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Construction 4-10-04
After a hiatus due to work and weather constraints its time to get
back to work. Well it wasn't all work and weather that delayed
construction, there was some fun. On March 27th I took Jeff
Taylor's EX class and on the 28th got to fly one of the motors I made.
What a great time, learning in this case was a lot of fun. Jeff
has an immense amount of knowledge and experience in motor making and
try as we might no one was able to come up with a question he couldn't
answer. On the 28th I got to build a 6 grain 38mm motor with the
propellant I made the previous day. This motor (roughly a J600
with the fast burning "iron-man" formula) was used to send my tried and
true Eclipse on an excitingly quick trip. Of course on the way
back down it teased me by heading straight for my truck when under
main then hooking a sharp turn at around 200 feet and making a water
landing in the nearby river. My love of foam paid off and the SS
Eclipse stayed afloat allowing it to be retrieved with a linesman pole
(thanks Chris!). Since the electronics took a bit of a dunking I
didn't get to fly the 54mm motor I made, however later testing shows
that the electronics survived, I guess that electronic varnish I
sprayed it with when I first purchased it helped.
OK, time to discuss today's activities. First I did some prep
work for tomorrows session, namely getting the slots on the upper
airframe marked for the canards, the slots will need to be widened
just as was done on the lower airframe.
Today's goal is to do the foaming of the aft airframe. Now some
of you have already asked me, how in the heck are you going to foam
anything? The darn thing is all sealed up. The answer is
to drill holes. WHY? Well in the past I have done the more
common pull the aft ring out, stand it on end and pour in. But I
always ended up having to dremel out the excess to get the ring back
in. When I built my Quantum Leap sustainer I came up with this
method since the standard pour in the back wouldn't work due to the
limited space between the motor tube and the airframe along with the
aft ring being so deep due to the interstage coupler. It worked
great and I've been doing this way ever since.
Step 1. Break out the drill. I drilled one hole
between each fin pair, just above the aft centering ring. Click
the thumbnail for full size pic and use your browsers back button to
get back.
Step 2. It's foam time! For the first pour into each
"quadrant" I'm using a two part foam from US Composites. This is
their 8lb/ft3
density foam. It is as hard as wood when expanded.
Very tough very sticky stuff.
Step 3. Pour equal amounts of A and
B, in this case about 2.5 ounces of each. Then pour into a paper
cup and mix thoroughly (but quickly, the clock is ticking. In
less than a minute this will start expanding). Squeeze the cup
to form a spout and pour into the hole.
Step 4. Stand upside down, this
allows the still liquid foam to flow to the center bulkhead just ahead
of the fins. The foam will expand and fill up around 3 to 4
inches of space. It will adhere strongly to everything it
touches, these fins are there for good.
This is what a small amount of this stuff turns into. Now this
higher density foam doesn't expand as much as the lower density.
But it is tough. The above process is now repeated for the other
three "quadrants".
Step 5. I don't want to add too
much weight to the rear, so rather than fill it up with the higher
density foam I will now switch to the 4 pound density foam also from
US Composites (this is still denser than the typical small bottles of
foam from dealers). The same procedure as above is repeated.
Here is the finished pour. It
actually vented out of the hole and this is after a small cleanup
(scrapes off easily if not fully cured)
I actually got two of the pours to do
this, a perfect fill. Trust me, anything that gets these fins
off is going to wreck this rocket to the point that missing fins is
the least of my problems.
Construction 4-11-04
With the aft airframe mostly complete its time
to move to the forward airframe. Once again the slots are
widened slightly to allow the canards to be attached. To tack
the canards in place I used a different epoxy then what I normally
used in the past. Fasco Epoxo 88 from US Composites, a very fast
setting 6 minute epoxy. Not yet done is to reinforce the
internal fin mating areas with some glass tape.
Here is the box of epoxy (inside are two
squeeze tubes).
Upper and lower airframes mated, the nose
cone is sitting to the right. It's finally starting to look like
something.
