From Hawker Sea Hawk to Hawker Hunter

[Quorneng]

I was given a big packet of XPS 5mm thick sheet foam used as an underlay for laminate flooring. It appeared suitable to make RC planes using my stressed skin type of construction.
I had a spare low power 6 blade 55 mm EDF so I looked round for a suitable plane to model and chose the Hawker sea Hawk. Being a jet of the 1950s it used a straight wing but was well streamlined as required for the relatively low power turbo jets of the time.

The big challenge would be not only its bifurcated inlet but also a bifurcated exhaust.
Perhaps a printed duct would be a practical way to achieve the appropriate varying diameters required for a single EDF
After a bit of experimentation this is what I ended up with.

Printed in single wall PLA.
Due to the layout of the RR Nene turbo jet it proved difficult to create efficient paths so the inlet was sacrificed in favour of the exhaust. On a set of scales it did generate what hopefully would be sufficient thrust but to be sure the airframe would have to light.
A rather usual construction sequence.
First a half of the centre fuselage, planking over formers, was built over the plan.

Next the complete 'one piece' duct was inserted into the completed half shell so it was exactly 1/2 way in. Fortunately the XPS formers are very easy to cut so it could all be "adjusted" appropriately.

Once satisfied and the glue hard the other side of the fuselage was built up

.
Note the EDF wires run through the formers before the skin completely builds everything in.
The wing are built and simply glued onto the side of the fuselage. To save weight they too are just top and bottom skins with a foam shear web to create the required scale wing section.
The rear and nose of the fuselage are built separately.All the servos are include during the build of each part and the wires run through the fuselage before being glued on.

Experience had shown that a well prepared edge to edge joint was virtually as strong as the foam so in theory at least the wing should not fail at the glue joint.
From then on it is just the tedious job of installing the ESC & Rx and creating a suitable box for the 1800mAh 3s battery with the only access being through the canopy aperture.
The finished Hawker Sea Hawk. A nice simple scheme "Atlantic Grey" top side, "Sky Blue" under.

To my relief it flies pretty well.

No speed merchant but docile and dependable rather like the full size. Its good stream lining means it glides well too.

During my research I discovered that Hawker built a set of modest swept wings and added them to a standard Sea Hawk fuselage as the P1052. Interesting!!
Even more remarkable it still exists stored (but not usually on public display) at the Fleet Air Arm Museum.

To be continued.

 

[Tunedfrog]

I'm intrigued, nice work.

 

[CertifiedMike]

Its a beautiful looking plane.

 

[Quorneng]

As I am free this afternoon I will continue the story.
The Sea Hawk sacrificed the inlet path for a good exhaust. I should have known that it is the inlet efficiency that has the biggest impact on an EDF's performance so for the P1052 I moved the EDF back a bit, which was probably going to be required by the swept wings, to give a better inlet duct path.

To help account for the rearward EDF (still a 55mm as for the Sea Hawk) the exhaust is printed if lightweight PLA. When in use it is under a positive pressure (unlike the inlet) so the reduced stiffness of the LW-PLA is not an issue.
The construction of the fuselage was otherwise identical to the Sea Hawk as were the wings except of course they are swept and of a slightly smaller area. The tail plane is also swept.

When built the full size was painted in a very pale blue reserved for Hawker prototype aircraft. Not an ideal colour for an RC plane! As the full size was later painted in conventional Fleet Air Arm colours I did the same.

The better duct arrangement gives it a significantly improved performance over the Sea Hawk allowing it to do this trick!

The P1052 was taken seriously by the Navy and was modified with a hook and strenghened UC so it could be test flown on HMS eagle in 1952. Not surprisingly by Eric "Winkle" Brown who was by far the most experienced test pilot!

The performance improvement of the swept wings over the basic Sea Hawk was not considered worth the added risks from its higher landing speed on the "modest" sized aircraft carriers of the time so it was not adopted.
Anyway I now have two EDFs to add to the collection.

This was not the end of Sea Hawk development as they actually built a second P1052 but modified it during construction to have a "straight through" exhaust to reduce the losses from the bifurcation. It was hoped the new layout would be better suited to achieving transonic speeds. As it was such a major change it was given the design number P1081.
Interesting again!
To be continued.

 

[Quorneng]

The second swept wing Sea Hawk, the P1081, still basically used the same fuselage and I still had plenty of the 5mm XPS sheet so I decided I would build it too.

The wings, tail and forward part of the fuselage were identical to the P1052 but the rear fuselage with a single straight through exhaust was new. Interest in the design was expressed by the Australian government so it became known as the Australian Fighter.
For me the inlet duct would be the same as was the EDF still a 55mm six blade but with a slightly more powerful motor. The long exhaust with a 90% FSA nozzle at the end completed the duct,

The long duct suggested a rather different construction sequence where the duct was used a "spine" and the fuselage constructed around it.
The formers were glued to the duct and then planked.

Once sufficient planking was added the tail was built on and the wings added but making sure to run all the wiring through to nose before the last plank went on!
As before the nose was built separately and glued on.

The P1081 was only ever flown in the prototype pale blue so that was what it had to be.

With an efficient exhaust and a bit more EDF thrust it flies nicely with plenty of reserve power but the co;our makes it hard to see at any distance in anything but strong sunshine.

Still docile and easy to fly but not easy to see!
Anyway I now have three Hawker EDFs all built to the same scale.

The full size P1081 did not fare well. Whilst making a high speed run at 9000' there was some some sort emergency. The test pilot ejected at 2000ft but did not separate from the seat and was killed when it hit the ground.
Although there was nothing fundamentally wrong with the design of the wings and tail Hawker was now convinced the "portly" fuselage resulting from the RR Nene's big diameter centrifugal compressor was never going to be suitable for a transonic fighter.
Perhaps you can see where this is going.

 

[Quorneng]

The final chapter.
Following the loss of the P1091 Hawker brought forward a follow on design that used the RR Avon turbo jet. More powerful than the Nene and using a axial compressor had a significantly smaller diameter although quite a bit longer. Not really an issue with a tail pipe take to the end of the fuselage.
Obviously based on the P1081 design it had rhe design number P1067 later to be named the Hunter.

It followed that the construction techniques I had used on the P1081 would work just as well for the Hunter.
First the one piece duct.

As the fuselage was a smaller diameter it uses a more power full 50mm 12 blade EDF to match that of the RR Avon.
Built in the same way. The tail plane and fin added.

The nose added with all the wires brought forward into the cockpit.

Complete and painted in Hawkers very pale blue.

With the strong sunlight the camera decided it was almost white!
As hoped it flies nicely with plenty of thrust but it is still hard to see at distance in a blue sky!

Rather hard work in what was a rather too strong wind for what is still a light weight EDF.
It rather shows how old I am but in 1958 the display team the Black Arrows from 111 squadron looped 22 hawker Hunters in formation and I was there as a 12 year old lad with my Dad!

.The remarkable bit was there were only 14 all black hunters from the display team so the rest of the 22 were made up from normal 111 squadron planes and pilots.
It says something about the skill of the pilots and the wonderful flying characteristics of the Hunter. It is a feat that has never been equalled.
I just had to build one of the Black Arrows Hunter F6s
There are some differences to the prototype. The F6 has a saw tooth drooping leading edge, an airbrake added onto the bottom of the fuselage and not forgetting the bulbous cartridge case collectors under the guns known as Sabrinas after a well endowed actress.

It too flies nicely.

So there it is Sea Hawk to Hunter F6.

All built in sequence and to the same scale.