New FWC camper, wind fairing suggestions

[Flyfisher]

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

 

[Wallowa]

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

 

[Bad Habit]

Ive always wondered if these would help at all

Www.airtab.com

 

[billharr]

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.

 

[ntsqd]

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.

 

[Shadyapex]

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,,,,,

 

[broncotime]

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....

 

[dasadab]

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

 

[Wallowa]

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?

 

[ntsqd]

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%.

 

[Bill D]

As mentioned above... wouldn't it be easier, cheaper and safer to simply slow down a bit.
The reason I bought a FWC is so I didn't have to rush to my destination.

 

[Wallowa]

Bottom line, and I agree, is slowing down makes one hell of a lot more sense that chasing the aero of the package...at least with our trucks and campers...now space craft.....gaining or losing 10-15% mpg prorated over the total miles that I will be driving at highway speeds does not make sense for me since I hope most of my miles will be off-road where "aero be-damned".

Phil

Ps...Cd of C6 Corvette = .28

 

[Bill D]

I've found slowing down to 55MPH with the Hawk gets me about the same fuel economy as going 70/75MPH without the Hawk.

When we were tent camping we always had to rush to get to our camping destination, so we would have a place to sleep that night. Now we simply slow down to about 60MPH and sleep wherever we feel like. We've discovered a few new camping spots (and Walmarts) by doing this as well. It's a much more relaxing adventure.

All the power to you and your aerodynamic solutions. Best of luck finding something that works for you and is worthwhile.

 

[JaSAn]

As mentioned above... wouldn't it be easier, cheaper and safer to simply slow down a bit.
The reason I bought a FWC is so I didn't have to rush to my destination.

Aw, your no fun! As a retired engineer, I need a problem to occupy my mind (can't help myself)

I am going to do some experimenting next summer; mostly just because it is fun And I have another motive: having an older camper, I get some moisture being forced in the front when driving in heavy rain, getting my front lift panels wet So I want a deflector to protect the roof/overhang seam. I know from bug splatter that the air is hitting the flat front sections and that isn't helping my gas mileage.

I've also looked at the 'trailer tails' on the rear of semi trailers; really want to observe them during a snow storm.

jim

 

[Shadyapex]

Ive always wondered if these would help at all

Www.airtab.com

Vortex generators work on airplanes and raptor's wings, so I don't know why they shouldn't work on a camper's trailing edge. I would be tempted to try them, why not?

 

[Wallowa]

Just a WAG...but addressing the turbulent air behind a camper on a truck lumbering down the road or worse yet off-road will have quantum levels less of any decrease in the energy it takes to move down the road than an airplane or bird that rely on very low frictional drag to stay aloft...it is a matter of degrees and yes decreasing the turbulence behind a camper will decrease the energy it takes to move it through the air...but compared to the benefits of streamlining [decreasing turbulence] a plane the camper is a lost cause...kinda pissin' into the wind....

Or as my buddy likes to say: "You can put lipstick on a pig, but it is still a pig".. Phil

 

[ntsqd]

Decreasing the size and/or the magnitude of the vacuum bubble behind the camper should have one benefit that may not be obvious until pointed out, less dirt road dust sucked up against the back wall of the camper where it can potentially leak into the camper.

 

[Vector1]

Wind resistance squares with speed, so 2 times faster is 4 times more resistance.

I'm with ntsqd on this. Slowing down can make a big difference, depending on the road, wind direction, and total time. Under ideal conditions, speeding up will gain you a small amount of time at best, but will suck more gas and can increase your chances of, well--you read about it in the papers, especially in the winter. The proportionality with the square of the difference in speed also applies to wear and tear as well as to collisions. I'm on a bit of crusade with this, I'll admit.

 

[Stalking Light]

I get way better mileage at 55 than at 65-70, plus I feel like I see more of the countryside. I usually try to plan my routes away from interstates, but even 2 lane roads have 65+mph speed limits in many states these days.

 

[Vic Harder]

Took a quick look at the airtab www site. Seems like most of the benefit would be to stability, rather than mpg. Not to mention they look cool. I wonder if stability is another plus for a fairing, in addition to lower noise levels?

As an aside, when I was lurking last year, I recall seeing a post where the fairing served double duty as a solar panel. Makes sense to me to gather power too, not just use less. Does anyone recall seeing that post too?