| Scamroc
A tribute to the old Estes Camroc with Astron Delta booster |
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| Inspired by the Delta booster, I
decided to build a truly fake,
non-functioning Camroc clone, I call the Scamroc. I got some decals this week and was able to finally finish it. (Thanks, Don.)  From a 1960's era Estes
catalog.
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 I'm really pleased with how the name decal turned out. Not having the original font, I had to swag a lot, but it looks quite close (in my opinion). |
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To build the payload/fake Camroc
section, I culled some dimensions from the web, got some others from
old forum posts and extrapolated a few from various jpegs. I
ended up making the Camroc section out of BT-60 tubing about 4.5"
long. The forward plug is
balsa. Below: I turned the transition from cedar, then hollowed the forward end out to save a little weight.  |
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| The dark
stain on the balsa is apparently just that. Supposedly, the
wood had been used to decorate the set for a play, and when the
production was completed, the wood was donated to DARS where it was
subsequently distributed at a club meeting. I've built several rockets
using it. The dark stain poses no added challenge. |
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For now, the camera section is non-functional. But, from what I've read of the original Camroc, mine will take almost as good of pictures 
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The launch lugs
were mounted differently than specified in the directions.
Rather than putting one on each stage, I opted to put them both on the
sustainer. This way, the lugs don't need to be aligned each time the
rocket is prepped - instead they're permanently aligned. Also, I
upsized them to 3/16", and used a standoff with the grain properly
oriented, unlike the original plans, which had the grain parallel to
the airframe  |
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 Again deviating from the plans, I made the booster
24mm.
Stock, it's 18mm, but without the old, high thrust B14-0 booster motor,
getting a heavy payload rocket
moving
is
a
challenge. The 24mm D12-0 and C11-0 motors are well
suited for this and thus make good replacements for the B14-0, provided
there's a 24mm motor tube  The aft end of the coupler (pink dashed line) was intended to act as the motor block. But I later inserted another ring to move it back a bit further, where the blue line is. |
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| Gap staging will be used in this
rocket, so vent holes are needed to relieve the pressure present during
staging. The two vent holes are visible in this pic. They
are ~1/8" in diameter and directly oppose each other. Also
visible in the pic is the extra ring I added just below the coupler. |
| An external hook is included to
secure the
motor. This ensures the motor stays with the booster, or even
better, the booster stays with the motor. Sometimes at staging,
the booster motor will be ejected while the booster stage stays
attached to the upper stage, with the upper stage motor firing down
thru the booster. The result is a fried booster unsuitable for
re-use. This happens often enough to warrant using positive motor
retention - friction fit just isn't reliable enough in this case. |
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| Mounting the hook begins with
forming a C bend in some piano wire (~0.021" dia). This gives
plenty
of grip for anchoring it to the airframe. The bend prevents the
wire from rolling and from sliding fore and aft. |
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| The bend is curved slightly to
contour it to the airframe. This makes it lie much tighter to the
tube. While it seems minor, this little detail actually helps a
lot. |
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| Once all the bending is done,
the wire is held in place with some masking tape. |
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| I used some hobby epoxy and a
small square of 6oz fiberglass cloth to anchor the wire. The
cloth was cut to size, then I wet it with the epoxy and set it
aside. Some filler was added to the remaining epoxy which was
then placed over and around the C bend, then the wetted cloth was
placed
over that and allowed to cure. The filler thickens the epoxy
which helps it hold its shape until it sets. |
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| Once it had hardened, I cut off
the extra wire and shaped the area with a coarse fiber wheel on my
Dremel tool. The aft end of the wire will be bent and cut to
length later. |
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| Wood filler blends in all the
rough spots. The final product looks pretty good. |
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| While the booster motor is 24mm,
the sustainer motor is 18mm. I use kevlar cord as the leader on
my shock cord/recovery harness. And I like to anchor the kevlar
to the motor mount. It handles well the heat of the ejection
charges, and having it anchored far aft keeps it from interfering with
the parachute during deployment - there's no "tri-fold mount" on the
inside wall of the body tube for the parachute to slide past at
ejection. In this case, I ran the cord thru a hole in the forward centering ring, and secured it to the motor tube with a knot and some glue. As it turned out, the knot stuck up too high, so I built a replacement unit to install in the rocket. The tape shown holds the free end of the cord against the tube to keep it from flapping around while the motor mount is being installed in the rocket. The forward knot in the cord is also secured with a few drops of yellow glue. When stretched taut, the loop stops short of the forward opening in the rocket. A nomex ribbon (below) connects thru the opening, and then kevlar cord will continue from there to the nosecone/payload section. With this setup, if the ribbon ever needs replacing, the cord shown above can be fished out the back of the rocket where a new ribbon can be easily attached. (Above) The aft ring of the motor mount is moved forward to provide clearance for the coupler from the booster. |
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| Since it's a clone of an Estes
rocket, I thought an Estes decal was appropriate. And, since the
booster is
rigged for 24mm, I figured the Cherokee "D Power" logo was a good fit,
too The black lines on the booster leading edges and the checks are trim monokote. One vent hole and the motor hook are visible in this pic. |
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| Next up, some flight pics. |
 8-25-2010 |