New FWC camper, wind fairing suggestions

[turn_one]

Picked up my FWC Hawk shell (from American RV Company, great service from Jeff and Clint) in Portland OR. Averaged about 19 mpg's on the way down and 15 mpg's returning with the camper. The truck is a 4WD 2500 Ram diesel.

I can't imagine the decrease in economy has as much to do with the added weight as it does with aerodynamics so it has me thinking of a wind fairing of some sort mounted to the trucks roof. I don't have much clearance between the roof of the truck to the bottom of the camper so I'm unsure if a Thule or Yakima basket with a fairing on the front would fit. Nor do I think a wing that small would achieve what I'm looking for. Also, the satellite antenna is mounted in a place that may interfere.

Anyone have experience with one of these? If so, what type and how did it affect your mileage? Is the top the big wind resistance or do you think the sides?

Here's the 2nd night on the way home (1st wasn't so picturesque as it was in a busy Wal Mart parking lot):

 

[Cayuse]

I have a wind deflector on my Tundra. Honestly it does nothing for the mpg, what it does do is keep the wind noise down. I have a pretty good gap between the cab and the overhang and had very annoying howling going on at most common driving speeds with the deflector that has gone away. I found the fairing on the local craigslist and had to adapt the attachment to get it on the truck.

 

[dsrtrat]

Do a search for wind deflector and you will see a thread with many fairing ideas. I have Yakima old style 54" long fairing on a single cross bar but I think longest they now sell is 50" long.
Dsrtrat

 

[Casa Escarlata Robles Too]

I have a wind deflector on my Tundra. Honestly it does nothing for the mpg, what it does do is keep the wind noise down. I have a pretty good gap between the cab and the overhang and had very annoying howling going on at most common driving speeds with the deflector that has gone away. I found the fairing on the local craigslist and had to adapt the attachment to get it on the truck.

Great Polebridge Merch,shot.
Frank

 

[Casa Escarlata Robles Too]

Do a search for wind deflector and you will see a thread with many fairing ideas. I have Yakima old style 54" long fairing on a single cross bar but I think longest they now sell is 50" long.
Dsrtrat

I think you might find some info at Bill Harr's site.
He has a deflector and had done some research.
Frank

 

[Cayuse]

Great Polebridge Merch,shot.
Frank

Thanks. When in the area gotta get some bread and bearclaws.

 

[Taku]

No mileage difference that we have noticed. But I built a fairing from 6061 aluminum stock (bent at ~35 degree angle) and 1/8" thick aluminum sheet metal - bought at Pacific Steel for less than $25 for the whole thing. Lot's cheaper than commercial, but more work to build.

 

[turn_one]

Thanks for the replies. Interesting that there's no mpg difference observed. I don't have an issue with wind noise and have less of a gap than Cayuse on the Tundra. Maybe I'll suck it up and hope diesel prices don't get to years past highs.

 

[ntsqd]

I've found that by reducing our speed to our 12 Valve's ideal of no more than 1750 RPM that our mileage has made a large step up. Had to have the trans rebuilt and that in combo has seen a change from a pretty steady 13 up to around 16 average with two known single tank spikes to 18.8 and to 19.7 I don't check every tank, so no idea how often or infrequent such spikes are. The 19.7 was from home to Delano going over the Grapevine on I-5. My strategy for the grade was to take over the throttle setting from the CC and hold the same throttle setting, not the same road or engine speed. As soon as the engine started to lug I turned off OD. Then as soon as we were at the summit to turn on the OD and bring the CC back in.

 

[BWSracing]

This weekend I found that with our Grandby in what I think is the identical truck we got 16ish below 70 14ish above 70mph. I think it's mostly the weight and very little to do with the aero.


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[turn_one]

This weekend I found that with our Grandby in what I think is the identical truck we got 16ish below 70 14ish above 70mph. I think it's mostly the weight and very little to do with the aero.


Sent from my iPhone using Wander The West

Seems to be the school of thought here but I'm not completely sold on it being only a weight thing. Our diesels shouldn't be as affected by weight as gas motors.

I've taken numerous (pre camper) 1-2 week moto trips with 1 buddy, gear, gas and bikes, etc which could be comparable in weight to my Hawk shell and noticed 1-2 mpgs less than being unloaded. Not the 4 mpgs I just got.

Either way, I agree the biggest factor is engine rpm and speed.

 

[ntsqd]

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

 

[BobM]

Even a car gets worse mileage @70. The higher the rpm the more fuel gets sucked in

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[snuffy]

Any large RV be it slide in camper or travel trailer motorhome etc is going to suck fuel. it is the price we pay to play..

 

[turn_one]

To keep this on track...

My original post was a question about the effectiveness of a wind fairing and how much aerodynamics plays a role on fuel economy with truck campers...at least that was my intent.

I realize that speeds plays a role in fuel economy, this is the case with any vehicle. I also know we have to 'pay to play'...but...

I made the trip down to Portland to pick up the camper and got 19 mpgs. On the way back I averaged 15 mpg. Same roads, same driving habits, sea level to sea level.

I think the 4 mpg difference is more aero related than weight (as I'm in a diesel) and if I understand ntsqd, this speaks to his point as I've greatly increased the wind resistance of the truck with the flat leading edges of a camper:

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

 

[Wallowa]

ntsqd was speaking to the speed vs wind resistance drag...not just to the "flat leading edges'...on any vehicle dependent on the coefficient of drag/friction for that vehicle the frictional drag of pushing through the air is going to increase much more rapidly than the speed increase..double your speed and get four times more frictional drag as ntsqd pointed out.

In short form, with or without the camper, slow down to lessen air drag and save fuel...

The wind deflector that many of us use to "streamline' the air flow over the squared front surface of the camper reduces the coefficient of friction and theoretically reduces the air drag. How significant is it? Tough to accurately quantify but several forum folks have reported measurable improvements in mpg after installing wind deflectors.

You [Turn-One] reported losing 4mpg in a diesel [with superior torque] this seems a bit much, but your speed was not mentioned...and most of us never truly get an accurate mpg determination until after running numerous tanks of fuel through the vehicle...way too many subtle but significant variables to have a sample size of "1" and call it accurate. Many runs are required to smooth out the variables and really find out the amount of any mpg fluctuations.

Just my take..and in any event...like was posted, add weight/wind resistance and expect to pay for it at the pump. it is all good.

Phil

 

[cerve137]

My cheapo solution to this: Look on your craigslist for Yakima Q towers and a wind deflector. Best time to buy is now during the winter. The old style is not only available wider but was also considerably taller. Really you only need 2 towers, 1 crossbar and a fairing.

 

[billharr]

Drag hurts, my wing might save one MPG but sure cuts the noise. Now who is going to be the first to address the flat back of our campers?

 

[Stalking Light]

My cheapo solution to this: Look on your craigslist for Yakima Q towers and a wind deflector. Best time to buy is now during the winter. The old style is not only available wider but was also considerably taller. Really you only need 2 towers, 1 crossbar and a fairing.

That's what I use on my Tacoma, it does help the noise but I haven't noticed much difference in mileage.

 

[Wallowa]

Yup...I already have installed the QTowers, 80" bar and 50" wind deflector. I purchased the second set of towers and another bar just in case I can fit a basket under Hawk cab overhang between the bars to stow even a few pieces that I don't need to get into often. Space will definitely be at a premium even in my Tundra Access Cab.

Yakima gear is not cheap but it is a good fit and quality build. Bill H. has a larger deflector that I might copy if my Yakima deflector proves to be inadequate. Limits crap impacting front of camper, hopefully lessens wind drag and reduces wind noise.

Phil