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Self stabilizing Silican tube rounds

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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Self stabilizing Silican tube rounds

Unread postAuthor: queensland spudder » Thu Aug 20, 2009 7:04 am

hey i was wondering wether stabilizing a projectile with a tube fins design like this but only apply the same concept on silican tubes

http://users.bigpond.net.au/mechtoys/gifs/wr_rocket.jpg

do you guys predict that this method of stability will give my round any avantage or only give a disavantage. cause i think if i do this .

1. the round will that alot more drag that it did by itself meaning alit less range

2. the round will be alot more stable especially in long distant firing cause the round will still be stable even when it reaches apogee and losses speed.

3. i think loosely that my round will be more accurate than with a stablilization system.

BTW im going to try to use only ONE tube to make it cost effective not that i have to pay anything anyway) but it justs saves me time trying to search for more empty silican tube in dumpsters. i will also make a card nose cone to drastically reduce the drag, will this also increase range and accuracy.

will more weight at the nose make the effective range go down cause won't a round with a heavy nose kind of loose it range cause there is more force trying to bring the round back to the ground? .

im thinking of using ye old method for testing rocket stability for my stabilized rounds using the "swing test".

sorry for the all the questions but im just passionately curious :wink:
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Unread postAuthor: inonickname » Thu Aug 20, 2009 7:16 am

That fin design is dependent of the mass distribution, so you will need to experiment.
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Re: Self stabilizing Silican tube rounds

Unread postAuthor: ramses » Thu Aug 20, 2009 3:40 pm

queensland spudder wrote:cause won't a round with a heavy nose kind of loose it range cause there is more force trying to bring the round back to the ground? .



all objects fall at the same speed , not counting wind resistance.

The method of stabilization that you proposed will work, and should increase range and accuracy.
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Re: Self stabilizing Silican tube rounds

Unread postAuthor: jackssmirkingrevenge » Thu Aug 20, 2009 8:23 pm

queensland spudder wrote:I will also make a card nose cone to drastically reduce the drag


I doubt that would survive being fired...
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Unread postAuthor: queensland spudder » Fri Aug 21, 2009 2:05 am

well as you said i will have to experiment,i will hardern the card with super glue which works well, cause ppl from my rocketry club uses card and they harden their card nose cones.

Im not expecting this thing to survive when it hits the ground or its target , but i am expecting this thing to keep its integrity through out its flight.
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Re: Self stabilizing Silican tube rounds

Unread postAuthor: FORE!!!! » Fri Aug 21, 2009 2:21 am

ramses wrote:
queensland spudder wrote:cause won't a round with a heavy nose kind of loose it range cause there is more force trying to bring the round back to the ground? .



all objects fall at the same speed , not counting wind resistance.

The method of stabilization that you proposed will work, and should increase range and accuracy.


all objects fall at the same speed???

correct me if im wrong= http://www.calctool.org/CALC/eng/aerospace/terminal
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Unread postAuthor: queensland spudder » Fri Aug 21, 2009 2:51 am

hmmm
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Re: Self stabilizing Silican tube rounds

Unread postAuthor: jackssmirkingrevenge » Fri Aug 21, 2009 2:53 am

FORE!!!! wrote:all objects fall at the same speed?


In a vacuum all objects will be accelerated by gravity and the same rate and fall at the same speed.

In the presence of air resistance however, things get a bit more complicated. For example, take a bottle full of water and an empty one. They both have the same aerodynamic shape, but since the full bottle has a higher sectional density, it is better suited for cutting through the air and therefore have a higher terminal velocity.
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Unread postAuthor: ramses » Fri Aug 21, 2009 1:54 pm

yes, but I was simplifying. just as technically a bullet has lift because air is less dense above it than below it. It is true, but doesn't have a big enough effect to consider. The nose-down tendency will be offset by the tube not tumbling.
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Unread postAuthor: moonmaster » Fri Aug 21, 2009 3:38 pm

As long as the center of mass is ahead of the center of pressure in your projectile, it will be stable. This tube stabilizer and weights at the nose both help in the stabilization process. Increasing the amount of mass at the front will decrease the speed at which the projectile exits the gun but increase the terminal velocity as JSR said. Somewhere between unweighted and excessive weight is a happy medium at which the projectile will be stable and have the greatest attainable speed specific to your cannon and firing conditions.
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Unread postAuthor: queensland spudder » Fri Aug 21, 2009 7:05 pm

well i make up some prototypes and aexperiment on different lengths on the tail ect.

If i can i will even try to get a video up but first i will have to repair my cannon from a faliure when one of the crew cap failed , mostly cause of the cold condition and probably cause the round was to tight.

Luckily i didn' t subsatin any injuries to myself , especially my hand where the cap failed. the only hting i got was a stinging hand for a day.
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Unread postAuthor: jimmy101 » Sat Aug 22, 2009 2:40 pm

queensland spudder wrote:well i make up some prototypes and aexperiment on different lengths on the tail ect.

You can test the stability by just tying a string around the shell at the front to back center of mass. Spin it over your head on the string. If it tumbles it is aerodynamically unstable. If it doesn't tumble it's stable. Crude but gives the answer you need without having to actually launch the thing.
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Unread postAuthor: queensland spudder » Sat Aug 22, 2009 4:13 pm

i already know that but i want to see what works best in terms of stable flight, i could use the swing test to also determine what prototype is more stable cause say if i were to start the swing test with the projectile going in the opposite direction and then turns around. I could estimate what is more stable by seeing what one turns around in the shortest amount of time.

however there would be inconsistency cause im the one doing the swinging and well humans aren't exactly reliable in repeating actions. So i wouldn't get accurate results so i will just fire 4 different projectiles using different tail lenghts . the gap being cut out will standardized.
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