Soyuz 1/50 build

[wrad]

Thank you for the reply and your detailed build report. I refer to it often to help with my build. Here is a picture of the Upper Stage & Vostok spacecraft that I 3d resin printed.

No problem, it would be great to see more soyuz/r7 builds flying, so anything i can do to encourage people i will as they are somewhat intimidating builds.

That is one rely nice looking print! love the amount of detail in the model.

 

[grafgulch]

gave version 2 of the spider a go tonight in the dark tonight and it worked perfectly.

link below

[video=youtube;z1S7eMiKu7g]

Hi WRAD, can you share your dimensions of your spider ignition system? I built one out of 4” pvc coupler with 3/8” plywood top and bottom. i tested it 2 times and the first time it blew out the bottom and second time it blew out the top. How much space do you have between the top and bottom? Thanks Paul

 

[wrad]

Hi WRAD, can you share your dimensions of your spider ignition system? I built one out of 4” pvc coupler with 3/8” plywood top and bottom. i tested it 2 times and the first time it blew out the bottom and second time it blew out the top. How much space do you have between the top and bottom? Thanks Paul

The internal dimensions of mine are about 120mm in diameter and 30mm in height. The brass ignitor tubes were all 6mm OD tubes.

Are you using pyrodex or BP for it? in this application pyrodex is far more effective as you want a burn not a pop. I cant remember exactly how much I used but I think it was a couple of grams of pyrodex p, just loosely held in a cup within the ignitor.

 

[grafgulch]

The internal dimensions of mine are about 120mm in diameter and 30mm in height. The brass ignitor tubes were all 6mm OD tubes.

Are you using pyrodex or BP for it? in this application pyrodex is far more effective as you want a burn not a pop. I cant remember exactly how much I used but I think it was a couple of grams of pyrodex p, just loosely held in a cup within the ignitor.

Thanks.. I am using Pyrodex RS and I put in about a teaspoon amount. Also, I am using the plans for the igniter from Meatball Rocketry as a go-by . PVC Spider - Meatball Rocketry . The inside dimension on mine is 115mm dia. x 18mm. Maybe I should increase the inside dimensions?
For the ignitor tubes I am using 5/32" brass tubes and slipping in 1/8" tubes as suggested in the Meatball Rocketry plans.

 

[wrad]

Thanks.. I am using Pyrodex RS and I put in about a teaspoon amount. Also, I am using the plans for the igniter from Meatball Rocketry as a go-by . PVC Spider - Meatball Rocketry . The inside dimension on mine is 115mm dia. x 18mm. Maybe I should increase the inside dimensions?
For the ignitor tubes I am using 5/32" brass tubes and slipping in 1/8" tubes as suggested in the Meatball Rocketry plans.

That all sounds relatively similar, your brass tubes are a bit smaller so probably a higher pressure build up from that. Are the plywood top an bottom just glued into place? might be worth adding some screws through the pvc into the plywood to add some more mechanical strength if you havent already, and adding thick fillets of epoxy.

 

[grafgulch]

That all sounds relatively similar, your brass tubes are a bit smaller so probably a higher pressure build up from that. Are the plywood top an bottom just glued into place? might be worth adding some screws through the pvc into the plywood to add some more mechanical strength if you havent already, and adding thick fillets of epoxy.

Thanks, Last night I did realize that the tubes I used where not the right size. I will try adding a bit more mechanical strength too>

 

[grafgulch]

Good day wrad,

I have another question for you. Do you remember what "margin of stability" you used for your Soyuz? I am getting close to launching my prototype Vostok. My plan it to start with a stripped down version, without all the fiddley-bits and no paint just to make sure this thing will fly before I build a more detailed model. I am trying to get the CG in the most optimal spot. Short & fat models like the Vostok are hard to make stable.

Thanks,
Paul

 

[wrad]

No idea on the margin numerically. The problem regarding the Cp isnt just that its short and fat, the whole shape is far to complex for basic modelling. I was advised that Cg in front of the side booster tips (for the soyuz anyway) is normally stable. I spin tested mine and adjusted the Cg until I was happy, and my tests agreed with that advice.

 

[grafgulch]

No idea on the margin numerically. The problem regarding the Cp isnt just that its short and fat, the whole shape is far to complex for basic modelling. I was advised that Cg in front of the side booster tips (for the soyuz anyway) is normally stable. I spin tested mine and adjusted the Cg until I was happy, and my tests agreed with that advice.

Thanks.. I did spin test mine. I going to try and replace my ripstop nylon parachutes with some home-made mylar parachutes to save some weight. I am getting close to launching my prototype.

 

[5thDay]

I was very concerned about CP and other stability measurements with the prototype build for my 1:17 scale Soyuz which was roughly 1:40 scale.
The difficulty in modeling such a bird in OpenRocket, (pre recent beta) led me to doing a single motor test flight with all stages secured together. The attached video clip led me to a few conclusions:

The R7 design is remarkably stable, at least through stage 1. Perhaps the various diameter changes or the way canted boosters and tiny fins work together.

I needed a LOT more weight and a LOT bigger scale if I wanted to do a more accurate cluster launch.

The video is real speed on a F72-10. Everything was recovered except the shroud and launch escape tower. I didnt have near as much detail on the model as you do so am only commenting on the naturally stable configuration without any nose weight.