Round vs Squarish Eggs - Page 3 - Fiberglass RV


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Old 05-10-2011, 10:56 AM   #29
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I believe that it is not the weight that kills fuel economy so much as the extra drag caused by aerodynamics. For example, I am sure you could load 3,000 lbs of cement bags in the bed of a pickup truck and it would have little effect on fuel economy because it would all be down in the bed of the pickup and not catching any wind. But, if instead of cement, you hook onto a 3,000 lb trailer you will see a definite reduction in fuel economy because of the extra drag created by wind and additional wheels and tires.
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Old 05-10-2011, 11:28 AM   #30
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Here is another extreme example: In 2007 I bought a new Ford F-350 with a gas V8. I had it about three days when my brother called. He had bought a corvette over the internet in Eastern Kentucky. He had a large enclosed trailer and was going to go get it. He ask if I would go and help drive. I told him I had a new truck that I needed to break in and if he would buy the gas we could take my truck. We hooked onto the trailer pictured and pulled it 1000 miles in 24 hours. That trailer was NOT aerodynamic. That huge flat front caught wind like a sail. The truck had a six speed manual transmission. We never got into overdrive. The average speed was about sixty mph. On a level road with no wind that was about all it would do. It got 8 mpg on that trip.
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Old 05-10-2011, 11:36 AM   #31
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So the general agreement seems to be shape matters more than weight. So a 3000lb Egg shaped Trailer would do better on gas than a 3000lb Trillium/Escape etc even though they are both fiberglass.
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Old 05-10-2011, 12:35 PM   #32
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Hi, Norm

My TV is a '97 Kia Sportage 4cyl 4x4.
I get your point about your 25% heavier Casita- I'm just wondering if that's what Tony means, too!


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Old 05-11-2011, 12:25 AM   #33
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Hi: Bruce H... What A Drag!!! Aerodynamics is why I like our Escape 5.0!!! Here's a pic of our former TV& Trailer on the road... and the new tug is only 2" shorter in height.
Alf S. North shore of Lake Erie
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Old 05-11-2011, 07:56 AM   #34
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Originally Posted by Francesca Knowles View Post
Hi, Norm

My TV is a '97 Kia Sportage 4cyl 4x4.
I get your point about your 25% heavier Casita- I'm just wondering if that's what Tony means, too!


Francesca
Francesca,

What does a Trillium 4500 weigh and what kind of mileage do you get towing and not towing?

Thank you,

Norm
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Old 05-11-2011, 04:59 PM   #35
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I asked a friend who is an engineer and he says the same thing. Shape matters more than weight since weight is has the greatest effect during acceleration/climbing. So due to inertia it has periods of more or less impact on energy cost.

However, wind drag always has some impact. He says that cars have a non-aerodynamic design. Optimum shape is like a teardrop -- round front and tapered rear. I told him about the Lil Snoozy's and he said that was the exact reverse of an aerodynamic shape.
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Old 05-11-2011, 05:30 PM   #36
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Originally Posted by Tony Nowak View Post
We get about 3 less MPG with the Bigfoot versus the Scamp, of course the BF is 130% heavier, but as Dave comments the frontal area is a killer.
We lockout overdrive on the Ford 150 (4 speed auto) when using the BF.
Tony
I'm still trying to understand Tony's results above.
He says that the Bigfoot is "130% heavier".
I don't know the Scamp's weight, but for ease of calculations, let's pretend it weighs 2,000 lbs.
"130% heavier" means that the Bigfoot weighs 4600 lbs m/l.
Is it the findings of the group that the extra 2600 lbs is a measurably less important factor than trailer shape when it comes to gas mileage???

Francesca
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Old 05-11-2011, 06:05 PM   #37
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Generally speaking, I think that's a valid assumption. Another example: my gas mileage towing my cargo trailer does not vary significantly between unloaded and loaded (with about 1800 lbs). The mileage change between 65 mph and 55 mph is about 2 mpg, however. Wind resistance is the key.
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Old 05-11-2011, 06:47 PM   #38
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Hi, Mike,

That IS very interesting...
I've always thought my mileage worse when I'm traveling all loaded up with passengers, extra tanks, etc. than when I'm out on my own.
I'm going to have to pay closer attention this year!
In your opinion, are the rounded edges more important than overall width, height, etc.?
And how "round" should they be to realize measurable gains?

Thanks

Francesca
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Old 05-11-2011, 06:56 PM   #39
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Quote:
Originally Posted by Francesca Knowles View Post
I'm still trying to understand Tony's results above.
He says that the Bigfoot is "130% heavier".
I don't know the Scamp's weight, but for ease of calculations, let's pretend it weighs 2,000 lbs.
"130% heavier" means that the Bigfoot weighs 4600 lbs m/l.
Is it the findings of the group that the extra 2600 lbs is a measurably less important factor than trailer shape when it comes to gas mileage???

Francesca
Running on a flat highway that extra 2600 lbs will not matter much.
IN hilly terrain or stop and go traffic that extra will eat gas and brakes - engine breaking may often be not enough.

At highway speeds, trailer / TV shape / wind resistance will play significant role in gas mileage.
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Old 05-11-2011, 07:57 PM   #40
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Is cutting wind resistance the purpose of the V-nose design I see on some cargo trailers?
That would be an interesting modification to contemplate for my Trillium...

Francesca
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Old 05-11-2011, 08:06 PM   #41
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Originally Posted by Francesca Knowles View Post
Is cutting wind resistance the purpose of the V-nose design I see on some cargo trailers?
That would be an interesting modification to contemplate for my Trillium...

Francesca
Ken would have to substantiate this, but I believe that's the reason he put the beak on his extended BigFoot: Stretching my 1988 17 ft Bigfoot and if not, he got that added benefit anyway.
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Old 05-11-2011, 08:22 PM   #42
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Originally Posted by Francesca Knowles View Post
Is cutting wind resistance the purpose of the V-nose design I see on some cargo trailers?
That would be an interesting modification to contemplate for my Trillium...

Francesca
Kinda sorta. Also some V nose cargo trailers have a downward slope in the V nose, they say that helps a lot.
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