2020 V-1 rebuild

[Simon Chaddock]

A very long time ago (2013) I built a V-1 or rather the US copy Republic JB2 Loon out of Depron and powered it with a 55 mm EDF in the pulse jet.

It flew pretty well and survived the odd crash until I took it this year to the September DVMFC fly-in.

It was pretty windy and was late in the day before it had died down enough to even consider flying my lightweights.

The first flight did not last long about 20 seconds and it ended up like this.

I decided it was too far gone so I salvaged the the wing, tail plane and pulse jet.

They were all consigned to the attic mainly because I hate to throw anything away.

Then of course the second lock down arrived and with not much else to do I deduced that if I used printed fuselage formers rather than Depron ones I would have enough 3 mm Depron to rebuild the fuselage.

I still had the original plans so I had all the required former dimensions.

The first fuselage was built full length as a 'half shell' over the plan but this time I decided to build it in 5 complete sections vertically!

First a test former. It is the largest diameter former at 150 mm (6 in) diameter.

It has a 'U' channel section 20 mm wide with 3 mm flanges..

Then it is just a case of printing. The rear fuselage 'stack.

There will be a further sets for the final tail cone  as well as the fuselage middle, forward and nose sections.

I was beginning to see why I had originally chosen to scrap it!

Edited By Simon Chaddock on 27/11/2020 01:13:47

[Colin Leighfield]

You do like a challenge Simon and why not? I hang onto my wrecks for future resurrection. They go back forty years or so!

[Simon Chaddock]

Other things did get in the way but progress was made.

First the rear fuselage built in my usual "unusual" style, vertically!

 

Its very empty inside.

The biggest former has been removed so it can be joined to the centre section with an internal overlap.

The centre section is built slightly differently using the wing as a support with some temporary jury struts.

 

 

The planking goes on and the jury struts removed..

The end result is strong, rigid and light but will be extra ordinarily difficult to repair.?

A short front section is also required but as the fuselage is completely hollow front to back it is safe to join then all together.

 

The extreme front and rear fuselage sections will actually have stuff inside them so are bit more complex to make. 

 

Edited April 1, 2021 by Simon Chaddock

[Dwain Dibley.]

Amazing stuff Man.

D.D.

[Colin Leighfield]

Looking good again Simon!

[Simon Chaddock]

The fuselage tail end section was built like the wing using the tail plane to support the formers.

As it was a 'straight' cone each plank was a simple taper although a large section had to left open on the underside to allow the pull/pull elevator to be connected.

Note the printed tail cone.

The  tails section is then glued to the fuselage and the fin glued in place. Like the tail plane it has a symmetrical section with 3 m Depron skins.

Note the printed EDF support 'spar' It will be streamlined with a Depron skin. 

Finally the original undamaged EDF 'pulse jet' is added.

 

Held in place by tape until the glue hardens.?

The nose is a bit more complex as it contains the elevator servo, the ESC, the Rx and of course the battery.  

[Simon Chaddock]

The nose is built as a 'half shell over the plan' but as the fuselage is completely symmetrical the half can be used as the lower half.

This gives excellent access to install the elevator servo, build in the battery box, mount the ESC on the right side and the Rx on the left.

Then make good the skin and finally a battery box hatch and its back to hanging on the wall - along with quite a lot else! 

Now just wait for suitable weather.

After such a major rebuild it will in effect be a new maiden on a plane with a mid mounted wing with a true symmetrical section that has no dihedral or washout. ?

[J D 8]

        In the last pic I just realised how large your model is, hope it goes well.

       The full size V1 did not have ailerons and did not have any dihedral so how was it laterally stable in flight? [ can not have been very as fighters could tip it into  dive ] and how did it steer with only rudder given the lack of dihedral ? Just asking out of interest. Cheers, John.

[Simon Chaddock]

John

I think my V-1 is long rather than large!

There tends to be a bit of a misconception about lateral stability and dihedral.

A wing with no dihedral will still bank when yawed simply because the 'leading' wing will be slightly swept forward to the airflow. This reduces the tip losses slightly so there is a net gain in lift. The opposite occurs on the 'trailing' wing so a bank is created. The effect is modest and it only works if the wing is truly aerodynamically symmetrical left and right. I believe this was an issue when the V-1 was in mass production particularly when unskilled 'slave' labour was used.

As you suggest 'tipping' a V-1 was possible simply because of the limited roll authority and coupled with the fact that if a sudden and significant roll input was put it the gyroscope would 'topple' loose the heading so there would be no recovery input. I understand the V-1 gyro was capable of gently manoeuvring the plane to a predetermined heading up to 30 degrees from its launch ramp path.

 

[J D 8]

Hi Simon, Was the Loon just a copy of the V1 or were there any improvements like ailerons ? I also read of in the past of a follow on project called Regulus which I think was jet powered. John.

[Simon Chaddock]

John

The Loon was to all intents and purposes an exact copy re-engineered by Republic Aviation to US standards. The US ordered 40,000 to be used prior to the invasion of Japan. The ailerons are my innovation to allow it to operate as an RC model and undertake manoeuvres well beyond that of the V-1!

The Loon airframe was built by Willys Overland, the pulse jet by Ford. Over 1000 had been manufactured by August 1945 when the order was cancelled following Japan's surrendered after the Atomic bombs.

The stock of Loons were thus used extensively post war to develop radar/radio guidance systems both air dropped and submarine launched. It played an important part in the development of the US Matador turbojet powered cruise missile.

The US undertook a development programme to increase the Loon's range which was limited by the 20 - 25 minute life of the pulse jet's inlet shutters. The original Argus developed system was not improved on.   

[J D 8]

 Thanks Simon, all interesting stuff.

[Simon Chaddock]

The weather has been just about kind enough to try a flight after the rebuild. It did not go too well! ☹️

The motor kept cutting out (ESC overheating?) which coupled with its high thrust line and a slightly rearward CofG made things a bit of a nightmare.

Each motor cut resulted in a serious porpoise. Got it almost on line to land and the motor cut but this time to low to recover from the porpoise so a nose plant!

The Depron stressed skin did it usual brilliant job of absorbing the impact. Nose completely crushed for the first six formers but no other damage.

  

Build a new nose - simples!

 

Once skinned this became the lower half of the new nose giving easy access to add the top half formers and build in the battery box.

To address the CofG problem the battery will go right forward into the nose cone.

Next was the question of why was the motor cutting out. A quick a meter check gave the answer 36A at full throttle and I am pretty certain it is a 30 A esc.

To make sure it will be replaced by a 50A that has a 'fingered' heat sink that protrudes into the slip stream.

The Rx is mounted on the fuselage side.

Not that much more to do. ?

  

 

 

[Simon Chaddock]

With the final bit of skin added, a battery hatch, a bit of sanding and a light wash of white acrylic it is complete - again!

If the weather says calm(ish) I hope to try it again tomorrow.

 

 

Edited April 14, 2021 by Simon Chaddock