MrCATO Posted June 15 Share Posted June 15 (edited) Well this is kind of embarrassing. I've never seen this happen before. This is my third rocket with these big boomer headings and it failed in such an interesting (possibly amusing) way. This is also my first failed rocket in a long time. The rocket barely left the tube before the heading with a quarter pound of fun powder disconnected from the top of the motor and went off maybe six or seven feet from the ground. The motor is a cored nozzled 8oz (cohete tooling) rocket. The fuel is 75/15/10 + 2% mineral oil with homemade airfloat ERC then granulated with water. Each 1/2 tsp fuel increment is pressed to 2000lbs on the PTF gauge. The nozzle is a single 1/2 tsp increment of kitty litter pressed to 2000lbs on the PTF gauge. I ran out of delay so I started using my older batch of fuel which is slightly slower than my newer batch but still probably too fast to be used as delay. It's the same comp as the fuel for this motor. I made the delay charge pretty short because I only needed it to finish the rocket so I could use the spollete to time the heading. I've got a few 1/8 tsp increments rammed into the spolette at 500lbs a piece that adds up to a half inch of powder. Again, using my old batch of fuel because I ran out of delay. In order to secure these big headings to the motors I do two things. I run a length of masking tape around the bottom of the spolette to bring it's OD to the ID of the motor tube, then I use a bead of white glue around that tape to secure the spolette (and the heading it's attached to) to the inside of the motor. Then as an extra precaution I fill in the gap between the top of the motor and the heading with hot glue then "weld" the perimeter around the motor with hot glue. It would appear that due to the accumulation of string at the base of the spolette combined with the paper pasting, I can't get these headings to sit perfectly flush without a gap. I suppose that might not be a problem, but maybe it is. TLDR; I just made a batch of six of these right after this one. I recall something interesting that I think may possibly be the reason or at least a contributing factor. I made one of the spolette tubes too short for one of these rockets. I was going by the skylighter formula and cut down the length of my spolette tube. By the time a heading was spiked and pasted the tube didn't stick out far enough for me to wrap the masking tape around it so I could secure it to the inside of the motor. I'm not 100% on which rocket this was but I think it might have been this one. Naturally I decided to stop cutting the tubes after that and just use them as is. If it was than all that was holding it on would have been the hot glue. Essentially it would have been the folds of pasted paper that were trying to hold it together. I don't know though, what do you guys think? big boy fail.mp4 Edited June 15 by MrCATO Link to comment Share on other sites More sharing options...
DavidF Posted June 15 Share Posted June 15 My vote is for a blowthrough. Link to comment Share on other sites More sharing options...
mabuse00 Posted June 15 Share Posted June 15 5 hours ago, MrCATO said: I made the delay charge pretty short because I only needed it to finish the rocket That's obviously your problem. If you want to do the timing with an extra spolette, you need at least some kind of plug. Link to comment Share on other sites More sharing options...
MrCATO Posted June 15 Author Share Posted June 15 I'm almost certain the six I got left have the tape around the spolettes but you guys may be right about that. Maybe it was the path of less resistance type of situation and the delay blew out before the rest of the propellent grain did. I just wish I didn't use the last of those bigger tubes so I could test that theory lol. Link to comment Share on other sites More sharing options...
Kalifireworks Posted June 15 Share Posted June 15 Well ther isnt really any other possiblity.. the delay blew trough Link to comment Share on other sites More sharing options...
DavidF Posted June 15 Share Posted June 15 You can clearly see the fire coming out the bottom and the top of the rocket at the same time, and the shell fuse going upwards. It's handy to watch videos frame by frame when trouble-shooting. One time I had a buddy helping me attach shells to rockets with the tape wrapped around the spolette tube to friction fit it. He put too much tape on, and he was trying to manhandle the thing into the tube, rather than taking off a bit of tape. I should have pulled that motor from the bunch, but I didn't. It CATOed because the manhandling separated the delay from the tube and caused the blowthrough. In that case, there was enough delay, but it simply got by-passed. I really think the extra work of using a rammed spolette for shell ignition on a rocket is extra work and an extra thing to (possibly) go wrong. I always use the delay to ignite the black match the spolette is stuffed with. On a 1lb rocket, I use at least an inch of delay. Just a suggestion. Link to comment Share on other sites More sharing options...
MrCATO Posted June 25 Author Share Posted June 25 (edited) On 6/15/2024 at 4:48 PM, DavidF said: You can clearly see the fire coming out the bottom and the top of the rocket at the same time, and the shell fuse going upwards. It's handy to watch videos frame by frame when trouble-shooting. One time I had a buddy helping me attach shells to rockets with the tape wrapped around the spolette tube to friction fit it. He put too much tape on, and he was trying to manhandle the thing into the tube, rather than taking off a bit of tape. I should have pulled that motor from the bunch, but I didn't. It CATOed because the manhandling separated the delay from the tube and caused the blowthrough. In that case, there was enough delay, but it simply got by-passed. I really think the extra work of using a rammed spolette for shell ignition on a rocket is extra work and an extra thing to (possibly) go wrong. I always use the delay to ignite the black match the spolette is stuffed with. On a 1lb rocket, I use at least an inch of delay. Just a suggestion. Thanks for the advice guys. The next time I do any of these big ones I'll try the method with a larger delay and unrammed blackmatch spolettes. Finally got around to making my first batch of blackmatch. Unfortunately the rocket tubes I get from woody's are out of stock and I don't know of anywhere else that has them so I gotta find some other ways to use this. Probably gonna convert some of it to quickmatch and string up a finale chain with it. Always fun learning new things. I love the smell when this burns btw. Edited June 25 by MrCATO Link to comment Share on other sites More sharing options...
MrCATO Posted July 1 Author Share Posted July 1 (edited) No option to edit. I put masking tape on the bottom where the nozzles were on the remaining 4 rockets and they actually all worked perfectly when I lit them today. Come to think of it, all the ones that failed didn't have the tape. Maybe it's just a coincidence but prior to that the five that I shot only two of them worked correctly. I honestly don't know how to explain how a thin strip of tape does anything but I'll take any wins I can get. Quite amusing how much these little half 8oz motors can lift. I think I finally found the limit/redline and before too long I might be ready to graduate to full 8oz or 1lb. Edited July 1 by MrCATO Link to comment Share on other sites More sharing options...
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