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Wind and fuel economy

I know a quartering or head wind will greatly impact my fuel economy but what about wind from the side?  Except in the desert most places I have experienced side winds have caused me to have to vary the pressure on the steering wheel as I went in and out of a wind shadow.  I'm sure tire scrub would have some impact but does a wind directly (90 degrees) from the side affect wind drag?  I think sail boats can have a true wind indicator, could that work on RVs?
John Cooper
'91 GV 36'
Oshkosh chassis
Cat 3208T 300HP

Re: Wind and fuel economy

Reply #1 –
Yes, side winds degrade fuel economy.  I'm continually surprised by how much it does.
Regards,
Brett

'99 42' Foretravel Xtreme
'14 Brown Motorsports Stacker
'05 Chevy SSR
'02 BMW R1150R

Re: Wind and fuel economy

Reply #2 –
Quote from: John Cooper –
I think sail boats can have a true wind indicator, could that work on RVs?
I have seen this one in action on Barry Levitts coach when we had that huge storm in Quartzsite 2010,
It does show wind speed and Direction
http://www.vantagevue.com/products/product.asp?pnum=06250
The selected media item is not currently available.Barry BEAM #16014
2003 U320 40' AGDS
Beamalarm, Foretravel technical help and specifications
"Whatever the mind can conceive and believe, it can achieve"

Re: Wind and fuel economy

Reply #3 –
I think any wind farther forward than about 30-degrees to each side of directly aft (from the back, in other words) has a headwind component. This is from many years riding bicycles when I had a slogan: everywhere is either upwind or uphill; or both.

Craig
1993 U225 36' Unihome GV with PACBRAKE exhaust retarder, Banks Stinger and Solar Panels.
Toad: 1999 Jeep Wrangler 2-door soft-top.

"No one has ever had to evacuate a city because the solar panels broke."

Re: Wind and fuel economy

Reply #4 –
I was heading into a huge headwind and got 3mpg and it was enough to bend back my mirrors too.
2025 Wanderbox Outpost 32 on F600 Expedition Motorhome
2015 Born Free Royal Splendor on Ford 550 nonslide version  for sale
Former Coaches  covering. 360,000 miles
1999 34 U270
2000 36 U320
2001 42' double slide U320
2018 Jeep Rubicon

Re: Wind and fuel economy

Reply #5 –
Yes, we have both APPARENT WIND and TRUE WIND speed and direction instrument on the sailboat. Push a button to scroll between apparent and true.

But, in the motorhome, I basically watch flags, movement of vegetation, etc to determine wind direction and speed.

BTW, on the way north to Gillette this summer, ran into a 45 mph headwind on a back road in Kansas.  Just dropped down to 5th gear and set the cruise at 45mph.  LOTS less drama and fuel consumption than trying to go faster.

Brett
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Wind and fuel economy

Reply #6 –
Remembering vector geometry, you can understand that the coach going forward at 60 Mph is one vector, and wind coming in at any angle to the side is another vector of so many miles per hour. The combination of the two vectors creates the directional vector comprised of the forward vector and the other sideways vector. Since the coach has to generally go forward and in a straight fashion, it takes additional energy in the form of additional fuel burn to maintain the coach going in a straight direction. This in theory would result in lower combined fuel efficiency.
Peter & Beth Martin
No Forrest? What have you done?
MC# 15890 until Dec 2016; FMCA #F329677
Cincinnati, OH

Re: Wind and fuel economy

Reply #7 –
                   Ahhhhhh the wind .Learned to hate the wind while doing my 25 years of Navy . This farm boy knows about sea sick . Since then and Foretravel , the only wind I like is the one from behind . One time  on I-90 in SD. and a strong tail wind , my dash showed 14 MPG .  Got used to that rather quickly , only to have the wind change and the  whole thing went up in smoke . Seeing as I am retired , I'll simply get in a rest area and wait it out . DW thinks wind means Wally World , so with all the money she saves all is not lost . :D  Brad Metzger
Brad Metzger
2010 Phenix 45'

Re: Wind and fuel economy

Reply #8 –
Brad, talking of the wind from behind, I believe if you put a match to it you will get more propulsion they say!!!
John H
Coachless, now use aircraft. 2003 Ford Travelair TC280 class C. Super shape. Just for 1 yr .
1994 Ford E350 ClassC,total renovation inside and out. Now sold.
2000 U295  36' Cummins 350 c/w Banks Stinger, Resonator upgrade,Solar, LED lites.Residential fridge with slide out pantry. Build 5674. Sold
ex 92 GV 022C ored Cummins. Sold
ex 95 GV240 cat 3116. Sold
2017 Mini cooper s & 2016 land Rover LR2 HSE  LUX.
jhaygarth@aol.com    SKP #130098
treat everyone as you would like to be.

Re: Wind and fuel economy

Reply #9 –
It is hard to say how much power it takes to overcome the rolling resistance (basically weight, tires, tire pressure, road surface, hills, drivetrain and driver etc) and how much power it takes to overcome aerodynamic forces.  Both add up to how much power is required to move from point A to B.  Aerodynamic drag is proportional to the square of the speed and the area presented to the wind.  60 mph with no wind compared to 60 mph with a 10 mph tail wind gives you almost 30% less aerodynamic drag.  60 mph with no wind compared to 50 mph with no wind reduces power required by maybe 10% (fuel mpg goes up about 10%). 

Rolling resistance and all of the other driveline losses may be as high a 60% of the total power required while aerodynamic resistance is about 40% at 55 mph.

This article talks about all of these sorts of things.  It is pretty interesting.

http://www.goodyear.com/truck/pdf/radialretserv/Retread_S9_V.pdf

A 15 mph crosswind while driving at 60 mph adds about 7% to the aerodynamic forces and all of the forces required to keep you in the lane add to the rolling resistance.

Big headwinds?  Slow down.  Big tailwinds?  Be happy.  Big or gusty crosswingds?  Drive with caution or just wait for a while and enjoy the tumblin' tumbleweeds with the Sons of the Pioneers playing in the background.

Roger
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: Wind and fuel economy

Reply #10 –
Quote from: wolfe10 –
BTW, on the way north to Gillette this summer, ran into a 45 mph headwind on a back road in Kansas.  Just dropped down to 5th gear and set the cruise at 45mph.  LOTS less drama and fuel consumption than trying to go faster.

Brett
Our experience has been that wind direction and speed make the biggest difference in fuel economy for the way we drive. If driving conditions allow, we drive at a very consistent pace with respect to the ground. The winds make for a variable pace with respect to the air.

Winds in Wyoming and southern Montana are frequently powerful, and can be dangerous. If you travel I-25/I-90 between Fort Collins, CO, and Billings, MT, check the wind forecasts and plan accordingly. We check Weather Forecast & Reports - Long Range & Local | Wunderground | Weather and look at wind forecasts to plan our routes in the area.

On one trip, we were going into Billings against winds reported to be 50-60 mph. Fortunately they were almost direct head winds rather than side winds. I slowed to 45 mph +- and proceeded in order to get into our campground before dark. I agree that it lowers drama, fuel consumption, and fatigue. I figure that side winds in that range may be a "show stopper" for travel.
J D Stevens
1997 U295 CAI 36' Build #5085
2002 Subaru Outback
Motorcade 16869
Bellville, TX

Re: Wind and fuel economy

Reply #11 –
Shoulda done aircraft carriers. I think I got queasy - once... 40 foot waves.

23.5 years, EMCM(SW) ret...
The selected media item is not currently available. Dave Head & Megan Westbrook
Titusville, FL - The Great Outdoors
'98 270 buying this month
Toad is a 2018 F150 XLT

Re: Wind and fuel economy

Reply #12 –
A close friend of mine showed me a photo of an aircraft carrier he served on in WWII after a large wave hit it. The front of the flight deck folded down into the shape of two big triangles, one port, the other starboard.

They brought it back to the SF Bay Area and it was repaired and back at sea in 30 days! Those were the days of giants...so many of them teenagers...

best, paul
1999 U320 40' 1200 watts on roof. 12cf AC/DC Cold plate fridge/freezer. VMS 240 CL Honda Element

Re: Wind and fuel economy

Reply #13 –
In my old SOB P30 chassis rig I encountered driver side winds going up hwy 1 that had me correcting with the wheel to the point where without the wind i would have been steering as if I was going around a typical cloverleaf insteaf of a straight line. i figure we had at least a 25 degree scrub angle on the steer tires. Sort of an extreme example but yeah, side winds will ding MPG pretty well, not to mention a bit of extra wear on the front tires!
Jay
1989 U280 SE, 36', 3208T Cat, build 3292