Questions for first DD

Forums Knowledge Base Questions for first DD

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  • #41757
    Geof Givens

    Hi folks. I’m nearly finished building my first dual deploy rocket, which is also the first attempt to use the missleworks RRC2 altimeter that I got from someone quitting the hobby. I have a few questions.

    How is an e-match different than a typical ignitor? Do only e-matches work with a 9-volt battery? Can I buy them at the next launch?

    Do you think that it’s imperative to ground test the ejection charges even if I have done (and double-checked) the black powder calculations?

    If I do the ground test, I’m not sure how. Should I remove the altimeter sled and send some wires through the air hole?

    Does anyone have a great checklist to ensure that I don’t skip any steps when preparing for launch (such as forgetting to turn on the altimeter!)?

    Can you recommend a good fps descent rate for the drogue? I’ll have no tracker and will be flying to only a few thousand feet.

    Thanks. I may have more questions, but that’s plenty for now.

    Geof

    #56882
    MikeS
    Moderator

    Great questions.

    Question #1 I use supplied igniters that come with the motors. They are tested and work the best.
    The following link will help with the other aspects
    of the question. Cool Rocket Stuff and Giant Leap Rocketry are at most
    of our launches and supply great products.

    http://www.privatedata.com/byb/rocketry/Ignitor/e-match_igniter.html

    I make my ejection charges with (Christmas bulb method) many others
    out there but got used to using them. If they pass continuity after being built, they have never failed.
    If I have my electronics correct.
    There are many options as to what the holder is. PVC adaptors to
    surgical tubing. Surgical tubing is great.

    Question #2 I tried some math. On an eight inch rocket, it sent my
    chute and all across the alley, slammed into my garage and brought
    a neighbor out. 😯 . The math seemed right but was not. ground test
    and ground test. I do not do enough. Always lean in the more powder
    direction. But testing will get it pretty close. May also mention. Temperature
    can effect how a charge works. not directly but with how tight sections
    fit. Tight fit in the morning may not be in the afternoon.

    Question #3 I test with a rocket almost ready to fly.
    Sealing the airframe is most important. Also being complete,
    you are testing the whole package, except motor ignition.
    Propellant does not need to be in but case is suggested.
    Shock cords attached and something supporting the base
    of the rocket. it wants to move backwards also. Or. The path of
    least resistance.

    Question #4 I am sure some do, and I wish they would post a couple
    for all to read. My last launch I left out shear pins. The rocket did pretty
    well considering BUT. It was unsafe and costly. A basic check list fits
    most rockets but each launch is specific.

    Question #5 Drogue. I just started this year leaving the drogue chute
    out. I still have extra long shock cords. For me the drogue chute caused
    too many tangles and spinning. Seems to work for me.

    Your choice of electronics is a good one. The RRC2 can be put in a test
    mode to check if it is working properly. And can be used to test out-put.
    I am hard of hearing and need help at the pads at times to hear the beeps.
    Always hear the beeps. If you can not, someone close by will help.

    Hope this helps some. Many people on the forum have great info. I also look back at past forum questions.
    Almost like a library. Have Great luck. Duel deploy is great fun and will
    open many flying doors.

    #56883
    Geof Givens

    Regarding your answer below…
    I would use the igniter that comes with the motor to ignite the motor. For some reason, I thought that a 9-volt battery would not be enough to ignite a standard ignitor, and that e-matches were different and therefore required for the deployment charges. Is that wrong?

    My holder is a pvc end-cap, but surgical tubing sounds more reliable. If I tie a knot in the far end, how do I close off the end where the igniter wires would go though? And where can I get such tubing…my local drugstore?


    Question #1 I use supplied igniters that come with the motors. They are tested and work the best.
    The following link will help with the other aspects
    of the question. Cool Rocket Stuff and Giant Leap Rocketry are at most
    of our launches and supply great products.

    http://www.privatedata.com/byb/rocketry/Ignitor/e-match_igniter.html

    I make my ejection charges with (Christmas bulb method) many others
    out there but got used to using them. If they pass continuity after being built, they have never failed.
    If I have my electronics correct.
    There are many options as to what the holder is. PVC adaptors to
    surgical tubing. Surgical tubin

    #56884
    MikeS
    Moderator

    Ematches vs. Igniters The difference between ematches and igniters is that ematches are intended to ignite an easy-to-burn substance quickly, such as the BP used in rocket ejection charges. However, an igniter is intended and constructed to produce a large, hot ball of flame for an extended period (say, 0.5-0.75 seconds) to ignite a rocket motor. Ematches typically will not ignite motors unaided as they do not produce a hot enough flame for long enough, whereas igniters certainly could ignite BP. Another significant difference between them, which is critically important for onboard rocket electronic use, is their current requirements. Igniters typically require much more current than an ematch; the current requirements are usually more than altimeters can provide. Therefore, for onboard altimeters, which need to ignite deployment charges, ematches are needed. For staging timers, which need to ignite motors, igniters are needed. Be sure to always check using the equations shown on our Electronics Page and/or in our FAQ to be sure an ematch or igniter will work with your onboard electronic device..

    FROM: https://publicmissiles.com/secure/components.asp?groupid=24

    As far as current. One 9 volt covers most applications. RRC2, Perfect
    Flight and others can take more volts if needed.

    I buy small zip ties to close the ends of the surgical tube. Some have
    made holders, I use Velcro dots.

    #56885
    new2hpr
    Participant

    Geoff,
    Mike has filled you in on just about everything. For MOST altimeters, you need to use a low current initiator like an e-match or a Quest Q2G2 igniter (if you can find them!).

    Always ground test before a first electronic deployment with a rocket (after that, just write down what you used with said rocket and keep the record for when you want to fly it again). It’s very easy. Don’t bother removing your altimeter. Prep everything as for a real flight. You could use any dummy plug for the motor hole. Run a pair of wires into your electronics bay through a vent hole and connect to the desired charge wires (test drogue and main separately). Prop the front end up a bit and make sure nothing’s in front of the nose. Touch the wires to a 9V battery and FOOP! Hopefully all comes out right, and not too energetically. Adjust the amount until you’re happy.

    To contain the charges, there are as many methods as there are rocketeers in the hobby. I use PVC caps epoxied to the bulkheads, put the ematch in the bottom, add BP, fill the rest with dog barf, top with masking tape. I run the leads to terminal blocks with wires permanently going through the bulkhead to the altimeter, but you could just pass the ematch leads through a hole in the bulkhead (seal with your choice of goo).

    -Ken (never going back to motor deploy for H and up.)

    #56886
    Geof Givens

    Thanks guys, that really helps. It looks like I need to buy a handful of e-matches to ground test things at home. Anyone in the Fort Collins area selling them?

    #56887
    edward
    Moderator

    Geof,

    If you want to get together I have some e-matches, but mainly for ground testing I use nichrome wire. I also currently have a dirt backyard where you are welcome to ground test.

    Edward

    #56888
    Geof Givens

    Thanks, Edward. PM sent.

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