Do air tabs work?
 

Hi (New Post),

I'm Martin, a biz student/Entrepreneur located in Boston but originally from Toronto.

I've been looking into retrofitting cabs/buses/trucks with simple aero mods. In the past, I have started several successful unrelated businesses and am eager to try and commercialize aero mods. I've been looking at the Canadian company aeroserve technologies ltd. (the makers of the airtab) and am considering pursuing a business venture with them.

Can someone please enlighten me to whether these tabs would work on a coach bus or if these vortex generators actually achieve a 2-8% increase in MPG?

Cheers,
Martin

Good question ... a friend of mine has them all along the roof line of his Scion tC and swears by them ....

They didn't do squat on my Jeep cept keep the back window slightly cleaner on the hard top

got some links or pictures ? Anyone have access to a wind tunnel?

No.
http://autospeed.com/cms/A_3061/article.html

Ahhh I know what these are. I used these on my CO2 Cars!! (you always had an exit flat because of the minimum reqquirements for the Co2 cart hole dimensions this smoothed out the airflow by generating a vorte of air current. Shaved almost 2 tenths of a second off my Co2 cars run time! (same model ran 10 runs without then I added them and ran it 10 times again) I was impressed. I am not as certain how this would work scaled up. My models had wacky reynolds numbers that just do not scale up.

Might be worth trying though as they are very easy to make yourself. I do not think they would help that much on a car like mine but if you do have some sort of hatch it might work. If you are good at building them it might be worth a try IE it would not cost much at all so if it did not help you lost nothing except some time.

NOW in my case I was producing THRUST from the rear. The the vorticies had somewhere to go IE merge with. The thrust plume from the CO2 Cart. I would not think they would have a beneficial effect on a ballistic example such as our cars (its thrusting but via the ground so that does not count aerodynamically)

They might clean up airflow but they will not reduce drag UNLESS they eliminate an increase in drag from sloppy flow that is larger than there own drag contribution.

Huh at $2.50 I would not even bother making them myself and just buy them. Suck though no quantity discount. the 80 unit kit for truck/trailer is the same $2.50 per price.

you say no but the article states that there is a minor potential for increase... what gives?

I had them on my xA and they hurt my FE.

They work great, I think 2-8% FE Gains are way too conservative, I bet you get 40-60% FE Gains....In fact, I'll bet you could just put them on your car and they'll just push it down the road on their own...so just go ahead and rip the engine out of your car and let the aitabs just push you around town. You better have good brakes to keep your speed in check.

I'd say they're just oversized for use on a car.
Turbulator tape for gliders is (less than) 1mm thick, but AirTabs are 25mm or 1 inch thick as they were intended for use on big trucks !

VGs also add drag by themselves, so you need to overcome that first before you start gaining.

MetroMPG found they smoothed out the airflow on the back of a small sedan.
Red above found them to keep the rear window cleaner (indicating reduced turbulence at the rear).
They were found to improve stability when mounted underneath an Insight (1gen).

But so far, they weren't found to reduce the fuel consumption by EM members.

in theory they could help but I don't think they will "as implemented or designed"

we know "golf ball" dimples will help by making the turbulent air more energetic allowing it to follow harsher contours than it could otherwise IE reducing "base drag" (that is what we call it in rocketry not sure what its called in the automotive industry

anyway they are way too big. they add frontal and base drag ie will never offset its own frontal and base drag not to speak of the car's

made significantly smaller and placed correctly they CAN help. alas its a T&E issue as non of us understand the math of the fluid dynamics nor can we model it to figure that stuff out.

Maybe if you combined them with a ridiculously huge wing, they could make the vehicle go even faster... ?

They do work. However they won't work for all cars. They work best on cars that have a blunt rear end that is almost as big as the frontal area. Before they were commercialized the inventor tested them on a Honda Civic in a wind tunnel and was able to prove a 4 to 6 percent drag reduction.

http://www.airtab.com/MicrosoftWordHondaWTReportV6.pdf


Looking at Neil Blanchards photos I don't think he used enough of them and might have had them too far forward. The install guide says they should be positioned 4 inches from center to center(Note that this distance can be increase some to accommodate mounting obstacles and lessening this spacing causes the vortices to interfere with each other ). It also states that the front of the air tab should be mounted 14 inches or less from the trailing edge of the vehicle.

do air tabs work, is that a valid question
 

if you want to run a business i don't see that is a good question. it doesn't matter if they work what matters is do people think they work. if you really must convince your self they work, i would suggest they likely do something good. if not better fuel econemy better stability. i haven't researched the air tabs patent position but i suspect it would be impossible to have a really sound position on technology that is 100 years old, so you might want to consider vacuum forming your own design that accomplished the same end.

I always figured placing golf ball divits in all regions of turbulence on a car would do more (AKA on suspension underneith, near trailing edges, etc etc)

These were proven to work but i am uncertain if any measurable gain would be made cheating as it were.

They would likely make the right amount of turbulence as compared to the oversized air tabs.

So the answer is no then ?

There is a thread here on EM that showed how to use these correctly -- if there is a taper on the rear that is too steep for attached air, then you can install them *just* down the slope (on the radius transition) so they do not add anything to the frontal area, but they can slow the air flow so that it then can remain attached.

I'll look for the thread...

Nobody on here has been able to proof they do improve FE, and it wasn't for lack of trying ;)

I still think they could work, but not in the usual massively/truck-sized variety on a regular car.

Something more subtle might do the trick.
Renault / Dacia had them on the rear roof line of their eco-Logan.

My friend got a bunch and we put them on his Ford E150 van. I posted on here a while ago that they did not help his Cd when installed per manufacturers directions. They actually increased drag by about 3%. They did pull the trailing wake in sooner, but I don't see that as being a real benefit to most people.

Has anyone who pulls a trailer on a regular basis tried them on the back of the tow vehicle? Somewhere on their website I remember they saying they actually saved more money in trailer tires than on fuel, due to stabilizing the trailer.

OK, but Dacia probably had some wind-tunnel time via Renault to try things out ?

We know there is a return with some people from a grill block (although both you and I have tried these and not seen a significant difference - but that might be the difference in Euro vs US driving conditions - long cruises and journeys in the US vs. our more busy and choked roads).

We have seen coast downs with boat tails which seems to suggest an improvement and with wheel covers (front and rear), new noses, wheel spats, mud flaps removal or reversal. Even some differences with mirrors folded and removed vs not.

The coast downs with tabs suggest minimal effect and threads testing them on cars longer term show no difference at all as far as I can tell, or whatever difference is recorded could well be inside an error range.

So at the moment we have to say at best "maybe" or it has "potential", but on a firm this-makes-a-firm-difference basis we have to say "no".

@Neil - I would love to see those instructions and for someone to do some proper testing having followed them.

The difference is that the barriers to implementing a grill block are about non-existant. I think the first one was wet newspaper or something, any sort of material can be bodged into a grill block (of varying durability), you can prototype one with coloured duck tape, or even cram neglected beanie babies into your grill.


VG's for fuel efficiency are surrounded by mystery, or bullocks if you prefer. There is no end to the number of things you could be told you are doing wrong after trying them, it isn't well defined how it is supposed to be helping car efficiency. There simply is no defined theory as it relates to efficiency or it's application. The potential here seems not worth mentioning in the "I think someone else should try this" sense, what you do with your own time is a different matter.

I'm confused, you don't think these other people did proper testing? On what basis?
Google Custom Search

Can you properly define proper testing of vortex generators? Can you also define proper testing for non-existence of invisible pink unicorns? :)

A-B-A, of which your search picks up quite a few :D I thought maybe Neil had something new. Maybe not.

Picking through the first page of results at random, nobody seems to show a measurable effect on FE, certainly not the "riches and world peace" claimed by the makers. The MIRA test linked in one of the posts seems to show about 2.8% improvement on a truck.

Heretic... :eek:

EDIT - The MIRA test appears on the Airtabs website too. But from memory I haven't seen any ParcelFarce trucks with tabs on that I can remember. Going to track one down and photo it.

Hi,
at the wheelhouse, I test a special version of vortex generators.
The goal was to improve the airflow at the wheelhouse.
In the windtunnel measured, the drag was not reduced by vortex generators, but the balance (lift/downforce) between the front and rear axis changed.

Ulrich

https://farm4.staticflickr.com/3909/...580647_h_d.jpg

So did they give you positive or negative lift?

I asked a guy who has some on a light plane about any mpg gain...said there was none...but they did result in a lower stall speed...which is why they use them on planes. They allow better control at lower speeds.

Results from the windtunel, vortex generators in front of the wheelhouse
 

Hi,

here is the answer:

the aritabs were not used at the rear edge of the car, but in front of the wheelhouse.

So this values are not to evaluate Airtabs as the intended use case.

CW Widerstand drag
CA Auftrieb gesamt lift
Cav Auftrieb vorne lift front
Cah Auftrieb hinten lift rear


Serial state, Serienzustand
speed 140 km/h
CW 0,323
CA 0,0402
CAv -0,0223
CAh 0,0626


Xanon aerodynamic bumper with vortex generators
speed 140 km/h
CW 0,2971
CA 0,0256
CAv -0,1053
CAh 0,1309

https://farm4.staticflickr.com/3909/...580647_h_d.jpg

Xanon aerodynamic bumper without vortex generators
speed 140 km/h
CW 0,2961
CA 0,0213
CAv -0,097
CAh 0,1184

Ulrich

:thumbup: Nice Find, this thread :thumbup:

Your "wishbones" are installed backwards ;)

That looks to be a functional opposite of a version I found a few years ago on the interwebZ. I'd be curious to see a comparo of the airflow patterns forwards and backwards...

Hi,

there are different concepts for vortex generators.

See, how "airtabs" work: http://www.airtab-uk.com/portals/56/...irtabflow3.jpg

Airtab UK > Airtab Information > What are Airtabs?

Ulrich

Very Nice, Ulrich!
I was being "tongue-in-cheeky" actually. These wishbones are producing 2 vortices as opposed to one from an older design I saw in the PJK "Guide to Free Energy Devices".
It was located in the mileage section.

Now don't everybody jump on about "Free Energy" :p

I think it is a misnomer and that nothing is free.

not even on big trucks!?
 

Apparently they don't even work at big-truck scale. See https://www.tc.gc.ca/media/documents...T-MAY_2012.pdf section 7.5.2.2

Wish they did. My boxy-backed Smart Fortwo should be able to do better than the measly 38-39 it gets. Well, I do break 40 when I can keep it to 65 with no stop and go traffic, but how often does that happen?

T

Not sure it's worth it's own thread so I'll drop this here:

http://www.mulsannescorner.com/LolaUnderbody.jpg
Mulsanne's Corner: GT-One, 101?

The three curved vanes spin the air under the car, increasing the downforce.

Spotted these on a Morrisons supermarket truck here the other day

http://www.globalcoldchainnews.com/w...orrisons-3.jpg

No info on if it helps yet.

That's a lot of air tabs!

Nice truck. Front corner turning vanes/air curtains, closely fitted cycle fenders on all the tires. Is that a spare or low-rider drive axle? And did you see an angle that showed the cab/van gap? In the picture it looks like 0.

Closing (or blanketing) the tractor - trailer gap could be one of their best appliances IMO


Also see Ulrich Steinlechner's posts with VG in front of the wheel arches: Cw is down - however slightly - by 0,001 despite the added drag of generating vortices.

That's in addition to the seriously reduced lift.
(Together with the nose, they've just about halved aerodynamic lift - that's massive ! )

And as lift induces drag ...

That's normal on Euro style cab-over tractors

Lowerable axle
It's not uncommon over here to see rigs with only half of their axles being used
(2 out of 3 on the tractor, and 1 out of 3 on the trailer) when rolling empty.

Most Euro tractors will have plates that partially cover the tractor-trailer gap.
From this angle, it'll look like there is no gap.

Still lots of low-hanging fruit on that Morrison's rig.