Semroc ThunderChief

Semroc - ThunderChief {Kit} (KA-7)

Contributed by Chan Stevens

Construction Rating: starstarstarstarstar_border
Flight Rating: starstarstarstarstar_border
Overall Rating: starstarstarstarstar_border
Diameter: 0.91 inches
Length: 31.90 inches
Manufacturer: Semroc
Skill Level: 1
Style: Sport

Brief:
Semroc Thunder ChiefSeveral years ago, Semroc introduced the first of what promised to be a family of Thunder designs, each featuring long sleek profiles, swept fins, and progressing up in size. The first of these was the Thunderbee, one of my favorite 13mm models, but the ensuing bigger brothers never came to light until now. At NARAM-51, Semroc released the upscale Thunderchief, which is about double the length of the Thunderbee, and the Thunderstrike, a 54" long 24mm brute. Down the road, the rest of the family will hopefully make it to market as well (Thunder Roc, Thunder Storm, Thunder Hawk and Thunder Bird), since these are such great fliers and simple builds.

Construction:
The bag appears a bit small for the $14.50 price, but that's partly because the body tube is comprised of 3 shorter tubes. The parts were all excellent quality, especially the nose cone.

  • Balsa nose cone
  • 3 Series 8 body tubes
  • 2 tube couplers
  • BT-20 motor tube, centering ring/tube
  • Laser cut balsa fins
  • Metal hook
  • Kevlar/elastic shock cord
  • 12" plastic chute
  • Waterslide decals
  • 1/8" launch lug

Semroc Thunder Chief

Instructions are standard Semroc: well written and illustrated. This would be a Skill Level 1 kit with about three pages of instructions. My build time was under an hour plus finishing time.

The motor mount on this is a little different, since the tube is slightly smaller than a BT-50 and doesn't leave room for a normal pair of centering rings. The solution in this case is to use a covering tube which slips down the motor tube, holding the motor hook in place and fitting to the ID of the body tubes.

I stupidly built this concurrently with several other Semroc NARAM releases, so I anchored my Kevlarto the forward end of the motor hook just like the other kits. That would be wrong according to the directions, which call for anchoring the Kevlarto the forward coupler. Due to my goof, I only have about 7" of shock cord outside the model, so I'll need to add more elastic on my own.

The body tube is marked for fin placement using a template. Early editions of the kit (including mine) had an oversize/incorrect template, although this has been corrected in later editions. After marking the first body tube, the other body tubes are bonded using the provided couplers.

Fin attachment is straightforward: tack on with CA then follow up with wood glue fillets. Add on the lugs (one at a fin joint, the other about a foot forward) and construction is done.

Finishing:
I very much like the color scheme of my Thunder Bee with white on the forward section and Dayglo yellow on the aft section. Unfortunately, Krylon's reformulation wouldn't cooperate and I was optimistic in taking the chance that it would.

I prepped all surfaces via grain and spiral filling, giving extra attention to the tube seams where the separate pieces are joined. I then hit everything with two coats of light gray primer and three coats of gloss white. So far, so good. For the yellow, I masked off the upper portion and hit the aft end with Krylon's old formula Dayglow yelow. Big mistake. It crazed and crackled. It wound up taking me 3 subsequent passes of sanding off the coat of paint, wiping everything down with rubbing alcohol, shooting with a light old formula primer, then topping off with the Dayglo yellow. The finished result looks nice but was hardly worth the effort.

There is also a basic name/logo waterslide decal provided, which is perfectly produced--nice and clear background, tough enough to allow the decal to be moved around for alignment, and thin enough not to stick up with that peel n stick look.

Construction Rating: 4 out of 5

Flight:
For the maiden flight, I caught a wonderful day over Labor Day weekend, light winds, clear skies, moderate temps. Since I had this and the bigger Thunder Strike both ready, I decided to dig up the Thunder Bee and make a family outing of it.

I went for the max, choosing a C6-5 over a 7. Boost was straight up with a slight trace of weathercocking. The -5 delay was just about perfect, and I think in general the recommended -7 would be too long under all but the most perfect of conditions.

I'm not sure what the apogee wound up being, but I suspect it was a tad less than the estimated 950' on the header card. Still, it strained my 44-year old eyes a bit to pick it up.

Recovery:
The 12" chute is just about right for this. I caught a little thermal on the way down but once out of it started coming down fairly quickly. I have to admit, though, given the altitude I hit on boost, the blue and white plastic chute included in the kit was not exactly an optimal color scheme as it was very difficult to pick up a 12" chute at that altitude, especially without strong contrast to the skies.

Flight Rating: 4 out of 5

Summary:
I'm biased and really like the Thunder line overall. There's just something about those long, sleek models that appeals to me. Of the 3 currently available, this one strikes me as the most flexible, being able to handle A through C (and comically could fly OK on a 1/2A6-2).

Overall Rating: 4 out of 5

Other Reviews
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    Brief: Semroc describes the ThunderChief as the third largest member of the Thunder kit series that they are producing. This series is essentially the same rocket scaled approximately 1.25 times each step up in body tube size. The series is based from the Centuri Engineering Thunder rockets that included the ThunderHawk, ThunderBird, and ThunderRoc. With Semroc's introduction of this ...

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