- This topic has 16 replies, 8 voices, and was last updated 18 years, 7 months ago by
Bruce R. Schaefer.
Bruce R. Schaefer.-
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Conway Stevens
Its all about mass and speed and better to be prepared then not. What if when the apogee charge opens things up and it tosses out a little hard and yanks the cone off? or what about if you ever or even if this flight has enough momentum going and as it hits burn out negative g’s happen it separates at the nose (as well as body). it can happen. And you don’t want it to. Each “6 is worth about 30lbs force. Those G forces multiply the weight of pressure on the cone area of contact. Its amazing how fast things get heavier under those circumstances. Besides I had several people like JW and James and Jim Amos and others recommend me the same advice, So I paid heed to experience. My charge for my rocket was 10 Grams on the apogee. Very very important to get that out or its lawn dart city. If you are flying higer altitude I recommend a bit more BP. My calculations for my apogee was 6 to 7 grams only and it wouldnt seperate the apogee with 4 X #4’s but its also got alot of space inside. Now my mains ended up right on at 6 grams on the ground with 4 number 6’s. But for safety factor I added to it. I went from 9 grams to 10 on the apogee charge for the primary altimeter. My secondary/Backup Altimeter fired a 12 gram charge. So I recommend not just redundant but make the next one a gram to two larger. Just in case it needs more. Same on my mains a main of 7 grams with a back up of 8grams. You can see where it got me I hope. Also here is a video of one of my ground test.
[video src="http://s13.photobucket.com/albums/a255/1n5an3o/?action=view¤t=rockets.flv" /]
Bruce R. Schaefer
You can see where it got me I hope. Also here is a video of one of my ground test.
And, I want mine to have that clean separation. I have (12) 12 gram Quickburst canisters–and as far as I know, still can’t buy ’em, and I need four for the flight. Best case, I’ll have some left over. If not, I’ll make my own. Can’t wait until the L3 is over and successful… so I can get a good night’s sleep. 🙂
Warren B. Musselman
You’re using dual charges? I would stick with a single charge, but dual matches and dual altimeters….but that’s just me….and I’m probably worse than Wilke when it comes to oversized charges. I don’t advertise this much, but I had one rocket look like Elmer Fudd’s proverbial shotgun after Buggs stuck his finger in the end due to a charge that was a “tad” oversized. I’ve had several others succumb to charges that were a might too big. My 38mm J570 bird flew beautifully, but the apogee charge was so oversized that it ballooned the apogee piston, not only wedging it in the airframe, but spiral fracturing the airframe besides… When the main went off, it was going probably 600 mph and it just completely stripped. I was lucky to find most of the bird (minus nose cone, main chute and one fin) a bit over a mile E-SE of the launch area…
Warren
Bruce R. Schaefer
I don’t advertise this much, but I had one rocket look like Elmer Fudd’s proverbial shotgun after Buggs stuck his finger in the end due to a charge that was a “tad” oversized.
I blew up the top of my VA’s booster section (and drogue) at Oktoberfest with an ambituous charge–which Ray LaPanze and his camera caught in great detail. Chute happens! 😯 🙂
Conway Stevens
You’re using dual charges? I would stick with a single charge, but dual matches and dual altimeters….but that’s just me….and I’m probably worse than Wilke when it comes to oversized charges. I don’t advertise this much, but I had one rocket look like Elmer Fudd’s proverbial shotgun after Buggs stuck his finger in the end due to a charge that was a “tad” oversized. I’ve had several others succumb to charges that were a might too big. My 38mm J570 bird flew beautifully, but the apogee charge was so oversized that it ballooned the apogee piston, not only wedging it in the airframe, but spiral fracturing the airframe besides… When the main went off, it was going probably 600 mph and it just completely stripped. I was lucky to find most of the bird (minus nose cone, main chute and one fin) a bit over a mile E-SE of the launch area…
Warren
TRUE redundancy is having 2 charges. If the charges are done correctly you will see all the 2nd charge is doing is make a chuff. Thats because the primary worked fine. Oh yea and my charges have 2 matches per charge as well as the 2 charges per event and 2 altimeters. So here is a question. what happens if under flight or at any point in time something happens to your BP. Moisture when making the charge or just bogus BP? maybe gets busted loose while assembling or in flight? Who knows what. 2 matches there aren’t gonna save you. How about if you calculated wrong and even with testing on the ground but due to a different altitude and Temperature it fails? (things do shrink when cold and BP is less effective at higher Altitudes) its best to have a 2nd charge with more umpf. Ask James Russell as a TAP and L3CC as well as the west Coat L3cc Chair for NAR what he thinks. I can tell you. He thinks that larger rockets that are of the magnitude that L3 projects are should have as much redundancy as possible. Did you know that even in some of the rules I belive NAR specifically it ask for redundant charges?
I just prefer to error on the safer side when it comes to the hard part of flying a rocket and that of course being recovery.
Conway Stevens
I don’t advertise this much, but I had one rocket look like Elmer Fudd’s proverbial shotgun after Buggs stuck his finger in the end due to a charge that was a “tad” oversized.
I blew up the top of my VA’s booster section (and drogue) at Oktoberfest with an ambituous charge–which Ray LaPanze and his camera caught in great detail. Chute happens! 😯 🙂
Bruce, Upon looking at video of your flight to me it wasn’t a large charge but it looked like something happened while under boost still. Maybe something came apart or separated early. I will watch the video again. Also important is where you place the charge and the direction its energy is releasing towards. never point outward towards an airframe. Never have it up against the airframe and keep it close to the center pointing so that the energy will go in the direction of the event if possible. It can make a difference of damage or not. Also phenolic or cardboard will never be as durable as a FG tube or CF tube. So be cautious there. A glassed tube is still more superior but still not as much as a full composite tube.
You probably know all of that but just a reminder.
Bruce R. Schaefer
All good points. It was phenolic and old and brittle at that. Even filament wound FG would have handled it. Ironically, it was an engine charge that blew it up. 🙄 Put a very long coupler tube inside, and she’s good to go a couple of more shots. Fiberglass from now on! 🙂
Conway Stevens
Bruce R. Schaefer
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