Hi Steve,
I have a lot of experience replacing rotted or missing floor, especially
along the rear as sandwiched between the cross frame and the monocoque. I
had to drive plywood into the space between the monocoque and a new cross
frame. After removing the old rivets and bolts, I reinstalled the fasteners
to bind the monocoque to the frame.
With regard to penetrating epoxy, the floor must be sound for the process to
be effective. By sound, I mean that the structure is still there. I
drilled many holes into the semi rotted area and then applied the
penetrating epoxy. It must be very fluid and slow setting to penetrate. I
doubten that the penetration would pass between the monocoque and the frame.
It's a judgement call about where you can use it.
The door area usually involves "holes" and a much larger area of semi rotted
floor. I opted to replace large sections, usually centering one edge of the
floor replacement on the frame rail and the out rigger. Being sure to
replace the bolts holding the monocoque to the out riggers and the
replacement floor. My activities required that I have access to both the
upper and under floor. In my opinion, it's impossible to rebuild the floor
between the monocoque and the outriggers without removing the belly pan.
Some areas require a scab plywood under sound wood to and using glue and
lots of zip screws to hold the stuff together.
I cut over frame rails with a circular saw set just above the metal. Other
areas, I used a Rotozip bit to cut close to the monocoque and to clean up
corners. To get out under the monocoque, I used drill bits and prayed.
Removing deteriorated screws/bolts required that about 6 inches of the inner
skin be removed. I opted to remove this band around the entire interior. I
used a 1-1/2 backing strip to reuse the the cut out. However, if I were to
do this again, I'd buy the aluminum tall enough to cover the cut out area.
Simpler and stronger.
IMHO, there are no quick fixes to floor rot problems. Especially in an
Airstream due to the construction and the materials. I doubt that Airsteam
used marine plywood; rather just plain exterior plywood. My '69 Safari used
3/4 inch plywood; however, I've heard rumors that 5/8 was used in other
units. Most exterior 3/4 inch is realy 23/32 or something like that and
it's not quite 3/4. Makes replacement challanging and difficult.
Both my Argosy and Safari previous owners failed to seal the lower trim
strip to prevent water from flooding the belly pan. Such a simple
maintenance step would have protected most units for restoration. Not so
with my Argosy as the comode was the main culprit as the leakage wasn't
obvious until considerable damage was done.
Just be warned that these are not simple restorations. The take lots of
patience and some skill and inovation to solve the problem at hand.
Good luck,
'69 Safari
'74 Argosy
Joy