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A Hawker Sea Hawk in 5 mm underlay.


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The LH wing joined (just glued!) onto the centre section.

LhUpper.JPG.feaaea172c8adb8bd3606cd627a88f4b.JPG

The big area open on the underside to give access to run the aileron, and in due course the elevator, servos wires through the centre section.

LhUnder.JPG.accb4ab6463c71a1f1cb622c4bf2c7cd.JPG

The quality of the final surface finish will depend on the paint and how many layers of it the all up weight can stand but the initial target is to get it to see how ell it flies with its bifurcated ducting.

 

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The other wing glued on.

Wing1.JPG.1c5e2b125bdc228e861c249a589943e6.JPG

With a 24" steel rule for size.

It is resting against the radiator like that because the RH wing has only just been glued on. It will have to rest like that for 24 hours.

Structurally the centre section is now complete apart from the open panels on the under side.

With the EDF and the aileron servos it weighs 233 g.

My target is 550 g ready to go. 

Rear fuselage section next. 

Edited by Simon Chaddock
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A start of the rear fuselage.

The radii involved are rather tight for 5 mm thick material even using many narrow planks.

One side complete ready for the other half of the formers to be added.

RearFuse1.JPG.abed788a5ae262f6d0a97458e12bc225.JPG

It is likely to require a bit of sanding and light weight filler.

At least the positions of the tail plane and rudder are clearly defined.

The really tricky bit will be to get the exhaust fairings to match up perfectly with the exhaust duct itself. I suspect the proximity of the fairing to the exhaust air stream will only add to the losses already created by splitting the duct.  

 

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The rear fuselage complete - almost.

RearFuse2.JPG.a721b82e6fd7c3610ef685128335b28e.JPG

The next big problem is making it fit the centre section. My normal method i to completely remove one former and then slit the skin in several places so each section can be 'adjusted' to make a smooth joint. Might not be so easy to do with such a thick skin.

The particular area of concern is ensuring the rear fuselage exhaust fairings exactly match the exhaust ducts. The exhaust will be moving fast past this areat so it needs to be smooth and exactly the right profile or there is a risk even more precious thrust could be sacrificed. ?

Joining sections was much easier with a simple cylindrical airliner fuselage!    

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After what seemed like a full days work the rear fuselage is mated to the centre section but as I feared it required quit a bit 'adjustment'.

To get the exhaust areas to line up required a 5mm wide 120 mm long triangular 'gusset' to be inserted in the bottom of the rear fuselage.

RearFuse5.JPG.64cc684962d658a7dc1f8ff61479ba7d.JPG

Perhaps even more alarming was the top line of the rear fuselage was not correct which required a substantial section to be cut out, sanded down and glued back in, hence the three strips of making tape whilst the glue sets. ?

RearFuse4.JPG.62bb4b5ab8460bd37d06382cc9bb6b9b.JPG

 A situation where the 5 mm thick skin was a distinct advantage.

Tail plane and fin next but rather than 5 mm XPS they will use 3mm Depron skins to achieve anything like a scale thickness.

 

 

 

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The skin components of the fin, tail plane and elevator cut out in 3 mm Depron.

966470066_3mmFinTail.JPG.cbb27e829821f70e2fd0ed284906f054.JPG

Although the tail plane has a tapered shear web it is too flexible so will be given the Ezedope/tissue covered treatment as will the elevator halves to give anything like an appropriate stiffness.

The fin should be ok being smaller, thicker and in part supported by the fuselage.

The fin and tail plane have a substantial streamline 'body' which will have to added later.

TailBody.jpg.027e2f155353b97124179f8809d9ae1f.jpg

   

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The tail feathers assembled and glued into position.

TailOn2.JPG.c3098ce6cb32c903b6b079cef601840b.JPG

The elevator halves are joined by a glass fibre tube.

TailOn3.JPG.bb9d70e9466e6572000d209567a6b09c.JPG

The elevator servo is positioned in the fin under the tail plane.

The RH wing has been given a light coat of "Dark Flint" to see what it looked like. It should be "Dark Sea Grey" but they don't do that in a match pot!

 I suspect it will need a touch of blue to get something like the right shade. Emulsion paints give a full matt finish but I do have a big aerosol can of Clear Acrylic Lacquer but it has to be applied in many thin coats to avoid it eating the foam.?

fuselage nose next.  

Edited by Simon Chaddock
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The beginnings of the nose section.

Built like before as a half shell over the plan. With only 3 formers each plank has to very carefully shaped, formed and twisted with the fingers so it can be glued in place with the minimum force on the structure.

Here the half shell has been lifted from th eplan and the other half of the formers added ready to start planking the other side.  

FrontFuse1.JPG.8fe6587df17a72a9e00b091419d7bf88.JPG

It is made a bit more complex to build as the cockpit canopy will be built on separately and later cut off to act as a battery hatch.

Reasonably happy with the final result.

NoseOn1.JPG.81b24af99fc1c7836e15f9cab0af96f7.JPG

Note the printed nose cone.

Sidney Camm definitely did a good job creating a streamlined fuselage around the big diameter of the RR Nene.

Although it is entirely made of the 5mm foam with no reinforcing anywhere the substantial diameter of the fuselage and the big wing root fairings give it a remarkably 'rigid' feel.

How well it flies is all going to come down to the thrust to weight.

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The cockpit canopy/battery hatch.

Canopy1.JPG.46e871b51bbb3a503fe7583f31dca1bd.JPG

 

Canopy2.JPG.b1d08e090d2d1501620602f65cc8ffdc.JPG

The very soft surface of the XPS foam is significantly 'hardened' by the emulsion paint and clear lacquer so unusually for me it will be painted before the maiden.

A start on the painting. The pale underside will need two coats over the grey XPS.

Paint1.JPG.e6d3dbc038550ff6ca66ffbcacd95dd4.JPG 

The underside is sky blue but the camera does not see it in artificial light. The tail is yet to be painted.

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With just some very minor touching up the painting is complete including some not quite correct decals.?

07May21a.JPG.3a29099a331968e58bc75a3b132da791.JPG 

It has been sprayed with clear lacquer to give a 'sheen' finish to replace the full matt of the emulsion paint.

07May21b.JPG.3061d0c153901e9c4c4e57619e19a863.JPG

The lacquer also hardens the very soft surface of the XPS foam.

With just the rx to be fitted it weigh 483 g including the 1500 mAh 40C 3s so it is well with my target of 550g.  

 

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Thanks each for the kind words.

The ultimate test before its maiden will be 'nose down' at full power on a scale to determine the thrust and compare that to its weight. ?

 

I almost wish now I had built the one off P1052. A Sea Hawk with swept wings.

P1052.thumb.jpg.c904ae52e7324ef1fe97d9953a86d5c1.jpg  

First flown in Nov 1948 you can certainly see where the Hawker Hunter Came from. 

Edited by Simon Chaddock
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A full power test in 'ready to go' condition gave the following results.

492 g all up weight

36.3A peak

335W peak. That equals 334 W/lb!

349 g thrust (70% T/W)

 

These figures do rather confirm the poor efficiency of the fully bifurcated duct. Even for an EDF 334 W/lb should give a sparkling performance with a thrust to weight close to unity.

I will just have to hope its clean aerodynamics work adequately with the thrust available.  ?

 

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 Its true maiden flight required almost full down elevator so it was seriously short but landed ok with no damage.

I judged the decalage was too great. not that surprising as it had only been set by eye.?   Obviously I could do nothing about the wing incidence but adjusting the tail plane would be easier.

So the underside of the tail plane was cut free and a narrow foam wedge glued in.

Tailinsert.JPG.bf42da823f321008690732fe00a249eb.JPG 

The foam of the fin had enough 'give' to allow the change.

Just to be safe I had intended to use a heavier 1800 mAh battery but in the rush to fly in the evening calm (21:30 hrs) I forgot and recharged the original 1500 so it was slightly tail heavy. This was its second ever flight.

https://www.youtube.com/watch?v=NgYjJjTJLEw&t=4s

It actually has adequate thrust and flies quite nicely at reduced power. It glides really well making a 'glide' approach quite simple.

As you can hear on the video I was approached by some teenagers whilst I was flying who started asking questions about the plane! It even attracted a "that's cool" on landing. 

As I expected even with throttle management the 3 minute flight took the battery down to just below storage level.

Hopefully some aerobatics next. 

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Thank you all for the kind words.

It has indeed ended up better than I ever expected.

This mornings video but this time with the 1800 mAh 3s which gives a better CofG.

https://www.youtube.com/watch?v=BeOw6Q7DdOc

I still get caught out by just how well it glides. The entire approach was power off and nearly ran out of field!  

Edited by Simon Chaddock
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