How To Build A Match Rocket

				Version 1.5
				  7/14/95

			      Brett K. Carver
			      brett@sr.hp.com

Disclaimer:  Please notice that the title is not "How To Build THE Match
	Rocket".  This describes how I built match rockets and represents
	only one method of construction.  Others will have different/better
	ideas.  Hopefully this should be enough to get one started.

Warning:  Improper construction of match rockets can cause them to explode
	KILLING YOU INSTANTLY.  Improper firing of match rockets can cause
	them to penetrate your body KILLING YOU INSTANTLY. (well, probably
	not, but be careful anyway).

Definition:  Basically, a match rocket is a paper match with something
	wrapped over the match-head to form a combustion chamber and
	focus the flow of escaping gas.  The match is then heated until
	it ignites and the escaping gases cause it to take off.

Parts:	You'll need the following:

	a book of paper matches
	aluminum foil
	cellophane tape (i.e. Scotch tape)
	two sewing needles
	scissors

Constructions:  This roughly how I built them...

	1.  Remove a match from the book.  Trim off the end to remove the
	    frayed edges from where it was ripped out.

	2.  Use about 1 square inch of foil and 'wrap' it around the head
	    of the match extending between 1/4 and 1/2 inch past the head.
	    I left 'wrap' vague since there a many ways to do it.  The
	    goals are to:  a) keep weight down, b) get several layers of
	    foil around the match head, and c) keep things neat and clean.

	3.  [optional]  I had a lot of trouble with blow-out (the force of
	    combustion tearing a hole in the foil), so I started wrapping
	    the foil with a few layers of cellophane tape.  It seemed to
	    solve my blow-out problems without adding as much weight as
	    additional foil did.

	4.  Add two exhaust ports, one down each side of the match.  This
	    can be done two ways:  a) after step #3, push a sewing needle
	    along the match-stick, under the foil, up to the match-head, or
	    b) do steps #2 and #3 with the needles already in place.  In
	    either case the important thing is to get a small well-formed
	    port.  I used the smallest sewing needles I could find (the
	    head of a regular pin caused it not to lay flat creating poor
	    ports).  In addition, I'd run my finger-nail along the side of
	    the needle to force the foil down so that I'd have a nice clean
	    tube rather than just a crude gap between the match-stick and
	    the foil.  I use two needles because with only one I'd always
	    end up damaging one port while creating the other.  Obviously,
	    remove the needles when done.

Example:  What follows is ONE way to wrap the foil around the match head
	(step #2 above).  This is the basic method I used, but I'm sure it
	can be improved:

	1.  Start with a one inch square piece of foil:
	
				##########
				##########
			foil ->	##########
				##########
				##########
	
	2.  Fold in half (it's now 1" x 1/2"):
	
				##########
			foil ->	##########
				##########
	
	3.  Fold in half again over the match head (it's now 1/2" x 1/2"
	    with the match head in the middle (the head is now covered
	    with a double layer of foil):

				#####
			foil -> #####======= <- match stick
				#####

	4.  Sort of fold/wrap the excess foil around the match as neatly as
	    possible:

		After wrapping one side:

			foil -> #####======= <- match stick
				#####

		After wrapping the other side:

			foil -> #####======= <- match stick

	5.  Move on to step #3 above (optional tape).

Firing:  Put the completed rocket in a launcher.  It is often suggested
	that one use a bent paper-clip as a launcher.  Don't waste your
	time.  I used a short piece of 1/4 inch copper tube mounted to a
	hinge.  The launch angle was adjustable by turning a screw.  The
	tube was short enought that the match-head just extended enough to
	apply heat.  The back of the tube was blocked off.  Besides the
	obvious ease of launch-angle adjustment, the smooth tube reduced
	friction or hang-ups when firing, and the blocked off tube produced
	some back-pressure that I think helped produce higher launch
	velocities.  Anyway, once in the launcher, aim it, and heat the
	match-head until it ignites.  A lighter works better than a match
	for this as it takes a while for ignition and sometime the match
	would burn out first.

Distances:  I saved my record-breaking matches writing the distances on them.
	Launches inside the house became limited by the ceiling and the far
	wall.  The longest inside launch I got (hitting the far wall) was:

		29' 6"

	Outside shots were not so limited.  The longest outside launch was:

		44' 8"
	
	So, there are some target numbers to shoot for...	:-)

Fine-tuning:  The point of building match-rockets is not to simply 'learn
	how to do it', but to get started and fine-tune the rockets to
	improve distance.  Construction materials, construction techniques,
	launcher design, launch angle, and many other things all come into
	play at getting a long-distance flight.  Experiment.  Have fun!

Things that didn't work:  The following are things I tried that didn't
	improve my flight distance.

	1. Wooden matches - they were too heavy.

	2. Using two or more matches - too heavy and I couldn't get a good
	   seal on the combustion chamber.

	3. Adding extra match-heads - adding extra 'fuel' presented two
	   problems:  a) I had trouble getting a nice tight wrap of the foil
	   with the extra material in there, b) if I did get a good one built,
	   it would 'blow-out' at launch (adding more foil just seemed to make
	   it too heavy).  I had my best results with simple one-head rockets
	   so I stopped trying for more fuel.

Final caution:  Don't play with matches.			:-)