While several Spitfires have been restored over the years, the same cannot be said of the Hurricane.
In its heyday, the Hurricane could be produced relatively quickly, but only with the support of numerous outstations supplying the hundreds of thousands of parts required to assemble the aircraft.
By contrast, the Spitfire, being of a monocoque construction, was virtually built and assembled simultaneously, making a true comparison difficult between the number of hours needed to complete a Hurricane as opposed to a Spitfire.
Hurricane technology was an expansion of early World War 1 designs which led to peacetime aircraft such as the Hawker Hind, Hart. The technology and material science requirement to rebuild a Hurricane today makes this an extremely expensive and difficult task. Hawker Restorations, with the financial backing of
New Zealand entrepreneur Sir Tim Wallis, was set up specifically to tackle the task of restoring Wallis’s own aircraft, plus a further two examples.
Some of the biggest technical problems on a Hurricane restoration involve the acquisition of materials and techniques which are no longer available. For example, the Hurricane centre section is made up of two 12-sided high tensile roll-firm sections nesting together. This assembly in turn envelops an inner liner tube, which eventually rivets to a flat, high-tensile steel web.
All of these items employ steels which are no longer available. Some direct modem equivalents do not possess the same properties as their 1930’s counterparts. As a result, the 12-sided centre section material had to be specially ordered, which ultimately led to the acquisition of some fourteen tons of strip material – only a few hundredweight of which was actually required.
This material then had to be heat-treated in large coils. After the design, development and manufacture of more than 120 different 18-inch diameter rolls used in the roll-forming process, the spars were eventually manufactured to a tolerance to enable them to nest together, secure the inner liner tube, and rivet to the shear web – which in itself has extremely high tolerances. These spars have recently been supplied to the Battle of Britain Memorial Flight for use on their existing flying Hurricane.
This same technology applies to many other parts of the aeroplane, such as the tailplane and fin. The investment in metallurgy, roll-forming and research was exceedingly high.
The Hawker Hurricane is a fascinating blend of early engineering practices, from a time when money was a secondary consideration. The fact that the aircraft was over-engineered was, at that time, of no consequence. indeed, its very complication only adds to the character and charisma of a highly underestimated aeroplane, one that was crucial to the outcome of the Battle of Britain.
More interesting engineering problems are posed by the Hurricane’s use of round tube that was squared at each joint and mechanically assembled. Sidney Carnm, the Hurricane’s chief designer, did not believe in the integrity of welded structures, the consequence of which being that Hurricane restoration becomes an overcomplicated nightmare of close-tolerance ferrules, tubular rivets and machine components.
One single Hurricane joint, of which there are many, can comprise over 100 individual parts. The limits on each joint can be as little as four-tenths of a thousandth of an inch. In order to recreate this structure, specific tube-squaring technology had to be developed by Hawker Restorations, along much the same lines as the original Hawker product. The Hurricane’s design – a complex steel structure surrounded by an intricate wood and fabric outer skin means that it is unusual to find an aircraft in good condition. The skin of what can appear to be a complete Hurricane generally turns out to be hiding a substantial pile of corroded tubework.
Hawker Restorations have now had to establish a full machine shop capable of manufacturing undercarriage legs, axles and all the design, stress and metallurgy inputs required to comply with Civil Aviation Authority requirements. This also means having the necessary approvals and infrastructure to support such a large operation.
It takes more than 40,000 hours to rebuild a Hurricane. Add together the labour content, the cost of an engine, propeller, raw materials, certification etc and it soon becomes clear that the Hurricane is an expensive aircraft.
But its rarity means that values will always remain high. There are currently around five flying Hurricanes, compared to at least 20 flying Spitfires in the UK to date, not to mention a similar number elsewhere in the world, plus probably a further fifty examples under restoration. Clearly, the Hurricane will always command a substantially higher price among true enthusiasts and collectors.
Hawker Restorations and its sister company AID Engineering have also been involved in the restoration of Spitfires, Yaks and numerous other World War 1 and World War 2 aircraft.
Hawker Restorations’ forte is engineering. Because of the symbiotic relationship which exists between collectors of fine cars and aeroplanes, the marketing of Hurricane AE-977 will be undertaken through the offices of P & A Woods, the well known Rolls-Royce and Bentley specialists. The aeroplane will be on display at their showrooms during the first part of 1999.
Next year, Hawker Restorations hope to utilise all the engineering skills used for the Hurricane to do selective, top quality work on historic racing cars. Owners should contact Hawker Restorations on (telephone) (01449) 740544/741496 or (fax) (01449) 741584. There is also a website: vvww.hawker-restorations.co.uk.