Rocket casings, are they thick enough?

[blindreeper]

Today I went to a material supply place and got some of the tubes they roll the material on. They are paralelle wound which is good. They have an ID of 32mm and a wall thickness of 2mm. They are brown papaer stuff and extremely stiff.
I was wondering if they would be good for BP rockets or if they would hold? I am planning on making some tooling for them on a lathe at school. I just want to have a good supply of tubing the right size before I spend money on the aluminium. I think I should make them thicker by wrapping some more paper around them to give them a wall thickness of 5mm or so.
I also got 2m of 17mm ID with 3mm thick walls spiral wound for some bigass salutes :D
There is a small ammount of this so I don't want to make a set of tooling for 10 rockets...

EDIT:
Just one more question on the tooling. For that ID of 32mm what size whould my nozzle be? (so I can make the tooling right)

[Guerilla]

To me, wall thickness of 2mm with that diameter sounds a bit thin, but it might hold as well.. As they might be sturdy enough to take the combustion pressure, thin walls tend to stretch and burst easily when ramming. Glue some layers of kraft paper on them and they will be fine. :)

[Crazy Swede]

A wall thickness of 2 mm is definitely too thin!

A good estimate is that the wall thickness should be at least 20% of the outer diameter, if the tube is made of paper.

[xyz]

Your nozzles for the 32mm ID tube should be approximately 9.2mm wide. Rocket nozzles should be 1/3 of the AREA of the ID of the tube. As all we rocketry enthusiasts know, area of a circle is pi X r squared, where r is tha radius of the tube ID (16mm in this case).

[Guerilla]

Apparently you forgot to tell how long rocket/core you were planning to use.. let's say you're making a rocket that has a core lenght of 180mm. To put this simple, we assume that the core is not a hollow, hence the burning starts from the dead centre of the grain. Also, I let the possible fuel layer that is on the top of the core, out of counts..


When the ID is 32mm and the core 180mm, the maximum burning area that is achieved in the end, is 180mm x 32mm x pi = 18100mm2 (that's not bad eh.. ;)).

Now, let's throw some nozzle diameters on the table, I start with 10, 12, 14, 16 and 18mm.

18mm core has an area of (18/2)^2 x 3,14 = 254mm2
With the same way we get
16mm: 201mm2
14mm: 154mm2
12mm: 113mm2
10mm: 79mm2

When we comparise these nozzle areas with that maximum burning area, we get so called KN-ratios. These ratios will give you some indication of nozzles, where you could start working from.

KN with 18mm nozzle: 18100mm2 / 254mm2 = 71
16mm: 90
14mm: 118
12mm: 160
10mm: 229

With a standard BP rocket, KN ratio should be around 100. So if I were to use that sized rocket, I would start from 15mm nozzles and find the optimal one by trial and error.

Hope this helped a little :)

[Anthony]

If you think that the tube should be reinforced, why didn't you do so and try it?

2mm wall for a 32mm tube is obviously too thin to hold the ~1000psi that motors typically operate at.

Concerning your nozzle related question, why didn't you search theforum or the web?

This thread didn't need making.