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Fairing On or Off?


Jemstone

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I have a 2010 Volvo 730, the low roof model versus the high roof 780. However, the former trucking company owner I have a 2010 Volvo 730, the low roof model versus the high roof 780. However, the former trucking company had installed a full roof fairing that continues the I have a 2010 Volvo 730, the low roof model versus the high roof 780. However, the former trucking company had installed a full roof fairing that continues the installed a full height roof fairing that continues the roof line to the height of a commercial trailer. It is not bad looking so keeping it on or removing it depends on if it is actually helping fuel mileage.

 

The fairing is located 10' ahead of the trailer. At that distance the fairing keeps the bugs off the 5ver's nose, but is it costing me fuel or helping make the rig more aerodynamic? Any thoughts about the fate of the fairing?

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I would keep the fairing. 10' seems kind of far to be effective, but if it's keeping the bugs off the nose of your rig then it is, most likely, not having any vortice issues that might contribute to lower MPG.. rather the opposite.. so if you don't mind the look It would be a keeper for me.

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For a fairing to be effective it needs to be as close to the front of the trailer as possible. If not, it will vortex, (the air) behind the fairing and actually cause more wind drag. Yes 10 feet is a lot of distance. Your air will still travel over the top of your RV, and still keep bugs off your nose without the fairing. The other thing to know, if you ever have to be towed, DO NOT let them pull your truck backwards. You will loose that fairing in a heartbeat.

 

Another thing, you can load most sleepers onto a double drop and sometimes a single drop trailer if you break down and need to transport it back home. and do Not have that fairing on your truck. 14 feet is the legal height out west, 13 foot 6 inches back east. Your trucks with fairings are 13 to 13 foot 6 inches overall height. You guys need to know the cost difference from a tow truck, to loading on a regular semi drop deck or double drop trailer. That is a whole other topic.

 

Bill

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The back of your trailer is the most sensitive aerodynamically. It pull a huge volume of air into the vacuum behind it. With the fairing you create a second vacuum. The rounded front on the trailer is much more efficient at cutting through the air. As Big trailer pointed out, you need continuity for the fairing to be effective, hence the appearance of side fairings in addition to roof fairings. BTW, the worst item inch for inch for drag are mirrors, but I certainly wouldn't eliminate them for mileage.

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The question you need to as yourself? Does the taller faring keep the back of the RV clean? If it keeps it cleaner its worth keeping. But if its always dirty then its not helping you. As posted being your trailer is 10ft back from the flaring. Your not getting the effect from it you would if it were closer to together. Years ago we had half bubbles on the nose of the vans. Those helped but it was hard to prove how much.

Then we started seeing the wings on the flat tops. Lost of people laughed at those, but they were good for 1/2 to 1 MPG. When you take a truck that ran 100,000+ every year. 1/2 Mile per gallons adds up to more then lots of people made driving back in those days.Then when we went to full flamings, with the trailer tucked as close as you can run it and still turn. MPG went up 1/2 to 3 MPG on some of the newer setups back then.

 

If and when we go with a HDT, I'm thinking about leaving it without a bed, move the RV as close to the truck as we can get it. As our plans are now to run it that way 3 years or so. Then if we see the need for a smart car. Will extend the frame back out to allow for the smart car. But thinking we would stick with the tractor as our transportation. After driving for years, and always having to bobtail where every I went. It would not be a big deal for us to use the tractor. Of if were seeing sites where its not going to work. Rent a cheap car for a few days to see the sites..

Pete

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If and when we go with a HDT, I'm thinking about leaving it without a bed, move the RV as close to the truck as we can get it.

 

It's really not possible to move an RV much further forward that what most of us are doing right now. Because of the need to place an RV hitch -- particularly an air-ride hitch -- between the frame rails to achieve a "normal" hitch height, it must be installed behind the rearmost "between the frame rails" obstruction, whether that's a crossmember, a torque rod, or a shock mount. Even if that could be overcome, your forward travel would then be limited by interference with the basement of the RV, a feature not present on most commercial trailers.

 

The most practical way to improve the aerodynamics of a truck-tractor/fifth wheel RV combination would be to install temporary or permanent extensions for the cab sides and roof to fill the gap between the truck and trailer.

 

 

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Phil nailed it. But if you do want to use your tractor as a daily driver it is certainly "do able". I did it as fulltime RVer for 3 years. Then we bought our Jeep which we double towed for 8+ years.

 

IF I was doing a daily driver again I'd probably have a 630, or equivalent in another brand. The very short wheelbase that is achievable if you single that truck is perfect for a daily driver. JMO....but your needs may vary. You can get right around 182" wheelbase on a 630, and around 198" on a 780....perhaps a little less if you drill new holes. But as Phil said, the hitch is the issue. My 610 was 182" with a Trailersaver behind the axle.

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I agree with those that state a mpg savings is nothing to be concerned with. If it is a hobby endeavor (trying to get the most mpg), fine. But to be worried about mpg in any serious fashion, I would say that one should not be buying an HDT. Because it will cost you too much to keep it running....the fuel is a minor concern. IMO.

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In your sig picture with the truck and Lifestyle hooked up, the airflow looks like it would travel over the top of the trailer. If you draw a line extending the lower fairing you would be catching the very top of the trailer at worst. Look at the aerodynamics of the truck, the trailer, and the gap between. The gap between the truck and trailer I'm guessing creates a low-pressure area that allows the high-speed air to flow over the top. Much like a pickup bed with the tailgate up.

I think the 2 biggest issues we face is the frontal area of the truck, and the vacuum created at the back cap on the trailer.

Best way I know to increase mileage is find the truck going your way at 62-64mph and tuck up behind him. Of course if he brakes hard, you get a face lift.

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You said it yourself: the bugs aren't splatting on the trailer. I'd say that's a sign that the aerodynamics are at least improved.

It's not quite as simple as that. The bugs aren't splattering because the air is wrapping into the large gap behind the spoiler and is incredibly turbulent. It stops the direct hits from the bugs, but it's far from efficient aerodynamically. As they say on the train... MIND the GAP

 

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It's really not possible to move an RV much further forward that what most of us are doing right now. Because of the need to place an RV hitch -- particularly an air-ride hitch -- between the frame rails to achieve a "normal" hitch height, it must be installed behind the rearmost "between the frame rails" obstruction, whether that's a crossmember, a torque rod, or a shock mount. Even if that could be overcome, your forward travel would then be limited by interference with the basement of the RV, a feature not present on most commercial trailers.

 

The most practical way to improve the aerodynamics of a truck-tractor/fifth wheel RV combination would be to install temporary or permanent extensions for the cab sides and roof to fill the gap between the truck and trailer.

 

 

Funny how the conversations sometimes fall into place......................

 

We are setting up a new-to-us trailer. It has a Mor-Ryde hitch with some sort of snubbers. It also is offset, forward, about 20-24". Preliminary measurements indicate that we may be able to "flip" said hitch so that the pin is 40-48" rearward from where it is currently, shortening our overall length to 65' 24", and still leave room for the smart on the bed.

 

It seems that most, if not all, of the commercially built 5ers have a significant offset built into the hitch for pick-ups. We really don't need 8' from our rear bumper to the belly of the 5er.

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