To do your L1 "on the cheap", you can do what I did:
Buy a RalphCo Crayon Bank at Toys R Us for $5 or $6.
Buy a 29mm motor tube from your favorite rocketry vendor for about $2-$3.
Buy 3 pieces of 6" x 12" x 1/8" 5-ply aircraft plywood at your local hobby store, or from some place like Tower Hobbies online, for under $10. Use this to make 3 fins, and 2 centering rings to fit your motor tube in your bank, and a third centering ring that's smaller to fit inside the plastic tail cone, and provide a place to anchor your motor retention.
Not to scale:
Code:
+---+
| \
| \
| |
~|~~~===|=============================
{ | |# #
{#| |# #
-----------------------
-----------------------
{#| |# #
{ | |# #
~|~~~===|=============================
| |
| /
| /
+---+
Legend: ~ and { are plastic
+, -, and | are plywood fins
# are plywood centering rings
---- is the motor mount tube
Use about 15' of tubular nylon for a shock cord, with the parachute 1/3 of the distance from the nose cone. Anchor the cord into the tip of the nose by drilling a hole cross-ways through the tip, tying a loop in the end of the shock cord, and passing a dowel through the holes and the loop. Pour an ounce or two of epoxy into the tip to anchor the cord and the dowel. If the dowel is a tight fit for the holes (e.g.: use a 1/4" dowel and 1/4" drill bit), then the epoxy won't leak out around the dowel. If it's not tight, tape around the outside of each dowel end before you pour the epoxy.
Trim the dowel ends flush with the surface of the nose when the epoxy has hardened.
Use a razor blade, utility knife, or Xacto to trim the "ribs" of the nose cone base to reduce how tightly it grips into the tube. Or, simply sand it down with coarse sandpaper.
Use an eyebolt or a u-bolt to attach the other end of the shock cord to the forward centering ring. Use washers, and add epoxy over the nuts to keep them from unscrewing themselves over time.
Use a couple of T-nuts with screws and bent scraps of metal for motor retention.
Total rocket cost, including hardware & epoxy: $25-$30, assuming you can borrow a nylon parachute (around 42" - 48" works great) from another of your rockets.
Then, buy the Aerotech L1 Cert special. You get a 29/180 motor case with closures, and an H128 reload, for about the price of the reload alone ($20, if I recall correctly). The default "medium" delay on an H128 is just about perfect for this rocket.
- Rick "the crayon rocket guy" Dickinson
