Brief:
A sleek scale-like rocket that first appeared in the 1972 Centuri catalog. It was a favorite of mine when I was a teen--I lost a lot of them on C motors!

Construction:
The parts list:

• Semroc BC-730 3" parabolic nose cone
• Semroc ST-7120 upper body tube, 12" in length, 0.759" OD (similar to BT-20)
• Semroc ST-8100 lower body tube, 10" in length, 0.908" OD
• Semroc BR-78 reducer
• 2 sets of 3 fins from 1/16" balsa stock (Fins may also be ordered pre-cut from Semroc, FV-43)
• Semroc EM-78 engine mount (3" length of ST-7, 2 CR-78 centering rings, 1 TB-7 thrust block, and 1 standard 18mm engine hook)
• Semroc LL-122 launch lug, 1/8" diameter x 2" length
• shock cord, 36" length of 1/8" sewing elastic
• screw eye
• 12" plastic or mylar parachute

Cloning the Excalibur began with downloading the instructions, parts list, fin patterns, and decal scans from JimZ's web site. A quick glance at the required parts rapidly led to the conclusion that I was going to have to place an order to Semroc or BMS as the ST-8 body tube had no Estes equivalent. The choice of vendor was settled when I saw that Semroc offered not only the tubes (cut to the right lengths, no less), but also the motor mount, balsa reducer, nose cone, and laser cut fins. I immediately placed an order, which arrived 2 days later.

The build was relatively simple and straightforward. It was very much like building a two-stage rocket but with no motor mount in the sustainer. The original Excalibur used die-cut fiber fins, but I found the 1/16" balsa ones quite adequate. I used Aleene's Tacky Glue for the engine mount assembly and to tack the fins in place followed by wood glue fillets. The only deviation from the instructions occurred when I adopted the standard Quest procedure of looping a length of Kevlar® thread around the top of the engine hook. This was then tied to a 36" length of 1/8" sewing elastic for the shock cord.

The use of Semroc parts made me feel like I was assembling a kit rather than building a clone. There was none of the usual body tube or fin cutting, which greatly enhanced the speed of construction.

Finishing:
The only downside of the Excalibur build was that there was a lot of balsa to seal--a nose cone, balsa reducer, and 2 sets of fins. 3 coats of AeroGloss sanding sealer, sanding with 400 grit sandpaper in between coats filled the balsa grain. The entire rocket was then sprayed with 2 coats of Krylon primer, again sanding between coats. This was followed by 2 coats of Krylon semi-gloss white.

The rocket's finish was completed by painting the nose and one fin in each set with Krylon gloss black. The Excalibur was then set aside to dry for a week, after which the decals were applied.

Fortunately, I did not have to figure out how to make the decals, as they were a gift from Carl at Semroc. Those of you with ink jet printers can make them from the JimZ scans or if you lack a suitable printer, put in an order with Excelsior or Tango Papa.

Construction Rating: 4 out of 5

Flight:
The first flight of the Excalibur occurred on Halloween 2004 on a B6-4. Estes wadding was stuffed into the lower body tube and the carefully folded 12" Estes parachute placed on top. The rocket shot off the pad very quickly, and the flight was straight with no noticeable windcocking. I estimated the max altitude to be around 400-500 feet.

Recovery:
Deploy of the chute occurred a little before apogee--a B6-6 would probably be a better motor choice--and the rocket slowly descended to a landing about 150 feet from the pad.

Flight Rating: 4 out of 5

Summary:
The Excalibur is an easy to build, sleek flyer that can easily top 1000 feet on a C. The ready availability of parts makes it a perfect rocket for first time cloners.

Overall Rating: 4 out of 5