There could be several reasons. The immediate one that jumps out at me applies to SP3. The mounts are considered an integral part of the wing, and no part of the wing may extend above the roofline of teh car. A swan neck style upright would then become the highest point of the wing. If it has to be notably taller than the end plate, then it would push down the wing farther, which would potentially make it less effective.

Most of the ones I've seen have relatively short uprights. The 911 is going to inherently have relatively tall ones. It could be that the added length of the upright inherent to a swan neck causes other issues. Frankly, the buiggest surprise to me is the shape of the upright. They look to me like they'd cause tons of drag.

 

Im pretty sure that gurney flap would cause more drag than help the wing, that is far above the GF to really effect flow to it. in any quick glance modeling in my head, i dont see any benefit. if there is, i would be interested in the theory there. but again, due to the height and position of the wing, i dont see how there could be any interaction.

 

great artilcle, but keep in mind, the main goal was to get around the regulations that were shortening the span of the wing. surprising as you say, the effect of something on the low pressure side, had a marked effect of the area around the attachment points. so, by attaching the wing on the top (high pressure side) they gained effective span , even though the wing had less span.

really shows why vortex generators are so effective in disrupting flow . but it doesnt necessarily mean you lose lift . it depends on where those attachment points are made. so , one coud also make the attachment points, much more rearward and gain some of the same things, but you dont see that often, due to strength issues more than likely, but im sure it could be done.

yep. that is the main reason for world challenge for example, where that rule of the roofline height max is enforced. however, i dont know if end plates followed that rule, so maybe the top mount brackets wouldnt either. interesting question.

i agree with the width of the uprights possibly causing turbulence to the oncoming air flow to the wing. i think you would have to see all of this in simulation to make an informed change decision

one other thing to consider, they are comparing center mount wings vs sprorts cars that have near the side mount wings. there might be less effect of the uprights, if mounted closer to the end plates. just a first glance there.

 

[QUOTE=Sterling Doc;12962028]Finishing up the "Menard's" nose on the car today. I left the front tires faired in/shrouded a bit as shown in the pics below. I think the drag reduction from that should outweigh the extra frontal area. Thoughts? [Splitter & touch-up/paint still to come]



you havent increased frontal area... you have just changed the shape, and the diversion of the air flow. the entire idea, is to have the flow , not go under the car and get diverted (splitter function) to the hood and over the car, or to the sides. you are getting both here. most effective would be the rounded frontal area, with a splitter and the inlet vent and exit vent out the hood.

It should work well and be an improvement over he prior design. nice work

 

look at those simulator pictures again.......... look at the uprights on the original car...... now, picture if the uprights ddnt end mid cord and went to the rear of the wing, as most mounts do for our sports cars.. the problem occurs when the mount ends, not around the mount brackets. there might be a regulation for the width of the brackets, as to not provide too much of a "vertical stabilizer" with extra width. if the bracket went to the rear of the wing, there would be a MUCH different out come.. more of the usable lifting area would be preserved. want proof.. look at the end plate flow. picture a continuation of the wing after the end plate. there would be very little disruptoin of flow if the wing had extention passed the endplate. in other words, the uprights are too short and end in a non optimal spot in the middle of the , high air speed, low pressure zone.

 

I am not really concerned with what you do or don't see. Modeling in your head? Do you ever read what you write?

The guy that built my car actually knows what he is doing.

 

they all think they know what they are doing.

yes, i do read and think about what i write. can you use your head and think about what is written? in my mind, I'm imagining the flows and pressure changes with two aero flow systems on your car. (one over the rear spoiler, which is not a wing, and one over the wing itself).

your guy may know how to build race cars, but and done a lot of testing, but that mod might be out of his relm of knowledge for effectiveness.
Its the same reason why here is a optimal height for GFs, and its not 1-2 " like yours, they are more like .15 to .25" on the edge of wings of our scale.
I'm sure i have a lot more aero time on the varied simulators and windtunnels then he does. this is a little bit of "uncharted territory" in that its a system, where no two are alike and there are many factors that not only i might be missing, but your "Builder". Ive seen plenty of the pro "builders" do things that i could prove were not as effective as they thought they were, and were then proven in the wind tunnel.

 

I'm not sure what you are looking at, but the CFD shows the flow being disrupted maybe 25% from the leading edge of the upright. if they are airfoils, it beings where the chord is at max thickness.

I'll try to dig through some of my texts to see if I can find any elaboration on what happens on the low pressure side of the wing.

 

look at the pictures of the CED.... the first 25% of the upright, its not effected. its only when the (i assume its a air foil shape upright), flow comes off the upright, do you see the flow dispersion . again, just look at the ends... if those were uprights, flow would NOT be effected and there could be an airfoil on the otherside as well.

the only real way to know what i am saying is true, is if they did a wind tunnel test with the uprights along the entire cord of the air foil. from what ive seen in the use of winglets, inlet guid vanes, and vortex generators, i would imagine the flow exit off the ends and through the uprights, along the wing would be MUCH better.. wouldnt you agree?

 

you can see how the back side of the 911 is almost void of flow at speed ...



and some basic aero 101 video .

you can now laugh at the competitor with a high wing angle, unless he has the power to plow through the drag

 

Here are the famous GF graphs and plots

you can see, its very easy to get over stall with a wing with too much angle, only to have very little increase in downforce, but a huge increase in drag you might not be aware of. (the AoA is the area most get wrong in setting up the wing)

Scott you can see the effects of large GFs, but in your case, its not a GF its a parachute. 2% GF for example on a 11" cord GT3 cup wing is about 1/4" tall. 5% would be near .75". Scott , your flap looks to be about 2"s.
Your set up, is more about the Kamm body approach of reduced drag , not really working with the wing for downforce.

GF is in percentage of cord.

the net net of the GF discussion is if you near max angle of the bare wing (no GF, say near 12 degrees AoA), thats about a Cl of 1.0. drag woud be about .075
Now, if you did this with a wing with a gurney flap of 5%, the angle would only have to be 5 degrees, to get 1.0 Cl, BUT the drag would be .1. 50% more drag for the same downforce!!

Now, say you need more downforce than the stock wing can provide....say 1.5 Cl. using the 2% vs the 5% GF gives 25% less drag for the same downforce and the AoA is 15 vs 12 degrees and drag is .15Cd vs .17Cd

 

Jim, yes I will be adding back a splitter, much like the one I got from you. I need to cut the air dam a bit shorter. I am working to see where the floor has to be to keep it flat, and will put the splitter at that level.

I will likely make the airdam depth adjustable by having an overlapping lip on the bottom of the airdam on slotted holes.

Doing the nose this way was labor intensive, but is durable, allows some customization, and is good on the effectiveness/$$ front.
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Really interesting stuff on wings here guys, thanks!

 

[QUOTE=mark kibort;12963030]
Going wider to shroud the wheels increases the frontal area a bit, but at a worthwhile payoff in drag reduction from the wheels, I believe.

Splitter, and more hood venting coming.

 

[QUOTE=Sterling Doc;12963941]again, nice work... but dont discount the efforts.. the tires were still frontal area. now you are covered, so only very slightly more frontal area, but much more effective flow characteristics. you might make that front hole even biger , to negate the flat plate flow situation you have now. thats why i like the stock nose, with just the inlet widened and opened to the low pressure zone in the hood. very effective. did all sorts of testing, like Jack Olsen and it does what you would think i would do! you have the air dam low too, which keeps much of the roll off air flow from going under the car. going to the sides is the key.. splitter will help that even more.

 

Wow. You have zero credibility here. My car builder may not be an "aero god", but when he says something works better one way than another, you can take it to the bank. He tests things on the track and knows how to drive and how to test. He has been building cars in basic configuration for decades. I'll take his knowledge and experience over your rantings any day.

You, on the other hand? You pontificate about all you think know yet you have no history to back it up. Your driving history? Give me a break. Showing up at the track and driving around on old tires for 15 plus years doesn't mean you actually learned anything. You aero knowledge? Your wind tunnel time? I look at you race car and hear the crap you say and know to not listen to you.

You do realize that the wind tunnel isn't the end all be all, don't you? Even in Formula One, with all their money, time, and fancy full size rolling road wind tunnels, they find that what works in the wind tunnel does not always work on the race track.

That huge "Gurney" on my race car? My suspicion is that it speeds up the air flow under the wing by forcing any air that flows along the flat part of the tail base higher and closer to the bottom of the wing.

Basically, Mark, if you type it I assume it is wrong unless I know it to be correct or some other source confirms it.