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Steven88

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Haven’t found time yet to test. Hopefully soon...
 

rcktnut

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I'm getting error on the link, looks like something about high altitude flights. Granted I know of problems with all the BP burning at high altitudes, but your post did not state that. No worries about that for most of us most of the time.
 

Steven88

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I’d like to hear more about problems with bp at high altitudes or if anything needs to be adjusted or changed such as a different amount of bp or anything. I’m planning to fly up to 9k for the first time in the near future, weather permitting. Is there anything I need to do differently for a flight that high? Not sure if that’s even considered high altitude yet? So far I haven’t flown over about 3,400’. As long as ground tests are good, then everything should be fine?
 

g.pitts

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I’d like to hear more about problems with bp at high altitudes or if anything needs to be adjusted or changed such as a different amount of bp or anything. I’m planning to fly up to 9k for the first time in the near future, weather permitting. Is there anything I need to do differently for a flight that high? Not sure if that’s even considered high altitude yet? So far I haven’t flown over about 3,400’. As long as ground tests are good, then everything should be fine?
9k' should not be a problem - still plenty of oxygen at that altitude to support the combustion. I'm curious to hear from those experienced in high altitude flights where you make the transition from BP to a CO2 system though!
 

SDramstad

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Try this.


I found that putting the BP in first. Inserting the igniter a very short distance into the powder then packing dog barf in tightly and taping it closed with several layers of duct tape, I was able to get consistent, repeatable results. Putting the igniter all the way to the bottom of the charge well gave inconsistent results with unburned powder scattered inside the airframe and on the nomex blankets.
 

g.pitts

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Try this.


I found that putting the BP in first. Inserting the igniter a very short distance into the powder then packing dog barf in tightly and taping it closed with several layers of duct tape, I was able to get consistent, repeatable results. Putting the igniter all the way to the bottom of the charge well gave inconsistent results with unburned powder scattered inside the airframe and on the nomex blankets.
That's interesting... so it isn't the oxygen content of the atmosphere, it's the ability for that atmosphere to promote heat transfer. I learned something new today! :cool:
 

rcktnut

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Try this.


I found that putting the BP in first. Inserting the igniter a very short distance into the powder then packing dog barf in tightly and taping it closed with several layers of duct tape, I was able to get consistent, repeatable results. Putting the igniter all the way to the bottom of the charge well gave inconsistent results with unburned powder scattered inside the airframe and on the nomex blankets.
We helped the OP out and that is what counts. After all everyone has their own setups, different methods of containing ejection charges. When I seen your post (#21) I thought wait a minute here lets get this straight. Also how tightly do you pack your dog barf in the well? I try my hardest just to keep it as loose as possible before taping. Loose powder in the well will burn more completely than compacted. All being said this is why we ground test!
 

Steven88

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I got better results today with the same 2 grams of bp after adding tape to my NC shoulder and adding bronze sheer plates. I had 74” of separation. I still wish the deploy bag had ejected fully out of main tube. Instead it pulled most of the lines out of the deploy bag and just barely left deploy bag inside, but bag pulled very easily out of body tube so I imagine it would have worked fine. I may do one more deploy test with the deploy bag flipped around when it’s packed into the main tube. I think that way maybe the parachute lines won’t come out before the deploy bag does.
 

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Steven88

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Ya, lol the blanket really wasn’t that necessary to catch just a flying nose cone. Does
it win me any rocket brownie points that I nailed the blanket? 🤣
 

SDramstad

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You are better off with a bit too much then too little. The couplers get dirty and rough after use and sooner or later "just barely enough" isnt. I would use the full 2.4 if not more.
 

Steven88

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Since I have redundant altimeter, I’ll probably do something like 2.2-2.4 grams for primary and up the secondary by 25%
 

Banzai88

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Blow it out or blow it up is poor methodology when you have the time and the tools to get it right.

+25% is a HUGE step up.

Make sure you ground test it, too. The last thing that you want at altitude other than a charge that doesn't go off resulting in one falling object is one that destroys your rocket or separates all the pieces from each other and creates multiple falling objects.
 

SDramstad

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Blow it out or blow it up is poor methodology when you have the time and the tools to get it right.

+25% is a HUGE step up.

Make sure you ground test it, too. The last thing that you want at altitude other than a charge that doesn't go off resulting in one falling object is one that destroys your rocket or separates all the pieces from each other and creates multiple falling objects.
I will have to disagree in the friendliest way I can. :):):) With redundant altimeters especially the primary should be as close to your calculated size that you can get. If that doesnt open your rocket up something is jammed and bad things are about to happen. The backup charge should be big enough to "Blow it out or blow it up". 25% bigger seems very reasonable to me. I have never seen this size charge actually damage anything. Just for the sake of argument let say it blows the body tube apart at the coupler. The 2 sections will still be attached to the recovery harness and rate of descent will be acceptable. To blow it to pieces would require a huge amount of powder, not an extra 25%. A ballistic recovery is the worst possible scenario, anything else is preferable including "pieces raining down"
 
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