My rockets does not go straight

[allrocketspsl]

How you can find the CP ?

 

 

 

I thowgth that the stick cause of his weight it keeps the nozzle stady on when it flyes

 

What about the surface area ?

 

if you have a hollow tube and a solid tube and blow wind over it as the wind comes off the back of the tube it creates a vaccum which creates the drag,both tubes same size differnt weights creat the same drag,because of area of both are the same.Quite simple,I never balance any rocket,no point to.

[dagabu]

Quite simple,I never balance any rocket,no point to.

 

Bravo! I too never balance my rockets, faster fuels get shorter sticks, slower fuels get longer sticks, heavy headings get longer sticks, windy days get shorter sticks (due to windvaning).

 

 

-dag

[THEONE]

if you have a hollow tube and a solid tube and blow wind over it as the wind comes off the back of the tube it creates a vaccum which creates the drag,both tubes same size differnt weights creat the same drag,because of area of both are the same.Quite simple,I never balance any rocket,no point to.

 

The same happens with the fins ? so the more surface the better it will be more or bigger fins , but why some people make heavier the nose cones (as no point to the weight) ?

[allrocketspsl]

The same happens with the fins ? so the more surface the better it will be more or bigger fins , but why some people make heavier the nose cones (as no point to the weight) ?

 

suggestion: start with bottle rockets when you get good move on but not till your bored with them and have fused them to break same time everytime,harder than it seems,then step up to maybe a 4oz and so on.To be honest your learning curve is a long one good luck go to web sites like pyro guide do some of their projects or skylighted or the green man etc,you have more work than you think so get started and enter the contest you will learn more than you think

 

Bravo! I too never balance my rockets, faster fuels get shorter sticks, slower fuels get longer sticks, heavy headings get longer sticks, windy days get shorter sticks (due to windvaning).

 

 

-dag

 

yep!

[dagabu]

The same happens with the fins ? so the more surface the better it will be more or bigger fins , but why some people make heavier the nose cones (as no point to the weight) ?

 

No, bigger fins cause more drag, smaller fins cause less drag. Use the smallest fin you can while still providing stable flight. A guide rod is also highly suggested for use with rockets that don't have a lot of initial thrust. Endburners need longer guide rods then core burners.

 

http://www.pyrobin.com/files/100_2543_1.jpg

 

 

-dag

[Thunderr1]

Those are high quality fins right there, I have seen them

[THEONE]

No, bigger fins cause more drag, smaller fins cause less drag. Use the smallest fin you can while still providing stable flight. A guide rod is also highly suggested for use with rockets that don't have a lot of initial thrust. Endburners need longer guide rods then core burners.

 

-dag

 

I have confused, ok with rods, end burner --> less thrust --> bigger rod core burner --> more thrust --> smaller rod (the more surface the better it will be correct ? )

But what about the fins.... and what exactly you mean DRUG i can not understand...

Edited August 28, 2011 by THEONE

[nater]

DRAG in this sense is the physics term that describes the forces that oppose an aircraft's motion in the air. You want to minimize it as much as possible, while still maintaining lift and stabalility. Overcoming these forces at odds is what gives aeronautical engineers a job.

[Thunderr1]

I think he might be using a translator that is not correctly making it easy to understand?

[THEONE]

I think he might be using a translator that is not correctly making it easy to understand?

 

Yes exactly

[THEONE]

Boys the nose cone except that minimize the resistance of the air, it helps somewhere the flight stability ?

 

DRAG in this sense is the physics term that describes the forces that oppose an aircraft's motion in the air. You want to minimize it as much as possible, while still maintaining lift and stabalility. Overcoming these forces at odds is what gives aeronautical engineers a job.

 

So the drag is the resistance of the air ?

Edited August 29, 2011 by THEONE

[THEONE]

Here is a second fly test with a wooden dowel... better than before but no perfect... i have notice that except it doesn't do straight, it wriggle also a little bit...

 

http://www.youtube.com/watch?v=KhtAPesRRxc

Edited August 29, 2011 by THEONE

[Thunderr1]

Yes exactly

 

What is your native language? May be easier to help you.

 

Send us a picture of the rocket and stick in the launch device. We need to see how you attached the stick and that can help us.

[THEONE]

What is your native language? May be easier to help you.

 

Send us a picture of the rocket and stick in the launch device. We need to see how you attached the stick and that can help us.

 

Greek my friend. i simply tape the stick on the motor

 

Here is a photo with the motor and the stick untaped

[dagabu]

Greek my friend. i simply tape the stick on the motor

 

Here is a photo with the motor and the stick untaped

 

Your stick is many times too big, use a stick no more then one half the inner diameter of the motor and no longer then 6 times the length of the motor.

 

Also, don't use round sticks and don't use hard woods, use a soft and light wood cut square.

 

Σας το ξύλο είναι πολύ μεγάλες, προς χρήση σε ξύλο αριθ. περισσότερο, τότε ένα εξάμηνο την εσωτερική διάμετρο των πυραύλων και στη συνέχεια 6 φορές το μήκος των πυραύλων. Επίσης, να μην χρησιμοποιήσει γύρο μπαρ και δεν κάνει χρήση της βελανιδιάς, χρήση μαλακών και φως ξύλο έχουν κοπεί τετράγωνο.

-dag

[THEONE]

Your stick is many times too big, use a stick no more then one half the inner diameter of the motor and no longer then 6 times the length of the motor.

 

Also, don't use round sticks and don't use hard woods, use a soft and light wood cut square.

 

Σας το ξύλο είναι πολύ μεγάλες, προς χρήση σε ξύλο αριθ. περισσότερο, τότε ένα εξάμηνο την εσωτερική διάμετρο των πυραύλων και στη συνέχεια 6 φορές το μήκος των πυραύλων. Επίσης, να μην χρησιμοποιήσει γύρο μπαρ και δεν κάνει χρήση της βελανιδιάς, χρήση μαλακών και φως ξύλο έχουν κοπεί τετράγωνο.

-dag

 

 

Xaxaxa OK thanks dagabu i know a few English... it is difficult for me to find this exactly wood... i want to know more about the rocket with fins...

Edited August 30, 2011 by THEONE

[dagabu]

Xaxaxa OK thanks dagabu i know a few English... it is difficult for me to find this exactly wood... i want to know more about the rocket with fins...

 

Use Pine or Fir (πεύκο, έλατα) for your sticks, they should be square (πλατεία, τετράγωνο). These trees are high up and make up 10% of all trees in Greece, you should have no problems finding it at a hardware store like this:

 

Ioannidis, G., - K. Kyrilidis O.E. "Emborotechniki

Σίφνου 41, Larissa 41335Greece2410-627010

[THEONE]

Xaxaxa ok my friend i will try and i will tell to you, thanks a lot

[THEONE]

Dagabu can you explain to me also what happens with the fins and also what fins you must use with a core burner rocket and what with an end burner rocket ?

[r1dermon]

the fins make no difference from core burner to end burner...the difference noticed in stability, is due to the lower initial thrust of the end burner, in relation to the higher initial thrust in the core burner. for the fins to function properly, your vehicle needs to be moving. the speed of stable flight will be determined by the area of your fin surface. a larger fin=a more stable rocket at a lower speed. a smaller fin=a less stable rocket at low speed. correlating this to a stick rocket is in the same manner. ie. longer stick=more surface area=more stability at a slower speed.

 

to compensate for an end burning rocket's lower initial impulse, you can use a longer guide rod, or larger fins/longer stick.

 

the largest drawback of having large fins, is increased drag. conveniently, since high thrust rockets can achieve stability with fairly slim CG/CP relationships, physics allows them much smaller fins, and thus, much less drag. fin design plays a large part in drag as well...while not applicable to bottle rockets, the clipped delta is known as the optimal fin for high speed applications where drag is a major consideration. (drag increases exponentially after mach transition).

 

think of air as a fluid. as your fins "cut" through the air, the fluid is forced to move around them. if your fins are the same shape on either side, the pressure will equalize and your fin will be forced to remain straight by the resistance caused in the air. a good example of how fins work is weathercocking...when you launch a rocket on a windy day, the fins will be affected by the breeze blowing towards them. what will happen is, your rocket will turn INTO the wind and fly downrange. overstable rockets display this effect very clearly in even a slight breeze.

[pyrogeorge]

THEONE check your pm

[allrocketspsl]

the fins make no difference from core burner to end burner...the difference noticed in stability, is due to the lower initial thrust of the end burner, in relation to the higher initial thrust in the core burner. for the fins to function properly, your vehicle needs to be moving. the speed of stable flight will be determined by the area of your fin surface. a larger fin=a more stable rocket at a lower speed. a smaller fin=a less stable rocket at low speed. correlating this to a stick rocket is in the same manner. ie. longer stick=more surface area=more stability at a slower speed.

 

to compensate for an end burning rocket's lower initial impulse, you can use a longer guide rod, or larger fins/longer stick.

 

the largest drawback of having large fins, is increased drag. conveniently, since high thrust rockets can achieve stability with fairly slim CG/CP relationships, physics allows them much smaller fins, and thus, much less drag. fin design plays a large part in drag as well...while not applicable to bottle rockets, the clipped delta is known as the optimal fin for high speed applications where drag is a major consideration. (drag increases exponentially after mach transition).

 

think of air as a fluid. as your fins "cut" through the air, the fluid is forced to move around them. if your fins are the same shape on either side, the pressure will equalize and your fin will be forced to remain straight by the resistance caused in the air. a good example of how fins work is weathercocking...when you launch a rocket on a windy day, the fins will be affected by the breeze blowing towards them. what will happen is, your rocket will turn INTO the wind and fly downrange. overstable rockets display this effect very clearly in even a slight breeze.

 

flight:: when air rushes over a surface a vacuum is formed, high pressure below, low pressure on top you get lift, like you said vacuum on both sides keeps it true ps watch a 747 take off in a crosswind as soon as it leaves the runway it points in the wind,size has nothing to do with it,its a principle of flight

[dagabu]

flight:: when air rushes over a surface a vacuum is formed, high pressure below, low pressure on top you get lift, like you said vacuum on both sides keeps it true ps watch a 747 take off in a crosswind as soon as it leaves the runway it points in the wind,size has nothing to do with it,its a principle of flight

 

Size increases the drag, drag allows for more straightening like a long streamer. Did I miss your point?

 

-dag

[allrocketspsl]

Size increases the drag, drag allows for more straightening like a long streamer. Did I miss your point?

 

-dag

 

what I meant but didnt articulate very well is a J3 piper cub that takes off at 6o mph and a jumbo jet taking off at 225 mph will both behave the same always wanting to correct into the wind

[dagabu]

what I meant but didnt articulate very well is a J3 piper cub that takes off at 6o mph and a jumbo jet taking off at 225 mph will both behave the same always wanting to correct into the wind

 

Gotcha!

 

-dag