Soyuz 1/25... why not ?

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PieroAcme

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I open this thread with the hope of getting suggestions or experience done on similar solutions I have set to allow the building of a scale model 1/25 of the Soyuz.
Soyuz is one of my favourite scale model has unique shape and it is full of detail. I did already a model ... now is almost 10 years ago. It was 1/50,two stages with booster separation. It was originally supposed to fly for 15..20 flights. But It was so reliable to survive 57. Then at RJD 2017 a problem to the shock cord led to parachute separation and then to the crash of the main body. The sad thing is that flight was supposed to be the last. Tube and first stage were quite worn. The idea was to leave it on the shelf as display only. I like the look of the "used" rockets. Unfortunately the repair was almost impossible. So I decide to do nothing... but no rocket on the shelf. My friend Wrad did similar model time ago and in one of his posts he wrote about the possibility of an upscale. This idea start to run in my mind... re-built.. or upscale ? Final answer... Go for 1/25 !
 

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The first problem that pop up when you do a Soyuz with detachable boosters is about lauch rod.
You need some fins to drive the second stage fins need to stay beween the boosters.. Where do I place the launch lugs ?
The solution found was to have launch rod passing trough one of the fins.
Here a picture of model engine view where it is visible the hole in the bottom fin.
 

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Is the last video showing a launch with a mixture of Klima and Estes engines?
Hi Whisky, yes! You are right. With Klima is possible to have C engines in the boosters
D9 Klima burns for 1,8 s like a C6 Estes. With A D12-0 instead the time is just 1,6. When D12 light the upper stage you still have the C6 burning. Because of that I was forced to use the B6 in the 1st configuration.
 
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The system works like a normal Estes staging, but 1st stage hold the boosters in position.
There are a couple of hanging elements (full blue in the drawing) that retain them on the body. When 1st stage fly away the bosters slide down and then are disengaged and free to fall.

We arrive to the first point.
With a scale 1/25 you have to use a rail... The rocket is 2meter height.. and with 20 D engines at first stage.
You must use a rail to lauch and you have to place rail buttons not lugs..
We can't have a rail passing within a fin...

The decision is to go for hidden fins within the bosters. Here below a drawing to show the conceptSoyuz2.jpg
 
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All I’m gonna say is awesome project and go for it.
 
Hi PieroAcme, great to see you back. It looks like we are very much on the same page again, I have been slowly working on a 1/26 scale Soyuz for the last 6 months and had planned to make a build thread.

What motors are you thinking of using? My 1/50 scale was a little under powered due to its weight, so for this build I am going much larger with a central 54mm motor mount and 4 x 29mm motors, so I can build with phenolic tubing, 3D printed parts and some fibreglass and not worry about the weight.

Do you plan to drop the boosters on your upscale? I would love to see how you plan to do so, I haven’t worked this out yet with my build.

IMG_7829.jpg
 
Hi Wrad! Nice to hear you again :)
HuHu, I see you launched the project. Good to see, 4 29mm and 1 54mm... for sure no power problem! I saw you have developed excellent 3d modelling and printing. I'm curious to see how you think to light the engines. With composite engines I don't have an 100% bullet proof igniter for this purpose.

I select 1/25 scale since with this size you can place the 20 engines using the 18mm motors.
I will use 20 D9 and of course booster are detached. Second stages has 7 D9 instead
Here below a draft of the system. Fins are passing inside the booster into a slot. These are also used to hold the booster.Soyuz2finsstaging.jpg
 
Piero, I've seen your scale model videos on YouTube. You're the finest scale model rocketeer this 52 year NAR member has ever seen
 
This system works like the previous one. It has the same mechanical principle. What is new for me in a 2 stage configuration is that the fins will get the air flow only once the boosters go away. I did model with flip out fins, but these were out before the 1st stage is disengaged. This make sure 100% the aerodynamic stabilization. In this case when the 1st stage detach you will have some tenth of second where booster are sliding away before that the fins are fully exposed. Would be good to know if someone has used similar technique .. and if it was working well..
 
One thing important for this project I forgot to write.
Soyuz real height is 51.316mm, scale 1/25 means 2.052mm (6,56 ft).
 
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CIMG0050.JPG

Here fins and slots preparation. Fins are made with plywood veneered with a betulla layer 0,4mm.
 
Hi neil and Mbeels, nice to see that you like it :) . I think it is challenging, since this scale is not my usual one, and resulting rocket size in quite big. It need a different approach in terms of building.
But let's continue. Here the components of the main body.

CIMG0090.JPG

To avoid tube coating with fiberglass or other reinforce material , I decided to go for this solution. It is a coaxial tube with space beween the two tubes filled with foam. This will give the right robustness without having problems in keeping the right external diameter. The sections will be assebled one by one and filled them in the same order.
 
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Here the cones that will cover the boosters.CIMG0753.JPG
When you do a shroud for a scale model normally this is quite easy. Size is quite small and a normal paper 160g/m2 is quite easy to bend and glue. Here the story is a bit different.
To have a good stiffness the paper needs to be thicker. Bend this size of cone ... is not a joke.
Paper need to be pre formed with hot iron to allow the bending, then formed with steam and finally glueing. Initial trial with old technique (just hot iron to bend) was a disaster. Steam froming was necessary to add.
 
Hi Wrad! Nice to hear you again :)
HuHu, I see you launched the project. Good to see, 4 29mm and 1 54mm... for sure no power problem! I saw you have developed excellent 3d modelling and printing. I'm curious to see how you think to light the engines. With composite engines I don't have an 100% bullet proof igniter for this purpose.

I select 1/25 scale since with this size you can place the 20 engines using the 18mm motors.
I will use 20 D9 and of course booster are detached. Second stages has 7 D9 instead
Here below a draft of the system. Fins are passing inside the booster into a slot. These are also used to hold the booster.View attachment 401072

Absolutely fantastic, the cluster of 20 motors will make for an amazing scale takeoff. I had considered doing the same but wanted to attempt a high power cluster, I will be electronically air starting the boosters after the centre, rather than lighting all on the ground.

You have done a great job on those cones. I know how challenging large paper transitions are.

All your progress is inspiring me to do some more on mine.
 
Good solution Wrad. I think that central core first and then booster just after take off is a reliable solution. With some speed the aerodynamic stabilization works and even in the case of a little delay in ignition of the boosters the rocket will maintain the stability. Said in this way seems a joke, but instead it is a good challege since air start of a cluster is not easy at all.
... I'm waiting you thread! I'm curious to see your progress.
:)
 
Here the continuation of the boosters workCIMG0553.JPG
After the bonding of the paper cone, the booster is filled with foam.
You see a column of engines cases , here the explanation. Klima engines have a quite strong ejection charge. The behaviour is quite explosive. Normal tubes cant resist for long. I had problems after 3 flights. Not having thicker 18mm tubes I used a series of cases bonded inside a BT-20 tube.
This tube is necessary to bring the gases from the engine to the side of the tube where is located the parachute without pressurizing the slots of the fins. ( You can see the drawing I posted some messages before)
 
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