The Body Tube, or Airframe Tubing, refers to the main cylindrical body of a model rocket. Body tubes are typically made from lightweight wound cardboard tubing to keep the weight of the rocket down, since the weight of the rocket is the major factor limiting how high the rocket can fly.
Most major manufactures for model rockets design to a standard set of dimensions for body tubes, so that model rocket engines, engine mount kits, nose cones, and other accessories can be consistent. Body tubes and accessories that do not follow this standard, typically use the diameter of the body tube as their naming convention.
Standard Size Nomenclature
The names for the different sizes are BT followed by a number (ex. BT-50). The larger the number, the larger the diameter of the body tube.
The standards are as follows:
BT-5
The BT-5 model rocket body tube is the smallest of the body tubes.
- Inside Dimension: 0.518"
- Outside Dimension: 0.544"
The inside of the body tube is the same dimension as the outside diameter of the mini model rocket engines, so that this body tube can be used as an engine mount for the mini engines.
BT-20
The BT-20 model rocket body tube is the second smallest of the body tubes.
- Inside Dimension: 0.710"
- Outside Dimension: 0.736"
The inside diameter of the body tube is the same dimension as the outside diameter of a A-class, B-class, or C-class model rocket engine, so that this body tube can be used as an engine mount for these engines.
BT-50
The BT-50 model rocket body tube is probably the most common size of body tube. The BT-50 can be used in a rocket with an engine mount kit for A-class, B-class, or C-class model rocket engines. The BT-50 can also be used directly with a D-class, or E-class engine for rocket designed for high altitude flights.
- Inside Dimension: 0.950"
- Outside Dimension: 0.976"
BT-55
The BT-55 model rocket body tube is typically used for more substantial model rockets. It has a nice combination of size and strength while not being too large as to cause a lot of aerodynamic drag during flight. This is an excellent choice when designing a model rocket which is to be flown with a D-class or E-class model rocket engine.
- Inside Dimension: 1.283"
- Outside Dimension: 1.325"
BT-56
The BT-56 model rocket body tube is slightly larger than the BT-55. Mostly used in model rocket kits, but unfortunately this size of body tube is not sold separately.
- Inside Dimension: 1.304"
- Outside Dimension: 1.346"
BT-60
The BT-60 model rocket body tube is typically used for most substantial model rockets. It has a nice combination of size and strength while not being too large as to cause a lot of aerodynamic drag during flight. This is another good choice, along with the BT-55, when designing a model rocket which is to be flown with a D-class or E-class model rocket engine.
- Inside Dimension: 1.595"
- Outside Dimension: 1.637"
BT-80
The BT-80 model rocket body tube is the largest standard body tube for model rockets. Care must be taken in the design of rockets with the BT-80, as the large diameter of this body tube compared to the thickness of the wall of the tube can lead to unstable designs. Often, a BT-80 tube coupler is used to reinforce the strength of a rocket using the BT-80 body tube.
- Inside Dimension: 2.588"
- Outside Dimension: 2.600"