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Old 05-10-2011, 07:17 AM   #25 (permalink)
mateospeed
10MPG w/ 8.5'x16' Trailer
 
Join Date: Dec 2010
Location: Morehead City, NC
Posts: 11
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Quote:
Originally Posted by Fat Charlie View Post
I think there's the most effective aero mod. You need a cap. Slap a cap on the truck and you've faired over the worst of the problem. A nose fairing and side skirts can follow, but a cap will stop you from doubling your frontal area unnecessarily. Plus, you'll get more storage and sleeping space.
I think I'm going to jump on this bandwagon. In the current setup, I'm pushing the truck through the air, with its Cd of, let's say 0.5, then an additional portion of a box, at Cd (pretty dang close to) 1.0. Now, the whole trailer face isn't whetted, but about 48 sq ft of it is directly impacting the air, judging by the bug splatter.

Then, if I add a bed cap, I'll probably see no significant drag increase as far as the truck is concerned. However, I'll have decreased my frontal area on the trailer by 10 sq ft. (3x5 cap, but the airflow will get sucked back into the gap b/w truck and trailer). I'm just not sure that's enough to make a significant difference. At about $400 for a used "extra headroom" bed cap, it's difficult to justify. I also don't have a good basis yet for estimating the aerodynamic gains to see how long it'd take to make a return on the investment.

Now, if I add a wing/ 3 wings to it, I could very effectively drop my frontal area of the trailer to very little, and the portion of the trailer that does see some air is mostly rounded. I'll take pictures the next time I go to the storage unit (which is soon, because I left my jack stands in there!).

Does anyone have any experience with gains made by adding a bed cap alone? And how much difference would a standard (cab) height cap vs. a slanted or extra-headroom cap make? Hmmmmm..


Thank you all for taking the time to scratch your heads with me. It's nice too see!
-Matt
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