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Looks like a track focused car, so I assume you want your wing to work properly and be able to utilize AOA data from others ??
Aero 101 Hardtop wing doesn't work, and hurts wing performance.
And what's up with the draggy cross wire supports?
my understanding without a hardtop wing the air sticks to the body of the car and goes under my rear wing. So adding a hardtop wing will direct the air straight to the rear wing creating more downforce. Maybe I’m wrong but it makes too much sense to me. Either way I feel like my car looks bald without it lol
my understanding without a hardtop wing the air sticks to the body of the car and goes under my rear wing. So adding a hardtop wing will direct the air straight to the rear wing creating more downforce. Maybe I’m wrong but it makes too much sense to me. Either way I feel like my car looks bald without it lol
What about that big negative pressure area created between your hardtop spoiler and your rear window, how does that affect the air going over your car?
Edited to ad: In the sticky thread at the top of the forum, can you find the pictures of fast cars with hardtop toupees?
In essence you are disturbing & loosing boundary layer air creating a larger low pressure area at your rear window. Increasing drag and decreasing the effectiveness of the wing. The guy wires are creating a lot more drag than their size reflects.
Cant compare toupees as it is apples and oranges. Simply put hardtop is much less draggy than toupee, toupee slightly better than convertible, with a long tail fastback being better yet however most classes will kill you on points if you use one.
Pretty much duplicate an S2000 or C5 Vette and you'll be faster.
+1 to the above. Ironically that gap which you complain about, if enlarged between the 'wing' (aka sunshade) and HT just might help, by directing air below the shade, into the otherwise enlarged low pressure area behind the rear window. I'd reckon you'd need a big gap, 50mm minimum, and the shade would act as a flow straitghtener - maybe. It'd be a lot simpler though to just do what other people have found works best - and it isn't sunshades and wire bracing.
Like others have said the hardtop wing will separate the boundary layer over the top of your car. Instead of your wake being your rear facing bumper and trunk area, it now also includes the hardtop. Bigger wake = more drag all else being equal. You can't think of just the streamlines closest to the body, but the whole mass of air surrounding the car. It's all connected. Here's an example (obligatory not a Miata but...)
See where your wing would end up? Assuming airflow remains attached to a hardtop window your wing will get nice fairly clean air. Add a typical hardtop wing and those nice streamlines over the rear trunk area become chaotic unpredictable messes, and your wing no longer works very well.
As for the cross wire supports if you don't need them, and are looking to improve performance, ditch them. Cylindrical shapes are incredibly draggy. You'll be adding a lot more extra drag than you would think.
The difference between a wing and a spoiler is that air goes over the top of a spoiler, and air goes both over and under a wing. The underside of the wing is doing most of the work, and if you look at pressure plots, it's about 3x stronger underneath the wing than on top. Based on this, your primary supposition is wrong, which is that you want to direct air to the top of the wing. Also, you should call this roof-top device a spoiler, not a wing, since air is not going underneath it. I would simply call it a roof extension.
There were some CFD tests run on a Porsche 914 using a similar roof extension, and the result was slightly more drag and less lift. I did some simulations on this, and the net result was equal, performance wise. I wrote about this a while ago, scroll to the very end for the roof spoiler. https://occamsracers.com/2019/11/21/...s-porsche-914/
If you are dead set on using the roof extension, angle it downwards a bit. That might feed the wing cleaner air and be a net benefit. No way to know without testing, tho.
07-28-2021, 05:01 PM
Hardtop wing on Lexan window??
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