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Several years ago, before Semroc offered their 2.3" tube (Series 225),
Firefox had one. And the DARS gang put together a group order, getting a
variety of items including rocket tubes. The Firefox RBT225 struck me as
a good size between 54mm and 2.6" tubes.
When we got them, we were disappointed. They aren't kraft paper,
but instead appear to be recycled paper. That means two things -
surface mounted fins will need lots of external reinforcement, and the
tubes will need a layer of fiberglass in order to get a decent finish
on them. The added strength from the glass is probably needed, too.
The other guys in the group order tended to shy away from the tubes and have just let them collect dust, but I decided I
was going to make something with mine regardless of the added work
required.
And
this is the outcome. It's still not quite finished. I want
to add a black roll pattern to the silver paint, which turned out
crappy - it's rough to the touch. So I sanded it down and shot it
again, this time laying it on thick hoping to avoid the gritty feel.
Now I have a forward section that's rough to the touch and has runs in
it 
Silver and black is the color scheme of the Oakland Raiders, and while
I long ago soured on the team, I still like the colors. Some time
after picking this paint scheme, it occurred to me to call the rocket
Raider.
As for the crappy silver, I'll sand it and shoot it again, this time
using a different brand of silver. But if it comes out crappy
again, I'll sand it down once more, paint it yellow, and call it
Steeler 
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The rocket is setup with my interchangeable motor mount system for BT-70 tubes.
The RBT225 slip fits over BT-70, so I lined the fin can with that
thereby making the rocket able to use any one of the six motor mounts
in the system.
This precludes thru-the-wall fin tabs, so the fin roots (and fins, too) are reinforced with fiberglass.
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Here's a good shot of the
fin can. The 4-40 all-thread at bottom retains the motor
mount. The 1/4-20 screw at 10 o'clock is the aft end of the screw
eye which anchors the kevlar shock cord.
The trick here was to make the bulkhead opening large enough to
accomodate a 38mm motor. This required moving the screw eye and
all-thread as far outboard as possible.
The nuts on the screw eye and all-thread are recessed into the stepped
ring. This allows the motor mounts to be flush against the ring.
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The Raider was setup for dual deployment. It shares the same coupler/electronics bay used in my Cherokee 3DD.
At apogee, the altimeter separates the
rocket into two tethered sections. The subsequent main event blows the chute out with the
nosecone.
The switches at right are in the aft portion of the bay which slides
into the aft airframe. The center screw switch engages the
altimeter power while the upper and lower slide switches connect the
main and apogee (lower) charges.
As of now, I'm a just a little painting and trim kote away from having this one ready to fly.
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12-26-2008
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