Motorhome Aerodynamics

[dbircky]

Drafting, aka tailgating.

It works if you stay close enough:

https://www.autoblog.com/2007/10/28/...-improve-mile/

I’d rather spend a few more dollars on fuel and have a better braking distance as the crumple zone in the MH includes me. But that’s just my opinion, and some silly laws that say something about maintaining assured clear distance ahead. Which, incidentally, is the most common citation given in crashes to the at fault party.

[F4Gary]

Originally Posted by wimpy

This will directly relate to any vehicle of any size. I purchased a 62 Lincoln (5K pounds gvw) convertible online & had to drive it cross country from Seattle to Charlotte, NC as I couldn't find a reputable hauler. The fuel mileage ranged from 11.29 to 14.93 mpg.

What accounted for the 3.6 mpg increase? Drafting/slip-stream. I drafted (~180 miles on I-80)a Ram 350 dually with a camper cover as well as a couple of semis across Wyoming @ 80+ tucked close, about 1.5 car-lengths back.

If you have a instanteous trip computer for gas mileage, you can use that to determine ideal proximity for maximum fuel mileage. I was able to use the accelerator pedal to determine the sweet spot. Obviously, you want to be very aware of traffic in front, peeking out to judge closing rate, etc.

Doing a lot of interstate driving in my limo business & discovering drafting was worth 2-5 mpg dependent upon vehicle, I've practiced this for fuel savings for 20+ years. Your savings may vary.

This reminded me of the Jane Mansfield crash...

[Roadwarrior7]

Interesting. 30 years ago I drove my 71 Lincoln Mark 3 from Chicago to Olympia. When I picked it up it had a stuck intake valve and was popping through the carb. It ran poorly at low RPM but at 70 it wasn't too bad so that's where I kept it. I was surprised to get almost 17 MPG on the trip.
BTW, I also drove the whole way without power steering due to a bad windshield wiper unit. Figure that one out.

[wimpy]

Originally Posted by Roadwarrior7

BTW, I also drove the whole way without power steering due to a bad windshield wiper unit. Figure that one out.

71 didn't have vacuum wipers. Did have hydroboost brake system which was interconnected to the PS unit. Beats me!

[wimpy]

Originally Posted by TexasJeff

Just curious.. I read some time ago that drafting removes mileage from the truck in front of you. Is this an old-wive's tale? Or is there some truth to this?

Based on SCCA road racing for 5 years & talking to folks in NASCAR, definitely a wive's tale. Both cars can reduce RPMs & maintain speed.

One potential effect in NASCAR: Dependent upon spoiler & aero package, lead car becomes less stable. If you're below 130 mph, it won't be a problem.

[wimpy]

Originally Posted by F4Gary

This reminded me of the Jane Mansfield crash...

Non-interstate, poor visibility.

Not clear how drafting on an interstate & checking periodically for forward traffic, to avoid any potentially hazardous situation, equates to the Mansfield crash. I'm accustomed to seeing 4 or more trucks nose to tail on the interstate.

The Mansfield crash gave us ICC bars.

[Hpozzuoli]

Most diesel pushers have the aerodynamics of a brick.

[F4Gary]

Originally Posted by wimpy

Non-interstate, poor visibility.

Not clear how drafting on an interstate & checking periodically for forward traffic, to avoid any potentially hazardous situation, equates to the Mansfield crash. I'm accustomed to seeing 4 or more trucks nose to tail on the interstate.

The Mansfield crash gave us ICC bars.

And getting close enough to the rear of the semi to take advantage of his wake is tailgating. That's against the law.

[Daveinet]

Originally Posted by F4Gary

And getting close enough to the rear of the semi to take advantage of his wake is tailgating. That's against the law.

No you side draft. Who cares about all the angry drivers behind you

[Ray,IN]

Originally Posted by rickemo

Sitting here drinking my morning coffee and thinking back over our 1800 mile journey from Pennsylvania to South Padre Island Texas. We averaged 6.5 mpg in our 2020 FR3 30DS towing our Jeep Wrangler.
As a retired engineer I notice things such as architecture and the method other vehicles on the road are designed. The automobile industry including, the trucks that pull the 53 foot trailers, have made great strides in designing aerodynamic features into their product. Many 5th wheel trailers and Class C motorhomes are designed with aerodynamics in mind.
What about the Class A motorhome? There seems to be no effort by the RV industry to apply aerodynamics to these RVs. The majority are square flat front with little consideration to aerodynamics. In our age of computer simulation it seems to me the industry could put more effort into engineering the front of the Class A motorhome. Maybe an increase in fuel economy due to better aerodynamics would increase motorhome sales.
So now my coffee and thinking are done for today You all be safe and have a great day.

Using the words motor-home and aerodynamics in the same sentence is a contradiction in terms.

[Rob_M]

Originally Posted by Roadwarrior7

.

BTW, I also drove the whole way without power steering due to a bad windshield wiper unit. Figure that one out.

Hydraulic windshield wipers. My 67 T-bird had them. Loved that car.

[sregord]

Originally Posted by Ray,IN

Using the words motor-home and aerodynamics in the same sentence is a contradiction in terms.

Really?
If you can make something as pudgy as a C130 fly you can make a Class A aerodynamic

[Max Headroom]

My 97 Exec has a somewhat slanted nose profile. Doesn't waste much space since the 'nose' has a bunch of the mechanical and systems stuff in it.
The newer coaches are much flatter and taller. When I'm sitting at a stoplight next to a newer DP, the driver and I seem to be at the same height, but the newer coaches are taller. Not sure why. IMO all that extra 6"-10" of coach would do for me is make me cringe more going under gas station canopies and underpasses.
Does the pointy nose make the coach more aerodynamic? Maybe a smidge. I had a Grumman PD commercial van that was flat as can be. A brick. Out here in the west, driving into a stiff headwind is SOP. While anecdotal, I feel like the Monaco cuts the headwind a tad better then the Grumman did on same roads, same conditions. That said, is it enough to make a difference? In the long run, I doubt it. On those days when it's headwind all day, it might be good for a small increase. All the non-aero brick-a-brack on the roof, plus the awnings, etc., probably cost more MPG than the pointy nose adds.

[dbircky]

“If you can make something as pudgy as a C130 fly you can make a Class A aerodynamic”

I think the C130 burns around 740 gallons per hour. (AF guys?) At a cruising speed of 340 mph that’s less than .5 mpg.