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Question about cohete rockets/BP fuel in general.

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#1 gunner1



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Posted 04 March 2023 - 03:23 PM

I was hand ramming my first cohete rocket today and when I got to just below the top of the spindle, I couldn't get the BP to compress any more to cover the spindle. In fact, a bulge formed right where the powder stopped compressing. Is this because I was ramming dry BP? Would adding 1/2 of one percent of water of made a difference? When I removed the motor from the spindle the BP core was nice and shiny. Was the fact that I put in a clay nozzle make any difference? I put a fuse in it to test the motor and it pushed it at least 6" into a packed wet snow snowbank! Any help would be greatly appreciated.
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#2 davidh



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Posted 04 March 2023 - 05:50 PM

For the Tultepec-style rockets, I typically go with a short increment for the nozzle followed with about three dry increments with the hollow drift. This gets you around the end of the spindle. Then another dry increment or two with the solid drift. Just make sure you don't let your no-pass line on the solid drift enter the tube. If it gets close, just add a few pinches of comp until the line stays well out of the tube. When you've got room at the end of the tube for about one more increment, use dampened comp instead of dry comp, and ram until the tube is completely full. I use an extender made out of another tube for this. When you get the tubes from Tultepec, there are partial cutoffs in the bag that are ideal for this.


Deadblow hammers suck for making rockets and will make your rockets cato. Use a rawhide or wooden mallet, and not too large of one. Four or five good taps is all it takes to ram a BP rocket of this size. Bulging should be minimal with even a crappy tube. It's good to have just a little bulging when you ram the nozzle, however.


As long as you make sure each increment is rammed and the final increment is rammed damp, these rockets will rarely fail. The failures I have seen often seem to involve too little clay in the nozzle increment, resulting in nozzle blowout.


Last, you might want to test a few before you attach the 24g reports. You may want to test a few hundred before you start hand-launching them.


People that don't use clay nozzles in their BP rockets are the same people that dye their hair purple. I wouldn't spend much time listening to them. People that press their BP rockets have other types of mental issues and you probably want to stay away from them too.



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