Saturday, April 28, 2018

Building the Shrox Sniple - Part 2, Construction and finishing...

There are no instructions for building the Sniple, but it is very straightforward - only thing that is different from a "standard" rocket like the Alpha is that you have to note that the forward fins are 4" from the rear of the body tube. My build proceeded as follows:
  • An 18" length of BT-50 was cut to 13", using the Estes tube cutting guides (very handy for quickly cutting Estes tubes). The tube spirals were filled with water-thinned Fill N Finish and allowed to dry until late afternoon of the next day.
  • While the body tube was drying, the fin patterns were printed out on card stock. A 6" sheet of 1/16" basswood was sanded smooth using 400 grit sandpaper, and three of each pattern traced, making sure the grain was parallel to the leading edges. The fins were cut out using a sharp hobby knife, and the non-root edges rounded using 240 grit sandpaper.
Assembled Sniple motor mount (Click to enlarge).
  • The motor mount was assembled (an Estes BT-20J, Semroc AR-2050, Semroc AR-2050S, and a standard 18mm motor hook). Most folks use some sort of tape around the middle of the tube to help hold the hook in place, but I cut a strip of card stock and glue it around the tube; I find this to be much more durable than tape. A length of kevlar thread was tied to the motor hook and run through the upper centering ring - the sewing elastic shock cord was then tied to the end of the kevlar thread. To avoid "Estes dents", my shock cords are always at least twice the length of the rocket.
Sniple body tube with spirals filled (Click to enlarge)
  • After they had dried, the tube spirals were sanded smooth using 240 grit sandpaper, and the motor mount glued into the body tube. I used the spiffy Qualman Rocketry fin alignment guide to mark the fin and launch lug lines, which ran for 8" from the rear of the tube. A strip of card stock was used to draw a line around the tube at the 4" mark - this served as a guide for placing the rear of the forward fins.
BT-50 Qualman Rocketry fin guide for 1/16" fins (Click to enlarge).
  • The fins were glued on using Aileen's Tacky Glue with the double glue joint technique. The Qualman guide functioned as a jig to insure proper alignment of the fins - it's quite a versatile tool. After the glue dried, fillets were created using 3 applications of Titebond wood glue smoothed with a finger.
  • 4 coats of Brodak sanding sealer were brushed on, sanding with 400 grit after coats 2 and 4. At this point, the basswood fins were smooth as glass, and ready for primer and paint.
As of this writing, the Sniple has just been sprayed with the first coat of gray Krylon primer. I will wait a week to give it plenty of time to dry in the Southern humidity, sand most of it off, then hit the model with a coat of white primer. I will pick up this build thread when I have started the painting.

Ready for primer (Click to enlarge).

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