Cargo trailer drag estimating

[aerohead]

Here is one of the few examples for a trailer with a reported coefficient of aero. drag.
It's a 1988 Voyager 2000,from C.I.Caravans Ltd.,The Oaks,Fordham Rd.,Newmarket,Suffolk CB8 7AL,England. (Re. Popular Science Magazine,July,1988,pg 92.
They're claiming Cd 0.23.No mention of whether that's by itself,or behind a tow vehicle.

[aerohead]

Originally Posted by ennored

Something in that series of "buses" doesn't add up.

.88 Cd to .36 by just rounding the front? That doesn't agree with other known Cd's I've seen (NASA and others).

I think the claims of an Airstream being about 30% better than a "normal" trailer are probably close, some from a better Cd, and some from a smaller frontal area. Which is also in the same ballpark as one of the NASA studies where they rounded the front of a boxtruck. 30% better than .88 is .62, way off .36.

Which is all just speculation. No real wind tunnel tests = no real number. Seems like there isn't one out there.

*I don't have Hucho's book with me.I'll go back and check the numbers.
*Hucho's model has a smooth belly,something NASA's Econoline did not until later.
*Hucho's model had no 'features drag',(cut lines,gaps,ridges,laps,wheel-flop area ),and cooling system.
*Hucho's model had a larger fineness ratio that NASA's van.
*Hucho's model had full wheel covers.
*Hucho's model was @ zero-yaw,compared to some crosswind at Edward's AFB secondary runway.
*Hucho's softened,and boat-tailed model is in good agreement with NASA's belly-panned,boat tailed Cd 0.238.

[freebeard]

1988 Voyager 2000

0.23 is a pretty extraordinary claim, considering the total lack of taper in plan.

[aerohead]

Originally Posted by freebeard

1988 Voyager 2000

0.23 is a pretty extraordinary claim, considering the total lack of taper in plan.

Their number is contextual and they're not providing the context.
A drafting,zero-clearance bus has a lower Cd so maybe 0.23 is plausible.
With a stroke of a pen,the DOT could mandate that this sort of data be provided by each manufacturer.

[Hersbird]

Originally Posted by aerohead

Their number is contextual and they're not providing the context.
A drafting,zero-clearance bus has a lower Cd so maybe 0.23 is plausible.
With a stroke of a pen,the DOT could mandate that this sort of data be provided by each manufacturer.

So basically tow that trailer behind a giant bus or truck and the trailer might only add another .21 and even reduce the TV a bit but overall still higher then just the bus with no trailer.

[aerohead]

Originally Posted by Hersbird

So basically tow that trailer behind a giant bus or truck and the trailer might only add another .21 and even reduce the TV a bit but overall still higher then just the bus with no trailer.

*I suspect that the Voyager,when towed,has lower than 0.23.It would depend upon the TV.
*And it would definitely lower the Cd of the TV.
*If the trailer were sized as a box-cavity or streamlined it could conceivably lower the overall drag of the combination,as BamZipPow is experiencing with his 1-wheeler.
*Here are some values for some commercial vehicles.You can see that even 'conventional' trailers have relatively low drag.
*And you can also see the contribution of the full gap-filler.

[aerohead]

Originally Posted by aerohead

Here is one of the few examples for a trailer with a reported coefficient of aero. drag.
It's a 1988 Voyager 2000,from C.I.Caravans Ltd.,The Oaks,Fordham Rd.,Newmarket,Suffolk CB8 7AL,England. (Re. Popular Science Magazine,July,1988,pg 92.
They're claiming Cd 0.23.No mention of whether that's by itself,or behind a tow vehicle.

Here's an interesting comparison for a similar structure.

[freebeard]

Luggage Trailer

This is a fiberglass reproduction of a mid-century Westphalia utility trailer. It's a $1K box that drops onto a $200 Harbor Freight frame. I don't see what's to keep you from putting it on the frame backwards and using an eight-ribbed beach umbrella to fashion a collapsible boattail.

———

I like this a lot. The elastomeric snubbers for my Westy are unobtainium. Which is holding up getting it on the road.

[ennored]

Originally Posted by freebeard

For inspiration you could compare the classic Airstream to the Airstream Basecamp. It is a very utilitarian vehicle reminiscent of the Rumpler Tropfenwagen.

The Airstream basecamp has been mentioned a few times here. Saw this at another site and thought it was worth mentioning here:

Airstream Basecamp for sale

(No connection or knowledge...)

[aerohead]

I posted this for recreational vehicles but it's germane to commercial vehicles.




An addition is the 1973-78 GMC Motorhome,Cd 0.31,designed by John DeLorean