your practical experience needed

Discussion in 'The Watering Hole' started by hornet driver, Apr 16, 2015.

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  1. Apr 16, 2015 #1

    hornet driver

    hornet driver

    hornet driver

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    I'm looking for max t.o. weight for Estes D-12-0 vs E-12-0. It looks like the E-12 has just a bit more punch but I've heard rumors otherwise. I know the E has a longer burn time but is the initial kick higher? I also noticed that the thrust of both are all over the map with different ejection charge times, which frankly makes no sense to me. So what's the real deal ???
     
  2. Apr 16, 2015 #2

    JohnCoker

    JohnCoker

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    The D12 thrust curve:
    [​IMG]

    The E12 thrust curve:
    [​IMG]

    The D12 peaks at 30N just after 0.25s and E12 peaks at 33N, so I'd say the latter does have a bit more punch to get the rocket moving.
     
  3. Apr 16, 2015 #3

    The_Lone_Beagle

    The_Lone_Beagle

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    Not sure what you mean by that, but yes definitely, the ejection charge times are not exactly as advertised….E12 data sheet
    D12 data sheet

    For example, the D12-7 delay average is actually 5.75 seconds, while the E12-8 is delay average is 8.63 seconds...
     
    Last edited by a moderator: Apr 16, 2015
  4. Apr 16, 2015 #4

    hornet driver

    hornet driver

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    Thanks for that graph. That's kinda the way I read it. It looks like it--E-12--peaks just a tick quicker. The added n's are likely offset by the added total mass of the larger motor, so I'll call that part a draw. Average thrust is a bit higher with a longer burn and less fall off. So in the simplest terms--same motor longer burn--Am I off track?
     
  5. Apr 16, 2015 #5

    hornet driver

    hornet driver

    hornet driver

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    I couldn't pull up your data--but---what I was looking at on the charts I saw , the thrust was different from model to model---d's were different as were e's based on the ejection charges which made no sense to me--I guess, in the big scheme of things , I'm asking how accurate are these charts. It seems to me a d-12-0 all the way out to a d-12-whatever should have the same thrust curve. I am assuming they have the same nozzle and propellant blend (this is the part where my seat of the pants approach usually gets me in trouble)
     
  6. Apr 16, 2015 #6

    scsager

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    Length of the launch rod, shape/diameter of the rocket, launch conditions/wind speed... etc. all play a part in the maximum lift-off weight. My experience has been that playing-it-safe with a lower lift-off weight usually results in your ability to fly the rocket again. (as opposed to crashing it)

    D12 - 10 or 12 oz is pushing your luck in my opinion. Estes states 14oz max lift-off weight.
    E12 - Really about the same as a D12, I would not be comfortable over 12-14 oz max in dead calm air. Estes claims 1 pound (16oz) for a max weight on the E12.
     
  7. Apr 16, 2015 #7

    GregGleason

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    I will always pick a D12 over an E12 when a rocket is near it's max launch weight for one reason alone: The D12 is lighter and the fact that is is significantly lighter is often overlooked (30% heavier and at the wrong end to be heavier). The most important part of the thrust curve is what happens in that first 0.50 second. The curves for the D12 and E12 are nearly identical. You want to scoot it off the pad with as little as weight as possible, then quickly ditch it.

    My :2: anyway.

    MtrData_D12.ES_E12.ES_E9.ES_C6.ES.jpg

    MtrCompare_D12.ES_E12.ES_E9.ES_C6.ES.jpg

    Greg
     
  8. Apr 16, 2015 #8

    bill_s

    bill_s

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    Even with the E12, the limit on the biggest rocket you can fly tends to be minimum delay time due to lack of altitude, not rod velocity. And when you're looking at altitudes in the 200' range, a little shortness of actual altitude or extra delay time is a big deal.
     
  9. Apr 16, 2015 #9

    markkoelsch

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    Something else to consider. Both Aerotech and CTI make reloads for 24 mm the same size as a d motor. Considerably more thrust and total impulse. Just a thought.
     
  10. Apr 16, 2015 #10

    bobkrech

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    I fixed your hyperlinks.

    The allowable NFPA 1125 ejection delay variation (and you should expect variations) are: +/- 1.5 seconds for labeled delays shorter than 7.5 seconds, +/- 20% for labeled delays from 7.5 to 15 seconds, and +/- 3 seconds for labeled delays longer than 15 seconds. If you need tighter control, use electronic deployment, or buy a batch of motors from the same production lot and fire several and measure the actual delays for that batch.

    There are also variations in the peak thrust from lot to lot. You should expect the peak lift-off thrust to be approximately the same for the D12 and E12 motors. As the D12 is lighter than the E12, the D12 will accelerate marginally faster than the E12, but the E12 will go significantly higher because it has more propellant and therefore a longer burn.

    Bob Krech, Tech Officer NAR S&T
     
  11. Apr 16, 2015 #11

    tmacklin

    tmacklin

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    This is very good information and useful for all rocketeers regardless of their level of experience. Thanks! :cheers:
     
  12. Apr 16, 2015 #12

    Darian Rachal

    Darian Rachal

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    :puke:I don't feel no ways tard.
     
    Last edited: Apr 17, 2015

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