I HATE the Wind - Aero Semi Trailer Blew Over

[Shepherd777]

I'm new here, but I have been fighting the wind via aerodynamics, and trying to improve big-rig fuel efficiency for over 30 years now.

I built one of the worlds first aerodynamic 18 wheelers in 1983. I have been building the current one for almost 3 years now. It should be done in a month or two.

3 days before Christmas, the wind blew over my empty, brand new, 53' 2011 custom Strick dry van trailer. It didn't even seem that windy here that night. My house is 5 miles from my shop, and I only had two small branches down in my yard. I think it must have been low-level wind shear that was the culprit with the trailer.

The full skirts, completely covering the wheels and tires sure didn't help to avoid the blow-over. The wind was unable to go under the trailer. Still, I have never seen anything like this incident.

As I sit and type this, it is very, very windy outside in a rain storm and I am scared ship-less that when I return to my shop tomorrow, it will be blown-over again. I was going to move it next to the building to protect it after the blow-over, but there was no place to park the 53' monster next to the building.

[Patrick]

Wow, that sucks. Can you put some weight in it or connect it to a tractor? Or maybe turn it so that it's parallel to the prevailing wind? Or some tie-downs like they use on aircraft?

[Frank Lee]

Wow, that's the pits.

Tie downs and ground anchors are very effective for aircraft, mobile homes, and what have you.

Do you think it would have blown over without the skirts?

[BamZipPow]

Will it still blow over if you had something heavy inside? Water barrels filled with water would be cheap enough...

You could also pull the side panels/skirts temporarily so the wind could pass under the trailer...

[Kodak]

Sorry to hear about this mishap Shepherd. Have you considered mounting the skirts with some sort of hinge that would allow you to hold them up vertically when necessary? Just a thought - not sure how practical that would be in this situation.

[Shepherd777]

Thanks for the replies.

It's not really practicable to tether it to tie downs. Could you imagine the conversation with the industrial complex landlord? "Hi. I'd like to dig some holes in your asphalt, pour wet concrete in there, and install hooks into them to tie down my trailer"....

We can't really fill the trailer with water, weights, etc., as there is no loading dock at my shop, and we will be hauling real freight with it while testing. So I couldn't have it full of ballast, and then pick-up a hot load first thing next morning. The trailer needs to be empty while parked.

The tractor is not done yet, so we cannot couple it to the trailer to prevent blow-over. I am pretty sure it would not have blown-over with the tractor attached, even though the tractor has full skirts just like the trailer.

I don't think the trailer would have blown over without the skirts.

Each skirt panel has a full-length piano-hinge on top. But again, it's not really practicable to remove the skirts, or even raise them while parked. That would take hours to do that each time.

I think my only solution is getting a new parking place and park it adjacent to a large building to mitigate the wind.

[Frank Lee]

I was thinking there might be a gravel lot somewhere. It would be relatively easy to put tie-downs in that. Or, tie it to big heavy immovable things like a tree or a tractor or ?

Seems tractor trailers like to line up in a row like chickens on a roost. Perhaps there's a spot in a row of them somewhere accessible.

If the skirts are on piano hinges perhaps they can be affixed in an upright position, practically flush with the trailer sides, just like the collapsible boattails.

[JasonG]

I doubt the skirts had a major effect.
I have seen empty trailers walk up on one side before while connected to a truck.
I could easily see an empt trailer go over in a strong wind.
Your options are limited to:
Keep it coupled (risk of flipping the tractor too)
Keep it loaded (not practical)
Park in a group (best bet)

Many truck parking areas are in depressions for this very reason.

[Piwoslaw]

At first I also thought that the skirts shouldn't have much effect on blowing over, since they are near the ground where the force should be smallest. But on second thought, maybe the wind which would normally go under now is forced upward and adds to the wind already pushing at the top?

On the other hand, I've seen a normal trailer get blown over with the tractor pulling it at 60 km/h (35mph)! Some things you just can't beat.

[instarx]

I can easily see the skirts contributing to this. In a normal trailer air flowing under it relieves the low pressure area on the downwind side. The lack of air flowing under this trailer would have increased the negative pressure on the downwind side considerably.

Although I grew up around trucks I'm far from an expert, but I don't think I would put a tractor under it as first choice. I'd think moving the trailer closer to a structure or parking it along those trees in the background would be a better (and safer) solution.

But this raises an interesting question. Since it is pretty common for trailers to blow over while being pulled in high winds I'm wondering if that might be an increased danger for aero trailers on the road. In any event, it is something to think about when this one starts getting used. You seem to have years of experience modifying trailers - have you heard of aero trailers being more tippy in high winds?

Beautiful job on that trailer by the way!