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Old 01-03-2017, 01:33 AM   #1 (permalink)
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rust bucket - '95 GMC Sierra reg cab 8 foot box
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Airdam build using conveyor belt

Hi team i took some pics as i was building the air damn on the old gmc. The factory one was missing and my buddy gave me a length of belt, bout 1/2 inch thick (12 mm). The width was 7 inches which worked out real nice, no cutting needed.
ok so i started by removing the remnants and fasteners from the old one. Not too rusty.
Then i ripped a 2x4 in half with a generous angle on it... 24 degrees so the dam wouldnt be straight down, i wanted it leaning under somewhat... and fastened chunks of 2x2 using smaller roofing screws

I found center of both and marked where the tow hooks need holes. A chisel and stump made easy work of cutting the holes out

I then started screwing it on with some stainless screws with painted black heads (from decking) but changed to good old drywall screws as both the thread and head were larger for more secure attachment

I marked the end cuts then took it off and screwed metal reinforcing to the back, i used hvac tin straps and schluter bent to shape of bumper

i did add one metal brace in each corner to further add stiffness.

Clearance is 6 1/2 inches below dam to road, havnt scraped any kerbs yet. Im stoaked with the build, what do you think?
Oh yeah so the angle was probably a little more than needed, i think 15 degrees on 2x4 would be ideal.

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Old 01-03-2017, 08:40 AM   #2 (permalink)
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That is some stout looking material. Congrats on the "new" mod. I'd say try it out for a while and see how it treats you. The clearance should work; it should miss parking blocks. Snow shouldn't bother it, unless you run into big chunks of ice...
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Old 01-03-2017, 09:27 AM   #3 (permalink)
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Looks great! How was the rubber as far as a material to work with?
Current project: Heating the manual trans with engine coolant
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Old 01-03-2017, 09:30 AM   #4 (permalink)
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Very nice! I am on the way to check out that belting I posted about. Looks good man.

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Old 01-03-2017, 09:43 AM   #5 (permalink)
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Thanks Econoram and Daox, nice to finally get er done. I was surprised how easy it cut with a new blade in the olfa knife and a straight edge, cut it many times lightly rather than one heavy pass... and the chisel punches through it nicely. Hardest part was getting the old hardware off!
I will stick to the highways as its a little low for the snowy backroads round here, as is the wheel skirts on back, a bit of a process to get the chains on.

Cheers skyking, yea i was reading your post about the belting at the time... this is 7 inch wide, and i may have installed it differently (jrmicheller style or bigdave style) if it was wider, directly onto front of bumper. So maybe try to get a range of widths, dont limit it to 4 inches.

Last edited by rumdog; 01-03-2017 at 09:51 AM.. Reason: more info
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Old 01-09-2017, 02:32 PM   #6 (permalink)
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How far should the dam go down?

If it is flexible enough, one could make it touch the ground and it would scrape/file itself ot the proper length.

Also there are brushes such as these:
Door Excluder Brush - Door.bevrani.com

Would adding these to cover say the last parts to the ground be beneficial? Or is their nature just not aerodynamic enough?
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Old 01-11-2017, 10:13 AM   #7 (permalink)
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airdam height

Plug airdam and height into the search bar and check out the threads.
For me 6 inches or 150mm is a healthy gap... i do kiss my kerb on my driveway when reversing out too fast. any lower and i'd have trouble. Scraping going foward is not so bad but backwards theres not much flex. (In my case)
I have seen brushes like that on buses, round the wheel arch, im sure its possible for a dam or skirt, or wheel arch. But aero? Not sure.
i think the consensus is as low as your lowest underbody, and a little lower in front of wheels. Many new trucks and cars have this design.
Some under body flow is ok right, then this air feeds the difuser, which reduces pressure at rear. Thats how i see it.
Many are becoming more rounded from bumper down to underbody, which makes some sence if smooth flow is desired underneath.
Also i tested out a new mpg measuring route for highway. Quite a mission! Makes me want a mpguino! 14.9 l/100km doing 100 km/h. Minus 25 C, calm day warm truck, no muffler. best yet at that speed, but the goal is to ABA test the cap. This is just a point on the graph!

Last edited by rumdog; 01-11-2017 at 10:35 PM..
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