My first EDF

[Quorneng]

Having built and modified a number of own design planes out of sheet foam I wanted to try a scale jet.
The forums generally considered scale EDFs to be fast so either had to have under carriage along with a suitable take off surface or some form of catapult launch.
My planes so far were significantly lighter than average and further had to be hand launched as my field is rough grass. Could I make a scale EDF jet light enough to be easily hand launched?
First to select a suitable plane. The Douglas Skyray seemed suitable as a delta it had plenty of wing area with a modest span and the design philosophy was to cram the biggest turbo jet into the smallest airframe.
The fuselage thus had a considerable internal cross section for any given size so was there a possibility of using a ducted prop? If the prop diameter is maximised for the fuselage cross section it would likely produce a similar static thrust to an EDF but be considerably lighter. It would not have the same high speed capability but for a light weight that would not be an issue.
The duct was built using foam planks around a piece of plastic drain pipe with an external diameter of 116 mm (4.5").

When complete the appropriate formers were added.

Next came the forward fuselage.

Also skinned with foam planks.

When the planking was complete the nose was "inserted" into duct

The inlet duct were then slowly built up.

The pusher motor mounted in the fuselage tail cone.

Finally the basic fuselage complete

By comparison the wings are relatively simple. Top and bottom one piece skins with 2 spars.

The wings are simply glued onto the fuselage like a plastic kit!

The top skin is left off until all the electrics are installed. After many finishing bits it is painted

The only non scale features are the bigger inlets and exhaust cone to suit the needs of the 4.4x7 coarse pitch prop.
With a 1500mAh 3s LiPo in the cockpit it weighs just under 18oz (500g) and flies very well.

Its success set me off building another plane using the same ducted prop principle but that's for another post..

 

[Doom!]

I used to have a Skyray, awesome flight characteristics. Yours looks fantastic! I wish I had the time to build from scratch. The sky's the limit!

 

[Quorneng]

As mentioned its success prompted me to build another using the same ducted prop principle.
The Skyray has a generous fuselage for its wing span but convention jets tend not too.
In the 1950s with limited thrust available "area rule" was important to reduce transonic drag. This usually resulted in a fuselage bulge at the wing trialing edge. Would this help in the installation of a big diameter prop?
I came across a rather nice 1950s Hawker the P1121. This is the mock up.

The prototype was under construction but was cancelled in the infamous Government White Paper of 1957 where ground launched AA missiles took precedence over manned interceptor fighters. Hawker did continue as a private venture for a bit. Amazingly the part complete fuselage still exists in" "storage" but not on display at the Imperial War Museum Cosford.
A 3 view.

Certainly the rear fuselage and huge tail pipe looked to have adequate proportions for a prop. The impressive inlet although big would likely need some more area.
Starting with the same size motor and prop ans the same sort of construction (3mm Depron) as for the Skyray it came out only slightly bigger span and a good bit longer.

Note the additional "cheat holes" above the air intake. Not entirely non scale as there were doors there for the internal storage of missiles.
The biggest issue for me was its all moving tail plane coupled with a rather short rear fuselage!
First hand launch was a bit stressful but it actually flies pretty well. As this video shows it can do aerobatics.

That big underside air intake does rather dig in!
Having proved it was possible it was all true EDFs for this point until a ducted prop as a big airliner turbo fan.

 

[Hobbydude2]

Lookings beautful sexy beautiful!

 

[CertifiedMike]

As mentioned its success prompted me to build another using the same ducted prop principle.
The Skyray has a generous fuselage for its wing span but convention jets tend not too.
In the 1950s with limited thrust available "area rule" was important to reduce transonic drag. This usually resulted in a fuselage bulge at the wing trialing edge. Would this help in the installation of a big diameter prop?
I came across a rather nice 1950s Hawker the P1121. This is the mock up.
View attachment 225612
The prototype was under construction but was cancelled in the infamous Government White Paper of 1957 where ground launched AA missiles took precedence over manned interceptor fighters. Hawker did continue as a private venture for a bit. Amazingly the part complete fuselage still exists in" "storage" but not on display at the Imperial War Museum Cosford.
A 3 view.
View attachment 225613
Certainly the rear fuselage and huge tail pipe looked to have adequate proportions for a prop. The impressive inlet although big would likely need some more area.
Starting with the same size motor and prop ans the same sort of construction (3mm Depron) as for the Skyray it came out only slightly bigger span and a good bit longer.
View attachment 225615
Note the additional "cheat holes" above the air intake. Not entirely non scale as there were doors there for the internal storage of missiles.
The biggest issue for me was its all moving tail plane coupled with a rather short rear fuselage!
First hand launch was a bit stressful but it actually flies pretty well. As this video shows it can do aerobatics.

That big underside air intake does rather dig in!
Having proved it was possible it was all true EDFs for this point until a ducted prop as a big airliner turbo fan.

Beautiful planes!!! Nice landing too!