I sent a PM to Sleepy with some thoughts, but he suggested I should post it here as well......
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I have been following the air tabs / air foil discussion with great interest. I cannot buy the materials here in Canada to make Sleepy's design so I thought I might try the air tabs so purchased some which I now have in hand. However, when I thought about it some more and read all the posts, I am not sure which way to go.
I asked Sleepy to answer a couple of questions.
1) From Sleepy's posts, I understand that the only reason you use perforated material is to prevent a low pressure area forming behind the air foil and sucking in dirt and bugs. Is this correct??
2) Have you considered the Bernoulli effect resulting from the alignment of the cab and camper overhang??
I am thinking that this effect will greatly intensify the force exerted on the camper bulkhead behind the cab. Probably several times higher that that exerted on the front of the camper overhang and truck itself. This is a result of the dynamic pressure (kinetic energy) which is a function of velocity squared.
Is it possible that the air foil works in part more by slowing the volume of air between the cab and camper overhang and therefore reducing the velocity and thereby the dynamic pressure? This should enhance the improved fuel economy being experienced.
Also, the lower velocity above the cab would draw in more air and bugs from the sides before "splattering" them on the bulkhead. This might explain what I have observed where the density of the bugs on the bulkhead on my camper is much higher than on the front of the truck or camper overhang.
At this point, I am thinking that dampening the Bernoulli effect might have more of an effect than the displacement of air to the sides (like your barge analogy). Although displacing the air sideways also reduces the air volume and therefore velocity!********************************
I am going to work this some more, but for now, I will hold off on installing my air tabs until I understand the physics a little better. :? Where is Sheldon Cooper when I need him!! :D
