# RG-2

Robert's second full-custom rocket, with TeleMetrum electronic-deployment.

## Motivation

After the success of [RG-1](../RG-1), Robert decided it would be fun to build
a similar rocket in smaller diameter to try and get more than a mile above
ground on a G motor.  The timing coincided with the first prototype builds of
[TeleMetrum v0.2](http://altusmetrum.org/TeleMetrum), so naturally he insisted
on designing the rocket to fly one.

Bdale and Keith both liked the design and wanted to join in the fun, so the
plan is to be ready for a 3-way drag race on Cesaroni Pro29 full-G motors
at [NCR](http://ncrocketry.org) Mile High Mayhem 2010.

## Design Details

* 38mm phenolic air frame
* 29mm phenolic motor mount
* [Giant Leap](http://giantleaprocketry.com/) Pinnacle 38mm nose cone
* 1/8 inch birch plywood fins in a custom shape, with rounded edges
* 1/4 inch birch plywood centering rings and bulkheads, CNC milled, the two 
  that hold the fins are notched for perfect fin alignment.
* avionics bay design similar to Bdale's Trick-o-Treat

[OpenRocket](http://openrocket.sourceforge.net/) 
[RG-2 Design File](./RG-2.ork)

## Build

The build began on 21 March 2010, cutting all the phenolic and fin blanks for
4 "kits" of parts.

The first step was to CNC machine all the rings and bulkheads, then clean them
up and fit them by sanding carefully.  

Next, we cut out the fins using our radial arm saw, and beveled them by hand 
using sandpaper flat on a table surface, hand-holding the fins at the desired 
bevel angle.  Bdale cheated a bit on his fins using his Dremel with sanding
drum to quickly remove most of the material then finishing up with sandpaper
on the table... but that requires a very steady hand with a Dremel!  We 
beveled the leading and trailing edges for looks and to reduce drag, but 
since these rockets won't break mach on a G the exact profile isn't critical.

Assembly started by sanding the outside of the 29mm phenolic motor mount, 
and using a piece of angle to mark a reference line along the entire length 
of the mount.  We use this reference line to get the first fin aligned
perfectly.  Next, we put the two fin-locking rings on the MMT along with the
HAMR retainer body, and used the fins to work out from the aft of the MMT
exactly where the fin-forward ring needed to be, marking the aft edge of this 
ring's position on the MMT.  The fin forward ring's position is the critical
part of building a fin can the way we do, so we take extra time to get this
right.

We then smeared 5-minute hobby epoxy around the MMT at this mark, and 
pushed the fin-forward
ring into place from the aft end of the MMT, pushing an epoxy fillet on the
ring's leading edge, and leaving the aft side of the ring fairly dry.  We
align the ring so that one of the locking tabs is positioned with one edge 
on the line up the MMT, so that when we put the first fin in place we can use 
that line to ensure it's straight along the MMT.  And we're very careful to
make sure the ring is "square" to the MMT.  While we have some spare epoxy,
we also smear the front of the MMT and slide on the zipperless fin can ring
from the front.  Then we let the epoxy cure.  Do *not* glue the aft ring to
the MMT yet!  That comes much later.

## Flights