When N-5490 was surveyed
at at Harvey Field before being rescued, slack fabric was noticed on the
port side of the fuselage.
A closer inspection revealed
that there was a bent vertical tube in the port sideframe, caused almost
certainly by a heavy landing.
Once dismantled, the full
extent of the damage was apparent - the main 7/8" square tube directly
above the port undercarriage
compression leg was bent
and the 7/8" circular tube immediately forward of this member was split
just under the top rail.
Described here is the method
of repair employed.
N-5490 being de-rigged at Harvey Field during recovery. Note the slack fabric just under the front cockpit door - a sign of serious damage beneath.
A closeup of the slack Ceconite.
Hidden horror. The
cause of the slack fabric was found to be this bent main vertical member
in the port sideframe
directly above the port
undercarriage compression leg.
There was clear evidence
that the fabric had been opened up in this area and then patched, so the
conclusion must be that
this Tiger had been flown
in this condition for some time!
The wooden front seat frame
bolts to this vertical member and was also found to be damaged, so a new
seat frame is being made.
The replacement section salvaged
from an otherwise damaged sideframe. This section will be welded
into the port sideframe.
Note that the vertical member
has a round 3/4" 4130 steel tube inserted. Once installed, this vertical
member will be
far stronger than the original.
It will also ensure that this critical member is perfectly straight.
From the Tiger Moth Maintenance and Repair Manual, these are the various fishplates to be used in the repair of Tiger Moth fulseage frames.
These are some original DH
repair fishplates that will be used to weld in the repair sections.
The three fishplates at top right are 20 SWG and used on the top longeron
(H35774 Mk. 1).
The two lower fishplates
(H35774 Mk. 2) are the heavy duty 16 SWG plates that will secure the vertical
square member. The two 3/4" diameter round fishpates (H35771) at
top left
will be used to replace
some 5/8" tubes in the rear pylon, and the flat plate (35773 Mk. 2) will
be used to repair a small dent in one of the engine bearers.
These fishplates are the
totality of original plates that could be found during a worldwide search.
Additional plates needed to complete the repairs have been made
to the specifications in
the Repair Manual from 4130 steel plate and tube.
During the repair process,
the two sideframes will be bolted directly together to make sure that there
is perfect symmetry between the two frames.
A correctly executed weld repair of another Tiger Moth fuselage frame showing the pair of fishplates in place.
Once the rear fuselage had
been stripped of fabric, this damage was discovered in the aft bay of the
rear fuselage pylon.
Two of the 5/8" diagonal
tubes were found to be badly bent. Luckily there was no damage to
any of the surrounding structure.
How these tubes became bent
in this manner is a complete mystery. However, before the fabric
was removed, a pair of large
patches were noted in the
area of the damage, indicating that someone in the past knew of this damage,
opened up the fabric
to inspect, and then decided
to leave it and patch the fabric!
The bent tubes have been
cut out and replacement 4130 steel tubes have been prepared to weld in
place using the fishplates discussed above.
(After this photo was taken,
the stub ends of the cut tubes were carefully re-aligned.)
It has been nearly six years
since N-5490 was recovered from Harvey Field and restoration commenced.
In that time countless hours
have been spent researching, stripping, sorting, repairing and preparing
to refit countlesss fittings and components.
The completion of the fuselage
frame repairs therefore marks a tremendously exciting turning point in
the restoration project
allowing the re-assembly
to finally commence. Return to the skies is scheduled for the summer
of 2020.