Launch rod - how long?

Discussion on ground control/GSE and recovery equipment. This includes launch pads, triggers, chutes, streamers etc. Includes other items such as simulation and other computer software, etc.

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lorstin
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Launch rod - how long?

Postby lorstin » Sat Oct 18, 2014 3:42 pm

I'm planning on using a piece of 3/16" stainless rod to launch my rocket which is powered by a G64. The rod is about 2 metres long and I don't really want to cut it if I don't have to. On the other hand if it's length will interfere in any way I don't mind shortening it. So the burning question is - ideally how long should it be?
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Re: Launch rod - how long?

Postby october sky » Sat Oct 18, 2014 5:20 pm

At that length you will get "rod whip" for sure, especially using G64 which has quite a bit of power.

I would cut it at 1.2 meters and there is much less of the whip happening. I have had that experience in the past few times and your rocket takes off sometimes in not so ideal angle.. :roll:
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Re: Launch rod - how long?

Postby Kryten » Sun Oct 19, 2014 6:28 am

I agree. 2m of 3/16" rod seems unnecessarily long.
You can run a sim in OpenRocket and export the data for altitude and velocity to determine the length required for a particular rocket and motor
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lorstin
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Re: Launch rod - how long?

Postby lorstin » Sun Oct 19, 2014 7:14 am

Thanks guys, wobbly/whippy was what I was thinking, excessive drag too I would imagine. I'll checkout Open Rocket - I hadn't thought of that. :D
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OverTheTop
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Re: Launch rod - how long?

Postby OverTheTop » Sun Oct 19, 2014 1:08 pm

If you want a good way to store the rod I use a length of 25mm electrical conduit. One end is plugged and the other is fitted with a closure of some sort. I use the top of a softdrink bottle. I cut off the top of the bottle to where it fitted nicely on the conduit and then held it in place with some heatshrink with internal glue. The screw cap then just screws on and off as needed.

This makes a great way to protect the rod during transport. I don't want to risk any kinks.
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