Okay here we go. I am considering replacing the ping pong paddle mirrors with these tiny spot mirrors.
The question is, although it looks sleeker from the front view, am I actually helping or hurting the aero since the stock mirrors deflect air away from the open windows. I could put a wicker (or gurney) on the trailing (vertical) edge of the cover plate here to help with this and also shield the small frontal area of the mirror that sees incoming wind. This is just a prototype (sans gurney) for investigative purposes.
Other considerations are that Vision is less than ideal, but doable and the driver side mirror would come close to being kicked as one egresses the cabin. Are the stock mirrors really that draggy or are those facets on the stockers better than I think they are? Am I splitting hairs or is this worth doing?

@AJ Hartman and others....discuss.

IMG_2119.jpgIMG_2121.jpgIMG_2118.jpgIMG_2120.jpg
 

Dave_W

Cones - not just for ice cream
450
449
Exp. Type
Autocross
Exp. Level
20+ Years
Connecticut
Reminds me a little bit of this...
You forgot...
1620946769348.png

My gut instinct is that the small mirror may have less drag itself, but the stock mirror may cast a low-pressure "shadow" that reduces drag from the open window and B-pillar. Take a look at the B-pillar treatment used by NASCAR teams. Do the rules allow you to smooth the B-pillar transition so that air smoothly attaches to the car there (laminar flow), instead of creating more buffeting (turbulent flow) rearward of the B-post?
1620949410974.png

Look at 1:15 and 2:24 in the video here: https://www.nbcsports.com/video/testing-nascar-race-car-aerodynamics
 
4,621
4,533
Exp. Type
W2W Racing
Exp. Level
20+ Years
Pleasanton: 1/2 way between Sonoma and Laguna Seca
You forgot...
View attachment 65244

My gut instinct is that the small mirror may have less drag itself, but the stock mirror may cast a low-pressure "shadow" that reduces drag from the open window and B-pillar. Take a look at the B-pillar treatment used by NASCAR teams. Do the rules allow you to smooth the B-pillar transition so that air smoothly attaches to the car there (laminar flow), instead of creating more buffeting (turbulent flow) rearward of the B-post?
View attachment 65245

Look at 1:15 and 2:24 in the video here: https://www.nbcsports.com/video/testing-nascar-race-car-aerodynamics
Exactly why I ask.
When I was building/racing stock cars we did it with clear lexan, front and back of the window opening so that it was like a shingle and air couldn't enter, but you could crawl out in an emergency (to satisfy the rules). However, these damn shitbox cars have doors that open and don't lend themselves very well to this sort of thing.

If you look closely you can see what I did here:

180236_10150991802563535_566635198_n.jpg
 
4,621
4,533
Exp. Type
W2W Racing
Exp. Level
20+ Years
Pleasanton: 1/2 way between Sonoma and Laguna Seca
You can see here where I tied the B pillar into the body in a similar fashion for both rigidity and also to discourage air from entering the cabin. hard to see here but it’s sloped back at an angle to facilitate this.

3F1BD064-82D3-4444-A670-9A1E364091F1.jpeg
 

Ron McCall

Pantera1889
Something else to consider is the effect that the mirrors have on airflow getting to ( or not getting to ) the wing . These guys found a fair amount of downforce ,in the wind tunnel ,by getting the mirrors out of the airstream going to the wing.

Ron

95849295_3092588884112774_4538305694721376256_o.jpg

257873_10150206183462011_5673082_o.jpg
 
There is a video of a TIME ATTACK GTA SUPRA showing that open windows are notnthatndraggy asnwe could think.
The reason why (in their opinion) is that once at speed on the back seat there will be a "pocket of high pressure air" creating like a barrier for extra air to get inside. So not big difference.
Go at min6

Of course. Thisnis for a supra so different shape and smaller.

 
4,621
4,533
Exp. Type
W2W Racing
Exp. Level
20+ Years
Pleasanton: 1/2 way between Sonoma and Laguna Seca
There is a video of a TIME ATTACK GTA SUPRA showing that open windows are notnthatndraggy asnwe could think.
The reason why (in their opinion) is that once at speed on the back seat there will be a "pocket of high pressure air" creating like a barrier for extra air to get inside. So not big difference.
Go at min6

Of course. Thisnis for a supra so different shape and smaller.

I have seen similar.
@AJ Hartman has a wind tunnel video of a beemer that shows the bubble.
 
Okay here we go. I am considering replacing the ping pong paddle mirrors with these tiny spot mirrors.
The question is, although it looks sleeker from the front view, am I actually helping or hurting the aero since the stock mirrors deflect air away from the open windows. I could put a wicker (or gurney) on the trailing (vertical) edge of the cover plate here to help with this and also shield the small frontal area of the mirror that sees incoming wind. This is just a prototype (sans gurney) for investigative purposes.
Other considerations are that Vision is less than ideal, but doable and the driver side mirror would come close to being kicked as one egresses the cabin. Are the stock mirrors really that draggy or are those facets on the stockers better than I think they are? Am I splitting hairs or is this worth doing?

@AJ Hartman and others....discuss.

I'd run the smaller ones and ditch the factory mirrors personally. I don't even run a passenger side, and a small one like you pictured on drivers side with a "cone" blocking the bit of exposed mirror. You could also look at top speed on your data at the end of the straight. I feel like mirrors that large would be easy enough to see a trend of slightly higher speed so could be easy enough to test to know for sure.
 

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