Re: [A/S] Jack question (long response)

[GeorgeHumphrey <gah@xxxxxxxxxx>]

Hi John, Max and the jack group. hi hi  I'm not trying to force anyone away
from what works, and what John has described has worked for him. I just
want to mention a few more thoughts on jacking.  I have just retired from
almost 40 years in the aerospace industry, most of it making major
modifications to aircraft. That is why I like the silver bullet. ;-) My
thoughts, and anyone may disagree without hurting my feelings:

1)	The electric jack utilized by Airstream to raise and lower the front end
of the trailer is for leveling and attachment to the tow vehicle hitch.
While doing this job it is loaded with a share of the weight of the trailer
from the front axle to the hitch, with maybe a little weight from the rear
axle to the hitch if leveling a lot. By putting the jack 2-3 feet aft of
the rear axle then raising the electric jack on the tongue, you are now
raising the trailer weight between the jack point and the hitch.  Using an
educated guess, I suspect you have just added a lot of weight and
additional stress to the electric tongue jack. If you leave the tongue
attached to the tow vehicle then the tow vehicle will absorb the additional
weight as the rear jack is raised IMHO.

2)	Now to address the jacking at the spring attach point to the frame
between the axles. Probably nit picking here, but in normal use the weight
of the trailer is supported by the springs of both axles, which have a
total of 3 attach points per side, thus spreading the weight of that side
of the trailer out along the frame. Jacking one side of the trailer now
applies most of the weight to a single point, and seemingly one of the
spring attach points might be a good point. However, I don't know how much
load the frame can take in that one point versus the two or three points,
and I have heard the stories of rear end sag starting at the axle area. The
engineers at Airstream have reinforced a point on the frame and have
figured the stresses on the hitch point and that jacking point, and have
determined that the jacking point rear of the rear axle is the proper point
to jack the trailer. From working on those aircraft in my past history, if
the manual says to jack at a specific point, I assure you that is the best
point, and I expect the Airstream to be the same.

3) 	I have spent a little time in the technical publications area making
manuals, and I know that there are mistakes made. However, when the manuals
repeatedly, for years and years, tell me to jack the trailer at the point
where Airstream has painted the word "Jack" I rest assured that is exactly
what Airstream means to be done.

4)	I agree that safety is a real important part of the procedure. Blocking
the other side trailer wheels, putting the tow vehicle in park if an
automatic or low if a standard transmission, setting the tow vehicle
emergency brakes, using the designated jacking location and best of all
using the manual is generally the preferred method for safety.

So, in conclusion (and I bet you are glad to hear that), unless Airstream
engineering tells me to change the jacking method shown in years and years
of manuals, I will follow the manual, the marks on the trailer, and not try
to second guess a better location or method. I love my silver bullet, they
are made like aircraft.

George
'89 Excella 29'