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Old 06-12-2014, 08:42 AM   #1 (permalink)
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Question Aerodynamic work trailer.

When we sold the Saturn vue that left us in a bit of a pickle for carrying things.
As the new car would be my wife's she had most of the day in it. I wanted a wagon, but I was informed that is what old people drive.
Interestingly enough, the Jetta can fit 3 adults and a 6' ladder.
The problem is we sometimes need 2 8'ladders and a 6'
This car is NOT getting a roof rack, period.
The other option is to drive the truck (<20mpg)
This will also replace our camping wood/dirty/wet stuff trailer.(currently a 4x6 box)

So I've spent some time designing a tapered trailer for work.
It needs to be 100" long for the ladders and 32" tall in the front and 62" wide.
Here is the big question, I expect to use plan taper.

What benefit/loss will there be if I make the top/lid flat vs tapered?


Losses:

True kamm back air flow

Benefits:

Flat surface to work on.

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Old 06-12-2014, 10:29 AM   #2 (permalink)
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How much flat surface do you need? If it only needs to be flat but being level to the ground isn't an issue, then you can simply have it running at a constant angle from bow to stern, no problem.

If you want something close to level to the ground but also don't need a very large work surface, then you could achieve your goal with a somewhat faster angle near the bow, but it flattens as you approach the rear until the final 2-3 feet are more or less level.

Tapering the sides in toward the rear is a no-brainer in my book. And the closer the bow is to the tow vehicle, the better. Aerohead has posted a lot of good info on aeromodding trailers for maximum slipperiness.

Finally, if this is an option, why not build in either a removable work surface or bench, or include a large pullout that will both make unloading the trailer easier and also be already level (more or less) to the ground? That can be pricey and adds to the curb weight of the trailer, but I think you would get a lot of it back in convenience and the freedom to optimize your trailer's aerodynamics would more than compensate for the weight and encumbrance.
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Old 06-12-2014, 02:13 PM   #3 (permalink)
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Yeah, I didn't want the work of a teardrop so I was planning on a straight sloping parallelogram.
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Old 06-12-2014, 03:16 PM   #4 (permalink)
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I know this doesnt meet your requirements
but I saw it on the local CL recently

thought it would look good behind my silver Prius for camping

2007 Thule Utility Trailer

Quote:
Originally Posted by CraigsList add


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Old 06-12-2014, 04:03 PM   #5 (permalink)
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The top can be parallel to the ground, that way you won't loose interior space. Notice these flat-top fenders; if they were doubled with a piano hinge on the outer edge, they could fold out into work-benches.

Why the 32x62" dimensions? Will you taper all the way to a point or truncate to a flat back? Ignore that this is a tear-drop. The edges [to scale] are 4', 3' and 5' with a 2' wide rear, based on a 4x12' plywood sheet.



The axles are pushed back to keep them within max width. The next iteration [were there one] would have the edges 4', 4' and 4' with the axle[s] in the middle section in wheelwells cut into a 5' wide floor.

Here's the frame and floor laid out over a teardrop template:



What do you propose for materials? Plymetal Swingdoor panels are plywood skinned with aluminum

Quote:
The Nudo Ply-‐Metal Trailer Door Blank consists of a 3⁄4” 7-‐ply, Exterior Grade Plywood core with either aluminum on both sides or an aluminum exterior face and a galvanized steel inner face.
The door blank is primarily used as a replacement panel cut‐to‐size by a repair facility to fit all standard semi-‐ trailer rear openings.

The exterior aluminum skin is generally pre-‐painted white while the interior aluminum or steel skins are usually a mill finish.

The most common sizes are 49”x110-‐1/2” or 49” x 121”.
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Old 06-12-2014, 05:51 PM   #6 (permalink)
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trailer top

here's a link to an image of the 1917 Zeppelin-Staaken R VI 'giant-bomber'.
It's roof has a bit more side radii which you'd like in crosswind
http://www.internetmodeler.com/2006/...Staaken-01.jpg
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Old 06-12-2014, 05:56 PM   #7 (permalink)
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Couple of answers :

A ladder stood on edge is 29" so 32" seems about right.
A sheet of ply wood is 48", the taper cuts a 14" piece off, that turned around makes 62" W.
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Old 06-12-2014, 05:59 PM   #8 (permalink)
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top angle penalty

here's a drag table which shows some loss when the roofline doesn't descend
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Old 06-12-2014, 06:07 PM   #9 (permalink)
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I guess I'd need a picture. You're only tapering one side?

Starting with a 5x10' sheet, there'd be some waste but you'd have a one piece floor.
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Old 06-12-2014, 06:14 PM   #10 (permalink)
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Freebeard,
I'm tapering both sides equally from 62" to 34".

My big dilemma is to leave the top flat or taper it as well.

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