Closing Cylindrical Shells

[AirCowPeacock]

Previously, I had been closing my cylindrical shells by cutting 'rectangular' tabs around the overlap and folding them on over my cardboard disk. I realized I could cut 'triangles' instead to elimimate buildup. However, with this method a new problem has rose; I can't possibly cut 'triangles' perfect enough no to leave gaps in between the tabs. I figure by cutting alternating rows I can solve this problem. But, I want to know what you guys think? So, questions, comments, ideas? Edited January 6, 2013 by AirCowPeacock

[MikeB]

There are a few methods to deal with the build up of paper. One is to ignore it, as it actually improves the strength and fire seal. It does prolong drying times but an amatuer should not be in a rush. You can reduce the build up by shortening the overlap of preceeding layers of paper and allowing succeeding layers to extend further. This does compromise the fire seal somewhat. But in the larger calibers you generally have enough overlapping layers where it does not affect it.

 

Rather than cutting tabs or triangles I would suggest tearing the paper by hand. Not only is it faster but you get a better seal. The paper and fibers form irregular edges that lay flatter, interlock, and seal properly. Properly pasted and broken paper is also essential to a well finished shell.

[AirCowPeacock]

I have been ignoring it, but I feel there must be a better way. I like the idea of different lengths of tabs, that sounds like the solution I have been looking for. Thanks.

[AirCowPeacock]

I have also considered a trapazodial shape, which would just barely overlap on all edges, if alternating it could create a flat head. But it would be alot of work, I could not see myself doing it for small shells, and that is where buildup is a problem, it makes it more difficult to spike, it also presents a problem in multibreak shells, where it is difficult to hold the two convex ends together wile spiking them together. Edited January 6, 2013 by AirCowPeacock

[Mumbles]

Mike, I think he's talking about just closing the shell, not the final paste wrap. I agree with everything you mentioned though. I don't cut or tear the actual casing at all, just the paste layer.

 

This really shouldn't be a problem for any shell smaller than 6" or 8". Using a mallet or wooden block can help everything to lay down and get flat as well. I'm not sure why you think it causes a problem with spiking. The second disk on top of the paper generally evens everything out and gives something for the string to bite into.

 

Have you ever tried building a traditional shell according to Fulcanelli Aircowpeacock? Doing it the right way a few times can help determine where shortcuts are suitable or applicable.

[AirCowPeacock]

You throw a second disk ontop after closing the shell? Perhaps I should do that.

[Mumbles]

Yep, each shell has 4 disks. One set under the folded paper, and one set over it.

 

I really can't recommend real literature enough. Youtube is not a very good learning resource.

[AirCowPeacock]

I don't really use youtube very much anymore (if atall.) My primary references are F.A.S.T and creagan.net. Apparently the shells I make from the methods I came up with as adaptions from the crap methods I learned from youtube years ago. For the record, unless I'm in a rush, I use no hotglue or masking tape, just alot of gummed kraft and woodglue. I even use hemp cord to spike. For the first time today I incorperated a clamp into making my shells, it took care of build up problems. Next shell I make I will make as traditional as possible, but it really doesn't seem like it will be all that much different.

[psyco_1322]

With traditional methods, there will be a lot of paper that "builds up" during pleating. The center part of the disk with be empty, as in no paper should be pleated over it. When the outer disk is placed on, there will be that small area in between that is empty/void of pleated paper. That is normal, and totally fine.

 

A lesson on pleating... After the case is made, or after it's filled, drop in the disk that rests on the chipboard liner. The overhanging paper for pleating should be about 1/3ish the width of the disk. Using white/wood glue apply glue to the overhanging paper and disk where is will pleat down, a brush helps. Starting at the edge of the inside layer of paper, fold it down, moving around the inside of the case, folding in small sections. Pleat down the layers one at a time, folding the paper, not cutting. Once you have a layer down, take a big wooden dowel or some alike, and gently tamp down the layer of paper you just folded. The inside should be all dry paper, apply more glue, and continue to fold down the layers until it all pleated down, tamping every layer flat. When it's all pleated and tamped down, apply another layer of glue to the top, and add the outside disk, give it a good couple of tamps. Get yourself 4 pieces of masking tape, apply them to the disk/casing, 90 degrees from another, to hold the disk down. Also take a continuous strip and apply it around the edge where the pleating meets the outer disk, pull it tight as you apply it, and pleat the overhanging lip of tape to the top of the outer disk. This adds a little extra fire protection and also helps keep the disk in place. That's it, do that to both ends, and spike.

[dagabu]

For me, it all depends on the type of shell I am making and the size of the shell. On the 5" shell i just completed and fired, I used a tongue fold on the paste wrap and cut/pleat the inner dry wrap. The interesting thing is picking up end disks from the ground after a competition or after an Italian segment at PGI. Both the inner and outer disks are always attached to each other still and the stings are broken right at the disks or have a a small length of string attached to them.

 

Tearing them apart, i see the hand of the maker on the dry wrap, some pleats only go a fraction onto the disk, just enough to get them glued down, others are glued down in a perfect circle ending with zero hole in the center and a very small crown where the paper meets. Others yet are folded and torn.

 

I have made plenty of shells where the paste wrap was torn and pleated down and a kraft disk was pasted over the pleats but that makes me nervous and so i have settled on the tongue fold for the paste wrap for now with some judicious hammering (it's not at all hard, more of a tapping) on the tongue to flatten it down.

 

-dag

[AirCowPeacock]

I have been cutting gluing (wood glue) and folding tabs down (layer by layer) all the way to the center or timefuse, by not doing so it should help counteract the buildup. I use 4.75 layers #30 kraft for my liner, should I switch to heavier paper? Also I use very finely corrigated cardboard for my disks, would chipboard be better? After closing the shell I paste 2 layers #35 gummed kraft. onto the shell, spike, lather on a little wheat paste (6 parts water, 4 parts flour, 1 part wood glue) and paste another two layers of #30 with wheat past on after spiking. I pleat the final layers as I for closing the shell.

 

I will start pleating the closing layer only just over the edge, about 1/5 the the diameter, then pleat the first paste before spiking 1/3 the diameter. Put on outside disks before spiking the shell. Then tounge fold the final paste. Sound like a good improvement?

[dagabu]

I have been cutting gluing (wood glue) and folding tabs down (layer by layer) all the way to the center or timefuse, by not doing so it should help counteract the buildup. I use 4.75 layers #30 kraft for my liner, should I switch to heavier paper? Also I use very finely corrigated cardboard for my disks, would chipboard be better? After closing the shell I paste 2 layers #35 gummed kraft. onto the shell, spike, lather on a little wheat paste (6 parts water, 4 parts flour, 1 part wood glue) and paste another two layers of #30 with wheat past on after spiking. I pleat the final layers as I for closing the shell.

 

I will start pleating the closing layer only just over the edge, about 1/5 the the diameter, then pleat the first paste before spiking 1/3 the diameter. Put on outside disks before spiking the shell. Then tounge fold the final paste. Sound like a good improvement?

 

When making the case, you should use #70 paper, start with 2 turns for the smallest of shells and one turn for each inch of shell size, i.e. 5' shell = 5 turns #70 kraft. Disks should be 1/8" thick binders board or equivalent, this is more important as the shell size increases.

 

There is no need to use gummed kraft tape if you are going to use paste anyway. Just paste in your shell with two turns of #30 kraft after you have spiked the shell.

 

The rest sounds good, just make darn sure there are no pinholes at the edge of your pleating, I don't cut down all the way to the disk, I leave about 1/4" uncut and press it down flat when pleating.

 

-dag

[AirCowPeacock]

It certainly seems everyone has a different opinion on pleating. Where can I domesticly get #70. The best I have found here is #40.

[dagabu]

It certainly seems everyone has a different opinion on pleating. Where can I domesticly get #70. The best I have found here is #40.

 

In the US, you can get it at Berlau Paper, in fact, the have #90 as well.

 

-dag

[AirCowPeacock]

I don't know if I really want to pay that much on shipping if I can help it.

[AirCowPeacock]

Recycled kraft good enough? I found a source on ebay that is a little cheaper, but it is recycled.

[dagabu]

Recycled kraft good enough? I found a source on ebay that is a little cheaper, but it is recycled.

 

Sadly, no. Recycled paper will not hold together once wet. It is fine for the outer wrap as it is dry but is worthless one pasted.

 

-dag

[psyco_1322]

Go to Walmart, buy a roll of recycled craft. It's not 70lb, and it works great! Pick your self up some hemp twine while your at it, not the really thin, but the next size up. Edited January 7, 2013 by psyco_1322

[Mumbles]

Not all recycled kraft is all that bad. Avoid paper grocery bags. They're garbage, and not good for anything more than lining your work area. You can get full rolls of recycled kraft from places like Uline, and a variety of other places on the internet. Additionally, you can get short rolls (about 40-60 feet long IIRC) of approximately 60lb from many hardware stores, office supply stores, or even Walmart sometimes. This stuff actually isn't terrible. It works fine for dry applications, and if you're careful will hold together acceptably when wet. I've spoiled myself with virgin kraft by now, but if I was starting over it's not the worst thing one can do.

 

If you prefer to use lighter paper, you can generally just use more of it. Some people don't like using 70lb for shells 3" and below. I will admit that it can be challenging sometimes as the paper seems too stiff for the tighter angles. Some will use 50lb paper for some of these shells instead. A 3" shell would use 4 turns of 50lb for the casing and the paste wrap. As long as you get roughly the same thickness, you should get similar results. I suppose the same could be done with 30lb using 7 turns. I generally roll the casings from 70lb and do the pasting with 30lb in smaller shells.

 

Typically the case will be nominal inches in turns. A 3" shell has 3 turns, 8" shell 8 turns, etc. I also like to use a manilla file folder or poster board liner in the cases. This can be rolled with the casing or added later. I always add the liner. It gives a nice fill line, and can give some support to the casing in certain applications. I drop a disk in and fold the casing down in wedges one later of paper at a time. This does get tiring on big shells. I set all the folds down with a mallet or wooden rod or block. I don't use any glue at all. After filling, I repeat this closing procedure. I do tend to add a few strips of masking tape to the disks to hold them in place, but this is the most major departure from a traditional case that I make.

 

After this, I spike my shells with dry hemp twine. If I'm using cotton, I ensure it's well soaked with paste. I read stories about hemp taking a while to expand with paste, and actually resulting in limp spiking, so I never did it. From here it's traditional to paste the shell in with the same number of turns as the casing is made from of 70lb broken in kraft paper. I do believe that the final paste layer is more than just a fire seal. It also provides strength to the break. To avoid excessive buildup of the ends on larger shells, a "belly band" is sometimes used. Some number of turns is applied just to the sides of the shell, while the rest go the full length from fuse to bottom of the shell. I tear the paper into strips as I'm rolling the wet paper around the shell. I feel more comfortable tearing as I go so that any gap made from a tear in the paper is very likely covered up by another flap from another turn. Once the paper is on the shell, I typically wet my hands with additional paste and rub the shell down well to get out any air, and ensure everything is well seated.

 

I have some in processes pictures of me building cylinder shells here: http://www.amateurpyro.com/forums/gallery/album/63-pgi-2010-construction-pics/ It's not all inclusive, but they are what they are. You can see that even the 6" shells have pretty flat tops and bottoms.

 

This is generally fairly traditional. I can't stress enough that a copy of Pyrotechnica IX and Pyrotechnica XI are practically mandatory for anyone with a serious interest in cylinder shells. Much of the info is covered in Hardt as well. As you get more experience, you can learn where shortcuts, additions, or substitutions are acceptable or desired. Starting off half assing it is a great way to waste time and materials.

[AirCowPeacock]

I downloaded a PDF of Pyrotechnica IX yesterday. I have not yet read it all, but will shortly. I can get 40 lb kraft, I have not bought it, but I have seen it at office supply stores. I could get the 60 lb stuff, since it's pretty close to 70 lb. But I should honestly shell out $50 for good paper when I can, it will certainly be worth it in the end. I too put a little bit of sealent on after the shell is done, except I used 1/4 concentration wood glue, it gives it a good seal and luster.

Thank you for all your help guys, I hope to soon be producing better cylindrical shells.

Edited January 7, 2013 by AirCowPeacock

[Mumbles]

I'm sure you'll be doing great in no time. It's truly amazing how quickly things come together when you get all the little pieces together. Decent paper, good string, and Pyrotechnica IX will have you turning out good shells in no time.

[nater]

You should support the authors and buy the Pyrotechnica issues. They are still available as original copies.

[AirCowPeacock]

I should, and at some point will. Of course, that's what I always say... And so far usually do only about 50% of the time.

[chemtech89]

Sorry for going off topic but I didn't want to start a new thread for this one. Do you guys use a pass fire to the center of the cylinder shell like you would a spherical shell? I have been noticing that people just leave the fuse or spolette end just inside the inner disk.

[Mumbles]

With a spolette I find that to be unnecessary. The burst from the nosing gives plenty of fire. The nosing in itself is sort of a passfire though. I do regularly use a piece of quickmatch attached to the end if I am using time fuse though for full sized shells (3"+). I've never found it to be necessary for insert shells.