Horizon rocket and stability

Discussion in 'Mid Power Rocketry (MPR)' started by jbgust, Nov 15, 2019.

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  1. Nov 15, 2019 #1

    jbgust

    jbgust

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    Hi,

    I recently finished my new home made rocket.

    IMG_20191102_135431_HDR.jpg

    I have use Openrocket for the first time to check is everything is OK.

    horizon-openrocket.PNG
    I read in the "Handbook of model rocketry" that one-calidber is enough and 2 to 3 caliber can be overstable.


    I found a stability of 1.94 caliber. I think that it's correct, anyone can confirm?I think that it's good for static stability but maybe to low for dynamic stability.
     
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  2. Nov 15, 2019 #2

    Eric

    Eric

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    I think the stability is fine.

    Do you have anything keeping your parachute towards the front of the rocket? If not, it will want to shift back. That will lower your stability a little, but it will still fly fine.
     
  3. Nov 15, 2019 #3

    jbgust

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    I can't do that easily beacause I glued the part that maintain the parachute.
     
  4. Nov 15, 2019 #4

    Eric

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    If you have a shelf, bulkhead or baffle holding the parachute forward in the rocket then you are all set.
     
  5. Nov 19, 2019 #5

    jbgust

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    Maybe you can give me another advice, about the launch lug. I read some post on this forum about that, but I'm having a hard time getting an idea. I planned to use that as launch rail :
    IMG_20191119_212657.jpg

    For my launch lug I have 3D print this part (8cm long):
    IMG_20191119_212712.jpg

    I want to glue only one launch lug at the CG. Do you think that one launch lug is enough? Will the glue be strong enough?

    Thank you
     
  6. Nov 19, 2019 #6

    neil_w

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    Nice looking rocket. Is that carbon fiber in the middle? It is beautiful.

    I haven't seen a rocket using a single long rail guide like that. I think my biggest concern would be binding, but I'm not sure really. Low power rockets routinely have a single long (~5 cm) lug around CG, but I haven't seen it with rail guides like that.

    In other words, I am not too helpful. ;)
     
  7. Nov 19, 2019 #7

    Nytrunner

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    Make sure your launch guide (what you call the 'lug') slides easily up and down the rail.

    At 8cm long, that should be enough to constrain the rocket vertically (but I must ask in what direction you printed the part?)

    If I had a single guide such as that, I'd place it between my CG and CP

    What glue are you using?
     
  8. Nov 19, 2019 #8

    jbgust

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    Yes this is carbon fiber. When you say the binding, it's between the tube and the guide?
     
  9. Nov 19, 2019 #9

    jbgust

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    I plan to use expoxy. About the print direction, I have printed it verticaly, so the layers are perpendicular to the launch direction.
     
  10. Nov 19, 2019 #10

    neil_w

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    Between the guide and the rail.

    But Nytrunner is probably right, it's long enough that it should be OK (obviously you need to confirm that the guide slides smoothly in the rail).
     
  11. Nov 19, 2019 #11

    Nytrunner

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    Binding of the rail guide within the slot of the rail. If you test your fit adequately, this shouldn't be a problem.

    That all sounds good
     
  12. Dec 8, 2019 #12

    jbgust

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    Hi,

    Today was the first launch. The flight was really straight.

    vol-1_HORIZON_00014.png DSC_8039.JPG

    Just one problem with the ejection system, the parachute didn't go out. The nose cone and one fin are broken.

    Thank you for your advice
     
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  13. Dec 15, 2019 #13

    rocketgeek101

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    That's a nice looking rocket! What motor did you fly it on?
     
  14. Dec 15, 2019 #14

    jbgust

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    It was an home made sugar motor F68. The apogee was 210m with a top speed of 215 km/h.
     

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