Background
Over the past year, the Edinburgh Alliance - a Babylon 5 fan club of which I am a member - has been working on a CD of songs parodying the show.  As it neared completion, we decided that when the time came to launch the CD, we really would launch it.  Being the club’s rocketeer, I got the job.

Design objectives
High performance was not an objective of this design.  The ability to put the CD in the air and then bring it back safely, possibly in significant wind, was.  Edinburgh Farce 1 is therefore somewhat underpowered, using a pair of mini-engines.  By using two engines in outboard pods, I was able to put the CD in a pair of slots at the rear of the main tube.  In addition, the nose-cone is a tight fit, sealing the forward end, and inside the tube is the rolled-up cover of the CD.

Pitch stability is provided partly by the triple-tube configuration and partly by two swept wings.  Yaw stability is provided partly by the CD and partly by two large rectangular fins, which hold further CD-related material - copies of the front and back of the cover are stuck to the outer surfaces.  The vertical fins also help protect the CD when the rocket lands.  The balsa sheet which I used for the vertical fins is only 1/8” thick, and more flexible than I liked, so I fitted three reinforcing strips to the inner surface of each fin; along the top edge, along the bottom edge, and in the middle.  The middle one is also the attachment point to the wing.

Recovery is by two small parachutes, cut out of stock Estes 12” ‘chutes.  These bring the model down more quickly than a pair of full size ‘chutes, but still gently enough to avoid damage.  They’re now about 8”.

 On the left is Edinburgh Farce 1 on the pad.  On the right is proof that it did actually work.

Parts
2 x BT-50 1 x BT-5 3 x BNC-50K 2 x 12” parachutes
3/16” balsa 1/8” balsa
2 x Screw eyes Sewing elastic
Spent D casing Spent mini-engine casing  Aerotech igniter tube
Edinburgh Alliance “Songs from Down Below” CD

Outer tubes are all BT-50.  The main tube is a whole BT-50; the outboards are each 152mm cut from a second tube. Horizontal fins are 3/16” balsa; vertical fins are 1/8” balsa.  Reinforcement strips for the vertical fins are 127mm x 14mm 1/8” balsa.  Reinforcement strips for the CD slot are 130mm x 7mm 1/8” balsa.

A launch lug, made from a tube which formerly held an Aerotech igniter, is glued along the joint between the main and starboard outer tubes.

To hold the CD in place, there are two rings cut from a spent D engine casing.  Each ring has a pair of diametrically opposed notches which hold the CD in place.  The forward ring is glued into the main tube so that its notches are level with the forward ends of the slots in the tube.  The aft ring is loose, and is held in place during flight by masking tape.

<Click for Full Picture>

Engine mounts
The engine mount tubes are cut from stock BT-5.  In each one is a blocking ring cut from a spent mini-engine casing, positioned so that the engine protrudes 10mm from the rear of the tube.  The engine mount tubes themselves extend 2mm beyond the ends of the outboard BT-50 tubes, and the centring rings are recessed.  This was partly to make the tubes look more like exhausts for the benefit of observers, and partly so that engines could be taped to the tubes, rather than relying entirely on friction to hold them in place.

Launch Report
Edinburgh Farce 1 has flown on two occasions.  The first was its test flight on March 7th.  Technical assistance was provided by Bill Gates, in the form of a free Microsoft Network CD-ROM - the “Songs From Down Below” CD was not yet available, and anyway, for this test flight, I preferred to use an expendable CD!  Then on March 21st was the launch of the Edinburgh Alliance “Songs From Down Below” CD, the event for which Edinburgh Farce 1 had been designed.  The rocket lived up to its name as, twice, it failed to fly when only one engine ignited.  But the next two attempts were entirely successful; both engines lit, the rocket went up straight, then both parachutes deployed.  Both photographs shown here were taken during the March 21st flying session by Dave Willis, another member of the Edinburgh Alliance.

More Power
You may wish to adapt your version for higher power.  If so, use BT-20 instead of BT-5 for the engine mount tubes.  You will probably need to extend the outboard BT-50 tubes to accommodate the longer motors, and you may need some nose weight to balance the heavier motors.  If you really want to make a higher power version, don’t bother with motor mount tubes; stick a pair of D class engines directly into the outboard BT-50 tubes, and you will certainly need to add some nose weight.