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New FWC camper, wind fairing suggestions


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#21 Flyfisher

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Posted 05 January 2016 - 12:45 AM

I'm in Bill. I'd be willing to work with you on a solution. I think that might be a large part of the drag coefficient for our campers. I have certainly looked at those trucks and wondered.

Gregg


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#22 Wallowa

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Posted 05 January 2016 - 01:17 AM

Geez...really?  Add something to back of our campers to decrease the drag?  At some point it will come down to what the man previously said..."You play, you pay".   You know "diminishing returns".  But to each their own and good luck with your project.

 

Phil


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#23 Bad Habit

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Posted 05 January 2016 - 01:25 AM

Ive always wondered if these would help at all

Www.airtab.com

Edited by Bad Habit, 05 January 2016 - 01:25 AM.

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2012 F350 Super Cab SB, 6.7l diesel, Hallmark K2


#24 billharr

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Posted 05 January 2016 - 02:36 AM

Geez...really?  Add something to back of our campers to decrease the drag?  At some point it will come down to what the man previously said..."You play, you pay".   You know "diminishing returns".  But to each their own and good luck with your project.

 

Phil

EDIT: Just saw Bad Habits post did not mean to duplicate. 

 

I have to agree, I bought the camper to camp. Did the wing because of noise not mileage. IF and that is a big if, you drove far enough the tail might make a difference. Just don't think it would be worth the trouble. 

 

One thing I have not seen except on the web are airtabs. They might be the answer need someone to test them out. Cost of kit  here.

 

trailflo1.gif

 

rv28.jpg

 

rv6.jpg


Edited by billharr, 05 January 2016 - 02:39 AM.

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#25 ntsqd

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Posted 08 January 2016 - 03:06 AM

Real world experience: Flat towed my fiberglass dune buggy all over So. CA with a '66 Econoline van. Neither of those vehicles qualifies as anything approaching "aerodynamic". Mileage was the same towing or not towing (dismal) at 55, and better when towing at higher speeds than when not towing at those same speeds. My tentative conclusion is that the dune buggy filled in the vacuum behind the van and made combination more aerodynamic than the van by itself.

 

Consider the classic rain drop shape. It's pure physics how it gets that shape. The reason for the shape of the 'tail' is due to two things, the high surface tension of water and the aerodynamics of a sphere moving thru the air. Basically the air pulls the water into that shape. If our campers were fluid enough they too would have that tail shape.


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Thom

Where does that road go?

#26 Shadyapex

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Posted 08 January 2016 - 04:20 AM

Real world experience: Flat towed my fiberglass dune buggy all over So. CA with a '66 Econoline van. Neither of those vehicles qualifies as anything approaching "aerodynamic". Mileage was the same towing or not towing (dismal) at 55, and better when towing at higher speeds than when not towing at those same speeds. My tentative conclusion is that the dune buggy filled in the vacuum behind the van and made combination more aerodynamic than the van by itself.

 

Consider the classic rain drop shape. It's pure physics how it gets that shape. The reason for the shape of the 'tail' is due to two things, the high surface tension of water and the aerodynamics of a sphere moving thru the air. Basically the air pulls the water into that shape. If our campers were fluid enough they too would have that tail shape.

It is definitely true that the trailing edge is at least as important as the leading edge in aerodynamics, and therefor fuel economy. And I think you're right that your trailer filled the low pressure area behind your van. There is a reason we're seeing these contraptions added to the back of tractor/trailer rigs. I wonder if someone will come up with an add on for campers that will be economical and usable given that we don't spend thousands of dollars on fuel each year. Given the low economy of scale and the relatively minor amount we spend on fuel it might not wind up being worthwhile. But it's an interesting idea none the less. I'll bet one could come up with a very aerodynamic long trailing edge camper, but it would probably be ugly as hell and fairly unusable. Too bad,,,,,


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"It's not an optical illusion, it just looks like one."


#27 broncotime

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Posted 09 January 2016 - 12:11 AM

R = ½ρCAv2

 

it probably is a lot of extra drag in addition to the weight, it's just not as solvable with the profiling or contouring of the front shape. "A" in this equation refers to the "projected" area of the front of your vehicle, so just having the little extra overhead, and the stick out on the sides does a lot....


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#28 dasadab

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Posted 09 January 2016 - 12:26 AM

I like the concept of a rear drag reducer that would also act as a small awning.  


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#29 Wallowa

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Posted 09 January 2016 - 01:03 AM

Bronco,

 

Can you break that down to lay terms?  Like how many Hp does it take to overcome R as increased by a FWC [your choice of veh and camper model]?   What would be the calculation translating that R increase into a decreased Mpg at say 55 mph?

 

Seriously speak slowly, my education [bio oceanography] did not prepare me for any fluid dynamic calculations let alone grasping how to quantify the variables.

 

In short form what would we folks toting FWC actually save in terms of Mpg by trying to streamline the rear of the camper?

 

Thanks,

 

Phil

 

Ps...had to look up "C"..how would you calculate the "Coefficient of Drag [C]"?  And how significant is this factor?


Edited by Wallowa, 09 January 2016 - 01:09 AM.

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#30 ntsqd

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Posted 09 January 2016 - 01:40 AM

To the best of my knowledge the Cd for any given object is found experientially, there is no direct way to calculate it. Similar simple shapes will likely have similar Cd's, though a first gen Tundra with an FWC on it is not going to have the same Cd as a second gen Tundra with the same FWC on it. As I recall Cd will never be grater than one. A brick likely is close to a Cd of 1 and the best Cd for a car that I can recall reading was about .34

Cd is the correction factor between the actual shape of the object and it's "projected area". Gains in this variable are worth pursuing, but at some point diminishing returns will arrive and given the total influence of this factor I suspect that will happen fairly quickly. It also explains why things done that should have made a dramatic difference in drag really didn't help a lot. The gain of those 'tail feathers' on big rigs probably isn't much, but when you add it up over one million miles it makes sense to do.

 

The other variable in the formula, (ρ), is the density of the fluid, in this case air. Again, I'm thinking this also can't exceed a value of one. A nuance might be that the air in the boundary layer will be slightly compressed and exhibit a slightly increased density, but I'm splitting atoms there.....

 

Which leaves projected area and velocity. Area is linear, but velocity is squared so it has the biggest influence on the air drag. Think about the net effect of reducing the area by 25% vs. reducing the velocity by 25%.

 


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Thom

Where does that road go?




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