Over stable Rocket

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rocket trike

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I Put my rocket in Rocksim after I got most of it done as I started this rocket before I got Rocket sim. It is saying that the rocket is overstable. The losest is 4.5 and goes to 12 over. What is there that I can do or should I woory about it being overstable? Here is a picture of it.

Thank You
 
In my meager experience, over stability is over rated. Supposedly it's more sensitive to wind gusts. The Mean Machine is way over stable and flies great in moderate winds. I personally wouldn't be concerned.
 
overstable is not a bad thing but can give you a long arcing flight sometimes

an overstable rocket has a tendancy to turn into the wind

If its windy enough it can literally continue untill its horizontal

it would be a good idea to fly it on low wind days and to have

enough launch rod and a high enough thrust motor to get good speed off the rod
 
I am going to use 3 B6 motor for the frist flight. Where we launch in town we can only launch up to d Motors. Our high power launch site just got put under a fire ban so we can not fly there. When I sim it out on rocksim the numbers say that we should hve no problems so I will see what happens Monday.
 
3 B motors will have a short flight and probably won't be affected by wind much. "Over-stable" is a bit over-rated. The mean machine, richter recker, corona, and many other rockets would SIm out as over stable, yet still make fine rockets.

I wouldn't worry too much about it. If anything, depending on fin thickness and material, fin flutter may be your greatest concern.

jim
 
What is the stability margin with the heaviest motor you will ever use in this model? Is it the 4.5? Are you referring to the stability using RockSim or Borrowman equations? Since this is a "longer" rocket generally more calibers of stability are acceptable (3 to 5) so the 4.5 should not be much of a problem. Note however that rockets with large fin surface areas such as on your design are more prone to fly into the wind. Run a few RockSim simulations at higher wind speeds say 15 to 20 mph to see how much the model weathercocks. If the model can't be recovered in the fields where you intend to launch it, with a 30 degree maximum launch rod angle, then either don't fly it on windy days, or decrease the fin area.

Bruce S. Levison, NAR #69055
 
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