With the BT-5 tube now at 1 3/4" long you end up with the engine hook extension only 1/4" out the back.
NEWBIES: I don't recommend using tri-fold shock cord mounts in smaller BT-5 and BT-20 diameter tubes. The bulky triple fold paper and double fold of rubber can block a chute or streamer ejection.
I substituted a Kevlar line.
The Kevlar line knot loop goes under the upper bend of the engine hook, Semroc style.
Like in previous builds,
The flat face of the exposed lower centering ring will be seen, rough layer wraps and all.
Rub in some white or wood glue and let dry. Sand with 400 grit. On the finished model that flat ring face will be sealed, smooth and shiny.
To hold the split ring closed while the glue dries -
Slide the lower ring dry into the open end of the BT-20.
Here you also see the cardstock hook retaining wrap between the two centering rings.
That looks a lot nicer.
ReplyDeleteThe second model rocket I built was the Astron X-Ray -- it's the first where I'd seen the dual-slit retention of the shock cord (i.e. cut two horizontal slits, bend the center part in a bit, thread the shock cord through, then re-bend the center part out and glue). At first glance it looked fiddlier than the tri-fold mount (which was used in the Astron Alpha -- the first model rocket I'd built). After building the model, I'd realized the dual=slit method wasn't as fiddly as I'd originally thought, but also realized there would've been challenges in fitting a tri-fold mount (not only is there the extra bulk, but poking your finger far back into the tube to hold the tri-fold mount against the inside of the tube until the glue set might've been fiddly as well).
ReplyDeleteHI Naoto,
DeleteI always hated the dual-slit shock cord retention. The Wac Corporal (1969) was the first model where I tried to fill the body tube cuts.