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Can lead a horse to water but can't make him drink it. Good try though!
The problem is everything he has proposed here still leaves a vacuum pocket of turbulent air in the back. A few relocate it or reduce it but don't eliminate it. And this pocket is the cherokee's greatest overall drag point. Air flow needs to be "redirected" into that dead zone to increase the pressure behind the vehicle and it will eliminate the turbulent zone all the way down to the bumper.
It's a simple concept that has been used for a longtime on aircraft spoilers and in reverse principle in sail boat sail design. In fact it is a common practice to help "push" a teammate in NASCAR by coming up from behind and using the pressure created by the vehicle in the rear to "push" the car in front of it because this increased pressure reduces the drag in the dead zone at the rear of the car in the front.
But he is apparently hell bent on building something extravagant that is going to hit people next to him when turning in heavy traffic. He will have to hang a sign on the back that says "this vehicle makes wide turns" and then even that sign will create added drag. lol
I completely agree that the huge drag pocket in the back needs to be eliminated, It would be one of the most efficient changes you could make to that if you want to reduce drag on these bricks. But what you are sharing here will not do much to ELIMINATE that drag pocket. Reduce it maybe but not eliminate it. The cure has been around for many many years and has been used on station wagons (IE Cherokees) for a long time and IT WORKS.
Here is an Buick "Safari" with the cure as an example. Now to do this with an XJ would be a little tricky because of how the hatch and hinges work. But two of these, one mounted on each side of the hatch would absolutely accomplish the exact same advantage. The reduction in overall drag far far outweighs the very little resistance the scoops would add with this concept.
This is what I am going to do to mine to both reduce that drag pocket in the rear, and to keep dust from sucking up and landing on everything back there. But I am going to make mine out of plastic mounted on rubber so that bushes don't break them off the hatch when out in the sticks.
Keep it simple, because sometimes simple is the best answer.
just saw something very similar to this on a liberty today in traffic
just saw something very similar to this on a liberty today in traffic
If it redirected the flow down the back window like this one it's the way to go. But on a Cherokee a short one on each side the same length as the side window is tall would do the trick.
If it redirected the flow down the back window like this one it's the way to go. But on a Cherokee a short one on each side the same length as the side window is tall would do the trick.
Yep, that's the trick right there, exact same! The problem is with our XJ's that would get pinched between the roof/rack when you lift the rear hatch. So two, one down each side of the hatch would roughly equal the same surface area and do the same thing.
Did this just cause I like the look but does it do anything as far as the air flow goes?
Unfortunately that style is designed to force heavy rain off the top rather than have it suck onto your back window. It makes it clearer to see out the back window in heavy rains. Without redirecting the flow down the back window like the one on the liberty below it can't really do much to make the flow reduce drag.
I guess that Liberty spoiler wouldn't work with our hatches would it? It seems like there would be a problem with the spoiler hitting the roof when the hatch was fully opened if it were mounted in the appropriate place.
EDIT. LOL I just saw your post above...nevermind...
I guess that Liberty spoiler wouldn't work with our hatches would it? It seems like there would be a problem with the spoiler hitting the roof when the hatch was fully opened if it were mounted in the appropriate place.
EDIT. LOL I just saw your post above...nevermind...
Lol... Yeah, I already played with this because I'm getting tired of the dust on the back of mine and had to settle with the one on each side concept instead. But for my off road use they would have to be plastic and mounted semi-flexible so that they give a little if they catch brush instead of breaking the hatch.
Yeah, they wouldn't be very branch-friendly on the sides. Especially so on the earlier fiberglass hatches.
I figured I would mount them using a couple of layers of radiator hose, a smaller one inside of a larger one about an inch wide. It would then conform to both the wings and the hatch if I placed the bolts in the right place.
Not a bad idea. You could possibly find a stepped bushing to isolate the bolts in a larger mounting hole as well, to allow for some deflection without "wallowing" or warping the sheet metal.
Not a bad idea. You could possibly find a stepped bushing to isolate the bolts in a larger mounting hole as well, to allow for some deflection without "wallowing" or warping the sheet metal.
Absolutely, some rubber grommets to mount through. I first thought to myself that if they are mounted flexible they are just going to blow back against the window. But then I remembered the physics that would prevent this in reality.
02-03-2018, 06:41 AM
