Double Petals - How do you do it?

[pyroguy1960]

So I'm about ready to make my first double petal shell. I'm doing just straight colors, red inner, blue outer. My plan was to use a 4" inside an 8", both regular strawboard hemis.

 

I was going to use what seems to me the easiest method which is just laying out each half and then putting them together, using my KP burst on hulls for the 4" and my FAST No.5 on cotton seeds for the outer. I'm pretty comfortable with this approach as it's very straight forward.

 

I guess my questions would be, can you really get two nice symetrical breaks with this method? Seems like the innner shell because it's not pasted at all, just somewhat married together would not really break well. I did look at the methods perscribed in FAST for doing double petals and it seems somewhat more complicated.

 

Has anyone had good results with the approach I'm going to take?

[FREAKYDUTCHMEN]

Your burst seem ok I think.

 

You can lay the first row of stars in the 8" hemi, then put in a tissue paper, then fill for about 3/4th full with the cotton burst. Then take a 4" or 5" hemi with a sheet folded around it, and push and twisting it into the burst gently. Maybe you need a little more burst. Then fold the tissue open and put in the inner petal stars gently. Then again a tissue paper and finally the innerpetal burst. You can leave the tissue folded open or fold it inside. Be sure the innerpetal is not totally covered by the tissue, this is not good for the upper shell half for taking fire.

Slap the two filled hemis together and be careful.

 

Some people use perforated hemi's, but this is only done by some amateurs.

Edited October 29, 2010 by FREAKYDUTCHMEN

[pyroguy1960]

In that method you're describing, it seems like you're saying to not actually use the 4" hemi in the shell. But just use it to create a tissue paper lined cavity in the 8" break charge in which to build the inner petal correct?

[Algenco]

In that method you're describing, it seems like you're saying to not actually use the 4" hemi in the shell. But just use it to create a tissue paper lined cavity in the 8" break charge in which to build the inner petal correct?

 

 

that's the way it's done.

 

I've also saw perforated hemi's used, but most now use the tissue method

[pyroguy1960]

k..thanks for the clarification....I'll be trying it out next weekend....ran out of KCIO4 this week

[davis050594]

I'm interested in this process. Do you think maybe you could make a video when you build this shell next weekend? I think it would be pretty cool. I wish people would put more videos of the building process on pyrobin

[pyroguy1960]

I suppose I could video the build....but this being my first double petal, I'm not sure how usefull it would be. I'm obviously not qualified to give a tutorial on something I'm doing for the first time. But I'll film it and who knows maybe I'll get lucky and it will come out nice....

 

 

[GalFisk]

Do it. And if it should come out wrong, someone with experience could probably tell your mistake from the video, and you'll learn.

[Mumbles]

If you're going to get into these kind of shells, you'll probably want to find a copy of Jim Widmann's multi-petal shell article. It's in both the PGI bulletin and the recent anthology, which by the way is well worth the price. He builds them inside out, somewhat like shimizu, but using perforated full thickness hemispheres. If you've seen his shells, you can hardly find fault in the method.

 

Another thing you may want to look into is thin news paper or kraft hemis. Using just the cavity can be a little tricky to get right without some practice. The cotton seed is pretty forgiving with regard to packing it in and getting it to form a nice cavity though.

[helix]

If you're going to get into these kind of shells, you'll probably want to find a copy of Jim Widmann's multi-petal shell article. It's in both the PGI bulletin and the recent anthology, which by the way is well worth the price. He builds them inside out, somewhat like shimizu, but using perforated full thickness hemispheres. If you've seen his shells, you can hardly find fault in the method.

 

Another thing you may want to look into is thin news paper or kraft hemis. Using just the cavity can be a little tricky to get right without some practice. The cotton seed is pretty forgiving with regard to packing it in and getting it to form a nice cavity though.

 

I think this article was uploaded to pyrobin as a word file a few months back, the article filename was posted as "a method of construction for 12 double petalled chrysanthemum" hopefully you can find it from that as I cant for some reason copy a link and paste it here.

[Mumbles]

I found it, though completely by accident. I think Jim Widmann made the file himself. There are color pictures, and a few hand drawn diagrams that were computer generated for the actual article. I think the actual article is better formatted, and easier to follow, but the information should be the same.

 

http://www.pyrobin.com/files/a%20method%20of%20construction%20for%2012%20double%20petalled%20chrysanthemum.pdf

[WonderBoy]

Here it is

http://www.pyrobin.com/files/a%20method%20of%20construction%20for%2012%20double%20petalled%20chrysanthemum_1.doc

 

Edit: Mumbles beat me to it.

Edited October 30, 2010 by WonderBoy

[pyroguy1960]

I'm going to have to try the method desribed in that doc. I shot one tonight using just tissue paper to form the inner hemi and all it did was dump the stars, much more like a pistal effect than a double petal. To make matters worse I tried two new comps for blue and red and they both were just awful. Red was way to hot and fast and the blue was washed out had some ignition issues.

 

So back to the drawing board on this one.

 

Here's the video, but not even worth looking at.

 

 

Also here's a few construction pics:

 

[Mumbles]

That's really not too bad for a first try. It's hard to tell on the inner petal because they burned out so fast, but I do agree it looks like it just dumped out. It also doesn't look like they all lit. I don't think it matters much, but I use 5" inner petals on 8" shells. Your experience may vary, but I found I wasn't getting the inner petal symmetry and spread I wanted unless I reinforced the inner petal in some way. Shimuzu uses string wrapped around the tissue paper bundle. Widmann spikes the shell itself. If nothing else, it really makes sure the inner petal is packed tightly. You may also want to try a slightly harder burst in the inner petal.

[pyroguy1960]

yea the stars were just awful, very bad choices and bad ignition. But one thing was clear that the inner petal needs some containment to achive some symmetry. I'm going to follow that tutorial you guys posted with better stars and see how I make out.

 

 

[FREAKYDUTCHMEN]

Be sure the innerpetal is not totally covered by the tissue, this is not good for the upper shell half for taking fire.

 

Never fold all the tissue inside.

 

For better symmetry you'll need round stars first.

Edited November 7, 2010 by FREAKYDUTCHMEN

[pyroguy1960]

Shot another 8" double petal tonight, this one was better. The stars I chose worked out well. Still having a little trouble making the inner petal symmetrical. With this one I used a perforated & spiked inner shell. Next time I may add some additional spiking to give it some more confinement.

 

Below is a vid and some construction pics, in the pictures the inner shell doesn't look perforated but it is, I drilled the holes instead of punching them, so when I closed it up some of the material moved back into the holes. Didn't seem affect ignition at all though.

 

I was also really windy tonight, not sure if that affected the initial break at all, but you can see the stars drift when they're burning out.

 

 

Edited November 28, 2010 by jms04081974

[Updup]

Shot another 8" double petal tonight, this one was better. The stars I chose worked out well.

 

That was a great shell! You really do crank out those 8" shells don't you?

 

Would you be better off pasting the inner shell (And poking holes in that) so the break of the outer shell dosn't burn/damage the spiking of the inner shell?

[pyroguy1960]

I find the 8" ones to be more fulfilling not to mention more forgiving on break symmetry. I figure if I'm gonna do all this work it minus well be worth it.

 

I thought about trying that too but I was a little worried about damaging the contents of the inner shell trying to poke holes in it while loaded....

 

 

[davis050594]

I thought that one looked very good. Much better than the first. That shell looked as good as many commercial shells (not as good as yung feng, that's nearly impossible). Only thing I can suggest from my lowly position is a better camera

[Updup]

I thought about trying that too but I was a little worried about damaging the contents of the inner shell trying to poke holes in it while loaded....

 

 

 

Maybe if you just left the fuse holes open, that should allow plenty of passfire into the second shell. I just think that you spiking might have gotten scorched a bit from the first shells break, but maybe it all happends too fast for that to be an issue.

[Mumbles]

It would be useless to try to paste an inner petal and then poke holes in it, not to mention probably rather dangerous. Anyone who has ever built a solidly put together shell would be able to tell you that it is a bad idea. String will be resistant enough to fire to hold up for the fractions of a second before the shell breaks. If the string burns through, it'd be the same as no reinforcement, and it's pretty obvious there is a benefit from doing so to some degree. You could also use pasted string, or rub some glue on it if you're using the thicker paper casings. One thing I've often played with in my mind is the use of thin strapping tape instead of string.

 

If you drill through the casings into a piece of wood, there are many fewer flaps of paper and frays.

[Karlos]

Jsm: The strings are necessary for fixing the shape of inner shell wihout hemispheres(tissue paper), not for two hemispheres.

[pyroguy1960]

Jsm: The strings are necessary for fixing the shape of inner shell wihout hemispheres(tissue paper), not for two hemispheres.

 

I kinda figured as much, figured it wouldn't hurt matters though to spike it.

 

So how the hell do you make double petal shells that perform like these? http://www.youtube.c...feature=related

 

I know rolled stars are used, but I can't beleive that's the only difference to make shells this good....any ideas? Some double petals start at around a minute into this vid...

Edited November 29, 2010 by jms04081974

[Mumbles]

Jsm: The strings are necessary for fixing the shape of inner shell wihout hemispheres(tissue paper), not for two hemispheres.

 

When using hard inner hemispheres, it is still very common to spike them for reinforcement. There is a marked improvement in petal symmetry. There are more than one way to make multi-petal shells. When using less labor intensive methods such as building the shells with hard inner casings, or using recesses in the burst charge, every little bit helps. It is hard to argue with the results from traditional tissue paper petals as shown in Shimizu. Arguably, the Japanese make some of the best multi-petal shells in the world. If anyone knows if they've changed their methods from what Shimizu has published, they aren't talking much.

 

I kinda figured as much, figured it wouldn't hurt matters though to spike it.

 

So how the hell do you make double petal shells that perform like these? http://www.youtube.c...feature=related

 

I know rolled stars are used, but I can't beleive that's the only difference to make shells this good....any ideas? Some double petals start at around a minute into this vid...

 

That is a very easy process actually.

 

Step 1 - Apprentice for 40 years under a Master Japanese Shell builder

Step 2 - make shells

 

See, piece of cake. There are a few things you could try to get results like that:

 

Use the method outlined in shimizu building the shell inside out with tissue paper contained petals, which are strung.

Use perfectly round newspaper outer "hemispheres" (actually made from 3 pieces)

Paste with more, but thinner layers of paper

 

Honestly, I think that shell is actually quite good for one of your first attempts. You may want to look into using a stronger burst, or using a larger inner petal (5" instead of 4"). There aren't any pictures of the inner petal, but some people use a stronger burst in the inner petal. I've had mixed luck with that, but I'm still learning too. I had been experimenting with different burst carriers, but the same burst charge. I was using coated rice puffs on the inner petal, and cotton seed in the outer. I felt like they offered less compression than the shredded rice hulls we have here in the US.