Utility trailer hack (building an aero enclosure for a 1100 mile highway trip)

[aerohead]

Originally Posted by KamperBob

Phil, did you happen to notice where I mounted the generator on my Scamp?
http://ecomodder.com/forum/160036-post21.html

Cheers
KB

KB,is it the green unit next to the LP tank? Or the black ABS plastic-enclosed unit ahead of the SCAMP? Nice setup!

[KamperBob]

Originally Posted by aerohead

KB,is it the green unit next to the LP tank? Or the black ABS plastic-enclosed unit ahead of the SCAMP? Nice setup!

Thanks, Phil! It's taken some time to collect all those toys in preparation for some serious time on the road exploring this wonderful country of ours, hopefully in the near future. As you can see there are a number of elements that would be interesting to model. I'm planning solar panels too with the idea of double duty as a cab deflector. Hence a desire to use CFD as a design tool per my other topic (wake field of pickup).

Anyway. the generator is the black thing on the nose.

Except that's a nylon cover not ABS. There were a number of reasons why that was my best place for it. Blocking cross flow was not original motivation. It worked out that way though.

Regarding this trailer project, I made good progress today. Most of the hard parts are done. I can post some pix later. I changed my design based on final measurements so it will look a bit different from the animation but the first order idea is the same.

Cheers
KB

[wildfire8]

I was driving home today and saw a aerodynamic trailer driving down the free way. I was trying to take a picture of it. The traffic was not letting me. But got a few shots off with my phone. Sorry my windows where dirty. I thought this would help with some ideas. When I was this I thought of this thread. I like they way they taper the fenders.

Got a picture of the side for the company's logo.


Here is a rear picture


And here is the side profile. I lucked out on getting this one because I was on an off ramp and he was still on the free way and I just took the picture and got a good shot.

[Cd]

Wildfire8 : That aero trailer looks very sleek, but it's ......backwards . ( Actually the angle would be too steep for good aero, but almost certainly better than the way it is stock. )
Nice find !

KamperBob : I didn't read each and every post here, so this may have been discussed already.
What about a ( short ) Kammback tail section ? Even with a small radii on the front edges you can keep attached flow along the body of the trailer.
Shouldn't we be concentrating on the rear of the vehicle ?

[Christ]

KB -

I've got to second Cd's suggestion on the Kamm extension, especially since it's one-off anyway.

Some scrap pieces of strategically placed *anything* could be used to make a downward taper off the aft-edge of the roof that just might give you a few percent advantage over not having it, and it's a use for scrap material that doesn't require any real work.

[Cd]

I can't find the thread that I am looking for, but in case you missed it, MetroMPG did a test of his brothers van with a short Kammback that gave some very good results for just being a sloppy cardboard mock up.
The vans shape is very much like that of your trailer - a rectangular box.

[KamperBob]

Thanks guys! Maybe I can post pix later today. This project is mixed with other priorities.

Meanwhile, food for thought. Think about Phil's teardrop template. Now think about applying it to side view with ground reflection symmetry. The 6' high box sits on an 18" deck for a total of 7.5' height. Compare that to a half width of 3' for a 6' width. Think symmetry with the sides. Everybody wants to do everything: round the top, round the corners. But suppose, if only hypothetically, that you are just not allowed. If you can only curve one view, either the two sides (top view) or the one top (side view), which do you expect to yield more gains for this application? Pick one, not both. That has a lot to do with the method behind my madness.

Later
KB

[Christ]

According to some people, the 2 sides are nearly equal to the 1 top, actually.

If your object-in-motion were the lead object, that might be different, but since it's a trailer, it's going to have to follow the profile of the object leading it, which means that there will be a fairly large compression of fluid (air) above the vehicle/trailer as an assembly.

This is not to say that you shouldn't work the sides, but the top is still a desirable park in which to play, metaphorically speaking.

EDIT - If I really only had the choice to work on one objective, instead of top or sides, I'd simply choose "rear". That'll cover it!

[Cd]

Originally Posted by KamperBob

Thanks guys! Maybe I can post pix later today. This project is mixed with other priorities.

If you can only curve one view, either the two sides (top view) of the one top (side view), which do you expect to yield more gains for this application? Pick one, not both. That has a lot to do with the method behind my madness.

Later
KB

( Is that a typo ? I'm guessing that you really don't want to curve just one side of the side kammback extension, since that would cause the trailer to yaw back and forth. )

If I understand your question, you are asking which would be more beneficial - a curved roof line or curved sides.

From what I understand, curved sides are the winner, since you are working with twice the wind area.
Another benefit is visibility to other drivers ( since it doesn't slope down like a ramp ). Since the trailer is slimmer than it is tall, this will also mean that you might derive more benefit from it since the length doesn't have to be a great to come close to a teardrop shape.
The only drawback would be increased crosswind drag.

So did I understand the question O.K. ?

[KamperBob]

Originally Posted by Christ

According to some people, the 2 sides are nearly equal to the 1 top, actually.

If your object-in-motion were the lead object, that might be different, but since it's a trailer, it's going to have to follow the profile of the object leading it, which means that there will be a fairly large compression of fluid (air) above the vehicle/trailer as an assembly.

This is not to say that you shouldn't work the sides, but the top is still a desirable park in which to play, metaphorically speaking.

EDIT - If I really only had the choice to work on one objective, instead of top or sides, I'd simply choose "rear". That'll cover it!

Coffee break.

This is interesting. I'd like to hear more about who says one top and two sides are roughly equal. More importantly, why. Context. What applications are they talking about when they paint with that brush.

In this case, remember that the leading edge of trailer is 9-10 feet behind the cab of the truck, and it sits 1.5+ feet taller as well; 3.5+ above the tonneau cover.

As for tail, already covered. Profile includes front and back. Look again at my early posts for details, including animation. It's already tapered.

Cheers
KB