[Tesla]

Originally Posted by Sven7

.....Yes, the telescoping would need some soft portion but I was thinking the shells would be hard- ABS or fiberglass. You could actuate them any number of ways, one of which could be to pull it out by hand before you drive on the highway or push it in after you park. Some latches would keep it in place and rubber flanges/gap fillers would keep the wind out.

I think the side wind issue is that you get more "frontal" area on the sides. Since that area is behind the rear axle it tends to use your entire car as a lever... and the wind has the mechanical advantage! I noticed this with the Anal Probe (40"/1m boattail). It tended to want to turn itself slightly when hit by a strong crosswind.

If you want to run a trailer you may have a hard time making up for the extra rolling resistance, weight, etc. but it has been done. Aerohead did it on his T-100 and there's surely a very detailed thread about it somewhere

Still floating ideas around for the expandable type short boattail, does seem to need a solid skin, or reinforcing underneath to get a semi solid skin, which may be even better, like fish and birds, to allow some dampened pressure movement, but not oscillations.

As for the trailer idea, it is primarily as a trailer for utility that is aerodynamic, not the boattail. I did read Aeroheads entire trailer thread, an epic story like War and Peace, or as I said elsewhere "Gone with the Wind"

I am looking at a variety of options, so my current thoughts are permanent framework on rear of vehicle with short Kammback/start of boat tail. Then depending on requirements I could attach to this either hitch mounted or inflatable medium boattail or go even further when I need to use the trailer.
Sort of a multipurpose aero module plug in system.
So utility is the primary factor and trying to design some aero for a side benefit.

Originally Posted by Vekke

I have noticed in my lupo 3L that it more unstable at highspeeds 80-100mph in crosswinds with 800mm long kammback spoiler. On slower speeds no problems whatsoever. My car is light about 900 kg with driver and small. Without the spoiler the car goes like in tracks but with the spoiler I have to make small corrections every now and then specially in open sections and bridges etc. Its nothing that you cannot correct at least in 100mph speeds if you have done some rallying but you need to be more alert on windy days.

There have been a number of reports of crosswind issues, but as many or more of increased stability, this area is worth more investigation to try to nut out the differences and identify potential pitfalls.