Fi 103 - the other V weapon

For the moment I have put the winged V2 on hold.
To be a real challenge it ought to have a true vertical capability and that would not be possible without contra rotating propellers. Himax do a nice range of suitable motors but at a severe price - their smallest is $112!

So its into the "box of frogs" again - an EDF V2!

Its been done before but most, if not all, have had to compromise the scale of the pulse jet to do it. The duct is just too small a diameter for the necessary size of fan.

Using the super light Depron techniques of the Natter it should be possible to build a scale V2 light enough to use a 55mm EDF in a scale pulse jet duct.

With a 55mm ID duct the V2 is quite big, 62" long and 41" span. To give a reasonable margin of performance it should have close to 1:1 thrust to weight which means it has to weigh not much more than 16oz with a 3s or 24oz with 4.
The duct itself is relatively long, necessary in a pulse jet, but just thrust absorbing to an EDF!

I would like to think it can get away with just scale tail control surfaces acting as elevons but I suspect ailerons will be required to achieve a practical degree of manoeuvrability.

First the Argus AS 109 pulse jet.

29" long
With the EDF mounted right at the front it allows a full bell mouth for maximum static thrust and brings the EDF forward to ease the CofG issue.

A plastic gutter down pipe is just the right size as a building plug!

Eric
According to Wikipedia Fi 103 was the Reichsluftfahrtministerium airframe number for the standard V1.

The Fi 103 R was the manned version.

Oops!

I did actually contemplate a V2 EDF with folding cheat doors in the nose but thought better of it.

The first Depron planks go on the Argus duct.

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

That duct looks ever so long for its diameter!

this is handy as i will need to build on of these to go under the heinkel he111 drop plane i have started somewhere.
keep going.

The inner duct complete and off the plug for the first time with the EDF located at the front.

The formers are 'built up' using 3mm sq hoops.
The outer skin will be 2mm Depron planking.
The complete EDF Argus pulse jet should weigh about 4oz.


I have been doing a bit of research and I was relived to find the US copy of the V-1, the JB-2, was built in some numbers (1000) and although never used in combat was painted in bright colours during testing rather than the green and pale blue 'camouflage' of the German one!

Eric
The fan went at the front for two reasons
1. The bell mouth on the fan is not removable so would either have to have been cut off or the tail pipe made larger to accommodate it.
2. The EDF is relatively heavy and the end of the tail pipe is one a heck of a long way back!

16oz thrust is claimed on a 3s. As soon as the duct is complete I shall have to find out how much is lost.

Fortunately the V-1 is aerodynamically quite efficient with a reasonable wing area so I hopefully I can afford to lose quite a bit and still fly.

I suppose if the worst comes to the worst I could always put wings and a tail on the jet and fly that!

The Yanks did more or less do just that with the B-10.

"V-1 meets Me163".
The whole body was apparently a magnesium alloy casting with integral explosive. Presumably it was intended as a fire bomb!
Just one fight in 1945.

The outer skin progresses.

There are 32 planks but unlike the parallel centre duct each has to be shaped to fit!

The front duct support and the fin have to be added then the duct can be finish painted. A sort of metallic grey (any paint would quickly burn off) and matt back inside!

wow, beautifully neat Simon !!!

The duct complete.

The Balsa/Depron/Balsa spar sticking out will be incorporated into the forward mount to support the relatively heavy EDF unit.

As every one knows I'm not an admirer of electric models but I do admire the work Quorneng does. It's inspirational to any scratch builder. Well done mate.

Time to see it it all holds together.
The test power lash-up.

60A ESC and a big 3s. Not the best balanced fan in the world but it shoothed out nicely at high revs.

I wondered how to measure the thrust with nothing to fix to.
A very simple solution. Strap steel plates to the tail pipe until it would just hover at full power when held vertically

At an all up of 14oz it would still just rise up through my hands at full power.

If I can keep the complete V-1 to 16oz it should fly well but the duration will be limited to just a few minutes.
We shall see