Don't Call It A Bottle Rocket, 'Cause Some Folks Will Go Nuts

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lakeroadster

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My last post on this subject. As the ongoing "gain of function" research fall out illustrates sometimes certain things should not be pursued.

You might not know why you are pursuing this ("choice blindness") or might not be fully aware be of the "optics" of it and the potential greater harm to the hobby.

So regardless of your own personal perspective of "good intentions", many others including myself, do not see "good outcomes".
Sure I know some folks are like that, they accept being placed in a box as a means to ensure safety for the masses.

I'm not in that camp, I'm in this camp: "Those who would give up essential liberty, to purchase a little temporary safety, deserve neither liberty nor safety". Benjamin Franklin (1706-1790)
 

RocketScott

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Not sure if it's related or not, but the post I saw on the NAR faceplant page was clearly a troll. It was asking about sugar motors and showed a motor tube with stick attached. I'd copy and post it but they deleted it
 

RocketRev

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Hey, I found it! Skip ahead to about 7:30 for the bottle rocket.

No! Don't fast forward. Watch the whole segment and you get to see Tim Lehr from Wildman's back BEFORE there was such a thing as Wildmans. It was "Team Al's Hobbies" at the time because Tim got his start in rocketry working for Al's. The only problem was that Al's Hobbies didn't have the vision they needed for this hobby. Tim did! And after Tim left Al's Hobbies, then it wasn't long before Wildman's was born. So watch the whole video. Tim Lehr at Wildman's Rocketry has been a huge asset to this hobby of ours. He's not the only one, but he's one of the big ones. And this video show's his beginnings and his vision.

In some way's what Tim said summarizes this hobby of ours very well. If you didn't catch it, here's the quote as they are driving back with the busted rocket after the failed recovery. Tim said, "You know what? If everything worked, you wouldn't be doing it. It would be too damn easy. This will just make me do it again." That is the spirit of this hobby. We keep at it not because it is easy but because it is hard.

I doubt that Tim was thinking of it at the Time, but it reminds me of JFK's going to the moon speech. We choose to be in this hobby, not because its easy, but because it is hard.


Brad, the "Rocket Rev.," Wilson
 

Antares JS

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No! Don't fast forward. Watch the whole segment and you get to see Tim Lehr from Wildman's back BEFORE there was such a thing as Wildmans. It was "Team Al's Hobbies" at the time because Tim got his start in rocketry working for Al's. The only problem was that Al's Hobbies didn't have the vision they needed for this hobby. Tim did! And after Tim left Al's Hobbies, then it wasn't long before Wildman's was born. So watch the whole video. Tim Lehr at Wildman's Rocketry has been a huge asset to this hobby of ours. He's not the only one, but he's one of the big ones. And this video show's his beginnings and his vision.

In some way's what Tim said summarizes this hobby of ours very well. If you didn't catch it, here's the quote as they are driving back with the busted rocket after the failed recovery. Tim said, "You know what? If everything worked, you wouldn't be doing it. It would be too damn easy. This will just make me do it again." That is the spirit of this hobby. We keep at it not because it is easy but because it is hard.

I doubt that Tim was thinking of it at the Time, but it reminds me of JFK's going to the moon speech. We choose to be in this hobby, not because its easy, but because it is hard.


Brad, the "Rocket Rev.," Wilson
You know, I always wondered about the story behind it saying "Al's Hobby Shop" under Tim's name in that show. Thanks for the bit of history there. By the time he sold me the H148R I used for my level 1 at Midwest Power 3 in 2005 (I'm pretty sure you, Brad, actually are the one who signed off on it, but that particular memory is fuzzy.) I'm pretty sure he had already become Wildman.

Along with Rockets4Schools, Rocket Challenge is what got me into high power. At this point I pretty much have the show memorized. My daughter likes to watch it too.
 

BigMacDaddy

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By the way -- how did you model this in OR? When I add a 2mmx2mmx50mm skinny fin, tube fin, launch lug, etc... it does not affect CP.
 

BigMacDaddy

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Ah, now I see what the issue was. I had a nose cone on mine... Not sure I would trust this stability calculation since it gets much worse with a nose cone (even a 5mm stubby one)... Not saying it is not stable but not sure OR can model it...

1638474909944.png

1638475056018.png
 

lakeroadster

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Ah, now I see what the issue was. I had a nose cone on mine... Not sure I would trust this stability calculation since it gets much worse with a nose cone (even a 5mm stubby one)... Not saying it is not stable but not sure OR can model it...

View attachment 492374
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Trust, is earned, grasshopper.

I modeled it and Open Rocket says it's stable. If you shorten the stick, you can see it become unstable.

I mocked it up and swing tested it, it's not marginally stable, it's rock solid stable.

There are numerous video's of them flying, straight as an arrow.

Why does it work.... Ancient Chinese Secret


 

icyclops

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So one person makes one post on Facebook and you conclude that he spends all day on it?
Then by that logic we must conclude that since you made one post here you must spend all day on TRF.
Your logic precedes you….you can see from the date/time stamp on each post that some folks do check-in a lot of the day on here….I am not one of them….lucky if I spend 20 minutes looking around…how about you. Enjoy! :)
 
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Your logic precedes you….you can see from the date/time stamp on each post that some folks do check-in a lot of the day on here….I am not one of them….lucky if I spend 20 minutes looking around…how about you. Enjoy! :)
Good for you! I like to check in when I get a push notice of a thread I've been following. In between building rockets of course. It's one of my guilty pleasures in my retirement.
I have a FB account but that was only because my rocket club had a FB page, since deleted. My page is empty and I have made maybe one post in the past year or so.
Still waiting for your explanation of how you came to the conclusion that someone spends "all day" on FB after making one post. Or were you just being facetious? Because frankly, it seemed to more than one of us that it was a rather snarky comment.
Have fun!
 

icyclops

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Yeah, not worth it……enjoy
 
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Kelly

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By the way -- how did you model this in OR? When I add a 2mmx2mmx50mm skinny fin, tube fin, launch lug, etc... it does not affect CP.
I have an interest in stick rockets, and have tried lots of ways to model these and other 'odd' rockets in OR, and other Barrowma-based tools, and frankly, it just isn't up to the task.
Barrowman (used by OR) assumes that body tubes make no contribution whatsoever to CP; The CP is determined by a geometric average of the CP of the nosecone, fins, and whatever transitions you have.
So, for example, if your rocket is just a NC and a body tube, it makes no difference how long your body tube is - the CP will always be way up in the nose.
If you just have body tube and fins, then again nothing you do with the BT makes any difference - the CP will just be the CP of the fins. In fact, even changing something like the width of the fins won't have any effect, because the width of the fin has no effect on the Cp of the fin itself.
In the ORK design above, I think that what has happened is that OR sees two body tubes, places the CP of each in the center, and then uses some geometric average of these center points just to avoid a divide-by-zero error. You'll note that changing the diameter of either tube has absolutely no effect on the Cp of the rocket, which is counterintuitive.
So, I think that OpenRocket, and Barrowman (as originally formulated) is worthless for determining the Cp of a stick rocket. You might have gotten a stable design in OR, and a stable rocket in real life, but this is probably a pure coincidence and should not be counted upon.
I think the cardboard cutout method is probably far more reliable for stick rockets than Barrowman.
 

boomtube-mk2

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1638555324331.png

That top one looks like an old bayonet blade. You can see the part that fits over the barrel of the rifle.
 

lakeroadster

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I have an interest in stick rockets, and have tried lots of ways to model these and other 'odd' rockets in OR, and other Barrowma-based tools, and frankly, it just isn't up to the task.
Barrowman (used by OR) assumes that body tubes make no contribution whatsoever to CP; The CP is determined by a geometric average of the CP of the nosecone, fins, and whatever transitions you have.
So, for example, if your rocket is just a NC and a body tube, it makes no difference how long your body tube is - the CP will always be way up in the nose.
If you just have body tube and fins, then again nothing you do with the BT makes any difference - the CP will just be the CP of the fins. In fact, even changing something like the width of the fins won't have any effect, because the width of the fin has no effect on the Cp of the fin itself.
In the ORK design above, I think that what has happened is that OR sees two body tubes, places the CP of each in the center, and then uses some geometric average of these center points just to avoid a divide-by-zero error. You'll note that changing the diameter of either tube has absolutely no effect on the Cp of the rocket, which is counterintuitive.
So, I think that OpenRocket, and Barrowman (as originally formulated) is worthless for determining the Cp of a stick rocket. You might have gotten a stable design in OR, and a stable rocket in real life, but this is probably a pure coincidence and should not be counted upon.
I think the cardboard cutout method is probably far more reliable for stick rockets than Barrowman.
Interesting. That explains why if you put a nose cone on the bottle rocket I designed in Open Rocket, it goes unstable.

Question: What if you use a tube fin for the stick... That's how the OR model I made is made. Shorten the tube fin enough, and the bottle rocket goes unstable.
 

Kelly

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Question: What if you use a tube fin for the stick... That's how the OR model I made is made. Shorten the tube fin enough, and the bottle rocket goes unstable.
Yeah, that was what I was describing in the paragraph starting "In the ORK design above...". I don't think it's doing anything very intelligent. You can change the OD of either the motor mount tube, or the 'tube fin' tube, or even add additional tube fins, and none of this changes the CP location - which tells me it isn't really taking any aerodynamic effects into account at all.
(BTW, in 'fireworks' stick rockets, it's been shown that you can replace one long stick with multiple shorter sticks, and get the same stability.)
 

BigMacDaddy

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Is it the weight of the stick, induced pressure, or drag of the stick that makes a bottle rocket stable? I was under the impression that it might be a bit of all of these - I have had multiple people tell me that when a rocket engine is pulling a rocket behind it that this is a pretty stable design (possibly even regardless of CP/CG positioning).
 

Steve Shannon

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Is it the weight of the stick, induced pressure, or drag of the stick that makes a bottle rocket stable? I was under the impression that it might be a bit of all of these - I have had multiple people tell me that when a rocket engine is pulling a rocket behind it that this is a pretty stable design (possibly even regardless of CP/CG positioning).
Stick rockets still require Cg ahead of Cp. In air that’s a simple physical necessity.
 

Daddyisabar

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That top one looks like an old bayonet blade. You can see the part that fits over the barrel of the rifle.
The Real Indians sure scared the pudding out of the British with their sword rockets. Designed to go unstable in flight and chop the white devils to bits. By Jove this is a good idea the honkies said. Let's improve them and take out those problematic rebel Colonists with the rockets red glare! Good history. How did the olde tyme dudes do it with out computerized software, cardboard cut outs or even swing tests? Could it be....Aliens? ;)
 

lakeroadster

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The Real Indians sure scared the pudding out of the British with their sword rockets. Designed to go unstable in flight and chop the white devils to bits. By Jove this is a good idea the honkies said. Let's improve them and take out those problematic rebel Colonists with the rockets red glare! Good history. How did the olde tyme dudes do it with out computerized software, cardboard cut outs or even swing tests? Could it be....Aliens? ;)
Nope... It's an Ancient Chinese Secret.. see post #70.

You sir are a cesspool wealth of knowledge!

Mysorean rockets
It looks an awful lot like one of those bottle rockets?? Sorry if this get's deleted for not lighting it electrically.. :facepalm:

PS: is that a sword, or are you just excited about your new rocket?

1638573394201.png
 
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Daddyisabar

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Trust, is earned, grasshopper.

I modeled it and Open Rocket says it's stable. If you shorten the stick, you can see it become unstable.

I mocked it up and swing tested it, it's not marginally stable, it's rock solid stable.

There are numerous video's of them flying, straight as an arrow.

Why does it work.... Ancient Chinese Secret


After a hard day at the range flying tractor motored, oddroc abominations...CALGON, TAKE ME AWAY! :)
 

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