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RE: [PrairieThunderPyrotechnics] PYRO SECRETS OR QUESTIONS

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  • Andy Holcomb
    Hi Dean 1. A strobe rocket does produce a small amount of net thrust during the strobing stage, but not enough to really be meaningful. The original creator of
    Message 1 of 5 , Jan 23, 2013
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      Hi Dean

      1. A strobe rocket does produce a small amount of net thrust during the
      strobing stage, but not enough to really be meaningful. The original creator
      of the strobe rocket, William (Doc) Barr (not ex PGI president Bill Bahr)
      actually made his rockets with the entire fuel grain being strobe comp. They
      didn't have much thrust, so you couldn't really even put a small header on
      them. Steve LaDuke and a few other guys came up with the idea to use whistle
      fuel as a "booster".

      2. The first trick is to pack the shell so full that the contents can't
      shift around during pasting/handling; I think that's the important part, and
      use a layer of tissue paper across the top of one of the hemis to keep
      everything solid when you close the two parts together.

      On shells 5" and above, most guys use a perforated inner paper hemisphere.
      The best results come from "pasting" (2-3) layers of gummed paper tape on a
      plastic shell of the appropriate size for your pistil, the first layer
      sticky side out, and the others sticky side in. After it's dry, you slice
      the shell in half to form a thin set of hemis, perforate them with whatever
      your chosen method, and assemble the inner petal just like you were making a
      smaller shell inside. The perforations let the fire propagate more evenly.

      Jim Widmann was selling commercial perforated hemis from 4"- 8" a few years
      ago, that had 5/16" holes punched in them, so I suppose you could use a step
      drill to recreate those. Ned uses one of these to perforate his inner hemis:
      http://compare.ebay.com/like/290407649600

      If you want some inspiration as to what's possible, check-out this guy's
      video of his 4" shells: http://youtu.be/Ypm6kP7XSrc , and
      http://youtu.be/R59unyXC3vQ Amazing!


      3. Low humidity been my issue lately. The paper tubes shrink when they dry,
      and everything is stressed. I've even had the tube split/crack on the
      outside. I keep motors sealed in Ziploc bags now.



      -----Original Message-----
      From: PrairieThunderPyrotechnics@yahoogroups.com
      [mailto:PrairieThunderPyrotechnics@yahoogroups.com] On Behalf Of deanw3576
      Sent: Saturday, January 19, 2013 4:20 PM
      To: PrairieThunderPyrotechnics@yahoogroups.com
      Subject: [PrairieThunderPyrotechnics] PYRO SECRETS OR QUESTIONS

      I have some questions that i would like to throw out to the group.

      #1 Does a strobe rocket produce thrust in the STROBING stage of the burn?

      #2 How do you maintain a symmetrical pistil in a ball shell?

      #3 what do you think would cause a PROVEN whistle rocket to cato after
      storage(3 months)?



      ------------------------------------

      Yahoo! Groups Links
    • andys_junk_address
      Here s a photo of one of Ned s perforated hemis for the inner pistil:
      Message 2 of 5 , Jan 25, 2013
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        Here's a photo of one of Ned's perforated hemis for the inner pistil:

        http://www.fireworking.com/sites/default/files/Articles/double-petal/perforated%20hemi.jpg


        --- In PrairieThunderPyrotechnics@yahoogroups.com, "Andy Holcomb" wrote:
        >
        > Hi Dean
        >
        > 1. A strobe rocket does produce a small amount of net thrust during the
        > strobing stage, but not enough to really be meaningful. The original creator
        > of the strobe rocket, William (Doc) Barr (not ex PGI president Bill Bahr)
        > actually made his rockets with the entire fuel grain being strobe comp. They
        > didn't have much thrust, so you couldn't really even put a small header on
        > them. Steve LaDuke and a few other guys came up with the idea to use whistle
        > fuel as a "booster".
        >
        > 2. The first trick is to pack the shell so full that the contents can't
        > shift around during pasting/handling; I think that's the important part, and
        > use a layer of tissue paper across the top of one of the hemis to keep
        > everything solid when you close the two parts together.
        >
        > On shells 5" and above, most guys use a perforated inner paper hemisphere.
        > The best results come from "pasting" (2-3) layers of gummed paper tape on a
        > plastic shell of the appropriate size for your pistil, the first layer
        > sticky side out, and the others sticky side in. After it's dry, you slice
        > the shell in half to form a thin set of hemis, perforate them with whatever
        > your chosen method, and assemble the inner petal just like you were making a
        > smaller shell inside. The perforations let the fire propagate more evenly.
        >
        > Jim Widmann was selling commercial perforated hemis from 4"- 8" a few years
        > ago, that had 5/16" holes punched in them, so I suppose you could use a step
        > drill to recreate those. Ned uses one of these to perforate his inner hemis:
        > http://compare.ebay.com/like/290407649600
        >
        > If you want some inspiration as to what's possible, check-out this guy's
        > video of his 4" shells: http://youtu.be/Ypm6kP7XSrc , and
        > http://youtu.be/R59unyXC3vQ Amazing!
        >
        >
        > 3. Low humidity been my issue lately. The paper tubes shrink when they dry,
        > and everything is stressed. I've even had the tube split/crack on the
        > outside. I keep motors sealed in Ziploc bags now.
        >
        >
        >
        > -----Original Message-----
        > From: PrairieThunderPyrotechnics@yahoogroups.com
        > [mailto:PrairieThunderPyrotechnics@yahoogroups.com] On Behalf Of deanw3576
        > Sent: Saturday, January 19, 2013 4:20 PM
        > To: PrairieThunderPyrotechnics@yahoogroups.com
        > Subject: [PrairieThunderPyrotechnics] PYRO SECRETS OR QUESTIONS
        >
        > I have some questions that i would like to throw out to the group.
        >
        > #1 Does a strobe rocket produce thrust in the STROBING stage of the burn?
        >
        > #2 How do you maintain a symmetrical pistil in a ball shell?
        >
        > #3 what do you think would cause a PROVEN whistle rocket to cato after
        > storage(3 months)?
        >
        >
        >
        > ------------------------------------
        >
        > Yahoo! Groups Links
        >
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