Originally Posted by
Rick Kirchner
Couple of things about Airtabs. One of the reasons you don't see them on semis is because most of the guys are usually hauling other people's trailers, and the trailer panels/boattail are more effective at drag reduction. Everything I've read about airtabs (despite the manufacturer's claims) are that they are very effective at sway reduction, but the drag reduction is almost unnoticeable.
You'll see more Airtabs on trucks that haul their own trailers.
One of the reasons you see so many trailer tails is that CA requires drag reduction devices on any box semi trailer in the state - along with the big underside panels. Most fleets don't want to keep track of some trailers that can go and others that can't, so they put the devices on everything. Besides, they actually do work.
I'm not having stability issues when I'm towing the race trailer despite the fact that it makes the weight imbalance worse. The drag associated with the trailer must move the CP much farther back. It's when the coach is towing nothing or just our Honda on a dolly - then crosswinds and semis can make it a tiring day.
You would not have believed how bad it was before I added the steering stabilizer (a shock absorber with two centering springs that's over 2 feet long and 3" in dia) paid close attention to the alignment and added the weight up front! Not to mention the inability to stop. When they built the thing the brake pedal linkage was adjusted such that it would immediately go over center at the MC. Thankfully I figured that out in a hurry with a little help from Carroll Smith.
Ed, I bet your Winnie was a front engine coach. There's frequently only one wheelbase from each manufacturer of those, so length gets added behind the rear bumper with frame extensions - same with most class C's. you can literally tear the back of the house off if the hitch is overloaded or rust gets in those extensions - which are frequently pretty sketchy to start with. A 40' front-engine class A has crazy rear overhang, but it's all hollow-core wood and such, not much weight. The trailer toad was designed exactly for the situation where the trailer has more tongue weight than the coach can carry.