Stuffer Tube

[Engineer Kelly]

Im probably going to use a bt-50 stuffer tube on this tomahawk im building. The biggest motor ill put in there will probably be a 24mm E9. From the motor mount to the base of the nose is around 28 inches. So, around 22 inches or so of bt-50 stuffer tube. Then 5 inches of bt-60 (subtracted base of nose).

Ive never used stuffer tubes or even powered a rocket with a E motor.
Will the ejection charge destroy the bt-50, or should it be fine?

[tbzep]

Im probably going to use a bt-50 stuffer tube on this tomahawk im building. The biggest motor ill put in there will probably be a 24mm E9. From the motor mount to the base of the nose is around 28 inches. So, around 22 inches or so of bt-50 stuffer tube. Then 5 inches of bt-60 (subtracted base of nose).

Ive never used stuffer tubes or even powered a rocket with a E motor.
Will the ejection charge destroy the bt-50, or should it be fine?

Five inches isn't much volume, especially when a recovery system is stuffed in it. Give yourself at least 10" because today's ejection charges are really strong.

[Rocket Doctor]

Im probably going to use a bt-50 stuffer tube on this tomahawk im building. The biggest motor ill put in there will probably be a 24mm E9. From the motor mount to the base of the nose is around 28 inches. So, around 22 inches or so of bt-50 stuffer tube. Then 5 inches of bt-60 (subtracted base of nose).

Ive never used stuffer tubes or even powered a rocket with a E motor.
Will the ejection charge destroy the bt-50, or should it be fine?

The ejection charge will be more concentrated using the smae diameter tube as the motr diameter.

If you use a BT-60 without a stuffer tube, the amount of ejection charge should be great enough to deploy the recovery system.

Stuffer tubes are good when using a much larger diameter tube such as BT-70's and above. Motors aren't made to reflect the body tube diameter, basically one size motor ejection charge fits all, be it a BT-20 and a BT-70.

The smaller the diameter of the tube (motor mount) the more concentrated the force will be.

[Mark II]

Granted, ~32 inches of BT-60 airframe is a lot of tubing for LPR (although it is more typical for mid-power rockets designed to fly on BP motors). You won't need the stuffer for those motors, but you may want to consider installing a centering ring (such as a 20/60, or better yet, an ejection baffle) about halfway up from the motor mount. It will serve to keep your recovery system in the upper half of the airframe during boost, which will help with the rocket's stability. Installing a baffle will also cut down, or totally eliminate, the need to use ejection wadding.

Mark

[Mark II]

On the other hand, there are situations where you might want to install a stuffer for reasons other than facilitating recovery deployment. If you are building your Tomahawk for scale competition, for example, or just plan on really fussing over the paint job and finish so that it can also function as a fine display piece, you might choose to use a double-wall construction for the airframe. The purpose of that is to protect the outer airframe from the expansive stresses and even possible burns caused by the ejection charge. The stuffer will absorb those stresses and isolate them from the outer wall.

If that is the case with your model, then using a BT-55 as a stuffer (or actually, as a liner tube) inside your BT-60 would work well. It will provide the double-wall protection without excessively restricting the internal volume of the airframe. It would be a better choice in this case than using, say, a coupler tube as a liner, because most of the BT-55 will not be in contact with the outer tube, and so will be free to absorb the expansive forces of the ejection charge without transmitting them to the outer wall. If you choose to install such a liner for this purpose, then you should make it reach all the way up to just below the nose cone shoulder when the nc is fully inserted. It would still be a good idea to also install an ejection baffle in this scenario, but you would use one that was sized to fit the smaller diameter liner tube (the BT-55).

Remember that doing this will probably only be needed if you are putting a premium and finely detailed finish on your rocket and want to protect it from any internal stresses. Also keep in mind that it will decrease the space available to pack in the parachute and shock cord. (In your case, that probably won't be so much of a problem, though.)

As you are no doubt aware, installing a stuffer for any reason does increase the weight of the rocket a bit, which will lower its performance (i. e., its maximum altitude, its airspeed during boost and the maximum weight of any payload that you might want it to carry) to some degree.

Just another consideration.

Mark