I’m sure it’s been discussed here before but didn’t find it in a search. Was driving on the interstate and saw a motorhome with the very rear sides and top covered with vortex generators. I guess they are supposed to smooth out airflow for fuel economy and handling. Do they work and if so why don’t we see them on cars other then they are really ugly.
We did have a discussion about it somewhat recently. I think it was after stafford1500 was on the live stream. I may have even started that thread...
Let me see if I can find it.
Thanks for digging that up Nick. saves me time typing it all again...
The first-gen Honda Ridgelines have vortex generators on the mirrors. Learned that thanks to the hyper-detailed Honda Ridgeline wikipedia page.
There are quite a few VGs on modern production cars to help with Noise/Vibration/Harmonics (NVH). They tend to be small and in really unexpected places.
Worrying about aero drag on a motor home seems like putting lipstick on a pig...
Turboeric said:Worrying about aero drag on a motor home seems like putting lipstick on a pig...
Why? If it's the dominant drag source on the vehicle, it's a great idea to work on it. Going from 8mpg to 9mpg is a huge deal- over 10%.
In reply to alfadriver :
Exactly. It's like all of those add-ons you see on big-rigs to improve the aero. Does it do a lot? No. But when MPG is measured to the decimal place, a few percentage points of improvement can represent a lot of money over the distances trucks can travel. For an RV it can be similar.
They were probably these: www.airtab.com
ross2004 said:They were probably these: www.airtab.com
They did look like those on the web page. It drew my attention because there were so many pretty much touching each other all across the roof and down the sides from top to bottom. If they work do you really need that many?
You're supposed to place them about a thumbs width apart, according to them- so yes.
Ian F said:In reply to alfadriver :
Exactly. It's like all of those add-ons you see on big-rigs to improve the aero. Does it do a lot? No. But when MPG is measured to the decimal place, a few percentage points of improvement can represent a lot of money over the distances trucks can travel. For an RV it can be similar.
Interesting example- for personal reasons. I know one of the guys who made the trucks put those devices under them to get aero. They were put there to reduce heavy truck CO2.... But here's the odd part- given that the #1 cost in trucking is fuel, those were things that *should* have been on trucks decades ago. It's not as if aero things are new- we've seen the fairings on the tractors for many decades. No idea why they never tried that on the trailers, as that is such a simple change that has a pretty huge impact- it would have saved so many dollars in diesel over the decades....
Sometimes, companies confuse me. Simple and cheap modifications that can save way more in their cost are not used, even when diesel was $1/gallon- didn't happen until regulators stepped in. And then saved them millions of dollars in fuel costs.
In reply to alfadriver :
As I'm sure you are all too familiar with, the constant battle between the up-front cost bean-counters and the operational bean-counters. For various reasons, the former often win. It's pretty much my life every day in the architectural engineering world.
In reply to Ian F :
All I can do is shake my head.... 3 more years.
I think the vortex generators on the Evo 9 are there so people know you bought the expensive one.
Ian F said:In reply to alfadriver :
Exactly. It's like all of those add-ons you see on big-rigs to improve the aero. Does it do a lot? No. But when MPG is measured to the decimal place, a few percentage points of improvement can represent a lot of money over the distances trucks can travel. For an RV it can be similar.
I discovered thess "air tabs" a couple of years ago. From all the posts I've found on the webs they seem to help keep a RV or tractor/trailer more stable with some mileage improvement but not in all cases. I plan on getting some for my enclosed trailer.
In reply to jimbbski :
I was going to post speculation on this earlier... but didn't feel like going and doing background reading.
basically, all you're doing by putting a whole bunch of these kind of tabs on the back end of an RV is making small vortex's that might extend the point where the flow comes back together... effectively making the vehicle "longer" to the wind... but it'll have a pretty weak impact on the overall drag, at the cost of increased drag to produce the vortex's.
however, by introducing these "longitudinal" VG's, they can probably contain and minimize a 'vortex stree' that comes off the back
think of this like an alternating vertical vortex sheet coming off the back... which is why light tall cars will feeling like they're weezing back and forth behind a trailer on the highway at a certain distance from the rear.
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