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  1. #1
    Join Date
    31st May 2017
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    Houston, TX
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    218

    Working on first DD

    Hey all,

    Got my AV-Bay and payload section so about to start working on it. Question is do you prefer to have the NC pop off the payload bay to release the chute or do you like to pop the payload w/ NC attached to release the cute? I don't imagine there are any differences as far as performance or effectiveness. Also I know people prefer shear pins but I think I'm torn on X patterns of tape or 2 pins for attachment on this. (~70 oz cardboard)

    TRA #17256
    Tripoli Houston
    L1 - 7/8/17

  2. #2
    Join Date
    5th December 2013
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    If you leave the payload bay attached to the NC, you'll need to anchor your main to the AV bay instead of the NC bulkhead, to make sure the main gets out. Way is to blow the main out of the payload bay with the ejection charge. Doing it the other way would be like HED with a payload bay.


    John S. ---- NAR #96911 ---- TRA #15253 ---- MDRA #067
    L1, 3/15/14: Aerotech Sumo, CTI H133BS
    L2, 6/21/14: Giant Leap Vertical Assault, CTI J240RL
    L3, 3/12/16: MAC Performance Radial Flyer, CTI M1101WH
    Altitude: 13,028', L3 flight; Speed: Mach ???, L3 flight

  3. #3
    Join Date
    20th April 2012
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    Fredericksburg VA
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    The standard way to do dual deploy is to put the main chute in the payload section. The first deployment charge separates the payload section from the booster section at apogee, optionally releasing a drogue chute, and then the second deployment charge blows off the nose cone releasing the main chute from the payload tube at a preset altitude like 500 ft.
    NAR Level 3 #96210

  4. #4
    Join Date
    31st May 2017
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    Roger, thanks guys. I'll go with the nose cone being blown off. Just need one more harness and ready to go after testing.
    TRA #17256
    Tripoli Houston
    L1 - 7/8/17

  5. #5
    Join Date
    19th January 2009
    Location
    Stafford VA
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    7,188
    If you are building a cardboard rocket, I would avoid the shear pins and use the x form tape for friction fit. Shear pins will tear up the cardboard.

    Use CA or very thin slow laminating epoxy to seal and stiffen the ends of the cardboard tubes and harden the inside of the tubes where they slide together. You can sand it down after it dries, but having something that will soak in and harden the cardboard will greatly extend the life of the rocket. You'll have to redo the hardening of the ends from time to time, but that's just part of maintenance. I have one DD LOC tube rocket with 45 flights on it. It's always been friction fit which has worked great.

    Good Luck
    Handeman

    TRA #09903 L3 3/29/2015

    "If you don't use your head, you have to use your feet!" my Dad

    Tripoli Central Virginia #25 - BattlePark.org

  6. #6
    Join Date
    14th March 2009
    Location
    Ohio
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    3,394
    Quote Originally Posted by Handeman View Post
    If you are building a cardboard rocket, I would avoid the shear pins and use the x form tape for friction fit. Shear pins will tear up the cardboard.

    Use CA or very thin slow laminating epoxy to seal and stiffen the ends of the cardboard tubes and harden the inside of the tubes where they slide together. You can sand it down after it dries, but having something that will soak in and harden the cardboard will greatly extend the life of the rocket. You'll have to redo the hardening of the ends from time to time, but that's just part of maintenance. I have one DD LOC tube rocket with 45 flights on it. It's always been friction fit which has worked great.

    Good Luck
    I use the tape on the shock cord method too and it works well for me. I use 12 to 15 folds (or more if space is available) on the shock cord and usually have a few that don't break. Tried shear pins on a LOC cardboard rocket once and said never again after seeing the damage it caused.
    Zeus-cat
    NAR# 92125 L1
    Total Impulse for 2018: 491.6 N/s Flights: 10
    2017: 1/2A:0, A:2, B:1, C:2, D:2, E:1, F:1, G: I have NEVER launched a G motor, H:0, I:1

  7. #7
    Join Date
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    Houston, TX
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    Awesome, I’ll save the shear pins for the Formula 98 when I get ready to build it for lvl 2. Want to get a lot of DD flights first with progressively bigger motors.

    One mlre question - I know the booster is just like motor deploy but the upper bay with the main has two attachment points (Av-Bay and NC). Do you guys just friction fit both sides of payload bay? I don’t see how you could permanently attached it to th Av-Bay since you need to fill the well and put match in. I promise I understand the theory behind DD - it’s just the small parts I never considered!
    TRA #17256
    Tripoli Houston
    L1 - 7/8/17

  8. #8
    Join Date
    20th April 2012
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    Fredericksburg VA
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    The payload tube is usually attached to the av bay coupler with some type of removable bolts or rivets. What I do is drill and countersink 6 holes then attach 6 hex nuts to the inside of the av bay coupler tube with epoxy putty. Then attach the payload tube with stainless flat head machine screws . . .

    NAR Level 3 #96210

  9. #9
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    Thumb rivets on smaller rockets, screws on bigger. There is also the method where the coupler is glued into the payload and then the AV bay is slid down the payload into place. GLR kits use that method. Ask questions if you need more info.

    John S. ---- NAR #96911 ---- TRA #15253 ---- MDRA #067
    L1, 3/15/14: Aerotech Sumo, CTI H133BS
    L2, 6/21/14: Giant Leap Vertical Assault, CTI J240RL
    L3, 3/12/16: MAC Performance Radial Flyer, CTI M1101WH
    Altitude: 13,028', L3 flight; Speed: Mach ???, L3 flight

  10. #10
    Join Date
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    Ohio
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    You can friction fit the payload bay to the av bay, but this can be an issue if you need to make a change after you have prepped the rocket. I speak from personal experience. And I've seen rockets that require 2 or 3 people to pull them apart because of a really tight friction fit. And remember that temperature changes can cause things to get tighter or looser. What seemed like a good fit at home in a nice warm house may be too tight or loose in the field. Use screws or rivets as Bat-mite suggested. If you use screws, bring a power driver to drive them in and out; especially if it is cold where you are launching. Trying to use a screwdriver in the cold is really tough. And bring extra screws or rivets in case you drop some.
    Zeus-cat
    NAR# 92125 L1
    Total Impulse for 2018: 491.6 N/s Flights: 10
    2017: 1/2A:0, A:2, B:1, C:2, D:2, E:1, F:1, G: I have NEVER launched a G motor, H:0, I:1

  11. #11
    Join Date
    19th January 2009
    Location
    Stafford VA
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    Quote Originally Posted by Zeus-cat View Post
    You can friction fit the payload bay to the av bay, but this can be an issue if you need to make a change after you have prepped the rocket. I speak from personal experience. And I've seen rockets that require 2 or 3 people to pull them apart because of a really tight friction fit. And remember that temperature changes can cause things to get tighter or looser. What seemed like a good fit at home in a nice warm house may be too tight or loose in the field. Use screws or rivets as Bat-mite suggested. If you use screws, bring a power driver to drive them in and out; especially if it is cold where you are launching. Trying to use a screwdriver in the cold is really tough. And bring extra screws or rivets in case you drop some.
    +3 on using screws/rivets, power driver, and extra screws/rivets.
    Handeman

    TRA #09903 L3 3/29/2015

    "If you don't use your head, you have to use your feet!" my Dad

    Tripoli Central Virginia #25 - BattlePark.org

  12. #12
    Join Date
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    Quote Originally Posted by Nathan View Post
    The payload tube is usually attached to the av bay coupler with some type of removable bolts or rivets. What I do is drill and countersink 6 holes then attach 6 hex nuts to the inside of the av bay coupler tube with epoxy putty. Then attach the payload tube with stainless flat head machine screws . . .

    Jesus...I swear that's just a gratuitous shot showing off how gorgeous your paint jobs are! My Alfa Romeo Giulia doesn't even look that nice!!
    NAR 96681
    L1 - May 29, 2014 LOC Norad ProMax, H120
    L2 - Feb 21, 2015 Fiberglassed Madcow Frenzy, J280

  13. #13
    Join Date
    31st May 2017
    Location
    Houston, TX
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    Thanks guys,

    Have the av bay built and gonna mount everything on the sled this weekend. Couple questions - LOC seems to really want epoxy on all the nuts for the all thread - why? If I ensure it is tight and have nyloc nuts on the non wingnut side I don't see what problems there could be? I know epoxy on the eye bolts is a good idea.

    Also could you perhaps post a link to the plastic thumb rivets you use? Or a picture of how they are attached to the av bay? I would think just drilled into the coupler and stuck through the drilled hole and held in place with some epoxy on the backside?

    For reference this is a LOC EZI I plan to put up on a I161.
    TRA #17256
    Tripoli Houston
    L1 - 7/8/17

  14. #14
    Join Date
    5th December 2013
    Location
    MD
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    Riverts: https://www.mcmaster.com/#click-lock-rivets/=1bnj7df

    Drill a hole, push it in with your thumb. Pull it out with pliers (or fingers if you have good nails).

    I have never epoxied my nuts. Nyloc on the payload end, wing nuts on the drogue end.

    John S. ---- NAR #96911 ---- TRA #15253 ---- MDRA #067
    L1, 3/15/14: Aerotech Sumo, CTI H133BS
    L2, 6/21/14: Giant Leap Vertical Assault, CTI J240RL
    L3, 3/12/16: MAC Performance Radial Flyer, CTI M1101WH
    Altitude: 13,028', L3 flight; Speed: Mach ???, L3 flight

  15. #15
    Join Date
    31st May 2017
    Location
    Houston, TX
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    218
    Ahh, I was thinking it was a two part rivet that had one side stay put. I get it now - they are ordered!

    Lol, perfect. I think I am ready to go aside from e-matches. Think the ones from Chris' Rocketry are the ones I want to go with.

    Last question- even with a washer and screw in the charge well do you seal it with grease or epoxy?
    TRA #17256
    Tripoli Houston
    L1 - 7/8/17

  16. #16
    Join Date
    5th December 2013
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    Quote Originally Posted by viciouspeanut View Post
    Last question- even with a washer and screw in the charge well do you seal it with grease or epoxy?
    I use the Doghouse charge wells from Binder Design. I have never sealed them with anything. You do want to make sure that any holes in your bulkheads (to allow wires thru, etc.) are sealed so that the explosive gasses don't ruin the electronics inside.

    John S. ---- NAR #96911 ---- TRA #15253 ---- MDRA #067
    L1, 3/15/14: Aerotech Sumo, CTI H133BS
    L2, 6/21/14: Giant Leap Vertical Assault, CTI J240RL
    L3, 3/12/16: MAC Performance Radial Flyer, CTI M1101WH
    Altitude: 13,028', L3 flight; Speed: Mach ???, L3 flight

  17. #17
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    31st May 2017
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    Houston, TX
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    Gotcha, I intend to seal the hole for the e match up. Vasoline work for that?

    DD is simple enough in concept but trying to do it the first time is a little nerve racking haha
    TRA #17256
    Tripoli Houston
    L1 - 7/8/17

  18. #18
    Join Date
    27th July 2014
    Location
    south beloit, IL
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    Quote Originally Posted by viciouspeanut View Post
    Gotcha, I intend to seal the hole for the e match up. Vasoline work for that?
    Only if you want a mess. I use poster sticky tack.
    NAR# 99285
    Tripoli# 16283
    L1- 4/26/2015 Madcow Cowabunga- H123SK
    L2- 11/1/2015 Wildman Darkstar 2.6- J355RL
    L3- 11/3/2017 Wildman V2 6" - M1780NT
    Woosh
    QCRS

  19. #19
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    I use terminal blocks on the bulkhead and have a permanent wire that goes up from the altimeter, so I just put a drop of 5-min epoxy in mine. Clay or Play-Doh are less permanent options.

    John S. ---- NAR #96911 ---- TRA #15253 ---- MDRA #067
    L1, 3/15/14: Aerotech Sumo, CTI H133BS
    L2, 6/21/14: Giant Leap Vertical Assault, CTI J240RL
    L3, 3/12/16: MAC Performance Radial Flyer, CTI M1101WH
    Altitude: 13,028', L3 flight; Speed: Mach ???, L3 flight

  20. #20
    Join Date
    31st May 2017
    Location
    Houston, TX
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    Thanks guys. All set up now except for BP. Hopefully I'll have a positive report soon for my first DD flight.
    TRA #17256
    Tripoli Houston
    L1 - 7/8/17

  21. #21
    Join Date
    31st May 2017
    Location
    Houston, TX
    Posts
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    Hey everyone,

    Almost all set - have vents holes piloted (gonna CA them and then drill out tonight), and hope to ground test tomorrow. Since it is my first DD flight and I want to make sure it is safe I am using motor eject backup drilled three seconds after simm'd ideal delay and I was going to fly drogue-less but am now thinking about using a 24" chute I have as the drogue so if for some reason I have issues it wont come in so hot.

    Thoughts? Rocket unloaded weight is 77 ounces.
    TRA #17256
    Tripoli Houston
    L1 - 7/8/17

  22. #22
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    5th December 2013
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    MD
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    How are you going to ground test? Seal up holes and pull a vacuum with a vacuum cleaner? Pull e-match leads out thru a vent hole and attach an Estes launch controller?

    John S. ---- NAR #96911 ---- TRA #15253 ---- MDRA #067
    L1, 3/15/14: Aerotech Sumo, CTI H133BS
    L2, 6/21/14: Giant Leap Vertical Assault, CTI J240RL
    L3, 3/12/16: MAC Performance Radial Flyer, CTI M1101WH
    Altitude: 13,028', L3 flight; Speed: Mach ???, L3 flight

  23. #23
    Join Date
    31st May 2017
    Location
    Houston, TX
    Posts
    218
    I am planning on using estes igniters with a launch controller and wires ran through switch port.
    TRA #17256
    Tripoli Houston
    L1 - 7/8/17

  24. #24
    Join Date
    14th March 2009
    Location
    Ohio
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    Good luck.

    Label or identify everything that needs to be hooked up a specific way. For instance, drogue and main wires in the av bay so you don't accidentally wire them up reversed. The first time I did DD I was pretty nervous and could easily have messed it up. You might want to explain and show the whole setup to someone before closing up the rocket. They don't even need to know what you are talking about, but it is amazing how talking stuff through finds mistakes.
    Zeus-cat
    NAR# 92125 L1
    Total Impulse for 2018: 491.6 N/s Flights: 10
    2017: 1/2A:0, A:2, B:1, C:2, D:2, E:1, F:1, G: I have NEVER launched a G motor, H:0, I:1

  25. #25
    Join Date
    31st May 2017
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    Houston, TX
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    Thank you,

    I plan to have on of our seasoned guys watch my assembly and prep of my avbay and setup before launch. Hopefully this will help me catch and any whoopsies.
    TRA #17256
    Tripoli Houston
    L1 - 7/8/17

  26. #26
    Join Date
    27th July 2014
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    south beloit, IL
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    Donít forget to plug the motor tube before testing the drogue or it wonít pressurize properly. Also, make sure you plug it well, or youíll end up shooting a flaming dish towel across the yard.
    NAR# 99285
    Tripoli# 16283
    L1- 4/26/2015 Madcow Cowabunga- H123SK
    L2- 11/1/2015 Wildman Darkstar 2.6- J355RL
    L3- 11/3/2017 Wildman V2 6" - M1780NT
    Woosh
    QCRS

  27. #27
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    31st May 2017
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    Houston, TX
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    Quote Originally Posted by djs View Post
    Don’t forget to plug the motor tube before testing the drogue or it won’t pressurize properly. Also, make sure you plug it well, or you’ll end up shooting a flaming dish towel across the yard.
    Nice lol. My wife is extremely supportive but if I had flaming bits flying around that might test her haha. I’ll stick and empty casing in it for this.
    TRA #17256
    Tripoli Houston
    L1 - 7/8/17

  28. #28
    Join Date
    10th July 2007
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    Melbourne, Australia
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    Gotcha, I intend to seal the hole for the e match up. Vasoline work for that?
    I use hot-melt glue in this situation sometimes. Easy to apply, easy cleanup.
    TRA 13430, Level 3

    "Everybody's simulation model is guilty until proven innocent" (Thomas H. Lawrence 1994)

  29. #29
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    31st May 2017
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    Well ground test of one charge is done and 1.8 grams stretched the cord even with forgetting to plug the motor mount.. lol

    will test the other charge tomorrow.
    TRA #17256
    Tripoli Houston
    L1 - 7/8/17

  30. #30
    Join Date
    19th January 2009
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    Stafford VA
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    Quote Originally Posted by viciouspeanut View Post
    Well ground test of one charge is done and 1.8 grams stretched the cord even with forgetting to plug the motor mount.. lol

    will test the other charge tomorrow.
    Are you saying your drogue charge stretched the shock cord out without a motor case in the MMT? Just and empty tube and you still got ejection and cord stretch?

    If that's the case, then go back and do it again with the MMT filled. That amount of charge without anything in the tube will be way too much with a motor in. The result is a huge shock load when the two halves hit the ends of the drogue shock cord. Probably resulting in a main deploy at apogee. And that would be the least damaging result. Remember, the apogee charge only needs to open the rocket and get the drogue into the air stream. It doesn't need to push the two halves to the ends of the shock cord.

    Handeman

    TRA #09903 L3 3/29/2015

    "If you don't use your head, you have to use your feet!" my Dad

    Tripoli Central Virginia #25 - BattlePark.org

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