Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - Still trying to learn stuff.........box cavity?

slowmover · 08-04-2019, 08:37 PM

A fully-boxed tail on a 53’ van is worth having. It’s right at four-feet deep.

But with this caveat: increasing the length of the sail ALSO increases the leverage of wind against the vehicle. This is a serious concern. The crosswind has a longer lever to use.

So much so in this case I know drivers who otherwise run them WON’T when empty or nearly so (I can load 45k in the box. Today’s load is 7k. That’s “empty”).

Moving the trailer tandem axles rearwards can offset this effect (wind forces increase drastically every foot rearwards as they can’t escape the squared roof edge), but there’s a legal limit to how far back. AND it makes the trailer more difficult to get through every turn or curve with the increase in distance from the Drive Axles (Ackerman angle).

Were I the trailer owner I would have both skirt & tails (plus the nose cone arrangements we’ve seen to collapse the tractor/trailer distance from one another). The MPG benefit is obvious, and given a regular loading (25k plus) it makes handling the truck EASIER throughout the day. Wind problems are reduced, overall. But it’s also a new caution on a windy mountain pass. In a rainstorm squall line. Etc.

The pickup half tonneau looks nice. But the Aerolid is where to start. Even a simple one (as on a Dodge Cummins owners truck in aluminum sheet) provides an idea of benefits.

For a city box truck, or for a pickup, access to the box/bed has to be weighed against complexity in a tail. The forces at work back there are high. To replicate the industry TRAILER TAIL is no small matter given a cab-height bed topper.

Which is why you now see Coanda devices being used on the trailing edge of vans. Less problem and MOST of the benefit.

Tails are so 2014. (Ha!)

Obama-Age Obsolescence.

Now, for my pickup it’d be front airdam and side skirts. The rear cavity “ought” to be something I can dismount. A hitch-mount carrier with an extension (roof & sidewalls) that extends upwards from a transport case to meet my LEER bed topper roofline.

How to treat the exit UNDER that (under truck body) is where a big question mark exists (for me).

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08-04-2019, 08:37 PM	#22 (permalink)
slowmover Banned Join Date: Oct 2009 Location: Fort Worth, Texas Posts: 2,442 2004 CTD - '04 DODGE RAM 2500 SLT Team Cummins 90 day: 19.36 mpg (US) Thanks: 1,422 Thanked 737 Times in 557 Posts	A fully-boxed tail on a 53’ van is worth having. It’s right at four-feet deep. But with this caveat: increasing the length of the sail ALSO increases the leverage of wind against the vehicle. This is a serious concern. The crosswind has a longer lever to use. So much so in this case I know drivers who otherwise run them WON’T when empty or nearly so (I can load 45k in the box. Today’s load is 7k. That’s “empty”). Moving the trailer tandem axles rearwards can offset this effect (wind forces increase drastically every foot rearwards as they can’t escape the squared roof edge), but there’s a legal limit to how far back. AND it makes the trailer more difficult to get through every turn or curve with the increase in distance from the Drive Axles (Ackerman angle). Were I the trailer owner I would have both skirt & tails (plus the nose cone arrangements we’ve seen to collapse the tractor/trailer distance from one another). The MPG benefit is obvious, and given a regular loading (25k plus) it makes handling the truck EASIER throughout the day. Wind problems are reduced, overall. But it’s also a new caution on a windy mountain pass. In a rainstorm squall line. Etc. The pickup half tonneau looks nice. But the Aerolid is where to start. Even a simple one (as on a Dodge Cummins owners truck in aluminum sheet) provides an idea of benefits. For a city box truck, or for a pickup, access to the box/bed has to be weighed against complexity in a tail. The forces at work back there are high. To replicate the industry TRAILER TAIL is no small matter given a cab-height bed topper. Which is why you now see Coanda devices being used on the trailing edge of vans. Less problem and MOST of the benefit. Tails are so 2014. (Ha!) Obama-Age Obsolescence. Now, for my pickup it’d be front airdam and side skirts. The rear cavity “ought” to be something I can dismount. A hitch-mount carrier with an extension (roof & sidewalls) that extends upwards from a transport case to meet my LEER bed topper roofline. How to treat the exit UNDER that (under truck body) is where a big question mark exists (for me). .