Hell Boy > 19 motor cluster

Discussion in 'High Power Rocketry (HPR)' started by delta22, Oct 18, 2010.

  1. Oct 18, 2010 #1

    delta22

    delta22

    delta22

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    Always wanted to build an upscale Fat Boy, and Polecat's 5.5" Fat Man is a good kit to do it with.

    The kit comes with a fiberglass nose cone, pre-glassed body tube (looks like LOC 5.5"), bevelled fins, 2 CRs, 54mm engine tube, plus some other hardware and instructions. Flier supplies chute. A good deal at $99.

    The very wide body is ideal for clusters, 24mm motors are economical and 19x of these fit well in a 5.5" airframe, so that is what I am going to do.

    Robert DeHate built a nice 10" Polecat Fat Man, which had a slide out motor mount. Had a nice flight at CMASS and then went up on a P motor at LDRS which CATO'ed and took the rocket with it.

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  2. Oct 18, 2010 #2

    sylvie369

    sylvie369

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    After a moment of "Does this guy know what he's doing?", I looked at your avatar, and remembered ("yes, he does").

    I am starting to wonder if you're aware that you can fly a rocket using only one or two motors, though. ;)
     
  3. Oct 18, 2010 #3

    delta22

    delta22

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    Decided to go with a solid bulkhead 6" from the bottom of the airframe to separate the engine compartment from deployment area (first picture on right). For deployment plan to use altimeter and rig for possible dual deploy.

    Started by weighting the NC with 8oz of lead, with a 54mm tube to slide in more weight as needed. First picture on left is the bulkhead that attaches to the 4 Tnuts on NC.

    Judging by the smell as I sanded the NC it seems to have been build with polyester resin.

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  4. Oct 18, 2010 #4

    UPscaler

    UPscaler

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    Ridiculous
     
  5. Oct 18, 2010 #5

    DAllen

    DAllen

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    I cannot wait to see how you do the motor mount.

    *DAllen subscribes to thread*

    :pop:
     
  6. Oct 18, 2010 #6

    UPscaler

    UPscaler

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    I'll subscribe too, I can't wait to see this!
     
    Last edited: Oct 18, 2010
  7. Oct 19, 2010 #7

    judo

    judo

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    Smoooooke!
    Lot's of smoke!
     
  8. Oct 19, 2010 #8

    rstaff3

    rstaff3

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    Schweeeeet :cheers:
     
  9. Oct 19, 2010 #9

    Rocketeer Gator

    Rocketeer Gator

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    Reloads or Estes??? I just did the math for Estes D12's (At Hobby Lobby bought a 3pack @ 30% off $9.10) 19/3=6.33 6.33x9.10=57.607
    Holy crap $58 per launch....hope they all ignite!! :jaw:

    also subscribes :pop:
     
  10. Oct 19, 2010 #10

    HotRod Rockets

    HotRod Rockets

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    Excellent Name.

    what no -In-ate-or? you can always nick name it.... Smoke-in-ate-or..

    What's the ETA on this one Fall '10 or Spring '11 ? I don't want to miss this one.

    ------
    Rocket -E-Gator
    You can't measure it in dollars and cents. Or in Newtons of Thrust.

    You have to measure it in Gigawatts!

    .
     
  11. Oct 20, 2010 #11

    gdiscenza

    gdiscenza

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    1.21 Gigawatts?? This thing'll recover in 1985!!!

    G.D.
     
  12. Oct 20, 2010 #12

    powderburner

    powderburner

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    delta22,

    Was there any particular reason to arrange the outer dozen MMTs near the circumference, instead of "honeycomb" dense-packing them together with the center seven?
     
  13. Oct 20, 2010 #13

    rstaff3

    rstaff3

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    I don't know how he actually plans it but the chances are this is just what popped out of RockSim and, for that, was close enough.
     
  14. Oct 27, 2010 #14

    delta22

    delta22

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    Exactly correct.

    To model this complex a cluster mount in RockSim I had to add:
    1) one central motor
    2) a ring of 6 around that
    3) a ring of 12 around that one

    Interlocking of motor tubes is not depicted accurately in the model.

    It is a "honeycomb" in the real thing, for simplicity of build, motor density and strength.
     
  15. Oct 27, 2010 #15

    delta22

    delta22

    delta22

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    Yes, launches won't be cheap.

    However, big clusters are typically about the price of a single motor with twice the impulse.

    As David noted above, it's really more about effect than altitude in a project like this.
     
  16. Oct 27, 2010 #16

    DAllen

    DAllen

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    D12 = 16.8 newtons

    16.8 x 19 = 319.2 newtons

    One H268 = 320 newtons or roughly $30

    Yeah, it's about effect. I love big honking clusters like that.

    -Dave
     
  17. Oct 27, 2010 #17

    delta22

    delta22

    delta22

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    Used a jig from BMI to align fins.

    For this mod I glued a 6" coupler tube at the bottom of the body tube. Trimmed the tabs on the TTW fins. Then epoxied them into the slots in the body tube, butting them up against the coupler tube.

    Generous fillets with thick, fast Locktite 5 minute epoxy.

    Then glassed very lightly using thin 1.3oz FG layers. Three layers where fins join body, one layer everywhere else. West 206 epoxy.

    Just enough to help anchor the fins and provide a hard, smooth surface to the exterior.

    After plenty of sanding, applied a topcoat of epoxy and then sanded that down.

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    Last edited: Dec 25, 2010
  18. Oct 27, 2010 #18

    delta22

    delta22

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    Cut LOC 24mm tubing into 18 pieces 5.5" long and one 6" long for the center. The 6" tube in the center will contact the solid bulkhead, other tubes were shorter to avoid interference with the bottom parts of recovery hardware.

    Glued into a honeycomb using yellow, quick-tacking Elmers.

    Originally, I was planning to mount this into a stiffy tube until I weighed it, 8oz!

    Cut strips from a stiffy at 6 contact points. These 6 strips plus the top of the center motor tube hold the motor mounts into the rocket.

    Painted West 206 epoxy on the outside of the motor honeycomb and inside of the space they mount into, to bond and fire-harden.

    Rocket body (no NC) went from 2.0lbs to 2.5lbs with addition of motor tubes.

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  19. Oct 27, 2010 #19

    delta22

    delta22

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    Hoping to launch this at the next CMASS launch 11/6/10.


    My cluster box will put out over 1.2KW.

    http://www.rocketryforum.com/showthread.php?t=11766

    Haven't achieved GigaWatts or time travel yet. Maybe with a bigger battery or more motors...
     
  20. Oct 27, 2010 #20

    rstaff3

    rstaff3

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    Boris, with all those plugged tubes, what are your plans for the D12's? Or are you actually thinking about D11's? On my 10 D cluster, I plugged D12-0s for 9 of them and then used the other for ejection. I ran into a hobby shop which found a huge box of D12-0s and they were dumping them for $3.50!
     

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