[VAC] Airstream Loading and Tolerance

["Harvey Barlow" <harveybarlow@xxxxxxxxxxxxx>]

Sarah,

>
> 1.  Is frame separation mainly due to rotted floors in the rear bath
rusting the
> frame bolts, an bend in the frame that goes away when the weight problem
is
> corrected, or an actual kink in the frame?  Frame sag, which Roy Lashway
> described as a separate problem, is that due to tired shocks?  Are both
problems
> more common on the longer single-axles, or on the even longer double-axle
> models?

Frame sag or frame/body separation is, I think, mainly due to excessive
weight suspended at the extreme rear of the longer frames which caused frame
bending behind the axle mounts.  The frames were slightly weak for the
weight and flexed.  If the monoquoque shell also flexed, side skin bulge
resulted.  If the shell retained its shape, the two parted.  Rusted bolts,
screws, and rivets holding the body, floor, and frame together probably
allowed the separation but inadequate numbers and sizes may have
contributed.

> 3.  Is frame separation due to improper attachment to the frame (eg rusted
> bolts), structural fatigue of the shell (we all know what that's like),
> overloading, all of the above, or all of the above combined with having
been
> made of cream cheese in the Beatrice era?

The problem occurred when rear bath gray water tanks were added which was
either coincidental or the direct result of Beatrice ownership of A/S, you
decide.  Some owners never travel with full tanks so may not have
experienced the sag or separation problem.

> 3.  In photos I see of most slanted-rear models (those that took over from
the
> pointy-ends ones), there seems to be some amount of "droop" in the back.
It
> seems so common that I had come to assume it was a visual/stylistic thing
to go
> with the line of the back, or maybe even an optical illusion.  The
broadest date
> range I saw for actual frame separation was from 1965 (on the service
bulletin)
> to 1976 or 1977 (per Bill Scott).  Does anyone know of frame separation
problems
> for units outside those years?  Given the comments about weight I would
have
> thought it would be something that could happen to any airstream.  Also I
seem
> to recall pipe frame models, or at least Tuna's pipe frame, were also
> susceptible to this problem?

All long trailers seem to sag very slightly when not supported by stabilizer
jacks but apparently within design tolerances.  Apparently the engineers
never intended for A/S frames to support the entire weight of the trailer
but the combination of frame and shell firmly connected together are
designed to provide adequate strength as in aircraft design.  I have no
direct personal knowledge of the problem but based on my own observations
and comments on the list I would say that minor sag has always been present
in 28' to 35' trailers (and possibly single axle 24') but early (in the
trailer lifecycle) frame/body separation resulted between '73 when the gray
water tank was introduced until about '76 or '77 when A/S strengthened the
frames.  I think frame/body separation can occur in any A/S that has been
subjected to heavy loads on rear frame end, lots of travel on rough roads,
and failure of bolts, screws, and rivets.  My '66 Safari 22' shows no sign
of sag or separation but it has apparently never had a rear tire carrier
installed and does not have a gray water tank.  I've only owned it since
last July and have no idea how it was used or abused in its earlier life.

> 4.  Trike said "The frame on my SOB is a scrawny little 4" C channel just
like
> older A/Ss use" -- how scrawny, compared to what other sized frame
members, and
> which older A/S's is he referring to?

Newer, or at least longer A/Ss use 5" channel frames I believe.  Frame size
is easy to determine......get your ruler, yardstick, or tape out and measure
top to bottom of the frame at the rear bumper or front A frame.

> I have looked underneath mine ('62 24' single axle) and all I see is
smooth
> belly; I don't see any separation or rust around the bumper but then it is
> stabilized with jacks right now where it is sitting; and I have looked
along the
> side and don't see any telltale bulges near the wheel well.  But I don't
want to
> go around thinking a '62 is immune if it's not.  And if non-Beatrice A/S's
(yes,
> I know that was a more limited time frame, I'm just poking fun here) don't
get
> frame separation when you overload them, then what do they get then with
the
> spa, the cattle car (oops, sorry mom, no really, I was thinking of that
'48 that
> was in RVTrader in December with the 5' rear access door) (oh, okay, well
be
> that way then) and the golf cart in them?

If your trailer has been overloaded and abused and the frame and body sagged
together, it will show in sidewall bulge just behind the wheel cutouts.  If
frame/body separation occurred, it can be detected by looking at the point
where the rear of the body rests on the plywood floor and the frame at the
rear bumper.  A tight joint between body and bumper compartment cover
between the frame rails should indicate a lack of separation.

> PS is that (average of) 1000 pounds the carrying weight for actual towing,
or is
> that the sleeping weight, for all the goods plus mom-in-law and the brood?
> Wouldn't the stabilizing jacks help some with the sleeping weight, at
least if
> you didn't have any sleep-jumpers and/or dietary indiscretions filling up
the
> blackwater tank in the night?  Doesn't it make a difference how much
weight you
> can carry depending on where you put it?  I would think 1000 pounds
directly
> over the axle, for example, wouldn't be a big deal as long as the tires
could
> take it.

The 1000 pound average figure relates to carryied weight and is limited by
tires, wheels, suspension, frame strength, balance point, equalizer hitch,
and tow vehicle tolerance for tongue weight.  With stabilizer jacks down
additional guests seated or walking around in the trailer will not hurt
anything.  Yes, the location of carried weight matters considerably.  Your
assumption that additional weight carried over the wheels would be more
acceptable than weight near either end is generally correct.

These comments are only my opinion and reflect my understanding of the
problem but may not be precisely accurate or complete information.  Maybe
this will add to your understanding.  Your comments/questions indicate a
correct understanding of the issues.

Harvey Barlow
Lubbock, TX
WBCCI # 1171, WDCU, VAC