Air dam specs: Dave, you around? - PowerStrokeNation : Ford Powerstroke Diesel Forum
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post #1 of 18 (permalink) Old 05-22-2008, 01:31 PM Thread Starter
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Air dam specs: Dave, you around?

Instead of a PM I thought others might benefit, too.
Dave,
I'll be building my air dam this weekend.
I was wondering how tight to the front bumper the dam needs to be. I see yours appears to be screwed directly to the front bumper. I want to build a framework in the shape of the front bumper to follow it's profile, yet be independant of the bumper for easy removal, and be bolted to the snow plow frame. Would this design need to be 'taped' or sealed to the bumper in some way?
I also plan on having it start at a 'V' in the center of the bumper out a little.
Should this space between the dam and bumper be filled in?

How close to the ground do you feel is mandatory for full benefit?
I read 1" off the ground, somewhere, but when I started to mock it up, 1" looked near impossible with suspension travel more than that. What about 3" - 4", when the front bumper is already 24" from the ground?

Also, I am getting some 1/8" rigid plastic they use for circle track body parts, I can't find any belting cheap enough. If the plastic feels flimsy, then I'll double it up and glue it together. $40 for 2 layers (1/4") of plastic is hard to beat.
Any thoughts on this material?

Thanks!
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post #2 of 18 (permalink) Old 05-22-2008, 09:14 PM
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Re: Air dam specs: Dave, you around?

Were do you get this material? You could potentially stop the plastic 4-6 inches from the pavement and then go a couple of inches extra with thin rubber. This way it will keep its shape, flex a bit if you hit something and still give you full benefit...

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post #3 of 18 (permalink) Old 05-22-2008, 09:33 PM Thread Starter
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Re: Air dam specs: Dave, you around?

Yeah, I thought of that, too, but I think thin rubber will still blow horizontal at 65 mph.
If anything, I'd use some stiff rubber belt (cheaper-er) 6" - 8" strip along the bottom of the plastic, if needed, we'll see.
Plastic is from Speedway motors. 22" x 10' or 25' rolls...
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post #4 of 18 (permalink) Old 05-23-2008, 02:11 AM
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Re: Air dam specs: Dave, you around?

I have all sorts of thoughts about air dams. I’m fixing to get mine modified and back on by next week.

I don’t think an air dam has to be sealed up against the bumper. Mine is, but strictly to keep it from “working” and tearing my rubber material. My first version had no filler, but the second will just to give it a bit of a curve for deflecting air sideways.

Sprint Cup cars have a bit of a negative slope to their air dams but that is for developing downforce (negative lift). Racers who have to go around corners crave downforce but at highways speeds it is unnecessary. That big heavy engine you have gives you plenty of traction up front. A vertical air dam with a curve or angle to throw the air sideways rather than lift it over the truck would be optimum.

There are two schools of thought about how much clearance an air dam should have. Finite element analysis always calls for zero ground clearance. Obviously zero is impractical even for tough material. I initially cut mine for one inch clearance and the road (over a period of a couple months) wore it to an average of 1.5” clearance. Using the FEA school, the idea is to minimize the air flow under the truck and not worry about the roughness underneath the truck because the air fo low is not enough to sweat it. A guy named Phil Knox has beaten the shape of the pickup truck every imaginable way and he has a different theory. He did not lower his ride height (his test mule is a T-100) at all and contends that a zero clearance air dam adds frontal area. He has an air dam that is low enough to block direct air flow on the suspension parts and the oil pan but no lower (except in front of the wheels where he has shaped deflectors to fair in the front of the tires). This commits him to a full belly pan as there is significant air flow beneath the truck. Two schools of thought and both seem to work. Take your choice. Since I am lazy I opted for the (expensive) tough material and the lowest air dam I could make, but no belly pan. Once I get my side skirts made, the underside of my truck will be operating in a partial vacuum so I don’t have to do the belly pan.

With your less flexible material you may be best off to limit your air dam to blocking air flow onto the suspension and engine parts and using the same stuff to fair in the bottom of the truck. I do know from experience that if the bottom of the air dam is lower than 8” above grade, it will foul parking curbs.

Do make the thing so you can remove it easily when the snow flies.

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post #5 of 18 (permalink) Old 05-23-2008, 02:16 AM
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Re: Air dam specs: Dave, you around?

My wife gets this rubber mat for the bottom of the horse pens.It is close to 3/4 inch thick and very ridged and heavy.Wonder if that would work.Made from recycled tire rubber.


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post #6 of 18 (permalink) Old 05-23-2008, 02:17 AM
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Re: Air dam specs: Dave, you around?

Sounds H/D Kainers, worth a try if it's free.


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post #7 of 18 (permalink) Old 05-23-2008, 02:29 AM
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Re: Air dam specs: Dave, you around?

Quote:
Originally Posted by kainers View Post
My wife gets this rubber mat for the bottom of the horse pens.It is close to 3/4 inch thick and very ridged and heavy.Wonder if that would work.Made from recycled tire rubber.
I know exactly what your talking about kainers. Those rubber mats crumble way too easily and tear very easily, along with weighing a ton. Just as a test, we had one of the stalls in the barn fitted with a permanent sealed rubber mat, the cover was 1/2 material, but nylon re-enforced. The underlayment was 4" of rubber particles, turned out very nice FWIW.

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post #8 of 18 (permalink) Old 05-23-2008, 02:41 AM
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Re: Air dam specs: Dave, you around?

Damn those things are expensive too like 65 bucks for a 4X6 sheet.There is 4 of them laying in the back yard.


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post #9 of 18 (permalink) Old 05-23-2008, 02:45 AM Thread Starter
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Re: Air dam specs: Dave, you around?

We'll be headed from Cleveland to Indy, then St Louis on 5/30 - 6/3, so I'm really trying to get something done by then to try it out. Even a couple mpg would be great. If it doesn't work, oh well, I'll refine it and try it locally.
I know the curbs will be tight, I'll just have to remember it's there...

And since it'll be mounted to the plow frame, it'll be easy to come on and off with 4 large bolts.
That's the idea anyway. I'll post up some pics and info when done.

Thanks Dave!
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post #10 of 18 (permalink) Old 05-23-2008, 02:45 AM
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Re: Air dam specs: Dave, you around?

that and they are heavy as chit..... i have had the privilege of lining a whole barn with them.

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