Semroc Aphelion

Semroc - Aphelion {Kit} (KV-26)

Contributed by Chan Stevens

Construction Rating: starstarstarstarstar_border
Flight Rating: starstarstarstarstar
Overall Rating: starstarstarstarstar_border
Published: 2010-12-13
Diameter: 1.04 inches
Length: 14.80 inches
Manufacturer: Semroc
Skill Level: 1
Style: Clone, Sport

This is #4 of 10 "ready to build" models released by Semroc at NARAM-52. The original Aphelion was Semroc's 4th production kit, introduced in 1968 and included in their version of a starter set (with launch pad, controller, and engines).

Parts were excellent quality, and the sealed bag contained:

  • Balsa nose cone
  • Series 10 slotted body tube (1" ID)
  • Series 9 stuffer tube (1" OD)
  • 18mm motor mount (tube, metal hook, centering rings)
  • Laser-cut balsa fins (3)
  • Elastic shock cord
  • 12" plastic chute
  • Waterslide decals


The "ready to build" series is Semroc's answer to numerous requests for "ready to fly" rockets. In the RTB series, the modeler still has to actually do work to build and fly the model, but the design includes a number of features that simplify the build process, including slotted body tubes for thru-wall fin mounting, an alignment jig, and a stuffer tube to serve as shock cord anchor and reinforce the body tube.

The RTB series are all fairly easy to build, with almost all of the construction process using the same standardized steps. This is clearly a skill level 1 introductory type kit, and excluding finish/surface prep total construction is well under an hour.

The motor mount is a standard BT-20 tube, metal hook, and a pair of centering rings. Unlike the typical mount, though, there are two different centering rings involved with slightly different diameters. Pay careful attention to the instructions, as the white ring goes forward and the brown ring goes aft. This is critical later in the process. Surprisingly, the mount does not include an inner motor block, so the metal hook will have to hold for the life of the model. I found the centering rings a bit too snug, and had to peel off a layer of paper from the inside of each, plus one layer of paper from the outside of the white ring.

The stuffer tube contains a couple slits, which are used to slip the elastic shock cord through, serving as an anchor. After knotting the cord and reinforcing with a drop of glue, it's ready for the motor mount. The motor mount slides just a tiny bit into the stuffer tube, enough that the forward (white) centering ring is flush with the aft end of the stuffer tube. Do not slide the motor tube any further--the aft/brown ring is too large for the stuffer tube and instead is used to align inside the large series 10 body tube. Sliding the assembly into the body tube to dry fit is a good idea at this point, to make sure the forward centering ring is aligned properly inside the stuffer tube. Once the motor mount/stuffer tube assembly has completely dried, it can then be glued inside the body tube (though be careful to make sure the metal engine hook does not line up under a fin slot).

As noted, fins are thru-wall, and the fit against the motor tube was very good. Included in the kit is a nifty little cardboard fin alignment jig, which fits smoothly on the series 10 body tube and has notches to accept 3 and 4 fin patterns. The fixture fits well for most fins in the RTB series, though for fins that have a significant span and are not swept back very far, the slots in the jig are not long enough to be of much use. That was not the case with this model, though.

I went with the stock paint scheme on this, starting with two coats of primer, following up with a couple thin coats of gloss white, then masking off to paint the fins and forward section of the body tube yellow. Note that the cover art depicts a yellow/black roll pattern, but the decal itself is only clear and black. If you want the yellow (which does look nicer), you must carefully measure the decal length and paint about 1/16-1/8" less than from the tube top yellow.

The nose cone got gloss black.

The waterslide decals add the name and roll pattern.

Construction Rating: 4 out of 5

I went with a conservative A8-3 for the first flight, pinned into the corner of a crowded group of soccer fields. The flight was straight up and perfect, no roll, deployment right at apogee. The kit recommends a -5 delay, but I found the -3 to be just about right on this one.

The 12" chute performed fine, and in fact I used the same chute for most of the 8 flights for the day on various Semroc models, using only dog barf for protection.

Flight Rating: 5 out of 5

As a beginner's kit, I wouldn't expect interesting styling, and the 3FNC design is certainly nothing special, but it's a simple, quick build and will certainly provide quick, easy and reliable first flight experience that's sure to be positive. In fact, there was a steady flow of young soccer players walking past my pad area all day, and I'd often offer to let them launch these RTB models. Each one drew that wide-eyed "wow, that was cool" response from them, so the mission was surely accomplished.

Overall Rating: 4 out of 5


comment Post a Comment