Ventsi Posted March 8, 2009 Share Posted March 8, 2009 (edited) 4 Ounce BP endburner with flying fish and TT header Prefire Shoot 4 Ounce BP endburner with green header PrefireIt looks the same as the above rocket Shoot KNSU rocket with C7 Charcoal header Prefire Shoot was a little on the heavy side,and the fuel grain burned way too fast. Comments are most welcome Edited March 8, 2009 by Ventsi Link to comment Share on other sites More sharing options...
Yankie Posted March 9, 2009 Share Posted March 9, 2009 Good stuff, the FF one was nice Was that a split comet or just the rocket breaking up, because it looked nice. Link to comment Share on other sites More sharing options...
Mumbles Posted March 9, 2009 Share Posted March 9, 2009 The fuel didn't burn too fast in the KNSU rocket, it probably just wasn't compressed enough and CATO'ed. It's close enough to take off to consider it a CATO I think. Link to comment Share on other sites More sharing options...
Ventsi Posted March 10, 2009 Author Share Posted March 10, 2009 (edited) Thanks guys Mumbles: There was no way there were any airspaces in the fuel ,it was a solid grain. also you could call it a CATO but that is just the header going off at 10-15 ft. Yankie: Neither i used one of these for the header casing[ http://www.cannonfuse.com/store/pc/viewPrd...mp;idproduct=25 There was a tied bunch of FF and two large C7 stars on the side of the bunch {1/2"}it was broken with plain meal to ensure ignition of the unprimed fuse and pasted the heck out of. Which means i got a perfect break! Edited March 10, 2009 by Ventsi Link to comment Share on other sites More sharing options...
Mumbles Posted March 10, 2009 Share Posted March 10, 2009 Unless your grain was 1/2" long, there was something wrong with the fuel grain. No matter how solid you think it was, it very obviously blew through. This is indicative of a weak grain, airspaces, gaps, or cracks. You can call it and think what you want, but the rocket did not preform anywhere near correctly. Link to comment Share on other sites More sharing options...
Ventsi Posted March 10, 2009 Author Share Posted March 10, 2009 Unless your grain was 1/2" long, there was something wrong with the fuel grain. No matter how solid you think it was, it very obviously blew through. This is indicative of a weak grain, airspaces, gaps, or cracks. You can call it and think what you want, but the rocket did not preform anywhere near correctly. Well yeah I suppose you must be right.it was and end burner as well. well its not like i can check now. well im now working on some more rockets,since my 4ouncers are taking off as if they are cored!Ill try lifting some bigger headers next weekend. Link to comment Share on other sites More sharing options...
FrankRizzo Posted March 10, 2009 Share Posted March 10, 2009 Over the last few years, I've come to the conclusion that it's not necessarily voids in the fuel grain that causes CATO's, but instead it's the absence of the preload on the tube (usually accomplished by pressing). If the tube isn't properly preloaded with pressure (the layers of the tube not pressed together), the sudden pressure spike of the igniting fuel causes the tube to expand just slightly enough that hot exhaust gases slip between the grain and the tube wall. This exposes more of the fuel grain, which raises the pressure, and causes more separation which eventually leads to an overpressure rupture. Moral of the story is to use quality tubes, or press your rockets with high enough loading pressure that any "spongy-ness" in the tube wall is taken-up. Link to comment Share on other sites More sharing options...
Ventsi Posted March 10, 2009 Author Share Posted March 10, 2009 You know Frank your brilliant.Come to think of it i used a Home rolled tube that wasnt hardened.and the KNSU was ramed in HOT so it probably shrunk the tiniest bit. Man you just made my day.A+ for the reply.I have a bunch of SCH40 PVC tubes that ill be using for my KNSU 1lb's ! Link to comment Share on other sites More sharing options...
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