Shell making

I would like to thank to Andrej for
showing me details on how to make a good shell.

First you have to check what kind of mortars you have
available. I have available 75 mm mortars so I choose a tennis ball as a
model for my hemispheres (tennis ball is 67 mm in diameter). When using
tennis or any other sphere I first cut paper into a desired length. For one
paper sphere I need six peaces of paper that is glued on one side with
water-activated glue. The paper I used here is 50 mm wide.

After I cut the paper I put some foil on a tennis ball to
protect from gluing on a ball. Then I start gluing the papers on the ball,
perpendicular on each other. On a last paper I draw a centerline and
carefully put it on a center of a coated ball. Then I use a sharp blade to
cut it straight on a centerline and taking care not to damage too much the
tennis ball. After removing and marking the spheres so that later I can put
together exactly where they were separated, you put them aside to dry. After
drying you have two hemispheres with thickness of 1 mm. All details are
covered in pictures.

Later I have produced a mould so that I can simply press
the hemispheres. For pressing I use 5 pieces of a 10*10 cm paper with
water-activated glue. One by one I moisten with spray and put them into the
mould by pressing each one separately. I cut excessive paper with scissors
after it’s dry.

So
now hemispheres are finished now its time to make some rice hulls for filling
the interior of the shell. Since I live in Europe
where rice hills are not common and costs from buying it from Skylighter are enormous I have to use something else.
Simple hay is very useful. All you have to do is cut it on a peace of 1 cm
length mixed it with water, let it wet thoroughly and then mixed it with meal
powder. I didn’t use any dextrin with meal powder and it still sticks
to hay very well. Another good material for filling are
macaroni. I use small star shape. They are little heavier than hay but very
useful. Lately I discovered rice that is used as a dog food. This is not
ordinary rice it’s like rice in a rice chocolate. It is very cheap and
when wet since it contains starch, meal sticks very well on it.

Off course you have to have some stars to make a shell.
You can have cut, pumped or pressed and rolled stars. For a beginner I
suggest cut stars since they are easiest to make. There are lots of star
compositions but you have to be sure that it is not incompatible with BP
composition (chlorate). Great and simple star composition is Flash No. 5 from
Wouter
web page. I use atomized aluminum. Boric acid is added to prevent a reaction
between nitrate and aluminum.

I have used following formula

Potassium nitrate

50

Sulfur

30

Atomized aluminum

20

Dextrin

3% of total weight

Boric Acid to prevent
reaction between nitrate and aluminum

1% of total weight

I don’t use ball
mil for that composition simply mixing through screen is enough for achieving
good effect. Add approximately 10 % of water to mixed composition and then
mixed it well. It should have consistency of dough. Then make a plate from
that dough in thickness of 7-8 mm and simply cut it with a long knife on a
10*10 mm squares. Let it dry on the sun or on a radiator and separate stars
when they are dry. Then put them in a bowl spray it again with water and
prime it with BP meal. Stars should be thoroughly coated with meal to ensure
good ignition. Let it dry for a few days before you actually use them in a
shell.

After you have stars dry
it's time to process the shell. Drill or punch a bottom center of a
hemisphere with a drill bit in a size of your time fuse.

Cut desired length of
time fuse. I cut it diagonally to expose as much of BP core.  Use sharp
blade not scissors in order not to crush BP core.

Drill a hole in a time
fuse so that you can insert a piece of black match into that hole to assure
good ignition. Andrej is recommending inserting a
black match on both internal and external side of a shell. So far I haven't
had any dudes if I didn't put internal black match, but i
did have them if I didn't put external black match..

Insert a black match
into the drilled hole in a hemisphere and glue it with a
hot glue from the outside. You must be very exact when you glue it
because a fire from lift can easily pass through a bad glued hole and
producing a flower pot.

Put a
hemispheres onto a big enough glass so that it can sit on top of it
and start filling with stars. After reaching the top of a hemisphere you fill
the center hole with rice hulls or any other filling that you have chosen..

Filling all gaps with a BP filler you will then put a little spoon of whistle
mix in a center of each hemisphere. Well perhaps that little spoon isn't
very good description for a qty of whistle (thanks Steve) I measure it and it
is 2.5 g in each hemisphere that is 5 g on a shell.

Now it's time to put
those hemispheres together. Put a paper onto one hemisphere. Be sure that it
doesn't have any gaps between the paper and hemisphere so that you can loose
any of whistle mix (it's very important that hemispheres were cut in a
straight line).  Turn a hemisphere with a paper upside down and put it
onto another hemisphere. Have prepared a desired length of a tape so that you
can join the hemispheres. Carefully start pulling the paper out so that you
don't loose any of stars, BP filler. But if it happens don't worry there is
plenty left. Tap with a small piece of wood on a joint so that it fits
perfectly and then tape it with prepared piece of tape.

After taping we have to
reinforce the shell. That is done with 12 pieces of same water activated
paper. One by one perpendicular on each other and having in mind that the
thickness of the wall must me same all around we use all 12 pieces. After
each one paper you use a wood or plastic to adhere one layer of a tape on
other perfectly. Let it dry and then put a piece of hemp in a center so that
you can put it into the mortar. And here it is finished aerial shell just
waiting to put lift powder undo and to light a sky for you. I use 20 g of
home made lift powder to achieve medium altitude. I know that the shell can
stand even 40 g of lift and altitude is very good, and I don't know where is the limit but I will let you know.