Presented by Nine Lives Racing
sleepyhead the buffalo
sleepyhead the buffalo Mod Squad
10/16/19 6:43 a.m.

So, I got some mail today... 6-ish weeks in the making...



on first skim, it doesn't look like the fifth edition has the same spoiler info that "race car aerodynamics" indicated the first (Hucho) edition had (which was the main reason I shelled out for it).  But, there's a bunch of other stuff to sink my teeth into for now.

stafford1500
stafford1500 GRM+ Memberand Dork
10/16/19 6:48 a.m.

You may want to look for "Fluid Dynamic Drag" and it's companion "Fluid Dynamic Lift". Both are really just compilations of NACA/NASA/government research from way back, but still useful resources.

They are nearly coffee table books, at least for me. Love to pick them up and open to random pages every now and again.

Robbie
Robbie GRM+ Memberand UltimaDork
10/16/19 11:16 a.m.

haha I have "Race Car Aerodynamics" sitting on my desk next to me currently! (similar proximity to my coffee mug as you show in your photo). 

 

sleepyhead the buffalo
sleepyhead the buffalo Mod Squad
10/21/19 1:35 p.m.
stafford1500 said:

You may want to look for "Fluid Dynamic Drag" and it's companion "Fluid Dynamic Lift". Both are really just compilations of NACA/NASA/government research from way back, but still useful resources.

I'm taking the hint, and reading through the 'Trailing Edge Device' section of Fluid Dynamic Lift now, piecing together answers.

Interestingly enough... the device I'm fiddling with is probably going to be around 5" in chord, and on a NB miata (LOA = 155.7", Height = 48.4").  So, if we think of the car as the "profile"... then a 5" spoiler has a cf/c of 5"/155.7" = 3.2%

and taking away ground clearance (~6")... that means a miata has a maximum t/c ratio of .... 42.4/155.7 = 27%

so, if you start searching around on google for references to a 5% chord flap... you end up getting a lot of technical paper 'hits' on...

Gurney Flaps on race car wings.  So, in some ways... a spoiler on a car is effectively a Gurney Flap... or perhaps vice-versa.

 

there's also a realization of how I'm funny.  Hoerner's FDL is meant to collate a bunch of data, and plot it together in a concise way that was helpful for engineers to grab data off so they didn't have to plot it by hand... or go into the archives and find the company's one print off of A.M.O. Smith's AIAA #74-939, or whatever.  But, in the 50 years since it was originally complied, computers have gotten powerful enough that re-plotting that data is basically "free".  And, with the nature of the work I used to do with simulators, I have a fair amount of experience with curve-fitting raw data and extracting polynomial representations of it.

So, I'm at a place where I'm using a book, looking at graphs... and I kind of want to go hunt down the source material so that I can access the raw experimental data and make my own curves, because it's relatively easy to convert and approximation of that data into a formula.

surpriseblush

stafford1500
stafford1500 GRM+ Memberand Dork
10/21/19 1:51 p.m.

In reply to sleepyhead the buffalo :

Hoerner's books are, as you describe, shortcuts to a time before digital libraries.That might be why I like to use them as coffee table type books. Most of the information included in those books is also stored in the NACA's LARC server, but in scanned versions, not so much as easily searchable data. They are public access, lots of interesting reading...

Spoilers on cars is absolutely a Gurney/wicker/flap on a wing in a generic sort of way.

Make sure you consider the effect as a split/fowler flap and not a simple trailing edge deflected flap. Add in that there is significant ground effect, AND that the "wing" is inverted in ground effect.

sleepyhead the buffalo
sleepyhead the buffalo Mod Squad
2/11/20 9:05 a.m.

it's a good thing someone's not paying me for this... 'cause I'm going real slow... but, closing in a bit...

what I'm closing in on, isn't particularly clear... but as Abe Lincoln referenced once upon a time the words of the young lady who put her foot in her sock:

"it strikes me, there's something in it"

Appleseed
Appleseed MegaDork
2/11/20 9:44 a.m.

That title and nothing about blimps,  balloons, or Zeppelins?

sleepyhead the buffalo
sleepyhead the buffalo Mod Squad
2/11/20 12:39 p.m.

In reply to Appleseed :

nope, just trying to find some of my own answers for the answer

Adrian_Thompson
Adrian_Thompson MegaDork
2/11/20 12:49 p.m.

Light reading?  I thought you wanted downforce, how about 'A little heavy air reading'?

Our Preferred Partners
1Nmq5jRsrHRrRqltsHfo6kzyyeHVJDoG1ji6r5uv8oqkgPXeh1CZgdG0TaVT7sPG