Overview

A single-stage rocket with attractive styling. The body features three different diameter tubes that get progressively smaller toward the rear. The most eye-catching features are the fins, with a large set in the middle and a small set at the rear.

Kit Specifications (from the cover art)

"The RHR 2003 is a great rocket for those who would like to add a couple new building skills to their rocket building experiences. You will have to cut the fins and the kit takes 4 centering rings to join the body tubes together."

• 20 ½" Tall
• 5 ½" Fin Span
• 2.1 oz
• Hand turned Balsa nose cone
• 3/32" Basswood fin stock
• Kevlar® shock cord mount
• 15" Mylar parachute
• Water slide decals

Construction:

The kit fits into a surprisingly small plastic bag with a cardboard hang tag. On the back of the hang tag is a certificate for Rockethead Fun Points which can be collected and exchanged for other Rockethead products. Each kit is individually signed and numbered - mine was #20.

Chan Stevens has already provided a list of components in his review, so I won't repeat them. One correction to Chan's list: The fin stock is 3/32" basswood, not balsa.

The instruction manual is printed on 10 half-sheet pages and is copiously illustrated with color photos. If there is a weak point in this kit it would have to be the instructions. Typos and grammatical errors abound, and I found the instructions to be confusing in places.

Construction begins by sanding all the body tubes to remove the gloss. I find it much easier to fill tube spirals and sand fins before they are glued on, so at this point I deviated from the directions. The body tube spirals were very light, so I filled them with one coat of Rustoleum Painter's Choice gray sandable primer and then sanded most of it back off before attaching the fins. I made sure that the fin attachment points were stripped bare before gluing to ensure good adhesion.

Next, marks are drawn on the tubes for fin alignment, lug alignment, centering ring placement. An engine block is glued into the back end of the BT-20. Note that since the bottom tube is minimum-diameter, no engine retention hook is provided.

Next, a pair of centering rings are glued and filleted to the front of the BT-20 and the BT-50. I had to peel a layer from the inside of the rings to make them fit.

(SUGGESTION: Right here is where I would recommend attaching the shock cord anchor, before the tubes are glued together. See below for details.)

After that centering ring glue had dried, each tubing section was glued into the next larger size tubing. Like Chan, I was concerned about keeping the tubes aligned, but unlike Chan, I did not go to the trouble of making custom centering rings. Instead I used some spare centering rings and a piece of scrap tubing on each smaller body tube while I was gluing it into the larger tube. For this trick to work, it helps to start with the smallest tube and work up to the largest.

Next, the fin templates are cut out and traced onto the fin stock. The templates must be laid out in a specific pattern to fit on the wood and to ensure the grain is running in the right direction. Unlike most kits, the grain runs parallel to the trailing edge of the fins, not the leading edge. I tried many alternative layouts with the grain aligned with the leading edge, but none of them would fit all three large fins onto the provided stock. I went ahead and cut them out with the trailing edge alignment and everything turned out fine.

The final step in fin preparation was rounding the front and beveling the rear of each fin. A few strokes with my Master Airscrew razor plane quickly and easily did the job. Finish up the fins by sanding all the flat surfaces with fine sandpaper. At this point I went out of sequence by applying one coat of AeroGloss sanding sealer and sanding it smooth.

Next, the fins are glued to the body tubes. First a large front fin is tacked to the middle body using a few drops of super-glue. I used an Estes fin alignment guide to hold the fin at the proper angle while the CA set. The rear fin is tacked on with super-glue. To ensure proper alignment between the front and rear fins, I clamped a metal ruler to the front fin, then applied glue to the rear fin, and guided the fin into place using the ruler as a guide, and then clamped the fin to the ruler until the glue set. Only once did I manage to glue the rear fin to the ruler instead of the body tube.

Sharp-eyed observers may notice that I messed up the fin placement. I lined them up with the rear edge of the body tube. They should have been ¼" forward. I wish I had put the gap on properly so I would have a better surface to tape the motor into place.

After all the fins were tacked on, I used 5-minute epoxy and a Popsicle stick to create fillets along each fin joint.

Launch lugs are then glued onto wooden standoffs. I used 5-minute epoxy and lined them up by eye. As the epoxy started to gel, I used a launch rod to ensure their alignment.

The shock cord mount is unique. It involves tying knots on each end of short Kevlar® string, then forming a loop in the middle. The knots are then set into a large drop of glue inside the tube and held in place using masking tape. Finally the knots and masking tape are covered with glue. I used 5-minute epoxy and it turned out fine. The instructions show white glue being used for this step, which I have severe doubts about.

Chan suggested running the Kevlar® back to the engine block. Some people don't like that because it exposes the Kevlar® directly to the hot ejection charge. I think a good way to attach the shock cord anchor would be to wrap it around the middle body tube between the two centering rings and glue it in place. Then cut a small notch in the front centering ring to allow it to pass into the front body tube. I successfully used a similar technique on my EAT Tri-Atomic Futuristic. I wish I had thought of this before I had all the tubes glued together.

The shock cord anchor loop is tied to a 3 foot long ¼" wide elastic shock cord. The parachute attaches to a loop one foot down from the nose cone. This is a good arrangement that should keep the nose cone from banging into the body.

Anybody who has ever mentioned RocketHead Mylar parachutes has sung their praises. Add me to that chorus. They are by far the best Mylar chutes I have ever seen. They all come preassembled with plastic reinforcing rings on each of the eight corners. The shroud lines are tied on with good tight non-slipping knots that are very consistent from corner to corner.

While many people talk about RocketHead chutes, but I haven't heard much about their hand-turned nosecones. These things are works of art! The surface finish on mine was the best I have ever seen on a balsa cone. It was so smooth I did not need to sand it or fill it with Elmer's Fill-n-Finish -- I was able to go straight to primer. Very nice. (I found the same thing on the nose cone for the Rockethead Battle Axe that I was building at the same time.)

A hardwood plug in the nose cone base makes for a very durable attachment point for the screw eye. The final construction step is screwing a screw eye into the base of the nose cone and attaching the shock cord. It was hard getting the screw eye started into the hardwood plug in the base of the nose cone. I used a large safety pin to poke a pilot hole; that helped a lot. The screw eye is very firmly anchored now.

Finishing

As stated before, the body was primed and sanded down almost bare before the fins were attached. The fins were sanded, coated with AeroGloss sanding sealer, and sanded again before being attached. After assembly was finished, everything got two coats of white Rustoleum Painter's Choice sandable primer. I used a fine grit sanding sponge between coats.

For the finish coat, I wanted a silvery look, so I used Rustoleum Bright Coat Metallic Finish Aluminum. MISTAKE! This stuff is apparently quite a bit different than the other Rustoleum Metallics and Painter's Choice paints that I am used to. It smells different and has lower viscosity. Using the same technique that I use for other paints quickly turned a beautiful rocket into a runny, drippy mess!

After letting it dry overnight I sanded off the runs as best I could and started over with white primer. That turned out reasonably well, so I followed that with a coat of Rustoleum Painter's Choice Gloss White and called it done. Only one small run is still visible, and it's on the back side near the lugs.

The kit includes a nice set of decals. Rockethead makes their own decals with an Alps printer on clear water-slide decal paper. The larger decals were a little tricky to get into place since they kept wanting to curl onto themselves. Once they were in place, though, the result is very impressive. The lettering is nice and crisp and has good contrast against the white background.

Two coats of Painter's Choice Gloss Clear sealed the decals down and added a nice sheen to the whole rocket.

The rated weight is 2.1 oz. Despite the epoxy fillets and extra coats of paint, I managed to keep the weight on mine down to 2.3 oz.

Despite the fiasco with the runny aluminum paint, I am very pleased with the way this one turned out.

Construction Rating: 4 out of 5

Flight/Recovery:

The instructions provide no guidance on motor selection. The Rockethead web site suggests B6-4 and C6-5. RockSim confirms that these would be good choices. This kit is a bit too heavy and draggy for an A8-3.

Test Flights: Round 1

The first two test flights took place on a cold clear late afternoon, with a light breeze and temperature in the high 30's.

For the maiden flight I used a B6-4. Since there is no engine hook, I wrapped one turn of masking tape around the engine to provide a friction fit. Three squares of Estes wadding were used, plus one square wrapped around the chute as a protective pouch.

The boost was short and quick, followed by a long coast with a light arch into the breeze. The tracking smoke laid out into a nice horizontal line, and then the ejection charge popped. The silver Mylar chute deployed perfectly and gently lowered the rocket to the ground with minimal swinging. Great flight!

As I was carrying it back to the launch pad, I noticed a deep "balsa smile" (Nick's term for an "Estes dent" on a non-Estes kit) in the nose cone. I was surprised to see this with a 3 foot shock cord.

Between the first and second flights, we launched another rocket and took some photos and videos. By the time I went to prep the RHR2003 for its second flight, my fingers were already getting pretty cold. At this point I began to wish this had an engine hook because friction-fitting with masking tape is a lot harder with cold fingers. I also wished that the front tube was about half an inch longer because that long shock cord fills up most of the front tube. I had to re-pack the parachute twice to make everything fit.

The second flight was not as fortunate as the first. I loaded a C6-5 with the same one-layer tape wrap and same parachute packing. This time it zipped off the pad quickly, but then it went crazy. Slow motion video shows that about 25 feet up it took a hard left and started a large spiral. After completing one and a half powered loops, it pranged into the ground about 90 feet downrange. After a few seconds of smoking, the ejection charge popped.

When we examined the crash site, we found the nose cone had buried about 2 inches into the sod. Fortunately, it had rained the day before so the ground was soft and the rocket suffered no impact damage.

Post-Flight Failure Analysis I: RockSim

I'm not sure why this went unstable. RockSim says it should have 1.13 calibers of stability. I weighed the nose cone and found it was slightly heavier than the RockSim assumption, and verified that the fins were the proper size. I loaded another C6-5 and measured the balance point. I examined the spent engine nozzle for cracks or debris. I inspected the fins for cracks or bends. I inspected the launch lug and rod. Everything checked out fine.

Curious, I decided to explore further. I have heard reports of the Anubis kit by The Launch Pad sometimes having flight stability problems. Like the RHR2003, Anubis had large mid-body fins and small rear fins. Could these problems be related?

Enabling the Barrowman and cardboard cutout stability tests in RockSim pointed out a possible clue. The cutout test shows that this rocket is unstable, with a stability margin of -0.78 calibers! The cutout method assumes the rocket is flying sideways, with 90 degree angle of attack. This condition is unlikely in normal flight, but it does give an indication of the possible source of the problem.

The Barrowman and RockSim stability equations both assume that the rocket is flying near 0 degrees angle of attack, which is a reasonable assumption most of the time. However, if any disturbance ever makes the angle of attack too large, the CP moves forward and the stability margin goes down. If the disturbance is large enough, the CP will move far enough to make the rocket unstable, and it will never recover.

I exchanged several e-mails with Tom Priest at Rockethead. He was very helpful and open and was surprised to hear about my mishap. He has never seen this problem in 30 flights of the prototype kits and has never heard of it happening to anybody else.

The cutout instability is not the root cause of the problem. The instability should only occur if the angle of attack gets too high. That is unlikely to happen in normal flight without some fairly large disturbance, but if it ever gets into that condition, then it can never recover.

I used RockSim to simulate several possible changes, including adding nose weight, changing tube lengths, and increasing the size or number of rear fins. The easiest change would be gluing a washer to the base of the nose cone. Most of the other changes help very little, and some even make the problem worse.

I do not believe that +1.0 calibers of cutout stability margin is required. I think so long as the Barrowman or RockSim margin is more than 1.0 and the cutout margin is positive, the design should remain stable regardless of orientation.

Test Flights: Round 2

A few days later I tried to recreate the problem flights. Again the temperature was just above freezing, and the wind was quite brisk. All flights used C6-5 engines.

For the first flight, I angled it about 10 degrees into the wind. The takeoff was nice and straight, with a possible wiggle after burnout. Deployment was clean. That 15" parachute proved to be too big. The rocket drifted over a baseball field, a football field, a parking lot, over the school and landed in the woods. The rocket-eating trees must not have been hungry that day since it landed right between them unharmed.

For the second flight I switched to a 12" Rockethead Mylar chute. Once again the boost was straight and the deployment was clean. Even with the smaller chute, it still drifted the length of the field. Nice safe landing on short grass.

The rear fins have been holding up very well during landings. Basswood was a good choice for the fin material.

At this point my fingers were frozen and the battery on the camcorder died so we decided to call it a day.

Post-Flight Failure Analysis II: Wind Tunnel

As a further test, I set up a crude wind tunnel using a fan, a string, and a camera tripod. After an hour of tinkering I determined that my setup is not very good because the wind strength is not uniform enough, and that the rocket is not as unstable off-axis as RockSim predicted.

I couldn't reproduce the instability problem either in flight or on the ground , so the cause of the crash may remain an unsolved mystery.

Flight Rating: 3 out of 5. This may be harsh, but so was the crash. Three of the four flights were beautiful, though.

Overall:

PROS:

• Good-looking styling with the large mid-body fins
• Good quality parts, especially the nose cone and parachute

CONS:

• Instructions could be clearer
• Parachute a bit too big
• No engine hook
• Unexplained crash on second flight

Overall Rating: 3 out of 5. (*I feel bad scoring it this low. Without that one wild flight, this would be '4.5'.)