The second rocket that came in the kit is the Amazon. It’s about twice as big as the first rocket, roughly 30 inches and entirely black except for the decals. Having some bright colors or decals can help spot the rocket so you don’t completely lose track of it after launch.
Thoughts on assembly of the Amazon: Honestly, it was even more straightforward than the smaller Crossfire, so simple that there weren’t really any steps to document in photos. The fins are plastic and don’t require any sanding or painting like the balsa wood fins of the smaller Crossfire; these black plastic fins just slide into slots and require a bit of glue (plastic cement). The body tube and nose cone are also black plastic and simply fit together, again with some minimal adhesive to secure everything. The only non-visible part in the finished product is, as before, the parachute and shock cord, which are glued and fit inside the body tube.
For a size comparison, I included a photo of both rockets together. As I mentioned previously, the smaller Crossfire can actually go about twice as high as the larger Amazon. This was a bit counterintuitive to me at first – I assumed the larger rocket would be more powerful and go higher. But larger rockets weigh more, which is a big disadvantage – you need a larger, more powerful motor just to achieve the same maximum height as with a smaller rocket. Both of these rockets can be launched with class A, B, or C motors. Same motor in a heavier/larger rocket means it won’t go as high. This might be a good time for a quick detour to provide an overview of motor sizes, since this is pretty important to all my future rocket-related endeavors.
Class A, B, and C are some of the smallest motors; the only smaller are basically the 1/2 A or the 1/4 A. Each letter that you go up represents an approximate doubling from the preceding letter in total impulse, which is measured in newton-seconds (N-s). So the average total impulse of a class A motor is between 1.26 and 2.50 N-s; a class B motor has approximately twice the total impulse at 2.51-5.00 N-s, and a class C has twice the B at 5.01-10.0 N-s. Since they increase in total impulse exponentially, it doesn’t take long before the rocket motors start getting extremely powerful. A lot of beginner small model rocket kits (like the ones I’m using) can launch with class A, B, or C motors. Larger model rockets can use class D or E (though E and below are still considered low power motors), and the largest that are still considered “model” rockets use class F or G. The latter are considered mid-power.
Once you cross that threshold into class H or I, you’re dealing with high-powered rocketry, and this requires certification from the National Association of Rocketry (NAR) or Tripoli. Anyone can buy the smaller motors up through class G, but sales of class H and larger motors are actually restricted to individuals who have a certification from the NAR. Level 1 certification is required to purchase and fly class H or I motors; level 2 certification is required for class J, K, or L motors; and level 3 is required for class M, N, or O motors. There are motor classes beyond O, but these require FAA permits and meeting a variety of legal and regulatory requirements.
I’ll work my way up eventually. But back to the smaller model rockets for now: in my next post, I’ll document the first launch!
Improbable Ventures 