CF Fin attachment

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eggtimer rocketry
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sure and on the surface that definitely doesn't seem like enough, however, the proof is in the proverbial pudding...

if you would like to fly at AirFest, perhaps a video documenting the successful test with the proposed configuration would help?

also, worth noting that the underlying concner here is safety and not breaking the waiver. all for safe rockets...
 
Theory said:
sure and on the surface that definitely doesn't seem like enough, however, the proof is in the proverbial pudding...

if you would like to fly at AirFest, perhaps a video documenting the successful test with the proposed configuration would help?

also, worth noting that the underlying concner here is safety and not breaking the waiver. all for safe rockets...
Click to expand...
When your right, your right. This is why I like reading your build threads and any advise you have. Because you are right most all of the time. Don't let this go to your head!!:):)

P.S. I seen a pickup truck with the letters NO LIMITS in the back window. The first thing I thought was could that be Theory.;)
 
HyperSonic said:
Sent in my high altitude forms (for going over 23K in Argonia) and was denied on both flights. The 5800 flight I totally understand as it is getting close to 50K. I don't get why I was denied on the 2245 flight as it only goes to 23K. So much for Airfest.

Can anyone tell me what I have to do to fly my rocket at Balls? The altitude problem is no longer an issue. Who would I have to talk to in order to fly there? I certainly don't want to drive over a thousand miles there and back to be told I can't fly my rocket!
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Up the amount and reapply. And I have used that much in 38mm min diameter rockets with no problem at all. 4 inch minimum and I would use 1.5 to 2 grams with no hesitation at all.
 
SDramstad said:
Up the amount and reapply. And I have used that much in 38mm min diameter rockets with no problem at all. 4 inch minimum and I would use 1.5 to 2 grams with no hesitation at all.
Click to expand...

not sure i understand why he would add more if its not needed.

sounds like the issue is more proving out that the system works as designed.
 
OP, pure speculation on my part, but perhaps there is concern about track record? Meaning, have you flown other minimum diameter birds successfully? If so, and to Theory's point, perhaps sharing some of this data would help validate your experience and put some concerns to bed?

Best of luck!
 
sure, BP at 45,000 isnt the best, but as the 2045 flight is "only" going to 23K it is definitely a viable option.

as we say at work all the time, the devil is in the details. how the BP is packed and ignited is key, and much more important than just "adding more."
 
Theory said:
sure, BP at 45,000 isnt the best, but as the 2045 flight is "only" going to 23K it is definitely a viable option.

as we say at work all the time, the devil is in the details. how the BP is packed and ignited is key, and much more important than just "adding more."
Click to expand...
The online pressure versus altitude calculator says that at 23,000 feet the pressure is approximately 0.37 atm while at 45,000 feet its approximately 0.14 atm.

Neither one are good for fin stability control, breathing, or combustion but 45,000 is significantly worse.
 
Dan Griffing said:
The online pressure versus altitude calculator says that at 23,000 feet the pressure is approximately 0.37 atm while at 45,000 feet its approximately 0.14 atm.

Neither one are good for fin stability control, breathing, or combustion but 45,000 is significantly worse.
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BP works at any altitude and at the same quantities as would be used on the ground if it is contained in a manner that promotes complete combustion. I have done it many times.

Jim
 
JimJarvis50 said:
BP works at any altitude and at the same quantities as would be used on the ground if it is contained in a manner that promotes complete combustion. I have done it many times.

Jim
Click to expand...

quoting as Jim as significant high altitude experience

believe he has lit a third stage at an altitude higher than PePe will achieve on the 2245…
 
Serendipitously, I got distracted by this thread while on my way to review Tfish's method of making high altitude charges before sitting down to make some of my own. Vinyl tubing and silicon o-ring in hand. All I'm missing is a mustache...

https://www.rocketryforum.com/threads/98mm-min-dia-high-altitude-deployment.152590/#post-1883372
You may want to check that thread out, as well as Jim Jarvis' method. They seem to have arrived at similar solutions. I have a feeling that your "shotgun" may be something similar.
 
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Here are some pics of the shotgun setup. It looks like a double barreled shotgun to me. These barrels are made from 2024-T3 seamless aluminum tubing 16.625 inches long, .5 inch ID, .630 inch OD. This long charge well setup has been used before successfully. I think the 2 things that matter the most in my setup are how you contain the BP and the length of the barrel. Since these barrels are so long, you have to back off on the amount of BP your using. BP burns faster under pressure than it does when it is not under pressure. The containment doesn't last long, but gives it a good start to the burn. .8 gram done this way will eject my 2.5 pound nose cone with shear pins 75 feet before hitting the ground. Sounded like a cannon went off, had all the neighbors looking! This double barrel setup is very mean and you must be careful with BP amount and containment methods. I'm sure it will burn ALL the BP at any altitude with a big bang! Poor nose cone, must protect it from the blast. The top of shotgun barrels to the bottom of nose cone is 3 inches. The 3 inch chute cannon will house the main. It uses a piston to push out everything. It is only sized to separate the cannon lid and push things out. It is not big enough to separate the nose cone also.

I've read Jim's paper on vacuum testing along with tfish did some tests as well. I believe the phrase was "very energetic" That's putting it mildly!!!



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The containment of the BP here is done with plain white printer paper and elmer's white glue. Just the top part of paper tube burns off. I like the idea of putting the e-match on top of powder (turn upside down) but then if wire breaks I will have a projectile coming out the top. This way the force pushes what doesn't burn down and stays in the bottom of tube.

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Your design is a little out of my range of experience. I would use a shorter tube with an ID of 0.33 to 0.4 inches (for charges of 1 to 1.5 grams or so). So, you would be using fewer grams and a larger cross section. I suspect it would work at altitude, but I can't confirm that without testing.

Although not included in my testing, I would now recommend the match on top of the powder. I'm not sure why your design couldn't be adapted to that.

Pretty sure one of the Australian high altitude flights used the longer tube design. Might be another data point.

Jim
 
HyperSonic said:
They don't like the amount of BP I'm using for drogue or main. They think it's to small.
Click to expand...
Couldn't you just bump up the amount of BP you plan to use to meet their requirements? Sure, you might be overdoing it but better to fly than not?
 
JimJarvis50 said:
I would now recommend the match on top of the powder.
Click to expand...
+1. Especially at higher altitudes.

I've been told the optimum L:D ratio for full combustion of BP is 10:1. Apparently that ratio comes from black powder rifle enthusiasts.
 
JimJarvis50 said:
Your design is a little out of my range of experience. I would use a shorter tube with an ID of 0.33 to 0.4 inches (for charges of 1 to 1.5 grams or so). So, you would be using fewer grams and a larger cross section. I suspect it would work at altitude, but I can't confirm that without testing.

Although not included in my testing, I would now recommend the match on top of the powder. I'm not sure why your design couldn't be adapted to that.

Pretty sure one of the Australian high altitude flights used the longer tube design. Might be another data point.

Jim
Click to expand...
I'm sure I can come up with something to put the head of e-match on top of BP like a lot of you recommend. Maybe I'll look around on the OZ forum to find any info on high altitude flights using similar methods. Thanks for the advise Jim.
 
HyperSonic said:
Balls would be a good place to launch. The only thing I know about Balls is what happens at Balls stays at Balls!:):p
Click to expand...
There is a premium this year on recovery at Balls due to a bad record the last time around. (What happened at Balls didn't stay there) You'll likely run into the same issue. My suggestion is a design that follows pre-existing art and/or your own vacuum testing.

Jim
 
JimJarvis50 said:
There is a premium this year on recovery at Balls due to a bad record the last time around. (What happened at Balls didn't stay there) You'll likely run into the same issue. My suggestion is a design that follows pre-existing art and/or your own vacuum testing.

Jim
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Somebody broke the golden rule. With a lot of high altitude attempts at Balls every year, I can see bad things are bound to happen. As long as the only thing that gets hurt is some ones pride, or their rocket, and no people or property are injured, It's all good.

I'm not much on playing copy cat. I like to come up with things that came from my head. I read lots of things from lots of people, then put my own twist to it. Everybody on this forum will modify things to their liking. This is no different. The main thing I heard you say was "So, you would be using fewer grams and a larger cross section. I suspect it would work at altitude" The only difference between your setup and mine is length of tube. I will put the e-match on top of BP. You have already done the vacuum testing with a much shorter tube. In my opinion, just lengthening the tube is not going to be the reason that ALL the BP gets burned. Having a longer tube will promote more time for the BP to burn. The longer the tube, the more energetic the charge will be with the same amount of BP. The trick to getting all the BP to burn is you must keep all the unburned BP behind the front of the flame. Any BP that is blown ahead of this flame front will not burn. The containment method you use is key to making this happen. I'm sure that putting the e-match on top of the BP will help this process.
 
HyperSonic said:
Somebody broke the golden rule. With a lot of high altitude attempts at Balls every year, I can see bad things are bound to happen. As long as the only thing that gets hurt is some ones pride, or their rocket, and no people or property are injured, It's all good.
Click to expand...

I forget the exact statistic, but it was something like only one of 20 high altitude flights got recovery (mine, as it turned out, was the only one). Your project won't be reviewed in advance, but you can expect RSO questions on why you think your approach will work.

By the way, my belief is that the tube method works at high altitude because there is backpressure developed in the tube that helps the powder to burn. That is, it's more than just the flame front. My only concern with your approach is that there will be less backpressure. Conceptually, there will come a point where the diameter is too large (a 3" diameter charge tube for example won't work). I don't know where that point happens.

Jim
 
JimJarvis50 said:
I forget the exact statistic, but it was something like only one of 20 high altitude flights got recovery (mine, as it turned out, was the only one). Your project won't be reviewed in advance, but you can expect RSO questions on why you think your approach will work.

By the way, my belief is that the tube method works at high altitude because there is backpressure developed in the tube that helps the powder to burn. That is, it's more than just the flame front. My only concern with your approach is that there will be less backpressure. Conceptually, there will come a point where the diameter is too large (a 3" diameter charge tube for example won't work). I don't know where that point happens.

Jim
Click to expand...
I wonder what length would be optimal for this backpressure and if going to long will matter. Sorta like tuning to a multiple of the real value.

All I know is they are very strong down on the ground. Will they stay that way at altitude, I think they will. For the first flight, I will bump up the amount a little just in case. I can double the amount for backup to help blow it open should trouble arise. This excessive force at ejection is hard on my rocket so I don't want to get carried away. After a few flights I can zero in on correct value.
 
HyperSonic said:
Sent in my high altitude forms (for going over 23K in Argonia) and was denied on both flights. The 5800 flight I totally understand as it is getting close to 50K. I don't get why I was denied on the 2245 flight as it only goes to 23K. So much for Airfest.
Click to expand...

I flew a 2245 in a 4 inch Extreme Wildman with a more conventional recovery (CO2/BP Canister) when LDRS was at AirFest. At the time it was mentioned that they were swamped with high altitude requests with time running short. If that is the case now, maybe it is just that they don't have the time to figure out if your system is safe to fly. It may be worth an email asking what info they need to reassure them.

Jeff
 

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