The XV-JP Needs Help, Please, from a Jeep Aerodynamicist. (Really)
- Thread starter mhiscox
- Start date
mhiscox
Exp. Leader Emeritus
WOW! Epic fail. 
Sticking the Airtabs at the front of the cockpit roof, as shown in the picture above, totally did not work. I have no doubt that they made a big change in the air flow and could have eliminated the intermittent speed/wind direction dependent howl. The problem is that they introduced the generic wind noise from hell in the cockpit. Nothing complicated; just the wind-being-blocked general wind rumble. Pretty loud, and it shows up almost immediately. It's pretty noticeable even at 20 mph.
Plan B, which is but a slight modification of Plan A, is to take the Airtabs off the cockpit roof and mount them in the same relative location on the bottom of the cabin nose cone, like this:
I'm pretty much positive that this will produce a better situation. Whether it's good enough will take some driving around. Expect an update soon.
Sticking the Airtabs at the front of the cockpit roof, as shown in the picture above, totally did not work. I have no doubt that they made a big change in the air flow and could have eliminated the intermittent speed/wind direction dependent howl. The problem is that they introduced the generic wind noise from hell in the cockpit. Nothing complicated; just the wind-being-blocked general wind rumble. Pretty loud, and it shows up almost immediately. It's pretty noticeable even at 20 mph.
Plan B, which is but a slight modification of Plan A, is to take the Airtabs off the cockpit roof and mount them in the same relative location on the bottom of the cabin nose cone, like this:
I'm pretty much positive that this will produce a better situation. Whether it's good enough will take some driving around. Expect an update soon.
BlueGerbil
C´est le gerbil plus bleu
J.W.Speaker 6045 LED foglights and some brackets (like http://www.tlg-auto.com/JEEP_JK_Wrangler_LED_Foglight_Bracket_p/jeep002.htm)
bobholthaus
Observer
Thank you BlueGerbil. I'm going to order a pair! I truly appreciate it.
mhiscox
Exp. Leader Emeritus
Sure look like they ought to go the other way round, don't they? But they don't. The directions are very clear:
and the picture of the yellow Corvette above shows the proper orientation.
The idea is that the air flowing into the Airtab turns into a swirling vortex, which in turn eliminates turbulence. Here's a picture of the wind tunnel flow:
.By the way, I think that they may be doing some good. I was out today in the sort of conditions that seemed like they might have produced the wind howl and I didn't get it. Nothing certain, though. The definite good news is that the wind noise with the Airtabs off the cabin roof has dropped by an order of magnitude. There's still a little rumble, but pretty tolerable. But I'll probably move them around a bit again to see if I can clear that up.
mhiscox
Exp. Leader Emeritus
So . . . got back at it today and moved the Airtabs, which I'm still expecting to work, farther back on the cabin roof, one on each side, about 6 inches in from the side edge and the front edge about a foot from the rear.
I attached them to the underside of the nose cone, instead of to the cockpit roof, with the expectation that the wind noise in the cockpit will be less and that it won't make any difference to the resulting vortex.
I also attached them at a bit of a shallow angle to the truck's axis. My perception was that the wind howl we're trying to eliminate came up when there was a quartering crosswind rather than head one. There's a small chance that having the Airtab at the matching angle will be beneficial.
While I was doing this, I thought up another use of the Airtabs. With my opening rear window, there's no rear wiper, so in the rain, the back window gets pretty much covered with gunk. On my 100, there's a factory installed spoiler at the back edge of the roof and it makes a big difference. So I'm thinking that putting some Airtabs across the back edge of the XV-JP, under the rear of the roof rack, might do something.
We'll see if it makes any difference, and if it does, I can think about adding some more.
Updates will be forthcoming if/when I learn anything.
I attached them to the underside of the nose cone, instead of to the cockpit roof, with the expectation that the wind noise in the cockpit will be less and that it won't make any difference to the resulting vortex.
I also attached them at a bit of a shallow angle to the truck's axis. My perception was that the wind howl we're trying to eliminate came up when there was a quartering crosswind rather than head one. There's a small chance that having the Airtab at the matching angle will be beneficial.
While I was doing this, I thought up another use of the Airtabs. With my opening rear window, there's no rear wiper, so in the rain, the back window gets pretty much covered with gunk. On my 100, there's a factory installed spoiler at the back edge of the roof and it makes a big difference. So I'm thinking that putting some Airtabs across the back edge of the XV-JP, under the rear of the roof rack, might do something.
We'll see if it makes any difference, and if it does, I can think about adding some more.
Updates will be forthcoming if/when I learn anything.
mhiscox
Exp. Leader Emeritus
And the verdict is in . . .
Hung Jury.
The Airtabs I put under the nose cone on each side
aren't causing any problems and I think they are having a modest mitigating effect on the wind howl. It seems that the number of times I get the bad wind howl is smaller, and the noise seems less dramatic (less of a banshee wail) than without them. I'll leave them there.
I'll also leave the four I spaced along the underside of the roof rack:
as they, too, cause no trouble. But my hope that they would cause turbulence that would keep the rear window cleaner didn't pan out. I could add more of them, but four was my maximum for an idea that likely wouldn't work, and with no signs that I got even a little improvement from the first four, I'm not going to add any more.
While being made of some fairly thin plastic, the Airtabs are a quality product with some really nice adhesive (holds them on but will let 'em off when you want without damage) but in "off-label" DIY applications, it's a little hard to tell how to use them and what effect, if any, you'll get.
Hung Jury.
The Airtabs I put under the nose cone on each side
aren't causing any problems and I think they are having a modest mitigating effect on the wind howl. It seems that the number of times I get the bad wind howl is smaller, and the noise seems less dramatic (less of a banshee wail) than without them. I'll leave them there.
I'll also leave the four I spaced along the underside of the roof rack:
as they, too, cause no trouble. But my hope that they would cause turbulence that would keep the rear window cleaner didn't pan out. I could add more of them, but four was my maximum for an idea that likely wouldn't work, and with no signs that I got even a little improvement from the first four, I'm not going to add any more.
While being made of some fairly thin plastic, the Airtabs are a quality product with some really nice adhesive (holds them on but will let 'em off when you want without damage) but in "off-label" DIY applications, it's a little hard to tell how to use them and what effect, if any, you'll get.