Hurricane masterclass

EW introductions are needed to the work of Hawker Restorations Ltd based in Suffolk. Just look at the likes of Peter Vacher’s Hurricane I in the UK,Vintage Wings of Canadas Mk.lV,Tom Friedkin’s Sea Hurricane X at Chino,California, USA, and the Alpine Fighter Collections Mk.lla in New Zealand, and you’ll get the idea!

HRL was set up under the expert guidance of Tony Ditheridge in 1993 specifically to rebuild Hurricanes.And it’s a particularly challenging task as Sydney Camm’s fighter is one of World War Two’s most complicated structures to re-create. Hardly surprising then that the most respected warbird operators, such as The Fighter Collection and Flying Heritage, have entrusted their projects to HRL.

At the time of writing Hawker Restorations was working on three examples of the type, all for return to airworthy condition.They comprise Mk.l P37I7 (G-HRLI) being rebuilt for Hugh Taylor, Mk.l R2902 R-for-Robert (G-ROBT) for Rick Roberts and Mk.llb 5403 (G-HHII) for Peter Teichman.

‘HURRI-BOMBER’

Peter’s will be the first of this batch to be ready, with an anticipated completion date of December 2008. It will be restored to Mk.llb specification and to full ‘stock’ condition, complete with 12 machine-guns in the wings and two 2501b (I 13kg) bombs, one under each wing.

This aircraft was built in Canada in July 1942 for the RCAF as 5403. It went into service with 135 ‘Bulldog’ Squadron, which was formed as a fighter unit in June 1942 at Mossbank, Saskatchewan.

The ‘Bulldogs’ were employed on west coast air defence duties.

Post-war it was sold into private hands along with many of its sister ships. Numerous parts from not only Hurricanes, but also other military types that were sold off, were used to keep tractors and other farm machinery running throughout Canada. Fortunately 5403 remained substantially intact, and was discovered by Tony in Canada in the 1990s still with most of its major components in place.

After being returned to the UK, restoration work began in 2005. Peter Teichman bought the ongoing project in October 2006.

This ‘Hurri-bomber’ has been undergoing its restoration at HRL for about 24i years. Power is provided by an original Packard-built Rolls-Royce Merlin 29.This was overhauled to zero time standard by Maurice Hammonds Eye Tech Engineering, also based in Suffolk.

As the aircraft was substantially intact when found, every effort was made to refurbish as many of the original components as possible. When ready to fly the Hurricane will have a zero-time airframe, engine and Hamilton Standard propeller. It will be painted in original Canadian markings.

PROVENANCE GALORE

Running alongside the Mk.llb project are the two Mk.ls. Both of these have impressive provenances.

R-for-Robert is being authentically configured to its original specification. Its airframe is now complete and the systems are going in — and with 5403 almost finished, this aircraft is now receiving the lion’s share of HRL’s attentions.The Merlin 35 for this fighter has been rebuilt and is on site. R-for Robert’s principal point of historical significance is that it took part in fighter cover operations at Dunkirk and was shot down there.

Hugh Taylor’s P37I7 was flying with 253 Squadron which had just arrived at Kenley, Kent, during the Battle of Britain when it scored a confirmed ‘kill’. On August 30, 1940, while being flown by Polish Pit Off Michail Samolinski, P37I7 shot down a Messerschmitt Bf I 10.

Michail was No.2 of ‘Blue’ Section, flying in ‘vie’ formation at 12,500ft (3,800m). While over the Uckfield, Sussex, area at around I 1:15, the pilots spotted around 50 to 60 enemy aircraft comprising Heinkel He Ills and Dornier Do 215s, escorted by Bf 109s and Bf I 10s.

‘Blue’ Section’s leader attacked the bombers, while Michail engaged three Bf I 10s. He firstly attacked from astern and slightly above, giving a six-second burst of machine-gun fire. He noticed his bullets hitting the wings and fuselage of one of the Bf I lOs.The enemy aircraft entered a spiral dive to the ground.

A second German aircraft was then engaged by P3717 with a five-second burst, as the third ’ 110 came in for a head-on attack. Michail fired off the remaining ammunition but didn’t observe any damage.

(Michail went on to claim another Bf I 10 on September 4 and shared in the ‘kill’ of a Do 17 eight days later. He was killed in V7470 over the Channel on the 25th — he was 24.)

At around the height of the Battle of Britain on September 17, P37I7 was transferred to 257 Squadron at Martlesham Heath, Suffolk.This unit was at that time commanded by famous fighter ‘ace’ Robert Stanford-Tuck.

Similar to R2902, P37l7’s airframe is complete and the systems are going in.The wings are ready.

INTUITIVE AND PRECISE

That’s HRL and its latest projects in a nutshell, so now let’s turn to Tony Ditheridge who describes just some of the challenges to be encountered in restoring a Hurricane:

‘‘The Hurricane was designed by Sydney Camm, who was Chief Designer for Tommy Sopwith.

He was instrumental in helping design the Sopwith Camel and others. Camm was a very intuitive engineer — very precise. He believed in mechanically-linked structures, he didn’t like welded ones and adopted very complex structures to achieve his end.The Hurricane was in many respects a continuation of his experience with World War One aeroplanes.

“If you think how a typical aircraft of 1914-1918 was manufactured, it consisted of four square-section wooden longerons [the main longitudinal structural item]. At each bay where you have an upright and a cross member, you have a metal bracket that ties the longerons to the uprights and the cross brackets.

“To continue that argument, look at a Hurricane fuselage and you have four longerons, but they’re made of metal, and at each bay you have an upright and a cross member. In order to achieve the mechanical joining of these parts, Camm actually turned the round tube into a square section.This meant that where they joined they were almost exacdy the same configuration as a wooden aeroplane. So it was a continuation of that sound philosophy.

«But consider the speed, weight and role of this aeroplane and there have to be incredibly fine tolerances, on each individual that make up the structure. Each bracket and each tube has a hole in it and the accuracy of those dictates the rigidity of the complete structure.

“Tolerances on the Hawker drawings are typically between 3 and 5 tenths of a 1,000th of an inch.To put that into perspective that is an eighth of the thickness of a human hair.

«To achieve that in mass production required jigging and tooling that was incredibly fine.Today, because you haven’t got that equipment you achieve this by using staff that understand traditional tool-making engineering and can use the appropriate equipment to get to that degree of accuracy.

“To recap, the fuselage and centre section combined are made of round tubes, squared very accurately at each bay, very fine tolerance holes within, and then in order to hold it all together, a ‘top hat’ bush, called a ferral, goes between the bracket and the tube.The whole thing is held in sheer [completely or absolutely] by either a tubular rivet or by a nut and bolt.

“One particular joint on the Hurricane fuselage comprises about 160 pieces and in all thousands of parts make up a fuselage and centre section. So that’s one tricky thing about the Hurricane which sets it aside from, say, a Spitfire and other more conventional aeroplanes.

«Because of this level of accuracy in construction, there was an upside to operating the Hurricane.

If one was damaged in service, you could go and get, say a tube, from the stores and you knew that it would be manufactured to incredibly tight tolerances.You could drill out the old tube, and with a kit that would comprise of ferrals and the rivets etc even a fairly unskilled person could replace quite a complex and well engineered part, in the field.

This gave a lot of advantages over other aeroplanes, especially in desert warfare, inside Russia and places like that, where you didn’t have the necessary skills or facilities.”

SPARS AND WINGS

«The centre section spars are dodecahedrons — 12 sided — and each of the facets is manufactured out of a strip of very high tensile steel. In order to get the accuracy, and to get the shape correct, they have to be done on a roll-forming machine and those, and the drawings, are no longer available.

“Another dilemma is that there are two spars, one inside the other, so in total there are eight that make up four spar booms — two either side with a sheer plate in between them.We had to explore how we could make these and we did this in conjunction with Guy Black — of the present-day Retrotec in Sussex — because he had exactly the same problem on the Hawker inter-war biplanes.

“We had to find the material, manufacture the rolling device, work out how to close the dodecahedron, to make sure it is exactly the right size and how to put one spar inside the other.

None of this had been done since the war and it all has to be done with modern-day metallurgy.

“We manufacture our own wings, from scratch. They’re not overly complicated, but there are thousands of parts.The wings are where the most variation is found in the Hurricane.”

SMALL ‘FAMILY’

“As far as Hurricane variants are concerned, the type evolved from the Mk.l and eventually it went up to the Mk.IV.The Mk.l was 4in shorter in the nose than the Mk.ll.The latter were armed either with 20mm cannons, or 8 or 12 machine-guns, and some of the lies and libs had bombs and rockets.The Mk.IV was the ‘tank buster’ that could be fitted with the 40mm cannons as well. (See The Hurricane ‘Family’ on page 86 for more on the different versions.)

“In essence, other than the very, very early Mk.ls of which none exist as far as I’m aware, the lineage from the later Mk.l, around 1938-1939, when they disposed of the fabric-covered wings and fitted a variable pitch propeller, was almost unchanged right the way through to the Mk.IV.

“So the nice thing is that you don’t end up with hundreds of versions and lots of different considerations.The engines were changed and went from about l,000hp up to about 1,650 but there was very little difference other than that.”

MORE COMPLEXITIES

«Still another complexity comes into the equation — the whole fuselage has a series of decking and formers in wood, with fabric stretched over.The area where the pilot sits, which we call the ‘dog kennel’, is also made of wood and is attached to the fuselage frame. From there aft is the turtle deck, two side formers and ‘under trays’ beneath the rear fuselage. All these are made of wood and are exceedingly complicated and very time consuming.

«With the exception of the front cowlings, of which there are 16, the rest of the aircraft, including the tailplane, fins, elevator and rudder are all fabric covered in Irish linen. (For more of this, read It’s a Cover Up on page 66.)

“I’ve mentioned the front cowlings, with these and a lot of the metal panels on the fuselage and the centre section, they overlap. From an engineering point of view it’s very, very difficult to completely cowl up and finish all of the metal work on a Hurricane.This process is considerably more complicated than again on a Spitfire’s or even a North American Mustang’s set of cowlings.

“Other areas that are quite complicated include the undercarriage.The Hurricane was the first retractable fighter that the RAF had and in order to achieve this they had very, very complex retraction mechanisms. It folds up into the centre section and actually sits adjacent to the two fuel tanks, and here there is a complex snap-locking gear — with sliding trunions, universal joints, etc.

«The advantage is that the undercarriage is well outboard, and therefore it’s a very stable platform. From the pilots point of view this helps on landing and is very good on rough terrain.

“Look at the undercarriage legs of a Hurricane, they are very complicated.They have their own distinct airfoil shape and the intention is that when you release the undercarriage, then the air flow actually assists in pulling them down.

«We do get assistance from other people and I already mentioned Retrotec.We have our radiators made in New Zealand by Auto Restoration and the cores are very, very complicated.There are about 3.000 tubes in a Hurricane core and each one has a squashed hexagon at each end, and it has a round relief area in the middle. Every one of those hexagons is done by hand!”

EASIER THAN THE SPITFIRE?

“Some people have claimed that a Hurricane takes less time to build than a Spitfire.Well, that isn’t true.They do take the same, or slightly less time to put together than a Spitfire.

“Mitchell’s fighter is a monocoque in construction, which effectively means that you manufacture the fuselage and all the parts by making formers, putting these in a jig and then skinning the whole assembly, so that you get the rigidity via the skin.That means you are manufacturing and assembling at the same time.

«With the Hurricane, it may take a similar amount of time to assemble all the parts, but it probably takes the same again, ie 10,100 to 12.000 hours to individually create every single component. So it’s a bit of a myth that the Hurricane is faster to build.»

TEN UP

“One of the strengths of the Hurricane is it is an extremely strong aeroplane, and whilst it’s very difficult to reproduce in today’s world in a limited run, if we were to make 100 it would be substantially cheaper and easier!

“We specialise in Hurricanes because we feel that’s our niche. As you have seen, they are so time intensive, it takes between 25 and 27,000 hours, which equates to between 2’/2 to 3 man-years to complete a Hurricane.

“There are three Hurricanes on the go at the moment and one is very close to flight test. When the other two are finished, we would have done nine, and we have supplied an airframe to a third party. If you include that, we would have done ten. That will mean we have built two-thirds of the 15 I believe will soon be flying.

“I’d like to conclude by saying that without the dedication of Sir Tim Wallis, who committed the funds and enthusiasm to create the unique spars, it’s unlikely we would have seen the dramatic increase in the worldwide airworthy Hurricane population.»

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