Stellar Dimension Vector Review

Stellar Dimension Vector

Contributed by Mark Fisher

Construction Rating:
Flight Rating:
Overall Rating:

Rocket Pic The Stellar Dimensions kits looked so interesting that I had to try one. SDI has a lot of other kits like the Vector, and all are pretty reasonably priced; I paid $8 for mine from Discount Rocketry.

***Essence Ratings***
Construction	3
Flight	2
Overall	2½

Assembly

The kit itself is very different than others I'd built, consisting almost entirely of laser cut wood pieces, and a lot of them, 46 in fact. The only things that aren't are the nylon engine retaining ring, the launch lugs made from small brass rivets, and the recovery system. The later is a 12" plastic parachute and a freakish 12" length of rubber about 0.070" in diameter for a shock cord. While this rocket has a very ingenious ejection baffle system (wadding is still required), I was worried that rubber wouldn't hold up long, so I replaced it with a 12" length of Rogue's light duty KC-4 Kevlar® and an 18" length of ¹/8" shock cord. I also used an Estes 12" 'chute instead, as I already had one built. Plus, the SDI 'chute looks like a pain to build, and its shroud line mounts don't look very durable.

The instructions are poor, with only three illustrations. Also included in the kit is a brief science fiction story (that isn't very well written) on a separate sheet which would be better used for expanded kit instructions. If you've ever built a laser cut kit of any type before, you won't have any trouble, though, the pieces fit together rather intuitively, you'll only need to consult the directions in a few places.

***Specifications***
Overall Length	17⁵/8" 448 mm
Effective Diameter	1¹/16" 27 mm
Fin Span	4" 102 mm
Dry Weight	1²/3 oz. 47 g.

Many of the pieces would've broken if I'd've removed them from their stock without cutting them free. The material reminds me of the cheap wood I used to get in "wood burning" kits as a kid, somehow artificial but with a distinct grain and fairly friable. Most of the pieces needed only a light sanding to remove the tiny tabs left, though some had relatively large tabs and required some special attention. Also, my kit was missing two of the required slots in the lower body panels to mount the launch lug assemblies, so I used a short piece of Estes lug instead. Other than that, the kit went together very fast, not one piece failed to fit, and even bending the wood pieces that formed the nose cone wasn't difficult. Using CA really sped things up, the entire bird was together in under an hour, and ready for flight in less than two.

Finish

While most others stain (and even polyurethane) their SDI rockets to bring out the finely laser-etched details, I choose to paint mine with a translucent enamel I'd been wanting to try. It worked out all right, most of the etched details are still quite visible to the naked eye (the camera has trouble picking them up), though I'd like to add a gloss clear coat to help smooth the surface a bit. A combo poly-stain would make a great choice, too, though a thorough sanding would be required between coats.

The mediocre laser cutting and poor instructions and materials offset the phenomenal fit, finely etched details and ease of assembly enough that I'd rate this bird a 3 on the Essence scale for construction, just average.

Flight

Estimated
Performance
Engine	AGL (ft.)	Speed (ft./s)	Accel (Gs)
A8-3	160	105	15.1
B4-4	365	170	16.1
B6-4	380	195	16.3
C6-5	720	295	19.1

The instructions don't include a recommended motor list, though the bag art does claim that the Vector can be flown on A, B and C engines. I used wRASP to develop a list of those Estes and Quest motors that have appropriate delays. The Vector would also fly reasonably well on Estes' A10-3 mini engine and Apogee's A2-5, B2-3, B7-4 and C4-5, though you'd have to build custom adapters for them. Estes and Quest 18 mm motors fit the square engine mount like a glove, with positive contact on all four sides. The CG is about 4¹/8" from the aft end with an Estes B6-4 loaded.

Flight tests were conducted at Live Oaks Vocational School on Sept. 10th, 1999 @ 10 AM, before solar heating kicked up any serious winds, though there was a 2-3 MPH intermittent breeze from all directions. Sky was clear and temperature was about 75ºF. My Vector's first flight on an A8-3 was better than I thought it would be, but it did wobble a little and burned the 'chute a bit at ejection. She recovered OK, though, with no damage. Her next flight on a B6-4 had a lot more wobble, and she weathercocked into the wind some. I used more wadding this time (six squares instead of three), and the 'chute was none the worse for wear, but the wadding didn't come all the way out at ejection.

These flights caused no damage to the rocket itself, though the baffle plates were covered with soot and burned ejection particles. With no real good way to clean these, they'll eventually clog up enough to restrict the ejection charge, but I don't know if that's good or bad. After these two flights, the engine compartment and top of each engine also had some soot, indicating a poor seal between the engine and aft baffle plate. While a standard, cylindrical wound kraft-paper body tube would probably violate some paradigm held by the manufacturer, it would solve all these problems.

Both ejections appeared to be very close to apogee, confirming my estimated CD of 1.1. On the second ejection, the nylon engine retaining ring came off and was lost forever in the grass of the launch field. When I got home, I cut off the ring mounting tabs and added an Estes engine hook, which you can see in the photo at right. I cleaned up the soot in the engine compartment with a damp towel and retouched the paint before I took the photos.

Though the Vector presents no more frontal area than a typical Estes E2X bird like the Banshee or Hijax, and weighs about the same, her rough, blunt leading edges and poor surface finish detract from her performance. The Vector's less than "stellar" flights, wobble, poor ejection gas management, and the loss of the engine retaining ring make me rate her a 2 on the Essence scale, needs improvement.

Summary

While she was fairly easy to build and is an interesting concept, the Vector exhibits only fair performance and the design needs work, so I give her an overall rating of 2½, needs some improvement. I'm glad to have her in my stable, but I don't think I'll build another Stellar Dimensions kit unless the design is much more interesting. Their adaptation of the Flying Jenny is such a bird, but published reports indicate that its glide performance ain't that hot. If I may be so bold, the square rocket concept seems perfectly suited to two and even four engine cluster designs; a Vector-sized bird would fly pretty well on four (½)A3 engines, exactly the number in one pack. . .

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