Buy a new 5th wheel, ripe project for a boat tail

[slowmover]

Wind piles up and increases force the length of the vehicle. It also tips the trailer to one side. The frame twists. And, yes, wind under the trailer adds to the problem. Lower is better, granted. Let's note that skirt and tails on big truck trailers address aft and underside.

[skyking]

the low pressure pull over effect of a crosswind is described by Phil here back in 2011.
http://ecomodder.com/forum/showthrea...tml#post276968
Moving or not, the affect is the same. Piling up wind pressure is not the problem, it is the delta-P on the backside.
The skirts are all about drag reduction, improving the flow around the rear tires.

[ennored]

Just a post to prod/encourage you....

Get working on a that boattail!

[slowmover]

Originally Posted by skyking

the low pressure pull over effect of a crosswind is described by Phil here back in 2011.
http://ecomodder.com/forum/showthrea...tml#post276968
Moving or not, the affect is the same. Piling up wind pressure is not the problem, it is the delta-P on the backside.
The skirts are all about drag reduction, improving the flow around the rear tires.

The sail area matters. As do the winds passing underneath. Slowing enough in speed allows trailer weight to offset that problem. But steady crosswinds of 25-mph with higher gusts are enough to close some Interstates to commercial traffic. WYO DOT used to have a .pdf with calc chart on this (these) effect(s).

It isn't a good idea to consider a trailer as rigid over its length. Any type. Nor any tow vehicle. Winds will twist them. I've watched a 53' van tandems come off the ground at quite an angle. Driver couldn't feel or see it. The rig is turned over from the rear where pressures are greatest.

Where the wind pressure is blocked from passing -- non radiused wall joins -- gives better understanding, IMO, than delineating push from pull.

We're not saying much that is different except by emphasis. BUT low ground clearance is better. And it's not just COG.

.

[skyking]

we are saying quite a bit of difference. The template works why? Does it reduce the sail area as a trailer moves forward?
No.
It reduces the low pressure that happens at separation on a square ended vehicle, at the back end! Look at all of Phil's Hutcho charts. The front end, or front side does not matter in the wind tunnel.
This happens just exactly the same in a crosswind. Your Airstream is a prime example of how to do it right.