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Old 04-08-2014, 02:12 PM   #31 (permalink)
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This is all alot to think on.

I think the way I am going to go, is when I buy steel this summer is just build it and then test what affect it has. Then I will either skin it or modify it if need be.

One more oddball question, would a square rectangular or round tube, plus a pool noodle or mayby two = oval tubing?
And if it does would it look so janky it would be better to just pay for the gas haha

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Old 04-08-2014, 02:46 PM   #32 (permalink)
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Oval tubing may be around if you look for it, McMaster-Carr?

McMaster-Carr

I would suggest using flat rectangular solid stock, narrow end facing the wind.

The area in CdA is pretty important, I for one would not be increasing the size of a tube for attachment. A smaller size is a smaller footprint of resistance.

One thing to consider questioning is the assumption that the wind is going to act the same in free-flow as it would with the broad face of a radiator behind it. The pressure zone or pocket of air in front of the vehicle has got to be a significant factor with bullbars.

Aerocaps for pick-up trucks




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Aerodynamic Drag Effects of Pickup Truck Bed Configurations
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http://www.pro-touring.com/archive/i...p/t-69262.html


There is more pressure build up front than air flow found at the front of the truck.

Like I said, just keep away from the edges and you should do fine.
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Old 04-09-2014, 07:03 PM   #33 (permalink)
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round tube and angle

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Originally Posted by graver555 View Post
So it sounds like I either can put the effort into skinning it, take the mpg hit and make something that has maximum protection, or go buy a stock bumper.

Sound about right unless I can find some oval tubing or make some?

Was the round tube + angle idea a dumb one?
The 'dumb' idea would be the one never mentiond.
The Germans researched fairings for machine gun barrels.You can see that 'angle iron' attached to the trailing edge helps.The smoother,graduated taper has lowest drag.Sheetmetal could be creased,and bent to form a nice fairing.A neighbor did this on his gyro-copter control surfaces.
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Old 04-09-2014, 07:10 PM   #34 (permalink)
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oval

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Originally Posted by graver555 View Post
This is all alot to think on.

I think the way I am going to go, is when I buy steel this summer is just build it and then test what affect it has. Then I will either skin it or modify it if need be.

One more oddball question, would a square rectangular or round tube, plus a pool noodle or mayby two = oval tubing?
And if it does would it look so janky it would be better to just pay for the gas haha
In 3-D flow,an ellipsoid (oval bullet) and streamline body (teardrop bullet) have the same drag for a given thickness-to-length ratio.It might work similarly with 2-D flow.If so,you'd want the oval to be 2.5X the width of your tubing.Pool noodles would be easy.
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Old 04-10-2014, 03:32 AM   #35 (permalink)
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Quote:
Originally Posted by aerohead View Post
The 'dumb' idea would be the one never mentiond.
The Germans researched fairings for machine gun barrels.You can see that 'angle iron' attached to the trailing edge helps.The smoother,graduated taper has lowest drag.Sheetmetal could be creased,and bent to form a nice fairing.A neighbor did this on his gyro-copter control surfaces.
Where did you get a diagram of German machine gun barrel cd's......

With the radiator behind them tho as Kach22i mentioned may change the effects of air flow. So this may be past the point of diminishing returns for a front bumper except maby the edge if I decide to wrap around.

However I think this could be very effective if I make a rear bumper out of tube also. Then again I doubt I could build a less aerodynamic rear bumper then my current one if I made....
(Check the first post if you havnt seen the rear bumper)
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Old 04-10-2014, 06:53 PM   #36 (permalink)
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where did you get

The diagram is from Sighard Hoerner's self-published book,"AERODYNAMIC DRAG",published in 1951.
Hoerner worked for Messerschmitt during WW-II.He was brought to the U.S. under Operation Paperclip,rather than have him fall into other hands.
His book is a compendium of many researchers works and is often cited in contemporary research.Hucho uses his work.

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