Ringwraith

by Clive Davis 

Brief:
Cluster design (5 x 24 mm). A five-finned, forward swept design featuring a 3" body tube and a Big Daddy nose cone. My colleague at work found a lone Big Daddy nose cone in the woods. He thought of me and gave the nose cone. I immediately began thinking of a project to use this heaven-sent gift. Thus, the Ringwraith was born.

Construction:
Parts consist of:

• Big Daddy nose cone
• 25" long 3" body tube (I had a poster tube lying around that fit the Big Daddy perfectly)
• BT50s to make 5 24 mm motor mounts
• Five BT50 motor blocks
• screws, washers and wing nuts for motor retention
• screw eye, Kevlar®, shock cord, Nomex® heat shield, and nylon parachute
• 4 wine corks to plug unused motor mounts.
• aircraft plywood for fins
• 1/4" balsa/basswood for centering rings.

Construction began around the motor mount. I stacked the 24 mm motor mounts in a star formation, glued them together, and then test fit them inside the body tube. After some sanding of the body tube, everything fit fine. I created and glued a bulkhead above the motor mount and then drilled some holes in the bulkhead to allow the ejection charges to pass through. I then added a screw eye on the bulkhead, and then attached Kevlar® to the screw eye.

Next, I used epoxy to glue the motor mount inside the body tube. I then cut out the fins and began shaping and sanding them down. After marking the tube, I glued the fins on with wood glue, making sure I added plenty of fillets.

I had a 1 inch strip of balsa that I steamed and created a loop to fit around the five fins. I painted this silver and then epoxied this on to the fins after the entire rocket had been painted.

I added 1/2" shock cord (6' long) and a 30+" nylon parachute. Also, I added a Nomex® heat shield.

Next I added weight to the nose cone. The nose cone, painted with clay, should weigh 5 ounces.

I painted the rocket black, created three silver rings of paint at the top of the rocket.

Flight:
Maiden flight at my local club's (ASTRE) launch, summer 2004.

Motor retention is created by using washers and wing nuts. I also plug any unused motor mount with a wine cork.

Prepping the rocket is easy since the body tube is large and there is a heat shield. The first flight featured two E9-4s. Rocksim predicted 900', and the rocket got plenty altitude. It was a beautiful flight.

Unfortunately, the large balsa ring was too weak and basically crumbled upon landing. I simply removed it and prepped the rocket for another flight.

Second flight was on 3 x D12-3s. Rocksim predicted an altitude of 600'. Liftoff was spectacular. Rocket flies well without the lower ring (which was for looks, anyway). I kind of like the looks of the rocket without the ring around the fins.

Summary:
PROS: If you like BP clusters, this rocket gives you many options. I can fly it on a single F21 or on 2 D12's, or 2 E9's, or 3 D12's, or 3 E9's, or 5 C11's or......you get the idea.

CONS: The rocket is really heavy. It might make sense for me to downscale this to use 5 x 18 mm motors. This would reduce the weight of the rocket under 1 lb.