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Thread: Scratch Build

  1. #1
    Join Date
    28th November 2017
    Posts
    6

    Scratch Build

    Hello All! Been reading this forum for a long time but this is my first post. I am looking at doing a scratch build or maybe adapting a current rocket in order to have interchange motor mounts. I love the idea if having options of motors. After doing some research, I think I am going to do a 66mm (or BT-80) motor mount in order to have the following motor combos:
    7x or 5x 18mm
    1x24mm and 4x 18mm
    4x 24mm
    3x 29mm
    2x 29mm and 2x 24mm

    Looking around US rockets website I've seen a couple rockets that already have a 66mm mount I could base my design on.

    Mu question is, how will these various mounts change the center of pressure and gravity of my rocket and what might I have to do when changing to different mounts in order to maintain stability?

    Sent from my XT1585 using Rocketry Forum mobile app


  2. #2
    Join Date
    14th July 2015
    Location
    Randolph, NJ
    Posts
    3,237
    More weight in the tail will pull the center of gravity towards the back; if needed, this would usually be compensated by additional weight added to the nose, to keep the center of gravity safely ahead of the center of pressure. Your best bet for something like what you're planning is to grab OpenRocket and put together a simulation for it. That'll tell you where your CP and CG are and you can proceed from there.

    I recommend the self-contained installer.


  3. #3
    Join Date
    28th November 2017
    Posts
    6
    Got ya.... So already started some design work in open rocket. I'm hoping to design a retention system like semroc uses on the Brighton and laser SLS models. Think this is do-able?

    Sent from my XT1585 using Rocketry Forum mobile app

  4. #4
    Join Date
    19th February 2017
    Location
    The world, probably
    Posts
    471
    You may be interested in this page... http://www.marcsfatboyfleet.zapto.org

    Sent from my LGL44VL using Rocketry Forum mobile app
    NAR #104043

    crmrc.org

  5. #5
    Join Date
    28th November 2017
    Posts
    6
    Nah.... That's way overdone to me. I like multistage clusters. I'd really like to build one of the US rockets high test models. Either 4x29mm to 4x29mm, 3x29mm to 3x29mm, or 3x24mm to 3x24mm 2 stage rockets. Have to be an awesome launch..

    Sent from my XT1585 using Rocketry Forum mobile app

  6. #6
    Join Date
    27th August 2011
    Location
    West Tennessee
    Posts
    2,707
    So this will be high power rocket by propellant load and need a waiver?
    It is amazing what you can do when you don't have a choice.

    Smart people learn from their mistakes.
    REALLY SMART PEOPLE learn from OTHERS' mistakes.

  7. #7
    Join Date
    28th November 2017
    Posts
    6
    Didn't say I was building
    A Hi-test models.... Just said I like em....

    Sent from my XT1585 using Rocketry Forum mobile app

  8. #8
    Join Date
    30th January 2016
    Location
    US > OK > NE
    Posts
    3,483
    Quote Originally Posted by BABAR View Post
    So this will be high power rocket by propellant load and need a waiver?
    3x D12 to 3x C11 gets the job done in under 4oz of propellant, I believe.


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