Some folks just have the dream job. Fancy getting out of bed knowing you are off to restore a warbird and to preserve our history. That’s exactly what the team at Hawker Restorations Ltd do!
The Hurricane was an extension of the famous in-between wars, Hawker Bi-Planes and entailed complex tube squaring, exceedingly tight engineering tolerances and relatively exotic materials, heat treatment and metallurgy. Unlike the Spitfire and it’s contemporaries which are simple monocoque construction. Hawker Restorations had to have specialised steels manufactured, invest in extensive jigging and tooling and the acquisition of all the information to enable us to specialise in the restoration of this historic Mark.
The Fuselage – Sydney Cam the Chief Designer for Hawker’s did not believe in welded structures, only mechanically constructed joints. Thus involved taking special round tube and squaring it at each bay within the fuselage. This involved many precision parts, a typical joint in a Hurricane of which there are 100 ‘s comprises of anywhere between a minimum of 20 items up to over 150 items per joint. The tolerances on every hole are less than 0.0005 thou. Specialised tube squaring equipment and jigging had to be developed to accomplish this.
The Centre Section – this consists of a front and rear spar that are roll formed and are 12 sided with an interference fit overlapping additional 12 sided spar. The spars are manufactured out of a high tensile spring steel which entailed sourcing and purchasing specialised steel and heat treatment. Over 120 pairs of specialised rolls had to be designed and manufactured to be used in conjunction with the sole remaining roll forming machine in England. These are then attached to a shear web which form the front of the rear spar. These are then spaced apart by a series of squared tubes. At the end of each spar boom hand forged fittings link the wings to the centre section. The centre section includes the first retractable monoplane fighter undercarriage which consists of exceedingly complicated snap locking gear, trunnions and booms. Within the centre section are two of the three fuel tanks which are integrated within the unit with primary structure tubes passing directly through them.
The Tailplane – the tailplane front and rear spars are 8 sided high tensile, roll formed steel booms with overlapping spars. They are separated by a serious of diagonal roll formed booms. The basic box structure then has ribs attached to it to give it it’s distinctive shape. The elevators are manufactured using a steel torque tube with soldered and riveted cleats attaching a serious of ribs which are manufactured from round tube which in turn is formed to give an aerofoil section or P section. The same spar and rib technology is used throughout the fin and rudder. The manufacturing of these spars entailed the manufacture and purchase of a specialised steel, heat treatment and the manufacture of a series of rolls used in conjunction with the only roll forming machine available at the time.
The Wings – the wings involve four separate unique spar shapes. These are double T extrusions which correspond to the aerofoil section on the front and rear spars. They consist of 100’s of small handmade components and are assembled in a sophisticated jig. On completion of the basic structure the wings are skinned and the leading edge and tips attached. Depending on the customers requirements 8 original Browning machine guns complete with ammunition boxes, chutes, pneumatics and gun activation equipment is fitted prior to the wings being mated to the centre section.
The familiar and unique shape of the Hurricane is due to the whole primary structure having a series of wooden formers and individual wooden stringers fitted around the fuselage, including a plywood structure known as the dog kennel which houses the pilot, the instrumentation and canopy windscreen and canopy mechanism. A similar structure consisting of three removable undertrays are fitted beneath the aircraft giving the distinctive ventral fin around the tail wheel area. This was added to aid the aircraft spin recovery.
All wooden structure is covered with traditional Irish Linen, hand stitched and finished in nitrocellulose dope. There is an extensive amount of work in compound curve wheeling for the remaining exterior structure of the Hurricane consisting of sixteen hand made aluminium cowlings.
You can follow their here and may be you may be able to help locate some of the spare parts they need: www.hawker-restorations-ltd.co.uk