Saturday, August 21, 2010

Big Girtha Build Shock Cord Retention Part 7

I'm not a big fan of the old Estes "Tea Bag" method of shock cord retention.
This is certainly not a new idea, I remember seeing it in older Centuri instructions. This style of shock cord mount should only be used in bigger body tubes, BT-55 and larger. It won't interfere with parachute ejection on larger diameter tubes.
Grab some scrap tube, close to the diameter of your model. This scrap is larger than the Girtha's Quest 40mm tube. In the end, it won't matter. A 1" tall strip has been marked for cutting.





That piece was cut to about 1 3/4" wide. Sand the back side of this tube scrap for better "grab" with the glue. The 1/4" x 54" elastic shock cord was tied to it.








Glue the mount inside the front of the body tube allowing enough clearance for the shock cord knot and shoulder of the nose cone.
Here's the mount in place inside the main body tube. White glue has been rubbed around and over the mount.

2 comments:

  1. Interesting. It looks quite secure.

    How has the mount held up in the last five years?

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    Replies
    1. Hi Daniel,
      The mount is just fine! That first Big Girtha was lost at recovery and sat outside for over a month. I built a second one and have flown it a few times.
      This style of "Centuri" mount is good on BT-55 to BT-80 models .
      It would still block ejection on BT-5, 20 and 50 size rockets like a tri-fold mount can.

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