Wanting to add another Midget
upscale to my fleet of Midgets, I selected 30mm tubing from Quest as
the starting point. This tubing allows the use of full sized
motors versus shorties as used in the original K-40 Midget. The
Quest T-30 tubes make it about a 1.2x upscale.
I had already built one this scale, but after
a major wreck and repair, it had grown too heavy for flying on A
boosters. Wanting something a little lighter, I built this
replacement.
 I really
like the way the colors turned out. The red and blue monokote
trim tape make for easy finishing without all the effort required in
masking and painting.
Somehow, when I was sanding the booster fins, I took off too much
material on the root edse so as to change the sweep angle of the
fins. The result is that the rocket has a slightly un-Midget look
about it.
C'est La Vie. Stuff happens 
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| The recovery system
features kevlar from the motor mount connected to a nomex ribbon thru
the opening. |
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The ribbon is made from
nomex cloth which has been folded double and then stitched around its
perimeter.
The ribbon protects the body tube against zippers as might occur in the
event of an early or late deployment.
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The ribbon connects to
kevlar which continues on to the nosecone. The kevlar is stitched
to the nomex.
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For absorbing the shock of
a hard deployment, shock absorbers are included 
If
an early or late deployment occurs, when the chute opens, it tends
to jerk hard on the rocket. This can result in shredded
suspension lines, broken shock cords and zippered body tubes.
To make the shock absorbers, loops are formed in the kevlar shock cord,
and then masking tape is wrapped around the loops as shown below.
When the kevlar draws taught, if enough force is applied, the tape will
be torn. This dampens the jerk of a hard deployment and helps
prevent zippers, shreds and separations. I've had great luck
using this method.
Compared to elastic, this method disspates the energy. Elastic
will store it, and when released, it brings the nosecone crashing back
into the rocket.
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I like this shot.
The lighting makes it appealing to me.
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The nosecone was turned
from cedar. I hollowed out the base with a forstner bit to recess
the screw-eye. Space in these short rockets is limited, so having
a little extra room for the shock cord is very helpful.
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Since the screw-eye is
recessed in the nosecone, another attachment point is needed for the
chute or streamer. This ring is inserted in the shock cord where
the parachute can be readily connected.
In my case, all my chutes and streamers have snap swivels on
them. The swivels connect easily to the ring. Without the
ring, connecting the swivel directly to the kevlar makes it prone to
fraying thereby making it weaker.
The kevlar loops connect to each other and also thru the ring. If
any part fails, this will help to keep the pieces together.
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8-17-2010
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