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06-10-2013, 04:53 PM
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#41
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Rivet Master
2007 30' Classic
Oswego
, Illinois
Join Date: Jul 2010
Posts: 13,656
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Quote:
Originally Posted by 62overlander
if I were worried about mpg I would not tow anything and drive a hybrid.
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Oh, I agree, but some here want every 1/10 of an MPG they can squeak out. For those folks, a full tank carries and energy penalty.
__________________
-Rich-
"If the women don't find you handsome, they should at least find you handy." - Red Green
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06-10-2013, 05:09 PM
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#42
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4 Rivet Member
2005 30' Safari
Houston Texas
, Texas
Join Date: Aug 2006
Posts: 480
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I can tell you from 82k miles of towing my 30' safari with a 8.1 liter suburban with a full water tank vs empty makes no difference in mileage!
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06-10-2013, 05:10 PM
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#43
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Rivet Master
2007 30' Classic
Oswego
, Illinois
Join Date: Jul 2010
Posts: 13,656
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Free mass hauling! I'd bet the trucking industry would love to discover this!
__________________
-Rich-
"If the women don't find you handsome, they should at least find you handy." - Red Green
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06-10-2013, 05:16 PM
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#44
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Rivet Master
1995 30' Excella
Bowie
, Maryland
Join Date: Apr 2005
Posts: 2,345
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I agree mathematically there's going to be a slight reduction in mileage - more weight means more fuel; the physics are that simple. But practically it's probably not going to make a major difference; it'll be "lost in the noise" as statisticians say - during any given trip, dozens of things will affect your mileage, too, so it's hard to tease out a small increase or decrease attributable to any one factor.
__________________
1995 Airstream Classic 30' Excella 1000
2014 Ram 2500 Crew Cab with Cummins 6.7L Diesel
Sold but not forgotten: 1991 Airstream B190
Sold: 2006 F-250 6.0L Powerstroke Supercab
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06-10-2013, 05:26 PM
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#45
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Rivet Master
2007 30' Classic
Oswego
, Illinois
Join Date: Jul 2010
Posts: 13,656
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That is true, Skater, and more "lost in the noise" with larger displacement TVs, which are already wasting more energy than a small displacement engine simply by it's design. They are designed to be more energy efficient under load(strictly speaking from a physics efficiency standpoint, not to be confused with our colloquial use of the word).
Now if you add 60 gallons of water to an already stressed TV (some would say overstressed) like a minivan pulling a 30'er, you would see, on a percentage basis, a larger mileage penalty.
Likewise a diesel, or the 454 referenced above would realize a lesser penalty on a percentage basis.
__________________
-Rich-
"If the women don't find you handsome, they should at least find you handy." - Red Green
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06-10-2013, 06:43 PM
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#46
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Moderator
2004 30' Classic Slideout
Fenton
, Missouri
Join Date: Mar 2002
Posts: 10,403
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Typically we carry some water, enough to flush the toilet and wash the hands when in route to a destination. My fresh water tank is 60 gallons and quite honestly with food, clothing, and a slide out, that 9100 lb gross doesn't leave much room. We do one trip a year where we don't want to use the campground water. That trip is pretty much a flat land trip. So we depart with a full tank. Would I want to drag a full tank when I head out to Branson? No way. I have to gear down to get up some of those hills at a reasonable speed. I'd hate to think what carrying another 500 lbs of liquid would do.
But as far as the trailer goes, it was built to run with full water tank, so don't be fearful of that. Just make sure you understand that the water weight is one component to consider regarding your trailer's gross weight capacity.
Jack
__________________
Jack Canavera
STL Mo.
AIR #56 S/OS#15
'04 Classic 30' S.O.,'03 GMC Savana 2500
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06-10-2013, 07:06 PM
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#47
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Rivet Master
1976 31' Sovereign
Oswego
, Illinois
Join Date: Jan 2007
Posts: 2,017
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When I pur. 2000 chev. 6.0 liter gas I got 18 mpg now with 53,00 miles avg. 10 mpg engine is in top tune. I have always towed 70 to 80 mph. This a big Q. Why? G.M cannot answer. Also towing back hoe or other Impl. same story. May be Rich [dznf0g] can answer. also never since 1962 towed w/tanks empty & never dump when leaving camp grounds until get home, fertz. corn & beans [same wgt. out same wgt. back]
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06-10-2013, 07:10 PM
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#48
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Rivet Master
2007 30' Classic
Oswego
, Illinois
Join Date: Jul 2010
Posts: 13,656
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I'll PM you.
__________________
-Rich-
"If the women don't find you handsome, they should at least find you handy." - Red Green
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06-10-2013, 07:16 PM
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#49
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Rivet Master
1976 31' Sovereign
Oswego
, Illinois
Join Date: Jan 2007
Posts: 2,017
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Quote:
Originally Posted by dznf0g
I'll PM you.
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It won't let me open the pm call me 630 554 9409
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06-10-2013, 07:21 PM
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#50
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Rivet Master
2007 30' Classic
Oswego
, Illinois
Join Date: Jul 2010
Posts: 13,656
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emailed you....don't want to hijack the water thread.
__________________
-Rich-
"If the women don't find you handsome, they should at least find you handy." - Red Green
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06-10-2013, 07:47 PM
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#51
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3 Rivet Member
2005 30' Safari
Kanata
, Ontario
Join Date: Sep 2012
Posts: 210
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Once you reach highway speed, the output of the engine must balance the rolling resistance and the wind resistance of the rig. Rolling resistance will change with added weight, but wind resistance will not. I believe wind resistance to be the dominate of the two factors at highway speeds.
This is why speed is such an important factor in your mileage, as there is a non-linear relationship between the two. Doubling the speed of your airstream requires 8 times the power.
So I would think a change in mileage due to extra weight would be more apparent while city driving (lots of acceleration) versus steady state highway driving. Shedding weight in a vehicle is important - but not so much on long hauls.
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06-10-2013, 07:54 PM
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#52
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Rivet Master
2007 30' Classic
Oswego
, Illinois
Join Date: Jul 2010
Posts: 13,656
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Quote:
Originally Posted by MaxTow
Once you reach highway speed, the output of the engine must balance the rolling resistance and the wind resistance of the rig. Rolling resistance will change with added weight, but wind resistance will not. I believe wind resistance to be the dominate of the two factors at highway speeds.
This is why speed is such an important factor in your mileage, as there is a non-linear relationship between the two. Doubling the speed of your airstream requires 8 times the power.
So I would think a change in mileage due to extra weight would have more impact in city driving (lots of acceleration) versus steady state highway driving. Shedding weight in a vehicle is important - but not so much on long hauls.
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Yes, all true. In addition, elevation changes will impact MPG in direct relation to weight. It does take some additional energy to keep the mass rolling, but not nearly as much as acceleration and hill climbing (not necessarily mountains either). All of this discussion should be made in terms of long term mileage figures. Any particular day of even long hauling on flat territory could be different than the next day, due to the other factors at play, like wind, given the same weight.
__________________
-Rich-
"If the women don't find you handsome, they should at least find you handy." - Red Green
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06-10-2013, 08:27 PM
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#53
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Rivet Master
1974 Argosy 26
Morrill
, Nebraska
Join Date: Nov 2009
Posts: 6,014
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What!!! No mention of a "Body in Motion tends to stay in motion and one at rest tends to stay at rest."
I say! "If you can't afford a few tenths of a gallon. Then maybe you should stay home"
Based on all of this physics stuff. It would be better to travel in 100+ degree temps. Because the air is thinner and there is less wind resistance. Than at night or in cold places where it is thicker. But engines get less efficient in the high temps. So there you go! You should probably just stay home.
If you travel the same route going and coming. The up hill battle should be offset on the return trip by being able to use the "body in motion".
I find it amazing that anyone thinks like this when on vacation.
A person could drive their self nuts with stuff like this.
How much is the bug shield costing me on MPG? What about the radio antenna?
How much is the satellite receiver costing me in wind resistance?
What about the A/C? The vent covers?
How 'bout the awning arms?
Or the fact that the back of the TV and coach are pretty much flat? When maybe a boat tail would get me a couple of tenths.
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06-10-2013, 08:33 PM
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#54
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Rivet Master
2007 30' Classic
Oswego
, Illinois
Join Date: Jul 2010
Posts: 13,656
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I only think about it while on the forum...not on vacation. By the way, I presume you read it all???????? How sick is that?
__________________
-Rich-
"If the women don't find you handsome, they should at least find you handy." - Red Green
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06-10-2013, 08:44 PM
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#55
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retired USA/USAF
2001 30' Excella
Somerset
, New Jersey
Join Date: Jan 2009
Posts: 2,418
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Yes, the math IS the math. If you calculate using a calculator to many decimal places you may think that the water weight is impacting your mileage. If you do the math using a slide rule much less so. When traveling the water is optional until you need it. I always travel with at least 1/2 tank. Sometimes a full one. You never know when you'll need it.
__________________
Roger in NJ
" Democracy is the worst form of government. Except for all the rest"
Winston Churchill 1948
TAC - NJ 18
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06-10-2013, 08:48 PM
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#56
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Rivet Master
2007 30' Classic
Oswego
, Illinois
Join Date: Jul 2010
Posts: 13,656
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I hear ya Roger, And I load everything I want, including water. I just HATE overarching opinions like "traveling with a full tank of water has no impact on fuel economy". It is opinion expressed as fact that a newbie will adopt as fact. Truth is: ALL weight impacts fuel economy....every pound equally, water or steel or rubber............
__________________
-Rich-
"If the women don't find you handsome, they should at least find you handy." - Red Green
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06-10-2013, 11:26 PM
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#57
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4 Rivet Member
1997 25' Safari
Yakima
, Washington
Join Date: Jun 2011
Posts: 424
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I always tow with a full fresh water tank. And what Andy said, center of gravity, emergency water supply, etc.; and others with the hope of the next great boondocking location just around the next bend. These AS were designed to carry water. My only other advice, put the retaining straps and mounting hardware on your maintenance/inspection list.
__________________
Dennis
1997 25' Safari
2012 Chevy Silverado HD 2500
Duramax/Allison
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06-11-2013, 04:38 AM
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#58
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4 Rivet Member
2005 28' Safari
saline
, Michigan
Join Date: Aug 2010
Posts: 410
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I think it might be interesting if the effects of weight, wind, speed , etc., on fuel economy could be shown on a graph. I believe it would show how little the impact of 240# has on mileage towing an Airstream. Because of all the variables, I don't think one can notice any difference from a trip with full tank or empty. To show how big the difference is with wind resistance is easy. I get better mileage, by 1 to 2 mpg with my 28' Safari weighing about 6,500# loaded, than with my previous square box ultra light 18 ' TT weighing about 2800 #.
That was a shocking surprise to me but has proven to be the case after many thousands of miles going to the same destinations with both trailers. I have always been a fuss budget about weight but still opt to keep water tank full for all the reasons many have cited.
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06-11-2013, 05:26 AM
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#59
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Rivet Master
2007 30' Classic
Oswego
, Illinois
Join Date: Jul 2010
Posts: 13,656
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Yes, Kosm1o, with your Silverado and 6500#s, you are probably right....the 240#s has some effect, but small. You are operating within the design parameters of your TV. Both powertrain-wise and structurally.
How about the guy pulling his 30'er with a Sienna? 240# extra is a different story.
Overarching statements are what I have a problem with.
__________________
-Rich-
"If the women don't find you handsome, they should at least find you handy." - Red Green
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06-11-2013, 06:00 AM
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#60
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3 Rivet Member
2013 20' Flying Cloud
Cream Ridge
, New Jersey
Join Date: Mar 2013
Posts: 124
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Over the years I have towed smaller white box trailers with two different GM S-10 pickups. Both were V-6. Any difference in weight really showed up both in overall feel of the road and in mileage. For the last nine years I have towed with a GMC 2500 HD pick-up. My previous white box trailer had a GVW of 3800# and as most of our camping was without hookups I have always carried a full fresh water tank. The difference between towing that and my 20' 2013 Flying Cloud with a GVW of 5000 # is dramatic. The heavier A$ tows so much easier than the old white box I think nothing of going down the road with a full water tank.
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