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Author Topic: How big of a front air dam?  (Read 5989 times)
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barrybill
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« on: November 16, 2013, 12:54:17 PM »

We have a Studebaker hawk with a 54 nose that we run in the 130 club. We made a front air dam and it seemed to help but a question came up as to what speed do they generate a bonus, [we are at 120 mph] And then if it helps at that speed how tall should it be? All the way down to the salt = more drag. One racer who I really respect said no lower than the lowest part of the bottom of the car not counting wheels etc. Having looked at pictures of different Studes over the years I see all different sizes on equally fast cars, I don't mean equal to our low speed, but 200+. any help is appreciated. Currently working on turbo set up to make the Stude breathe.  Barry [lefty] Studebasher
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manta22
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« Reply #1 on: November 16, 2013, 07:53:42 PM »

I'd say get it down far enough to almost scrape the salt.
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« Reply #2 on: November 16, 2013, 08:04:34 PM »

The idea is to direct the air around the car not under.
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barrybill
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« Reply #3 on: November 16, 2013, 10:38:39 PM »

I understand keeping air out from under the car but does anyone know at what speed they become effective? My concern is if we are not going fast enough for the dam to work I don't need the extra drag. Barry
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Sumner
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« Reply #4 on: November 17, 2013, 01:12:35 AM »

I understand keeping air out from under the car but does anyone know at what speed they become effective? My concern is if we are not going fast enough for the dam to work I don't need the extra drag. Barry

Keeping the air out from under the car is going to cut down on the drag, but also lower the car as much as possible before making the air dam.  We also run stops in case the car wants to go further down to keep the tires out of the fenders and the air dam off the course ...



You need to keep in mind that the course is flat so a very low air dam will work on the course, but maybe not when you leave the course and drive thought the crunchies over to the return road.  We have broke ours before.  As you can see in the picture above it is a couple inches off the salt.  Lower would be better aero wise but it has to be practical also,

Sum
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« Reply #5 on: November 17, 2013, 10:00:34 AM »

As I remember - the Speed Demon's rubber skirt (which runs about halfway to the rear of the car) is designed with something like 3/8" ground clearance.  It's rubber, note -- and that means it can flex and even wear without doing much damage.  And if it's less than a half-inch from the surface of the salt -- that reduces the amount of air getting under the car to a pretty low amount.

The skirt is made of rubber that's maybe 2" tall and fastened to the bodywork every foot or two to keep it in line and reduce any flapping.

3/8" -- can't get much closer than that even on a very flat surface.  And yes, when turning out at the end of the course -- the rubber does hit the tops of the crunchies, and that's another reason to make the air dam out of a somewhat-flexible material.
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Sumner
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« Reply #6 on: November 17, 2013, 11:03:28 AM »

As I remember - the Speed Demon's rubber skirt (which runs about halfway to the rear of the car) is designed with something like 3/8" ground clearance.  It's rubber, note -- and that means it can flex and even wear without doing much damage.  And if it's less than a half-inch from the surface of the salt -- that reduces the amount of air getting under the car to a pretty low amount....

I'd love it if we could run that close to the ground but some of this also depends on the type car and maybe the class.  We run comp couple so can do anything up there we want.  Not sure if all classes allow an air dam so not sure what the OP can or can't do rule wise.

Hooley's Stude...



...is relatively wide and flat going into the wind.  Something that will flex when hitting the crunchies will also probably be deflected back under the car over 200 mph and at even lower speeds,  so could loose some of its effectiveness due to the force of the air on the front of it.

Speed Demon....



http://speeddemon.us/

....on the other hand is very pointed in the front and like you mentioned the skirts are mainly oriented going down the sides of the car so don't need to be as strong as the air is not hitting them head on.

Hooley likes to try and keep the Stude looking like one as much as possible so the front air dam is made from fiberglass to resemble a front bumper.  In pictures we have seen when the car is at speed it appears to be bending back some so we are adding stiff metal straps behind it for next year.

So low and close and flexible is good but be sure it is up to the job,

Sum
« Last Edit: November 17, 2013, 11:05:25 AM by Sumner » Logged

barrybill
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« Reply #7 on: November 17, 2013, 03:24:34 PM »

Thanks for the responses, we will use what we have which is pretty low and besides it looks fast. Barry
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redhotracing
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« Reply #8 on: November 17, 2013, 03:29:04 PM »

We've found a more rigid (read: plastic) dam down close then conveyor belt material, which will wear off for the rest... Given, we run asphalt, but the previous posts about getting the car down before you fab a dam. We can't go any lower without changing wheels/tires, then measure for aero aids...
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Luke- Winston Salem, NC
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« Reply #9 on: February 22, 2015, 01:55:52 PM »

We are doing the Texas mile for the first time in a stock bodied sti hatchback. Hoping for 185+... I have some plastic that I can make a air dam out of...but, what thickness are you guys running? I'd hate to have it just fold back under speed. I guess it would be about 3.5 inches tall...maybe 4...(writing this from the recliner)
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redhotracing
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« Reply #10 on: February 23, 2015, 10:24:49 AM »

The thickness of plastic isn't as important as the bracing behind it... I used 1/8" (thick), 1" wide metal and bent it to shape, then mounted the
plastic to it. Used 3/4" square tubing to brace it from behind. Think mini roll-cage construction to combat bending of the material at speed. You
can use the lower core support as a mounting point, or even the inner fenders (if metal). We saw no shape distortion after 200+mph runs.
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Luke- Winston Salem, NC
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Sumner
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« Reply #11 on: February 25, 2015, 07:51:28 AM »

The thickness of plastic isn't as important as the bracing behind it... I used 1/8" (thick), 1" wide metal and bent it to shape, then mounted the
plastic to it. Used 3/4" square tubing to brace it from behind.

Also what we ended up doing...





... and also ....



... added a pad to better support the front bodywork.



Above you can see the air dam in place.

More here on the bracing...

http://1fatgmc.com/car/14-Hooley/14%20-%20construction%20menu.html

Sumner
« Last Edit: February 25, 2015, 07:54:05 AM by Sumner » Logged

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