The Feisler F103 - better known as the V-1

[Simon Chaddock]

Most EDF jets have to 'cheat' and increase the size of the ducts to pass enough air to fly.

The V-1 had a very low efficiency pulse jet and hence a relatively big duct diameter compared to the rest of the airframe but the down side it had tiny wings so had to be catapult launched at great speed.

Using the same Depron techniques I had used on my prop driven Bachem Natter (which had even smaller wings) the challenge would be to build a V-1 light enough to work with the lower efficiency and greater weight of a true EDF.

By placing the EDF unit right at the front of the duct its full bell mouth inlet could be retained within the scale outline but would the losses from the long exhaust duct be too severe?

The first task would be to build the pulse jet itself and measure the thrust provided.

This would then give an indication as to the feasibility of it actually flying.

With a 55mm EDF the V-1 would have a span of 40" and a maximum fuselage diam of 6", dimension not far removed from those of the Natter. That weighs 13oz so the target for the V-1 would be 17oz to take into account the heavier EDF unit and the rather more complex airframe. This would give it a wing loading of 10oz/sqft, again similar to the Natter.

The V-1 airframe is quite aerodynamically efficient but at a rough guess it would still need a minimum of 12oz thrust to stand much chance of flying.

That is about as far as the calculations can go so on with building a Depron pulse jet!

[Martian]

look forward to seeing this project come to fruition

[Ruprect Spode]

The K & A Models V1 has the edf unit mounted at the pulse jet intake just as you have planned. See here **LINK**

Ruprect

[Tangental]

Imagine doing your B cert with a Doodlebug(could always drop it on the examiner if you fail I suppose)

Looks great Simon! Going to bookmark this one

[Sandy Colquhoun]

There were pulse jet control liners in the 60`s, not common, but I saw a few in action at Waterbeach . These days they might be a bit difficult to stick a silencer onto. They do have what you might call presence. EDF can be relatively noisy but not in the same league.

[Simon Chaddock]

The first planks of the inner duct go on the drawing tube 'plug'.

The carboard is covered with sticky backed plastic to prevent the glue sticking.

The completed inner duct with the combustion chamber formers added.

The front of the inner duct has a slightly larger siameter 'joggle' so the inner diameter of the duct exactly matches the inner diameter of the EDF.

That fan looks an awful long way away from the rear of the duct!

[Wingman]

Hmmm! doesn't look right to me, Si, could be a lot of problems with turbulence down the length of the tube and air friction on the sides with resultant loss of thrust - Worth checking how much thrust you're getting before you go any further??

[Simon Chaddock]

That is exactly what I intend to do.

On a 3 cell the 'bare' EDF with no duct is supposed to give 18oz thrust. If I can keep the complete V-1 to 17oz then it should fly ok with a static thrust of 12oz.

The EDF mounting and skin formers.

.

The outer skin goes on.

If all else fails I could just put wings and a tail on the duct!

[Martian]

it's looking good,after reading several other V1 models I don't think you will have a problem with it flying

[Simon Chaddock]

The pulse jet complete.

With so little to fix to I puzzled over the best way to test the thrust.

With a 3000mAh 3s and a 60A ESC it certainly seemed to pull quite hard.

The answer was remarkably simple. Tape steel plates to the outside until it would just 'hover' in my hands. Maybe not accurate but I was only after a rough figure to see if it was worth proceeding.

It just maintained a positive thrust when ballasted to a total of 14oz.

With this level of thrust as long as I can keep to my target of 17oz it should fly well enough but quiet it is not!

[Tangental]

BUZZZZZzzzzzzzzzzzz bomb!

[Simon Chaddock]

Made a start on the fuselage.

Again following the principles I used for my Bachem Natter although in this case it is made up of four rather than three sections.

The ring formers for the fuselage centre section.

The 2mm Depron formers are reinforced with a 6mm wide inner flange so in conjunction with the skin each formers is in effect a circular 'I' beam.

Built vertically with 3mm Depron planks.

Very wobbly to start with but 40 planks later its complete!

From inside it looks more like a section of a submarine hull!

But it is very strong and light.

[Caveman]

Simon, I was browsing and came across this:

http://www.outerzone.co.uk/plan_details.asp?ID=2212

I don't know if you've seen it already, but thought it might be of interest.

GDB

[chris edwards 3]

looks like it should go like a bullet, or rocket in this case

[Colin Leighfield]

When you've finished this one Simon, you'll need to send in your Hamilcar with a squad of Commandos on board to take out the launching ramp!

You've certainly got the knack with Depron.

[Simon Chaddock]

Caveman

Of course using a Dynajet is truly scale but there are not many places that would tolerate the noise!

Cant tell if it was actually built.

[Simon Chaddock]

The fuselage built continues with the two aft sections built in the same way.

Centre and two rear sections.

The tail plane is a simple ribless structure with 2mm Depron skins top and bottom over a hard balsa spar.

The complete tail plane with the elevators in position.

The elevators are joined by a glass fibre torque tube.

Each Depron elevator half is round nosed with a centre pivot hinge at each end giving 4 hinges in total.

A small triangular balsa 'shroud' is added to the tail plane top and bottom to cover the gap.

Almost perfect scale, light and very free moving.

 

Edited By Simon Chaddock on 12/03/2013 13:40:18

[Bill_B]

Excellent project! Watching with interest.

[Simon Chaddock]

The two rear fuselage sections joined.

The wing has wide but tapered 1mm balsa top and bottom spars with 3mm Depron webs between the ribs.

With the lower skin added the 3.7g aileron servo is glued in.

The aileron will be tape top hinged with the short servo link under the wing.

The wings 'plug in' to a matching balsa/Depron/balsa box spar spanning the fuselage.

At 40" span the V-1 will be small enough to be transported complete so the wings will be glued in to give maximum stiffness and strength.

[Simon Chaddock]

With the fin added and the duct on top it is starting to look like a V-1.

The nose section is built in the same way as the others.

The former at the join is just a dummy used for construction. It is completely removed once the planking is complete.

The centre section has a small 3mm sq Depron flange to locate the nose section skin accurately and to provide a bit more glue area.

Only when the fuselage is complete can I judge where to put the battery, ESC and radio to arrive at a suitable CofG.

[Stephen Stokes]

Excelent project and love the light weight design, I too have trawled the internet for a kit or drawings for the V1 but could not find anything so built two from scratch.

See you tube links

I say two as the first was true to form and crashed in spetacular fashion just like the real thing. The second is still flying.

[Simon Chaddock]

Stephen

Very impressive - I only hope mine flies as well.

It looks as if you gave yourself a bit more wing area!

[Stephen Stokes]

Yep added about 100mm on the wind span and increased the cord by 10%. don't think it needed it

[Simon Chaddock]

Before the nose is glued on all the cables have to be secured in the fuselage.

They are long enough to reach right to the nose if need be.

The wings and nose are fixed on thus completing the basic airframe.

So far so good but at this point I realised there was no way I could achieve even a 30% chord CofG without installing a much bigger and heavier battery.

The 'heavy' rear items are the EDF itself and the tail mounted elevator servo.

Obviously I can't do anything about the EDF but the 5g servo is a very long way back. A quick check of the moments suggest that nearly 60% of the weight of the intended battery in the nose was required just to counter balance it.

The obvious solution was to reposition the servo right in the nose with a pull/pull cable system.

The elevator servo extracted.

The elevator itself had to be removed to fit a double sided horn for the pull/pull cables.

The nose was always going to be cut open to instal the battery box, radio and ESC but now had to include a servo.

With all the components placed in the nose it now only required a slightly larger battery (1800mAh) which would push the final weight close to an acceptable 20oz.

[Stephen Stokes]

Try and set the ESC half way between the motor and the battery otherwise you might get timing problems, and don't forget some cooling holes to keep the battery and ESC cool.

On my Mk 1 I ended up with 100g of lead in the nose, Mk2 only needed 30g as I did as you have and moved the EDF unit as far forward as possible and stuck the battiers (2No 4s 5000mAh) in the nose.