leedrill Posted March 12, 2013 Share Posted March 12, 2013 i have recently stepped up to 3 lb motors core burners and {end burners but haven't flown any of them yet}. but my core burners are flying erratically have tried a few recommended lengths but still the same problem i have always used pvc tube for my last tooling and always good flights with some twirl at end of impulse {wich i kinda like } the tube i don't think would be that whippy during flight but i have an abundance of pvc can anyone tell me is there much of a difference in aerodynamics of flight with the dowel or the normal square sticks that are normally used id say they are the normal for a reason Link to comment Share on other sites More sharing options...
boule Posted March 13, 2013 Share Posted March 13, 2013 Well, there is a distinct reason to the square sticks - and that is that they are cheaper to make.Balancing a rocket is dependant on two forces. The acutal balance of weight during takeoff and launch and later the aerodynamic drag. While there is a calculable difference between the aerodynamics of a stick and a dowel being moved diagonally through an airflow, it is hardly relevant for the rockets. From my experience, using whatever you can get your hands on cheapest will work. And yes, that includes rolling "sticks" out of paper! Link to comment Share on other sites More sharing options...
dagabu Posted April 8, 2013 Share Posted April 8, 2013 i have recently stepped up to 3 lb motors core burners and {end burners but haven't flown any of them yet}. but my core burners are flying erratically have tried a few recommended lengths but still the same problem i have always used pvc tube for my last tooling and always good flights with some twirl at end of impulse {wich i kinda like } the tube i don't think would be that whippy during flight but i have an abundance of pvc can anyone tell me is there much of a difference in aerodynamics of flight with the dowel or the normal square sticks that are normally used id say they are the normal for a reason You might be having problems with the nozzle clay chipping or the spindle not being straight. A good motor will fly fine with a stick that is aligned well and does not "whip" when the rocket flies but if the gasses are coming out at an angle, you will spiral every time no matter how straight your sticks are. Dag Link to comment Share on other sites More sharing options...
leedrill Posted April 8, 2013 Author Share Posted April 8, 2013 cheers dag this might of had something to do with my first attempts but i think it was just that i was running really really hot bp with really low schedule pvc for sticks 15mm od and was way too long due to me doing the balance test. i ran a heap of pine through down to 9.5mm x 9.5mm x 960mm and now watching the bullet like performance im getting out of my coreburners i realise that shorter is better when there is alot of thrust Link to comment Share on other sites More sharing options...
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