Additive Aerospace "fly-away" rail guides ruined my big flight. How does this even happen?

[FredA]

Rod Whip and FARG strikes are both launch "events" that we can do without.

 

[jahall4]

As you move the FARG further forward above the fins, the chance of a fin strike is reduced. My preliminary data and calculations indicate that the chance of a fin strike is near zero at 24 inches for all but the highest accelerating and larger fin rockets. I hope to fly in November or December my first 500Hz instrumented rocket with a 500Hz instrumented FARG.

The chance of a fin strike is zero if the guide is setting on the fins OR even better, on what I think of as a FARG rest. The guide MUST NOT slide it MUST be lifted, must be accelerated with the rest of the rocket.

 

[jahall4]

The successful flight I have seen all had the guide push away from the rocket.

... and if the rocket is light enough, you'll even see the rocket move laterally as in this video. Newtons 3rd law is not trivial when it comes to FARGs so there is some performance and stability advantage with the guide closer to CG (shorter moment), but as others have posted a strike is more likely and shorter effective rail. No ideal config. Tower is way to go if you have access to one. And there are some enhancements that need to be made. Ditch the cork and AL rod, instead rubber and CF rods. You'll have less broken guides, and the CF is lighter.

 

[Spacedog49Krell]

Rod Whip and FARG strikes are both launch "events" that we can do without.

Rod Whip, from my data, appears related to rod/lug drag coupled with a secondary vehicle roll. This data graph shows both issues during the 135ms of time sliding on a 3/16" rod.