On May 20, 1:44*am, MKoerner wrote:
I suspect this problem has nothing to do with loads imposed by the gas
springs or bumpy roads or inertia. I think the tension in these bolts
that leads to failure results from “bridging” the trailer across dips
in the road.
Our trailers can be viewed as two beams, the floor section and the
lid, setting one on top of the other. These beams are pinned together
at each end; at the front by the hinge pins and at the rear by the
latch pins. During normal use the lower beam, the floor section, is
loaded along its length by the sailplane parts and supported in the
center by the axel. The trailer sags at each end. The resulting
bending loads put the top edge of the lower section in tension. These
bending loads also pull down on the front and rear of the lid.
Meanwhile, contact with the lower section along the claim shell joint
pushes up on the center of the lid. As a result the lid also sees
bending loads in the same direction as the floor section. This puts
the lower edge of the lid is in compression, not tension. As a result
the front bottom edge of the lid is pulled toward the rear, away from
the mating surface of the lower section. Loads in this direction would
be transferred to the hinge brackets and not to the bolts which clamp
the brackets to the lid. Furthermore, the deflections would probably
be small relative to the play in the pins.
On the other hand, when you tow the trailer across a dip, such as
starting up a steep driveway, the trailer may form a bridge across the
dip, with the back end dragging on the pavement and the front end
supported by the tow vehicle’s hitch. This causes the trailer to sag
in the middle, opposite to the normal loading. This puts the upper
surface of the lower section in compression. The lid is still pinned
in place at the front and the back, but it doesn’t carry much load so
it does not bend nearly as much. This would be especially true with
the fiberglass tops which are probably much stiffer than the aluminum
version. The lid effectively takes a short-cut across the gap as the
lower section sags away in middle. As a result the front bottom edge
of the lid is pushed forward, past the mating surface of the lower
section. Loads in this direction would be transferred through the
bolts, putting them in tension.
Some years back a number of us, led by JJ, myself included, found
substantial cracks on our trailer tongues, opening from the bottom.
Same story: Bridging.
The odd thing about the current problem is the sudden onset of
multiple events… unless you all drove across the same ditch???
Mike Koerner

To the best of my knowledge my trailer has never been "bridged". The
rear of my trailer is high and it is towed by a vehicle with a short
overhang.

Steve may have sent you my photos that support my suggested failure
mode. If not, send me an email and I'll copy you.

Andy (GY)