Trailer Sway or Fishtailing

[68 Overlander]

To me trailer sway is the rocking back and forth from wind or other external forces. The phenomenon of a conventional trailer changing its path behind a tow vehicle is fishtailing. Do we have to call fishtailing "sway" or is it just going to be that way because that is what we call it? The reason I ask is because I'm buying a different trailer for something not Airstream related and the ole boy wants to suggest a lower profile for sway. I sure don't care, just random thoughts as I listen to airplanes land in my back yard but I think RV people are actually incorrect and the hitch manufactures have followed because that is the common term.

[dwightdi]

"sway" as used by most of us Airstreamers, is the repeated side to side movement of the trailer rather than the rotational "rocking". Admittedly there is usually both occurring. I can see where some people might call the rotaional movemement as sway instead of "rocking" A higher CG will contribute more to the "rocking". I am not aware of a universal definition of "fishtailing". Whatever you call it, we do not want it and it is a sign of instability. You need to design the system to minimize it and dampen it out as soon as it starts for safety's sake.

[overlander63]

Sway is the side-to-side movement caused by raod conditions, load, suspension, and other factors.
Fishtailing is the loss of traction of the rear wheels, causing an uncontrolled movement of the rear of the vehicle.

[markdoane]

I think sway is an oscillatory yawing motion, rotation around the vertical axis. I think what you're calling rocking is more like roll, or rotation around the lengthwise axis.

Changing the height of the center of gravity will have minimal impact on yaw, much more effect on roll.

Lowering the profile will reduce the area subject to the bow wave from passing trailers, and will reduce induced sway.

[Hensley Ron]

Somehow we started calling it sway and it stuck. Motorhomers also refer to sway, essentially the body rocking on the suspension. Fishtailing is a more accurate term for what we experience with trailers. It immediately conjurs the image of a trailer wagging behind a tow vehicle.

Maybe we need an RVers dictionary for newbies trying to understand what we're talking about. We can call it "What's a Toad? An RV Forum Survival Guide."

[Inland RV Center, In]

Originally Posted by overlander63

Sway is the side-to-side movement caused by raod conditions, load, suspension, and other factors.
Fishtailing is the loss of traction of the rear wheels, causing an uncontrolled movement of the rear of the vehicle.

It's all semantics.

Caravanner Insurance, the old insurance division of Airstream, accepted the following words in a "notice of loss statement."

Fishtail or fishtailing

Sway

Zig Zag

Squirrelly

Yawing

Rocking

And a few others that I don't at this moment recall.

They, all meant the same thing.

YOUR RIG IS OR WAS OUT OF CONTROL.

Back then, a few years ago, there were entirely way too many gasoline stations that offered "expert" advice on how a tow vehicle and travel trailer should be rigged together.

Of course they also sold some of the parts that they suggested you needed.

Part of the old "I can get away with anything when I am towing an Airstream,"
MYTH continues to this day.

What is "NOT" a myth, is if your not rigged correctly, you are a statistic looking for a place and time to happen.

History, says so.

Physics says so.

Those, in the past, that have lost control of their rig, also say so.

I know many of them, going back to 1969.

Be safe, install the best rigging you can.

Spending $ 40,000.00 or more for a tow vehicle and another $ 50,000.00 to over $ 90,000.00 for a classy Airstream, for many today, is "no problem."

Yet spending another few hundred dollars on up, to assure proper rigging, to all to many, is foolish, at best.

I, in my almost 42 years with the Airstream products, think I can honestly say that "I have seen it all."

But, I really can't say that, because somebody is always around the next corner, that manages to figure out another way to "cut safety corners."

All I can say, is "WOW."

One thing for sure, insurance and human graveyards, in spite of politics and the economy, have never lost their popularity.

B.S., to some means #$%@, but fortunately to many, it means, "BE SAFE."

My soap box just got repoed, so I better get back to work.

Andy

[Safari-Rick]

Ok, here's what Wakipedia and RV.Net define "sway" as:

As Defined by Wikipedia

A sway bar (also stabilizer bar, anti-sway bar, roll bar, or anti-roll bar, ARB) is an automobilesuspension device. It connects opposite (left/right) wheels together through short lever arms linked by a torsion spring. A sway bar increases the suspension's roll stiffness -- its resistance to roll in turns, independent of its spring rate in the vertical direction.
http://en.wikipedia.org/wiki/Sway_bar

As Defined by RV.Net

Sway - generally a slow side to side rolling/rocking motion, also seen as a general lack of upright stability

Caused by: many things, including overloading, high CG, inadequate swaybars, inadequate springs, inadequate shocks, undersized tires, low tire pressure, etc

Controlled/reduced by: DRW, stiffer springs, airbags, Timbrens, Supersprings, swaybars, stiffer shocks, etc

http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/18111420.cfm

[HowieE]

Sway and pornagraphy are two words in English that are hard to define but you will know it when you see it.

Sway depends on what plane you are using it with. A tree, in the vertical plane, sways in the wind. A trailer, in the horizontal plane, sways when a truck goes by.

Fishtailing is when the trailer brake traction with the road, as on a curve, and jackknifing is when the trailer comes around and kisses your butt. It goes sway fishtail jackknife the end.

[68 Overlander]

Originally Posted by HowieE

Sway and pornagraphy are two words in English that are hard to define but you will know it when you see it.

Was that not profound?

Ron, I think you're correct that it just stuck and I can live with that but it sure does have a different meaning to a motor home, especially one towing a trailer where you've got it all going on.

[rangebowdrie]

Roll,...Movement around the longitudinal axis.
Pitch,... Movement around the crossways axis.
Yaw,... Movement around the vertical axis.
Sway,...Movement along the crossways axis.
Surge,...Movement along the longitudinal axis.
Heave,...Movement along the vertical axis.