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  1. #1
    Join Date
    6th September 2009
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    1,314

    Loading rocket on an angled rod/rail?

    Which method do you prefer?

    Click image for larger version. 

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    I used to go with A, thinking less contact with the rail and less friction. Wind would usually blow an Estes model on a rod into this orientation anyway. However, I worried that a top heavy rocket may torque/bind the buttons. This forced me to add a 3rd rail button near the CG on some models.

    Method B may be more secure riding up the rail with just a minor friction penalty.


  2. #2
    Join Date
    23rd July 2011
    Location
    Butte, MT
    Posts
    1,194
    I don't think it matters. Either way the friction should be the same, the y component of the weight x the coefficient of friction.


    Steve Shannon

    Steve Shannon
    L3CC, TAP, Director, Tripoli Rocketry Association

  3. #3
    Join Date
    26th November 2009
    Posts
    3,653
    Ditto,

    Also remember that if one has access to a simulator to run several simulations in a variety of wind conditions. One may find if they do a few degrees on the rail downwind of the prevailing winds, they may find the rocket does a curved flight to a minimal
    velocity apogee. That's an ideal state to dump the main or the drogue for a lower stress deployment.

    If one puts too much angle upwind (into the prevailing winds) the rocket may weathercock further into the wind (depending on the fin area)
    adding more of an angle to the trajectory and a higher velocity deployment at the "lower" apogee.

    It's a tradeoff.
    Kurt

  4. #4
    Join Date
    6th September 2009
    Posts
    1,314
    Quote Originally Posted by Steve Shannon View Post
    I don't think it matters. Either way the friction should be the same, the y component of the weight x the coefficient of friction.


    Steve Shannon
    Yep, I can see that. I was thinking that B, due to gravity, would more often make body tube contact with the rail (body tubes do get scraped up from rubbing on the rail.). So, two fiction coefficients at play: lug on rail, and body tube on rail. Very minor, I am sure.

  5. #5
    Join Date
    23rd July 2011
    Location
    Butte, MT
    Posts
    1,194
    Quote Originally Posted by Buckeye View Post
    Yep, I can see that. I was thinking that B, due to gravity, would more often make body tube contact with the rail (body tubes do get scraped up from rubbing on the rail.). So, two fiction coefficients at play: lug on rail, and body tube on rail. Very minor, I am sure.
    You're right, if your buttons allow your body tube to contact the rail that is another source of friction. That's more likely with the 1010 rails than the original Blacksky rails which weren't much wider than the buttons.
    When I set up the pads at our launch I'm more driven by the following:
    1. When the rail folds down it must point away from the spectators.
    2. I don't want the rail between the spectators and the rocket because it might be a distraction in photos. (Not a huge concern, but why not).
    3. I always tilt the upright rail slightly away from the flight line.

    Those criteria result in the rocket laying on the rail instead of being suspended from it.


    Steve Shannon
    Steve Shannon
    L3CC, TAP, Director, Tripoli Rocketry Association

  6. #6
    Join Date
    19th January 2009
    Location
    Stafford VA
    Posts
    6,645
    +1 on that. We do all the same things with all of our club rails. The only angle is slightly away from the spectator area, otherwise they stay vertical.

    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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