A Depron Harrier

My Valkyrie has a relatively big (70mm) EDF feeding through a large volume 'plenum chamber' to 6 individual nozzles so why not the same sort of arrangement feeding into 4 as in the Harrier?
The nozzles themselves would of course be rather more complicated (and less efficient?) as they also have to turn the air through 90 degrees but by using a plenum chamber (the empty fuselage?) there would be no complex ducting.
The question is would the simplicity and light weight of the construction compensate for the relative inefficiency of the ducting and nozzles?

At this stage there is no intention to vector the nozzles but simply to create a scale EDF

But before anything a simple 4 nozzle test rig using a 55mm fan (I have one spare) to get an idea of how it actually performs.
The 55mm fan has a FSA of 1761 sqmm which suggest for maximum static thrust each nozzle should have an exit area of 440 sqmm.
I am pretty sure that in the design of the Harrier type nozzle the effective outlet area is actually smaller than its inlet.

In other words it is a true 'accelerating' nozzle as well as a 90 degree deflector. I shall have to do some 'guestimating' to work out the relative areas.

This will all take some time and may of course come to nothing!

i have often thought about the harrier.
rotating nozzles is the easy bit, its getting enough thrust and the puffer jets.
but if anyone can do it, it will be you sir.

But as I said

At this stage there is no intention to vector the nozzles but simply to create a scale EDF

If there proved to be sufficient thrust to even consider any 'hovering' an alternative to puffer jets would have to be used as there is simply insufficient pressure.

But that is still a long way off.
In the mean time a nozzle test rig in under construction

The nozzle test rig under construction.

The 55mm EDF goes in the front.
A simple circular Depron 'chamber' to resist the internal pressure.
One Depron nozzle installed. It has a single aluminium vane.

Viewed from above.


Just a first attempt at this stage but it has given me some ideas to try out
.

Exciting stuff Simon!

For info and interest, there are 8 puffers on the Harrier: two at each wing tip (one pointing up and the other down), one under the nose, one under the tail and one either side of the rear fuselage.

In normal V/STOL manoeuvre, only the wing-tip down puffers are used. The wing-tip up puffer only comes into effect at large control column deflections when higher roll forces are demanded.

The design of the nozzles is going to be the key.
I have just bought some (I though rather expensive!) Litho plate to make the next set of vanes with.
The vane I made was from a PC processor heat sink and was a bit thick.

The 'flying' version will of course be a bit bigger as it will use a 70mm fan rather than a 55.

A bit of a change in direction (pun intended!)
Rather than a simple plenum chamber the next nozzles will be part of a specific internal duct directing the air flow.

The first part is this is a test nozzle with a double cascade using the 0.015" litho plate. It is built square for simplicity.
1/4 of the air flow from the fan will be directed to the first cascade which turns it 90 degrees.

The second cascade turns it rearward again and at the same time reduces the area so the sum of all four nozzles would have about 90% of that of the fan.

The cascade vanes are fixed in place with cyano.
Despite the metal it weighs only 1.7g so even four is not too much of a weight penalty, however the loss of thrust it causes may be a bigger problem.

Yes but it has been edited!

The completed 2 nozzle test duct with the 55 mm fan.

It shows the basic principle involved but of course the duct will have to be rather more complex to feed 4 nozzles.
This is really only the first 'proof of concept' as the combined area of two nozzles is only 54% of the FSA but it does seem to blow quite a bit of air and you can certainly feel the thrust it generates.
Only just a couple of brief proving runs so far but it is incredibly noisy!
Some more testing required before moving onto a four nozzle version.

The twin nozzle on its thrust test rig.

The extreme noise was largely down to a very out of balance fan. Now put right with the aid of my magnetic prop balancer.

It delivers 9.1oz thrust drawing 20A. It weighs 7oz.
The fan stand alone is supposed to give 15.3oz but this figure seems questionable. I will have to take the duct off and test it.

Next is a four nozzle version.
With a combined nozzle area closer to the FSA it should give a bit more static thrust.

The basic fan by itself in the same rig produces 18oz thrust.

Although the twin nozzle duct only generates half this thrust it is not as bad as it might seem as its nozzles only have 54% of the area. This suggests that the losses due to the complex ducting are not that severe.
This will be tested by the four nozzle version that will have the full fan area.

The four nozzle unit will also be built with the possibility of it actually being flown in a simple box type airframe.