Boat tail project based on a single wheel trailer...

[BamZipPow]

Originally Posted by euromodder

Maybe whatever air got in, used to go out an easier way before you added the trailer ?

You don't need much air to lift a slab surface.

The rear of the aero cap isn't really all that air tight so what ever air that enters the aero cap shouldn't push the window out like that at all. The only other time that I noticed the rear window moving is when my front top access door was open and the air was being diverted inside the aero cap. Needless to say...the rear window becomes my indicator that my air brakes are on.

I'll take the magnets off and see if the window will still move without the trailer attached.

[freebeard]

Was it as you drove past the corner of Vortex and Shedding?

[euromodder]

Originally Posted by BamZipPow

The rear of the aero cap isn't really all that air tight so what ever air that enters the aero cap shouldn't push the window out like that at all.
I'll take the magnets off and see if the window will still move without the trailer attached.

You could get air being sucked up between the bed and the trailer, and that could prevent the air from getting out the bed - maybe it could even blow some air back in.

Sorta like what you can get between cab and bed, if there's a gap there.

[BamZipPow]

Originally Posted by euromodder

You could get air being sucked up between the bed and the trailer, and that could prevent the air from getting out the bed - maybe it could even blow some air back in.

Sorta like what you can get between cab and bed, if there's a gap there.

Did some highway drives today at speed and the rear window didn't even budge. Guess I will have to do test drives with the trailer and see if the window will budge again.

It's probably gonna be a wash once I start building the trailer up to match the width of the truck and install the gap covers.

There is a gap between the cab and bed but the aero cap and belly pan should minimize the amount of air that should move through the bed. I guess if I really wanted to know, I'd have someone else drive the truck and I'll sit in the bed and see what moves the pinwheel or set up some yarn tuffs on a string and place a bunch of them under the aero cap.

[BamZipPow]

Went fer another run today with the trailer attached and the rear window didn't even budge. I guess the mending plate I have on the rear window now is enough to keep it from being sucked open.

Even though is wet and drizzly, I will start framing out the sides of the trailer so I can start to taper it.

[wyatt]

We did some testing on various sized (strategicly sized) trailers a couple years ago. We found that as long as there was attached flow along the entire top length of the trailer, that there was a strong down-draft at the front of the trailer. We tried a few things to stop the draft, coroplast on top (it bent right in half), coroplast on the bottom (bent until it dragged on the ground), fully enclosed (lasted until we had to turn around, still a lot of deformation). I don't doubt you are seeing the same down-draft, and to be honest, I don't know how to beat it without a full enclosure. My speculation is that when there is a down-draft, it means your trailer's front end could be smaller (if maintaining a gap). Presumably, very little down-draft would mean that the air is re-attaching optimally, but that's speculation on my part. We found that a much reduced gap helped also.

[freebeard]

We did some testing on various sized (strategicly sized) trailers a couple years ago. We found that as long as there was attached flow along the entire top length of the trailer, that there was a strong down-draft at the front of the trailer.

What was the case where there was not attached flow the full length, and what difference did you observe?

[wyatt]

Non-attached flow was seen when the front end was too small, and then it picked up further back. It was just too steep of an angle (we knew it would be at the time, but we liked testing). We didn't have the front end of the trailer tufted at that time.

We also saw poor attachment along the top when the front end was too high, presumably shoving the air out of the way, and having a hard time re-attaching. This is the case where we had monstrous down-draft. My buddy joked that we could have run a turbine in there. We implemented a stromform (ramped) front end that helped a lot, but did not correct the problem.

All cases had a large (9") diameter leading into the trailer body, so it wasn't some squared-off front end problem.

The most optimal case was a front end that was very close (about 2') to the lead vehicle (a ford 12 passenger van), and well below the roofline. The attachment was so strong that I thought we had no attachment (not a ripple the entire length). It wasn't until we slowed for a turn that the tufts all moved at the same time, and straightened out again when we picked up speed. In this case, we still had a down-draft, but not near what we had with the "high top" we had tried previously, and even a lot less than it had with the stromform front end.

[BamZipPow]

Got some more ideas fer the front and rear supports using some reinforced shelf brackets to support the side pieces.

Here's a quick mockup of where the rear window will lay on top of the trailer.

[freebeard]

If you lose the top to the trailer, you'd gain a few inches in plan taper, but more in profile.

kach22i just posted this in the Wind Tunnel thread: