by Mark Simpson
As part of my Level 3 project, building and flying a full-sized orange traffic barrel, I decided
to make a 1/6th scale flyable traffic barrel to test its dynamic flight stability.
I started with a 3" section of garden variety mailing tube, donated by an office mate. I scrounged a piece
of 6" mailing tube from another office mate to use as a larger ring fin. Since the "real" traffic
barrel, purchased for the L3 project, was sitting in my garage already, I got out my tape measure and went to town
Here's a summary of the major dimensions:
Height at top of barrel (flat surface) : 36"
Diameter at top of barrel : 18"
Flasher: 6" long, 4" high at top of battery pack.
Flasher dome: 8" in diameter
Now that I had the basic dimensions, I went to work creating the model.
Here's a materials list:
- 6" of 3" mailing tube for the body
- 1" of 6" mailing tube for the ring fin
- 1 Stainless Steel Fishing Leader for shock cord anchoring
- 1 small screw in eyelet for shock cord mount
- 3' of nylon shoelace
- Handful of politically correct steel bird shot mixed with non-hardening modeling clay scrounged from "the
- Scraps of wood cut into 1" x 2/3" _" blocks for flasher base
- 4 small wooden 1-1/4 convex disks (scrounged from wife's Michael's Craft Store supplies)
- 1/16" balsa wood scraps for centering rings and fin supports.
- Aluminum foil
- 4" of 29mm motor tube
- Titebond II Wood Glue
- 3" circle of basswood for barrel top
- 3" X _" strip of basswood for (something or other, Mark you left this out - ed.)
I started by cutting 6" of 3" mailing tube on my Miter saw, then cutting a 1" ring off of a
6" mailing tube, using an Exacto knife.
Using VCP I printed out a fin alignment guide using the following information:
# of fins: 8
I laid the 3" body tube on the alignment and positioned the 6" outer ring so that the radiating lines
from alignment guide were even all the way around the ring. This ensures that the 6" ring fin is equidistant from
all points. I then marked the inside of the radiating line so that I could measure the length of balsa needed to act as
supports for the ring fin. (It was slightly less that 1.5") I cut out 8 supports from scrap balsa that were
roughly 1.5" X 1", making sure that the grain was perpendicular to the body tube. I test fitted the 8
supports inside the ring fin, while sitting on the fin alignment guide. After some minor adjustments and sanding, I
glued all 8 supports in place. (Getting them straight was easy since I glued them on top of the alignment guide.) Once
dried, I filletted all joints to add strength and removed the assembly from the guide.
The motor mount assembly is made from a small piece of 29mm motor tube ~5" and balsa for centering rings.
To strengthen the centering rings, I made four and glued them in sets of two with one of each pair having it's grain
perpendicular to the other for strength. I glued both ends on and drilled a hole to pass the shock cord through.
A basswood sheet cut into a 3" circle forms the barrel top and a 3" strip of basswood acts as the flasher
support. (see below for details). For the flashers, I cut two 1" x 2/3" _" blocks from scrap wood to
serve as the battery pack (white base). The flashers were 1-1/4" one-sided convex "buttons" found in my
wife's craft box. Gluing two together gave a nice convex lens assembly. Then I drilled through the center of the lens
assembly and the middle of the flasher and inserted a small dowel to hold the lens on top of the base. (The dowels
aren't visible in the photo, but are located at the glue joint) I glued the flasher support and both flashers to the
top of the barrel at once so that I could ensure the support was perpendicular to the barrel top.
Now comes the shock cord attachment and weighting process. I used a small screw eyelet and screwed it into a
_" by _" block of plywood which I glued into the underside of the basswood barrel top (see photo below) Then
I added a _ thick plastic spacer from a brown paper roll endcap and punched out a section so that the launch rod could
go through the rocket. I filled the _" circular gap with a mix of modeling clay and steel shot (estimated at ~2-3
oz). Attached to the eyelet was a stainless steel wire fishing leader. I tied the other end of the leader to 3' of
heavy duty nylon shoelace.
The shoelace is attached to the motor tube assembly. The aluminum foil-covered disk in the picture below is to
protect the shockcord and upper portion of the barrel's insides. Since this is a model the whole motor
assembly should fit loosely in the body tube. The parachute is wrapped around the motor tube ( like in the Estes
Sizzler). Care should be taken when test fitting the assembly so that holes can be drilled to allow the launch rod to
pass through the rocket.
Since this was to serve only as a test vehicle for the real thing, I painted the rocket using water-based
acrylics. The completed project is below.
On Saturday, March 1st, I loaded up the rocket with an F50-4 and it flew perfectly to ~500'. Ejection was just
about right on and the rocket landed within 50' of the pad.