From a building standpoint, this model is quite easy. It uses the traditional construction techniques you are familiar with from building smaller model rockets. And the instructions are absolutely phenomenal; there are lots of excellent illustrations that clarify the text.
Note: While the illustrations are supurb, we still recommend actually reading the written portion of the insructions. You'll pick up a lot of new building tips that can be used on other rockets.
13mm diameter "Mini-motors" (these are designated by the "T" at the end of the motor name). These motors fit into the Apogee 13mm diameter Airframe Tube (Part Number 10062).
1/2A3-2T
First off, this motor is a "mini" size, which means it is 13mm in diameter. It is intended for relatively small rocket kits. It will work in the Apogee SR-72 Darkbird, and the Texas Twister kits. The 1/2A motor won't loft either of these models very high, because it doesn't have a lot of thrust. This could be an advantage for the first flight of both models; since you don't want either of them to go very high on the first launch. Otherwise, they could be caught by a gust of wind and drift away. You want to be able to get them back so you can fly them again, don't you?
Another use for this motor is when you want to video tape, or photograph the descent of the models. Since they don't go so high, you'll have a much better chance of being able to capture an image of the model in flight. For both the Texas Twister, and the SR-72 Darkbird, which have unique recovery features, this is the motor you'd want to use.
The 1/2A3-2T motor is a quick burning motor. Since it is small, it doesn't make much of a roar on lift-off. It is more of a pfffffsss sound. But that OK, isn't it. Some times, when you have small children that have never seen a launch before, you don't want to scare them the first time with a loud roaring motor like the D12. So this could be used to acclamate the kids and get them used to seeing a rocket take off. Then you can start launching those bigger rocket motors that make a lot more noise.
A3-4T
This motor is the same size as the 1/2A3-2T listed previously. But it has almost twice the propellant mass, and burns much much longer than the 1/2A variety. So it will push the rocket significantly higher into the air. How much higher? That is difficult to guess at. I recommend that you run Rocksim flight simulations to see the altitude difference. It
