Quote:
Originally Posted by Vman455
This is ridiculous. Hucho didn't "give" us a template! Here, direct from a 2010 paper Hucho posted on his own website:
His example of cars with attached flow due to vortex-induced downwash but high drag? Extreme angles such as this, yet with clearly attached tufts:
Which looks nothing like modern hatchbacks such as the Prius and Insight I.
As far as Hucho's depictions of spoilers, I'll say it again: You have done yourself a tremendous disservice by using such an old edition of "his" book (I use quotation marks because he was adamant that it is not "his"). The last edition he edited, published in 1998*, has several pages on spoilers fitted to production cars in attached flow:
This despite your often-repeated claim that Hucho wasn't concerned with lift. Note that the car referenced here, the 1988 VW Corrado, was still in development when the 2nd edition was published.
He also devotes several pages, with vector diagrams of the flow behind various car shapes, to vortex shedding from the rear.
If this was all as simple as using a template to predict flow, there would have been no need for a 900+ page book.
* I'm thinking about dropping the money to buy the newest 2012 edition since this one is now so far out of date. |
Glad someone else is challenging Aerohead's endless BS in this area. Aerohead is completely wrong in his beliefs about airflow over the rear half of any typical car shape (squareback, fastback or sedan) of the last few decades, and seems incapable of realising this. As I have said, and as you and I have easily shown with tuft and pressure testing, it takes only a few short tests to show how incorrect his theories are. (Or just read any aero text of the last few decades!)
Re the Insight: rather than just theorising out of a book, I actually did a major amount of testing and development and so I can say with certainty (not just guesswork) that:
1. The Insight has attached flow over the rear hatch in standard form (tuft testing).
2. Tested rear spoilers that increased wake size increased drag (throttle-stop testing).
3. The Insight's current spoiler, that has a trailing edge no higher than the standard Insight lip, is working in attached flow (tuft testing).
4. The Insight's current spoiler reduces drag (throttle-stop testing) and increases pressures on the rear hatch (direct pressure measurement).
To reiterate what I said earlier: had I followed Aerohead's advice and theories on rear spoilers, my actual on-road testing (not guesswork) shows that I would have gone backwards with the Insight.
Aerohead is spreading misinformation and people putting their faith in his statements (not all, but most) to guide their car modifications are going to get poorer results than they should. We're not just talking about an abstract theoretical argument - we're talking about flat-out wrong theories and guidance!
Re the 2012 edition - save instead for the
fifth edition (2016) edited by Thomas Schuetz. It's huge (over 1200 pages) and unfortunately expensive, but keep looking and it does turn up at less than the SAE new-book price.