All10Fingers Posted February 5 Share Posted February 5 I have an arrow jig that's made for attaching the "feathers" on the back of arrows. It's designed so each fletch is properly spaced and has two angle options for a faster or slower spin. My small rockets aren't much fatter than my big ass elk arrows and I see no reason why I shouldn't be able to fit a tube in the doohickey. Has anyone any experience with spin fins on rockets? Should I just stick to bbq skewers. I wonder if how short the rocket body is will not give the fins the necessary drag to pull the thing straight. I don't remember the exact dimensions of the rockets i make, but there identical size of commercial estes Link to comment Share on other sites More sharing options...
ThrownBiscuit Posted February 6 Share Posted February 6 Give it a try, I've done fins on larger rockets. They were mostly model rockets, but I was using homemade BP motors in them, and they worked great once I got the timings correct on the eject charge for the parachute. Link to comment Share on other sites More sharing options...
All10Fingers Posted February 6 Author Share Posted February 6 What sort of timing? Doesnt it just go when the flame reaches the top of the motor? I've never used a parachute or a commercial rocket. But I've sent plastic hemispheres high enough there's a pause between when you see and when your hear the burst. Do you use nozzles? Mine cato id I try and nozzle them, but I feel like a slower fuel with a nozzle might burn a little longer and therefore go a little higher. How big did your fins need to be to be effective?.... Relatively Link to comment Share on other sites More sharing options...
ThrownBiscuit Posted February 7 Share Posted February 7 Yes, getting the timing to match between the flame reaching the top of the rocket and the rocket reaching apogee. I use the top of the rocket as a large spollette to get the timing right. I do use nozzles, too slow down the propellant I add charcoal. For example, for 1lb core burners I use 69% potassium nitrate, 21% charcoal, and 10% sulfur. As for the size of the fins it is quite easy to get out in the weeds with this. As long as the longitudinal center of pressure (CP) is at least 1 rocket diameter behind the center of gravity (CG) you should be good. If you enjoy mathematics the Barrowman CP equations are excellent. Barrowman Equations (usu.edu) If mathematics are not your thing, simply perform practical experimentation. Record everything you do and test different variables like size and pitch. Record your results until you are satisfied. That being said with the diameter of arrows and the sizes of fletchings, I believe that it ought to work. Link to comment Share on other sites More sharing options...
All10Fingers Posted February 7 Author Share Posted February 7 Thank you that's all very helpful. I've been using regular hot bp dust and adding extra pine charcoal and/or titanium sponge. Been pretty successful with "try it and see what happens" but I think being able to solve it on paper would be nice. It's not like it's rocket science or anything. Now if I can find a way to get my nozzles to stop crumbling when I pull it off the spindle and afix a payload securely. I'm halfway to my childhood dream of owning a jet pack Link to comment Share on other sites More sharing options...
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