RESTORATION

An introduction to the restoration project

During the aerial combat over the Thames Estuary on 18 August 1940, as depicted in
the painting "A Grand Aircraft", 257 Squadron lost one of its Hurricanes to enemy
action. Sgt Alexander Girdwood parachuted to safety leaving Hurricane P3708 to
bury itself deep into farmland on the island of Foulness on the Essex coast.
Fifty years later that Hurricane’s remains were excavated and the objective now is to
recreate the fuselage of MkI Hurricane P3708 for display at the Norfolk & Suffolk Aviation Museum
(www.aviationmuseum.net), using as much original structure as possible.
To make the best possible use of the surviving material, professional assistance
is being sought where work is beyond that of the enthusiastic amateur.

The starting point!
Left: some of the main fuselage framework. Right: fuselage rear end beneath the tail fin.

Extracted from the piles above, some recognisable parts have been laid out in their relative positions.

After a considerable amount of work, what emerges is (left) part of the distinctive warren girder fuselage framework,
and (right) rear fuselage frame between the tail-wheel and rudder.

The fuselage joints are complex structures, each containing over fifty individual parts, as shown below.

All the original joints are distorted to varying degrees and straightening them requires professional assistance.
An example of what can be achieved is shown below in "before" and "after" views of two of the stainless steel joint plates.

A few other "before" and "after" examples:

Joint A, where the engine bearer joins the fuselage.

A heavy casting at the complex Joint H

Guide frame for pilot's step at Joint K.

Fairey fastener receptor housing on the fuselage lower longeron.

Rear fuselage frame at the Norfolk & Suffolk Aviation Museum, assembled to test-fit the straightened joints.
The next job is to replace the remaining wooden struts with the real thing; some are already in place.

While waiting for the fuselage struts to be completed, attention has turned to the Hurricane's "centre section":
a rectangular framework formed by two 9ft (2.7m) long spars joined together by four 4ft (1.2m) long composite girders.
It is the sub-assembly that forms the core of the Hurricane's structure.

A diagram of the Hurricane's centre section with trailing edge units attached to the rear spar (right). The aircraft's front is to the left.

The centre section is really the starting point when it comes to building a Hurricane. Everything else joins on to it:
the fuselage sits on top, the wings attach to the outer ends of the two main spars, the engine bearers attach to the front spar
and the undercarriage pivot points are at the outer ends of the front spar.
Most of the centre section is made of steel plate and steel tubes riveted or bolted together using stainless steel plates and brackets.
The two main spars have a dumbbell cross section and each is formed from a sheet of steel plate, the top and bottom
edges of which are capped by a steel tube wrapped in a 12 sided double skinned steel sheath that is riveted to the plate.

Spar cap construction.

Surviving centre section parts from P3708 were very badly distorted. Balancing finance against being able to complete the structure
meant that much of the centre section has been constructed from parts sourced from other Hurricanes but large parts from P3708 have been incorporated.

Inserting a large straightened section of P3708's original spar plate into the rear spar.

Each spar plate is strengthened by 16 top-hat section "stiffeners" riveted in pairs to either side of the plate.
Few of the original stiffeners survived to be straightened and so others had to be sourced to make up the deficit.
They are not the easiest of things to find! Not wishing to go down the route of producing replicas,
eventually some very corroded originals were located and pressed into service. They were in very poor condition.
The bottom half of each stiffener had completely rusted away. After cleaning, suitable "halves" were trimmed then welded together to make full length items.

Left: A bunch of badly corroded stiffeners. Centre: Suitable "halves" paired-up for cutting and welding. Right: Ready to be riveted to the spar plate.

Below are the two main spars with spar caps and stiffeners riveted in place: front spar to the left and rear spar to the right.
The wing attachment points are large steel castings inserted into the ends of the spars caps: 8 in all.

Below, testing the fit of the pieces making up one of the two "inner girders" which join the front and rear spars.
Front is to the left. The angled bottom part of the frame is to accommodate a raised undercarriage leg.

An example of trying to use as much original structure from P3708 as possible is shown below.

Some of the "as found" parts of the inner girder from the area marked in the picture above.

In theory it would have been possible to have re-used the fragments of the crushed duralumin tube but that would have been a step too far financially.
However the stainless steel joining plates have been straightened and re-used.

Left: Before Right: After

A greater challenge was this large, thicker gauge, bracket connecting the right-hand outer girder to the rear spar.

Assembling the centre section.

First, the end brackets of the four girders were detached from the girders and attached to the front and rear spars. The front spar is to the left and the rear spar to the right.

Then the spars were moved to their correct distance apart and the remaining parts of the girders inserted.
The four "arched" grey brackets (two on the top of each spar) are the connecting points for the fuselage framework which sits on top of the centre section.

Below. The centre section at the Norfolk & Suffolk Aviation Museum (Flixton) between a much younger Sydney Camm creation and a Spitfire.

Learning from the experience of others, before adding the forward fuselage
framework to the centre section it is advisable to insert the flying control sub
assemblies such as the support for the rudder pedals, the control column base and
aileron mechanism otherwise access for their installation becomes difficult.

The pedestal for the rudder pedals was in particularly bad shape when found and
needed a lot of attention but it has been saved and installed. "Before and after"
pictures are below. The slightly bent rudder pedal adjuster, seen on top of the pedestal
in the "after" photo, is made of steel. No attempt to straighten it has been made and
therefore it remains in the position set by Sgt Girdwood before that final flight. The
rudder pedal bar did not survive the crash and a replacement is yet to be inserted.
The complex brackets either side of the rudder pedestal, secured by three bolts to fore
and aft tubes, are one of the few occasions so far where new items have had to be
made. They are made of thin steel plate and not surprisingly the originals were in a
very bad way and were definitely a "step too far" to attempt straightening.

Below, some of the flying control sub assemblies have been added to the centre section.

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