1569 replies to this topic

[Phoenix]

Yes, I make shells by dry rolling a paper tube, inserting a card liner, end discs and stars, and then folding and gluing the dry paper to the end discs (and then spiking and pasting). This is the method given on Passfire, and is, AFAIK, the most common way to build a paper can shell. Weingart uses a heavy, wet rolled tube, but he has some very funny ideas about shells...

[BigG]

Italian shells are using non-pasted paper for the inside shell. Some builders do apply strips of white glue along the paper to make it hold better, but it is not a requirement.

Shimizu states 6 turns of paper, while Italian builders seem to go with one turn per inch ID, and similar amount for the pasted paper. It does vary.

On thing I really wanted to note about "this is being the most popular way of building an Italian shell" - this might be the most popular way in the hobbyist arena, but not in the industry. I loved Louis Semenza description of him coming back home with his father and two brothers after a long day in the family factory, and while sitting down for dinner his father mentioned to his mother "ahhh, we had a good day today - we made 200 shells" (can you imagine this? 200 shells a day between a father and three kids in 9 hours?!?!) - and then describing the modern methods that allow his two brothers - now running the factory - to make 200 shells AN HOUR. "My father would turned out in his grave if he saw how it's done today - but at this market, if you want to make the money, 200 an hour it is - and the effect is still pretty good" (well, not this words, but to that effect).

I hope one day we will all meet in the BPS first conference and show the video on a big screen

[Phoenix]

Good point, I suppose commercial operations are done very differently. I intend to get the Semenza video soon.

[paul]

Shimizu states 6 turns of paper, while Italian builders seem to go with one turn per inch ID, and similar amount for the pasted paper. It does vary.

This seems too less for me... For a 3" shell only 3 layers: Wouldn?t that be veryvery thin and instable?!


This video you talked about seems to be really great, so I looked for it at skylighter.com.
The shipping to germany costs 21$ !!! The video itself only 31$. So this is a bit expensive to me...


And another - maybe stupid - question: For larger shells you need very long sheets of kraft paper. Atm I don?t habe access to these long sheets, so I have to use a few shorter papers...

How do you join them, when you make shells?! Simply add a line of glue and overlap them?!
I only ask, because I am not sure if the use of, say 4 sheets instead of one long makes the shell weaker ?!

Edited by paul, 24 March 2005 - 10:53 AM.

[Phoenix]

This seems too less for me... For a 3" shell only 3 layers: Wouldn?t that be veryvery thin and instable?!

The paper used is quite thick - around 70lb kraft. I use my trusty lining paper. the card liner then provides quite a bit of rigidity. Spiking the shell with strong twine ensures a hard break.

If such a shell were loosely filled, then yes, it would be easily deformed and may not survive the lift. However, if the shell is filled solidly with stars and a physically hard break charge, such as BP on rice hulls/Krispies (sp?), or grain BP if you're feeling affluent, then the contents will provide a hard filling that is itself not easily deformed. An analagy which I have seen used is that of a suitcase - when empty, it will easily collapse if sat on, but when it is carefully packed with clothes it is quite robust.

And another - maybe stupid - question: For larger shells you need very long sheets of kraft paper. Atm I don?t habe access to these long sheets, so I have to use a few shorter papers...

How do you join them, when you make shells?! Simply add a line of glue and overlap them?!
I only ask, because I am not sure if the use of, say 4 sheets instead of one long makes the shell weaker ?!

Yes, this works fine. Just make sure that the grain of the paper is parallel with the straight sides of the shell - i.e. the strips of paper are cut "grain short."

Edited by BigG, 24 March 2005 - 12:00 PM.

[paul]

Phoenix, thanks for the fast and very informative reply!

Anyway, the link doesn?t work. The forum software says it is too old or something. Can you give me the Tpic name?! Did a search before of course but I didn?t find the answer to these particular questions...

[BigG]

Also don't forget - for 3 inch we are talking 3 turns for the inner case and then another three turns of pasted paper - that is not very thin. A finished shell, when done proper, will actually be quite hard, and together with stringing - can create very hard breaks as well. If we want to continue on the subject of industrial operations - many of them use pre-cast paper cans that wiggle when you wave them around - and are equivalent of a single turn of a recycled 30# Kraft - with no real strange to it at all! Those are fitted with one end disk (only one, as the paper can already sealed at the other end) with pre cut fuse hole and a fuse. They base the whole structure on the pasting layer, and they don't even include a string! Breaks look very good - although a bit less "full".

For the "purists" - where making a living is not much of an issue - going the traditional way to get the best effect is still very valid.

This thread has become a mix bag of round and cylindrical shells.... I'll put some order into it in the near future.

Edited by BigG, 24 March 2005 - 12:08 PM.

[paul]

This thread has become a mix bag of round and cylindrical shells....

Sorry for that I simply overlooked this thread...
The thread?s name was "Cylindrical shells" and I did not find it! Embarrassing!

Ok, guys you helped me a lot! Thanks to everyone ,

paul.

[italteen3]

Wasnt the original thread name spherical shells? Why not name it Aerial shells.

[BigG]

Wasnt the original thread name spherical shells?  Why not name it Aerial shells.

Yes it was - don't ask - someone open a different thread and I merged them back. I think we can keep the two type of shells seperate - it just means that one of the moderators (probably me) will have to go through the thread and make the seperation. It's a long process (many posts in this thread) so please be relaxed about it - we will get around to do it.

[al93535]

For about how many seconds should a star burn in a 4" shell? I have timed my own 4" shells I did on new years and one shells stars burned for 1.1 seconds and the other for 1.5 seconds! Thats pretty fast, but still they had a good full flower. It just seems that a 4" shell should burn for 3 seconds or so. So what do you guys know about star burn time in a 4" shell? Any ideas?

[Richard H]

It depends on the star composition really. A fire dust star will burn for longer than a colour peony for example. I would say 1-2 seconds for a peony and burn times of upto 4-6 seconds for a charcoal streamer in a 4". Some stars burn for so long they ground out - typically the ones with larger mesh sizes of charcoal present.

[seymour]

Made my first shell today! I have not set it off yet and will do that tomorow night. Well it wasn't realy my first shell because the other night I set off a 1 and a half inch spherical shell but as it was broken with straight bp ( no flash or whistle boosters) the break wasn't exactly symetrical, far from it actualy. But it prooved that my entrely homemade (no visco or commertial bp at my place) spoilette, lift powder, burst powder and stars worked. At this moment I am making two more shells like the other one( 3" spherical) but just have to wait for my stars to dry. I have a super star drying machine, they dry in just two hours! Some people call it a hair dryer on a low setting. Anyway, I am very proud of my finished 3" shell. It all looks very pretty with the lift cup atatched and the quickmatch all folded up neatly!

Edit:
Yay, all of my 3" shells are ready. I have one with 27 12mm diameter pumped stars, one with about 70 7mm diameter pumped stars and one filled with 6 tiny minishells. Each with about 6 7mm stars in is. All minishells have white KNO3.Sulphur stars glued on to them. The first shell also has 3 large stars glued on to the bottom to give it a rising effect and make it easer to see. With the exeption of the Potassium nitrate and sulphur all stars are, you guessed charcoal streamer stars: 75.15.10 Bp +20% charcoal mixed mesh+5% dextrin. They burn very fast and fiercly (around one second) so next time I might add some metal powder or +30-40% charcoal instead of +20.

Edited by seymour, 29 March 2005 - 04:47 AM.

[seymour]

I launched them!
The first one launched up with not as much power as I had hoped and broke half way to the ground. I blame this on a too loose fit. The secound one went off with a nice sharp thump but blew blind! It landed on the ground behind me with a loud thump about 20 secs after launch! . The last one lifted off with considerable power and broke nicely just before apogee. The minishells either failed to light or were shattered when the shell broke because the white stars never burst and there was also charcoal streamer in the burst. The shells shattered nicely and did not just split because I found bits of the shell everyware. Now I want to make 10 for the weekend! but I'l settle with three or four.

[adamw]

Some more work to be done on the timing delay I think...