big day!

[web/gag.com] / rockets / airframes / RG-2 / index.mdwn

diff --git a/rockets/airframes/RG-2/index.mdwn b/rockets/airframes/RG-2/index.mdwn
index 9281a9067f5275e14bf408ac81dc76c72ec8ebd3..7290bd6eda14edf4b84afc2bf6495911b2bbccf7 100644 (file)
--- a/rockets/airframes/RG-2/index.mdwn
+++ b/rockets/airframes/RG-2/index.mdwn
@@ -32,5 +32,38 @@ at [NCR](http://ncrocketry.org) Mile High Mayhem 2010.
 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.
+
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