Overview:
Since I had so many problems with the parachute cup jamming in my EAT Triatomic (see my review), it has not seen much flight time. I've been kicking around ideas for how to make it more reliable for quite some time, and last month I finally put something together. It seems to work really well.

The basic concept is to insert an inner BT-55 tube inside the main BT-60 tube of the Triatomic's upper body. The end of the BT-55 is loosely covered by a wooden cap to protect the recovery system from the ejection charge. The size and shape of the cap is not very critical. It is only important that it be large enough to cover the BT-55 but small enough to not touch the sides of the BT-60. A short piece of loose-fitting tubing coupler holds the cap centered over the BT-55 compartment.

At ejection, the motion of the lower body only has to jerk the loose-fitting cap free, rather than extracting a long snug-fitting cup.

Parts List:

• One EAT Triatomic kit
• BT-55 tubing ~3 inches long
• 2 CR5560 centering rings
• TC55 tubing coupler, 1/4" long
• Wooden disk, made from either:

• Use disk from EAT kit
• Make your own from 1.5" x 1.5" x 1/8" basswood or plywood

Below I will show how I made my own cap from basswood. If you have not already assembled your Triatomic, you could use the wooden disk provided with the kit.

Construction:

Use the original cup to trace a circle and the center hole onto the wood.
Drill a small hole in the center of the circle.
Rough shape the circle. I used a wood chisel to cut away the excess wood.
Chuck the disk into a Dremel tool collet. Use 100 grit sandpaper to smooth the edges and make a generally round shape. The exact shape and size is not critical. Test fit it into the BT-60 tubing. It should NOT touch the sides.
Cut the tube coupler 1/4" long.
Peel the outer layer from the tube coupler. Rub cyanoacrylate (SuperGlue) on the outside surface. Sand smooth with 320 grit or finer sandpaper.
Tack the tube coupler to the disk. It should be roughly centered on the disk.
Glue the coupler to the disk. I used Gorilla Glue, but have since decided that this was overkill since there is not much load on this joint. Simple wood glue would have been sufficient.
The cap should look like this when you are done.
Rub the inside end of the BT-55 with CA glue. Allow to dry. Sand with 400 grit or finer.
Insert the cap assembly into the BT-55. Trim the BT-55 so that the tube plus cap is the same length as the original cup.
Coat the outside face of the cap with epoxy to protect it from the ejection charge.
Attach the centering rings to the BT-55 tube. The exact position is not critical; anywhere from 1/4" to 1/2" from each end would be okay.
IMPORTANT: The cap and its coupler should fit VERY loosely into the BT-55. As this photo shows, the cap is almost falling out from its own weight. If it doesn't, either peel the coupler or sand the BT-55 tube until is does.
Putting it all together. Thread the shock cord through the BT-55 tube assembly. The rest of the recovery system and the lower rocket is attached as per the original Triatomic directions.
Insert the BT-55 assembly into the BT-60 tube until it touches the nose cone. It should make a friction fit into the BT-60 tube. It does not need to be glued into place.
Thread the lower Kevlarshock cord anchor through the hole in the cap and attach it to the elastic shock cord. Fold the parachute and shock cord and pack them into the inner tube.
Place the cap in place to cover the parachute compartment.
The cap assembly should fall out freely under its own weight when the tube is help nose-up. Note how the cap has slid all the way down to the lower body.
Insert the Triatomic bottom section into the BT-60 tube. Load engine and fly as per original directions.	No picture for this step.

Flight/Recovery:
I tested the alternative parachute cup on each Triatomic configuration.

The first flight used the Transition bottom on a C11-5. Since it was a bit windy and the Transition bottom is pretty light, I replaced the stock 18-inch chute with a Rockethead Rockets 15-inch mylar chute. The smaller size makes packing the chute compartment easier. As an experiment, I attached the chute to the ring at the bottom end of the elastic shock cord instead of the partway along its length.

At apogee, the top and bottom separated nicely and pulled the parachute and shock cord out of the cup just fine. Unfortunately, with the parachute attached at the back end of the shock cord, the lower body flew into the chute and the shroud lines got tangled in the fins. The chute acted like a streamer and never fully inflated. Landing was fast but the grass was soft. There was no damage.

The second flight used the Futuristic bottom on a C11-3. The Futuristic bottom is the heaviest one, so I reinstalled the stock 18-inch parachute partway up the elastic shock cord. On this flight the recovery system performed flawlessly.

For the third flight I used the Cluster bottom on A8-3's. Unfortunately, one of the engines failed to light so the igniter leads on the unlit motor jerked the rocket when it was nearing the end of the rod. The rocket did one and a half loops, then fell horizontally. The first ejection charge went off about 15 feet off the ground. The pieces separated nicely, the chute pulled out cleanly, and fully inflated about 1 foot off the ground. This was too late to do it's job though, and one fin popped off when it hit the ground.

In all three flights, the cap came off and the parachute came out of the cup cleanly with no scorching of the chute or elastic cord.

After three flights, note that the paper centering rings are still pretty clean. This indicates that they are not exposed directly to the ejection blast. If they ever do become damaged, it should be easy to replace them since they are not glued into the BT-60.

The cap has some ejection residue, but no permanent scorching.

Summary:
A fairly easy modification that dramatically improves the reliability of parachute deployment, while retaining the wadding free recovery protection of the original design.

PROs:

• Works reliably.
• Low cost.

CONs:

• Parachute compartment is pretty full when packed with parachute and shock cord.