Semroc Thunderbee

Semroc - ThunderBee {Kit} (KA-1)

Contributed by Craig Swinson

Construction Rating: starstarstarstarstar_border
Flight Rating: starstarstarstarstar_border
Overall Rating: starstarstarstarstar_border
Diameter: 0.54 inches
Length: 14.70 inches
Manufacturer: Semroc
Skill Level: 1
Style: Sport

Brief:
This is a very light, quick build kit from Semroc that is essentially a 3FNC but with some head snappin' zip when matched with the right engine!

Semroc Thunderbee

Construction:
The parts list:

  • 1 14.7" length of BT-5
  • 1 Balsa sheet of laser cut fins
  • 1 Balsa nose cone
  • 1 Cardboard thrust ring
  • 1 Launch lug
  • 1 Screw eye
  • 1 Elastic cord
  • 1 Kevlar® thread
  • 1 Crepe paper streamer
  • 1 Tape section
  • 1 Empty engine casing
  • 1 Q-tip
  • 1 Decal sheet

This is a relatively simple kit to build. The instructions are straightforward and easy to follow. As this is a minimum diameter body tube that is quite long, there are some precautions to take:

  • Read the instructions first. It is a simple kit, but it does have a couple pitfalls if not careful.
  • Do not over glue the thrust ring. I let one of the neighbors build one and he got the thrust ring stuck about 1/2inch into the tube. He used too much glue and could not overcome the friction while trying to insert the thrust ring to the proper depth.
  • If you push too hard on the thrust ring, you can easily crumple the body tube. If you are building this kit with children, this might be a step for the adults to do for them.
  • The kit suggests rounding the fins, which is not a bad idea for bigger fins, but on this kit, they are fairly thin already so it doesn't seem to make that much difference.
  • In building a set of seven (with two failures) we tried CA, wood glue, and instant glue. It really didn't seem to mater all that much. All flew well and have held up for multiple flights.

The only thing that we did differently on construction was to fit the thrust ring without glue then glued it in place using the Q-tip provided.

Finishing:
There is a small decal sheet and the only real direction for finishing is the color cover that is a standard part of all Semroc instructions. I did one as factory as possible, then did a couple variations. I would highly suggest using colors that you can easily detect in a natural environment. Paint it white or blue, you will lose it in the sky. If you paint it green, camo, or any colors that exist in outside, then make sure you have plenty of spotters or some good eyes. Day-Glo or neon colors seem to work best (unless you live someplace very odd).

Construction Rating: 4 out of 5

Flight:
Since the engines were relatively cheap and readily available at my local hobby store, I bought a retail case and just kept launching and launching the different variations of the kits. (All flights used A10-3Ts.) In retrospect, some of the smaller engines might have been nice to try as this thing moves out on an A10-3T!

I tried a variety of different motor retention techniques and even tested motor ejections to see if it would impact recovery. My favorite method of positive retention is to use a 1/3 of an inch of masking tape just wrapped around the body of the engine. This was strong enough to hold the engine in place on every launch.

Prepping the rocket is straightforward but is a bit difficult as the tube diameter is so small. Using a pencil really aids in sliding the shock cord and wadding in.

All flights were very straight with arcs at apogee.

Recovery:
This rocket uses the "standard" Semroc small diameter shock cord. A length of Kevlar® string tied to the thrust ring. In turn the other end of the Kevlar® is tied to an elastic cord which is then secured to the screw eye attached to the nose cone.

The crepe paper streamer is pretty long and can be a bit difficult to pack into the body tube. In testing, this rocket will recover with no streamer and recovers very gently with only half a streamer.

Flight Rating: 4 out of 5

Summary:
This is a very fun kit! It is easy and fast to build, cheap to feed, and gets some great height in a short period of time. I chuckle every time I launch the ThunderBee, it's just one of life's small pleasures. It's diminutive size belies a real fast mover. On 1/4A or 1/2A engines, I could see this being a nice back yard rocket. On the full A10, make sure you have some space.

Overall Rating: 4 out of 5

Other Reviews
  • Semroc Thunderbee By Chan Stevens

    Very affordably priced single stage, 13mm minimum diameter kit. Very high performance--it will zip up to incredible altitudes almost instantly. This is actually a Semroc original, not one of their retro/repro Centuri designs. The kit came sealed in a plastic bag with a header card and included a serial number identifying its production number. Components were all very good quality and ...

  • Semroc Thunderbee By Philip Handley

    Brief: The Thunderbee is one of the latest kits from Semroc. It's the first and smallest rocket in the "Thunder" family. Each rocket in the family is around 1.5 times larger than the rocket before it! The Thunderbee is a minimum diameter 3FNC rocket. It comes down on an orange crepe streamer. Construction: The Thunderbee comes with the following parts: 1 14.7" ...

Flights

Comments:

avatar
S.G. (February 27, 2008)
This was one of my first kit builds after getting back into rocketry after a 25 year hiatus. The quality is outstanding and was very happy with the way it all went together. I have flown this around 6 or 7 times now and have lost the streamer on a couple of flights (landing without damage). The heat from the motor has started to cause the paint to bubble.

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