Hello gentleman

Discussion in 'Mid Power Rocketry (MPR)' started by eggsmile, May 17, 2019 at 11:40 AM.

Help Support The Rocketry Forum by donating:

  1. May 17, 2019 at 11:40 AM #1

    eggsmile

    eggsmile

    eggsmile

    Member

    Joined:
    Mar 13, 2019
    Messages:
    7
    Likes Received:
    0
    Gender:
    Male
    I'm trying to make small size rocket for my hobby.

    The length is 70cm and my rocket motor size is 38mm

    also I will use the Aluminum body

    And this is my Question I will make bulk for fixing parachute and i dont know what is

    proper way for it.

    oh by the way, Using paper wadding is usefull?

    which one is learn from Youtube
     
  2. May 17, 2019 at 11:49 AM #2

    cwbullet

    cwbullet

    cwbullet

    Obsessed with Rocketry Staff Member Administrator TRF Lifetime Supporter Global Mod

    Joined:
    Jan 24, 2009
    Messages:
    21,181
    Likes Received:
    972
    Gender:
    Male
    Location:
    Glennville, GA
    Aluminum is probably not the best material for your first rocket.
     
  3. May 17, 2019 at 11:54 AM #3

    eggsmile

    eggsmile

    eggsmile

    Member

    Joined:
    Mar 13, 2019
    Messages:
    7
    Likes Received:
    0
    Gender:
    Male
    I used CPVC but it blow up during experiment for ejection... so it is my best what is good for body material
     
  4. May 17, 2019 at 12:06 PM #4

    dhbarr

    dhbarr

    dhbarr

    Amateur Professional

    Joined:
    Jan 30, 2016
    Messages:
    5,158
    Likes Received:
    375
    Cardboard, kradt phenolic, fiberglass, carbon fiber are commonly used.
     
  5. May 17, 2019 at 12:09 PM #5

    timbucktoo

    timbucktoo

    timbucktoo

    Well-Known Member Staff Member Global Mod

    Joined:
    Jun 13, 2014
    Messages:
    5,342
    Likes Received:
    363
    Gender:
    Male
    Location:
    Cocoa Beach
    How about fiberglass or some cardboard shipping tubes?
     
  6. May 17, 2019 at 12:26 PM #6

    eggsmile

    eggsmile

    eggsmile

    Member

    Joined:
    Mar 13, 2019
    Messages:
    7
    Likes Received:
    0
    Gender:
    Male
    May i ask why cardboard is good for body? the temperature of body is not that high during flight?
     
  7. May 17, 2019 at 12:27 PM #7

    David Schwantz

    David Schwantz

    David Schwantz

    Well-Known Member

    Joined:
    Jul 23, 2018
    Messages:
    360
    Likes Received:
    83
    Gender:
    Male
    Location:
    MN
  8. May 17, 2019 at 12:28 PM #8

    David Schwantz

    David Schwantz

    David Schwantz

    Well-Known Member

    Joined:
    Jul 23, 2018
    Messages:
    360
    Likes Received:
    83
    Gender:
    Male
    Location:
    MN
    Cardboard is lightweight/strength. Not so costly, easy to glue with just wood glue. Easy to cut.
     
  9. May 17, 2019 at 12:34 PM #9

    eggsmile

    eggsmile

    eggsmile

    Member

    Joined:
    Mar 13, 2019
    Messages:
    7
    Likes Received:
    0
    Gender:
    Male
    Thank you for reply David.
    If i have more time i will try it.
     
  10. May 17, 2019 at 1:15 PM #10

    David Schwantz

    David Schwantz

    David Schwantz

    Well-Known Member

    Joined:
    Jul 23, 2018
    Messages:
    360
    Likes Received:
    83
    Gender:
    Male
    Location:
    MN
    Welcome. Ask away, many helpful people on here. There are many manufactures out there, I posted only one. If you did a search you can come up with dozens or so. Sirius, Apogee, Mach 1, PML and the list goes on....
     
  11. May 17, 2019 at 1:49 PM #11

    jlabrasca

    jlabrasca

    jlabrasca

    Well-Known Member

    Joined:
    Oct 31, 2016
    Messages:
    930
    Likes Received:
    221
    Where are you located? In what country?

    Will you be using commercial motors -- like these

    https://www.apogeerockets.com/Rocket_Motors

    or will you be making your own motors?
     
  12. May 17, 2019 at 2:48 PM #12

    David Schwantz

    David Schwantz

    David Schwantz

    Well-Known Member

    Joined:
    Jul 23, 2018
    Messages:
    360
    Likes Received:
    83
    Gender:
    Male
    Location:
    MN
  13. May 17, 2019 at 5:18 PM #13

    jqavins

    jqavins

    jqavins

    Joseph Avins

    Joined:
    Sep 29, 2011
    Messages:
    1,290
    Likes Received:
    162
    Gender:
    Male
    Location:
    Bath, NY
    PVC, if it is old or has seen cycles of high and low pressure, can become brittle, which may explain your previous failure. Cardboard is generally not thought of as being very strong, but it will not go brittle as PVC can. Cardboard is by far the most common material for mid power body tubes.

    Another likely cause of your PVC tube failure is an excessively large ejection charge. What did you use (black powder or something else) and how much, for how much volume of tube to be filled?

    As for your original question, if you are installing a bulkhead to anchor your parachute to, where will the ejection charge be? You would need to have, from bottom to top, the bulkhead, the ejection charge, some sort of 'chute protector, then the 'chute. I'm just checking that you've thought that through.

    For attaching the parachute to the bulkhead, strictly speaking you don't. The nose cone (or as much of the top of the rocket as separates from the bottom) is attached to the bottom by a shock chord (that is, some sort of strap or other rope-like thing that is capable of withstanding the shock when it suddenly pulls tight, and preferably of absorbing some of the energy to mitigate the load on the rocket bits at its two ends) with the parachute's shroud lines attached to the shock chord. Attach them about 1/3 of the way from one end so that the rocket bits at the ends are not bumping against each other.

    So, the real question is how to attach the shock chord to the bulkhead, not the parachute itself. Actually, for what are classed as mid-power rockets the bulkhead is likely not necessary as you can attach the shock chord to the forward centering ring (CR). There are typically two ways to do this. One is to pass it through a hole in the centering ring that is just large enough to let it through. Make the hole close to the motor mount tube (MMT) or even use a slight expansion of the inner MMT hole in the CR in one area. Use epoxy to fasten a several cm of the end of the chord along the side of the MMT, and to fill the hole. And that's it. (In low power rockets something similar is often done. The shock chord is much smaller in these cases, so it is passed around the MMT below the forward CR and tied to close a loop.)

    If you must use a bulkhead, you can tie the shock chord to either an eye-bolt or a U-bolt. That's what's typically done for what are classed as high power rockets, though when I say "tie" I'm leaving out a bunch of details that are important for high power builds. You can also use an eye-bolt or U-bolt in the forward CR if the difference between the body tube and MMT diameters is great enough.
     
  14. May 18, 2019 at 4:09 AM #14

    eggsmile

    eggsmile

    eggsmile

    Member

    Joined:
    Mar 13, 2019
    Messages:
    7
    Likes Received:
    0
    Gender:
    Male
    Thank you iqavins
     
  15. May 18, 2019 at 4:10 AM #15

    eggsmile

    eggsmile

    eggsmile

    Member

    Joined:
    Mar 13, 2019
    Messages:
    7
    Likes Received:
    0
    Gender:
    Male
    jlabrasca I'm using my own motor, and I live in south korea
     
  16. May 18, 2019 at 6:34 AM #16

    jlabrasca

    jlabrasca

    jlabrasca

    Well-Known Member

    Joined:
    Oct 31, 2016
    Messages:
    930
    Likes Received:
    221
    When you say "aluminum body", do you mean the MOTOR CASING or do you mean the AIRFRAME?

    eggsmilequestion1.png
     
  17. May 19, 2019 at 7:21 AM #17

    eggsmile

    eggsmile

    eggsmile

    Member

    Joined:
    Mar 13, 2019
    Messages:
    7
    Likes Received:
    0
    Gender:
    Male
    It mean AIRFRAME yes is it not that good for body?
     
  18. May 19, 2019 at 4:00 PM #18

    jlabrasca

    jlabrasca

    jlabrasca

    Well-Known Member

    Joined:
    Oct 31, 2016
    Messages:
    930
    Likes Received:
    221
    Do you have any one helping you?

    What is your education?

    Most of the people on this forum build rockets from lightweight materials like cardboard or fiberglass. Metal airframe rockets are heavy and are more dangerous to fly.

    Many of us belong to organizations like Tripoli Rocketry Association, Canadian Association of Rocketry, the National Association of Rocketry . These organizations have safety codes that discourage metal airframe rockets.

    Most people on this forum also buy pre-made rocket motors. There are special rules for flying rockets with motors that your made for yourself. We call this Amateur Rocketry or Amateur Experimental Rocketry.

    https://en.wikipedia.org/wiki/Amateur_rocketry
     

Share This Page