An EDF Fieseler Fi103 - the V1 - in Depron!

[quorneng]

Most EDFs have to compromise the size of the inlet and exhaust ducts to generate sufficient thrust to fly.

I estimate that using the super light weight Depron techniques I used on my Bachem Natter it would be possible to build a V-1 big and light enough to fly using an EDF in a scale duct.

First a 3 view

This is really all you need as all the 'sections' are circular.
Draw out the Argus pulse jet.

Expand and tile print to give a 55mm duct to match the EDF.

Placing the EDF right at the front of the duct allows its full bell mouth to be retained which gives maximum static thrust. The unknown factor is how much of the claimed 17oz thrust will be lost by that long exhaust duct.
My target is to build the complete V-1 (61" long, 42" span) as close as possible to 16oz.

The first Depron planks go on.

The 'plug' is a cardboard drawing tube covered in sticky backed plastic.

[quorneng]

The inner duct complete with the EDF mounted.

That fan looks an awful long way away down the duct!

The Depron formers for the outer skin around the EDF.

The 2mm Depron outer skin planking is started.

Unlike the parallel inner duct here each plank has to be shaped to fit - and there over 30 of them to do!

I will not make a start on the rest of the V-1 until I have an idea of the actual thrust that is available. The Argus Pulse Jet may be the only bit that gets built!

[pmullen503]

Subscribed!

[quorneng]

The completed pulse jet.

It weighs 4oz complete.
The first power set up just to prove it actually hold together.

The next problem was how to measure the thrust with nothing to fix anything too. The solution was remarkable simple, stap steel plates to the outside until it would just 'hover' when held vertically.

At an all up of 14oz it would just rise try to rise up through my hands.

So if I can keep the complete v-1 close to 16oz it should fly well enough.

[CHELLIE]

Originally Posted by quorneng

Most EDFs have to compromise the size of the inlet and exhaust ducts to generate sufficient thrust to fly.

I estimate that using the super light weight Depron techniques I used on my Bachem Natter it would be possible to build a V-1 big and light enough to fly using an EDF in a scale duct.

First a 3 view
Attachment 166329
This is really all you need as all the 'sections' are circular.
Draw out the Argus pulse jet.
Attachment 166330
Expand and tile print to give a 55mm duct to match the EDF.
Attachment 166331
Placing the EDF right at the front of the duct allows its full bell mouth to be retained which gives maximum static thrust. The unknown factor is how much of the claimed 17oz thrust will be lost by that long exhaust duct.
My target is to build the complete V-1 (61" long, 42" span) as close as possible to 16oz.

The first Depron planks go on.
Attachment 166332
The 'plug' is a cardboard drawing tube covered in sticky backed plastic.

Neet project I dont think you will loose very much thrust if any with a longer exhaust duct , in fact you may gain a little thrust if the duct is the same dia from front to back, you may need to use ailerons because the rudder is rather small, Good luck to you on your neet project, Chellie

[CHELLIE]

with a tappered down exhaust it will give you more speed

[quorneng]

With hopefully adequate thrust work can start on the fuselage.
The tile printed plan.

For such a light plane it is quite long.
For the Natter I used simple ring formers cut from 3mm Depron. Although quite adequate to support the fuselage skin they were susceptible to crushing from a point load, typically your fingers on launching or a tuft of grass on a belly landing.
Solid formers would resist crushing better but would use 2 or 3 times the material
Ring formers are retained for the V-1 but even thinner (2mm Depron) however each has a 9mm flange on its inner edge.
The 6 formers of the fuselage centre section.

In conjunction with the skin each former in effect becomes a circular 'I' beam.
Soo far so good.

[soarrich]

Interesting project.

[quorneng]

The fuselage centre section complete.

A rather bland looking cylinder but actually it is barrel shaped.
The inside looks more a section of a nuclear submarine!

It weighs 1.3oz (37g)
The long tail section of course tapers to zero to will be built in two further sections to reduce the taper required on each individual plank to reduce the cutting wastage.

[pmullen503]

Beautiful work. Were the formers slipped over a tube again to hold them straight while planking?

[quorneng]

As each former has a different internal diameter it is not possible to use a centre tube.
The sections are built vertically, starting with just two planks.

The set squares are used to ensure it is symmetrical.
Of course it is terribly 'wobbly' to start with and the planks have to added equally on opposite to keep it true. Once about 30% of the planks are on and the glue set the structure is rigid enough to be handled and the planks added 'free hand'.
Each fuselage section is done the same way.

There will be 4 sections in the complete fuselage. The wings and tail will be installed in the appropriate section and 'wired up' before any are joined together.

It is not a construction method for the faint hearted!

[quorneng]

The three sections of the fuselage built so far.

The tailplane is built up with 2mmDepron skins with a hard balsa spar.

The tailplane with the elevators in position.

The elevator is round nosed & centre pivoted with balsa shrouds fitted to the tailplane.

The 5g elevator servo will be mounted on the tailplane itself but completely hidden inside the fuselage.

[pmullen503]

Nice way to do the stab and elevator. Did you glue the balsa shrouds on before of after the depron is folded into shape?

Your planking skills are phenomenal but I'm curious as to why you didn't just pre-form the depron into shape and use fewer, wider planks/sheets of depron?

[quorneng]

The balsa shrouds when on before the elevator was fitted and were square section but sanded to shape in-situ with a piece of sand paper with the same profile as the elevator leading edge.

This construction method rather relies on the planks applying virtually no load on the structure hence the rather small planks. It is actually not that difficult to do although rather tedious!
Wider pre formed planks would have to be very accurately made both in radius, taper and bend not to load the structure.

The tailplane and elevator under test.
https://vimeo.com/60609184

[quorneng]

The two fuselage tail sections joined.

This is always a bit of a test as it s the first time you can really tell if they fit and follow the same contour!
The fin and rudder.

Actually the fin is fixed. It will be a 'bank and yank' plane.
A start on the wing.

A full depth balsa/Depron/balsa box spar with a constant taper to the tip.
The wing will be fully skinned in 2mm Depron.

[pattern14]

Just to add in, I used a long cheater hole underneath the pulse jet tube between the mounts for my 70mm V1 made from EPP, a couple of years back. It flew really well until being claimed by the forest at the end of the block. They are actually quite airworthy, but I used ailerons and not rudder on mine. Good luck with the "honest" version

[quorneng]

The lower wing skin added and the aileron servo.

The aileron is tape top hinged with a short servo link with mechanical differential. With th eservo in place the wing is no longer truly symmetrical so this is the LH wing.
Once the servo is tested the top skin goes on.

Each wing plugs into a hollow box spar running across the fuselage.

The wings will be glued in so in effect the spar will be one piece tip to tip.

[quorneng]

Once the fin is in place the pulse jet can be added and the centre section of the fuselage added.
It starts to actually look like a V-1.

The nose section will have to be added to get some idea of where to put everything to achieve a suitable CofG and then it will have to be cut open again to finally mount them!

[mclarkson]

Crazy project! Best of luck.

(Once you finish it, you need to find someone with a Hurricane to chase you down. )

[pmullen503]

Looks great!

[quorneng]

I don't think a Hurricane would ever catch a V-1 but a Tempest could & did! (638 in total)

[quorneng]

The final bit of the fuselage under construction.

The former next to the joint is a dummy just used for construction.

It will be completely removed.
The matching former on the fuselage centre section has a small flange to locate the skin of the nose section and to provide additional glue area.

Compared to balsa Depron is fairly flexible so on a pure monocoque like this it is important to spread the stresses over the entire skin particularly at the join.

The nose will have to fixed in place to get a idea of where to mount the radio, ESC and battery. I expect it will be right at the front. The nose will then have to substantially cut open to gain access to mount them.
It will then have to closed up again but leaving just a battery access hatch.

[pattern14]

Looking great there Quorneng. I used no dihedral on my first one, but the wings were heavily modded glider wings from my original St330 "Easy fly". The sailplane specific airfoil section greatly assisted the flat glide with the power off, although I still wonder if it would have done better with the tips tapered, instead of cut "square". No dihedral meant it needed some input instead of hands off. The next 70mm version (that I am still working on a year later), uses a styro foam fuse with very thin EPP sheet as a skin, coreflute tail feathers and beer coolers joined end to end for the pulse jet. The wings are custom built competition glider wings from Canterbury sailplanes, that a customer decided not to use. I picked them up as factory seconds for less than the price of buying a block of foam. They are almost perfectly shaped for the V1, which is a total fluke. Hopefully she will go together over winter......Lokking forward to seeing this one fly soon.

[quorneng]

The tail plane is made up of upper and lower 2mm Depron skins over a hard balsa spar.

The complete tail plane with the elevators in position.

There are no ribs.
The elevators are round nosed with a small triangular balsa 'shroud' to cover the gap.

The elevator are joined with a glass fibre torque tube and each half is centre pivot hinged at each end, making 4 pivots in all.

The tips of the tail plane are completed with a 6mm Depron block sanded to shape.
Almost perfect scale, light and very free moving.

[NitroCharged]

Looking real good there! Been following from the start.