My rockets does not go straight

[THEONE]

Boys i have built some homemade rockets but they does not most of times go straight even thought the balance with the stick is very fine...

Edited August 21, 2011 by THEONE

[allrocketspsl]

Boys i have built some homemade rockets but they does not most of times go straight even thought the balance with the stick is very fine...

 

its about drag

[dagabu]

Drag and alignment... A stick that is not straight or is not aligned will cork-screw.

 

Fast fuels will also bend sticks and that will mess with flights as well.

 

-dag

[allrocketspsl]

try a 48 inch long 5/16" square

[THEONE]

What about the nozzle, it is possible the problem will come from the nozzle ? as a stick i use this 2 connected electrodes

Edited August 21, 2011 by THEONE

[allrocketspsl]

What about the nozzle, it is possible the problem will come from the nozzle ? as a stick i use this 2 connected electrodes

 

hum thats a new one never saw elcetrodes used before but Im kinda rookie also so try wood straighter the better but if it has cup to it make sure the cup is inside not outside mate

what size motor you making,bp?

[dan999ification]

they are sugar motors, i wouldnt call you a rookie and the reason you have never seen electrodes as sticks is because sticks are cheaper, lighter, safer, bio degradable the list goes on. if the motor is not lined up straight to the "stick" it will banana if your stick is bent it will banana if the motor doesnt produce enough thrust [coasting] after take off it will banana. if it loses fuel it will lose balance without sufficient thrust, you do have heavy motors[still using pvc right?]if your spear [stick] comes down and hits anyone i would go bananas.

sugar rockets fly quite well with a balanced body and no stick.

how well was it supported or guided before take off a launch tube going straight up to the motor may help if none of the above were problems

 

dan.

Edited August 22, 2011 by dan999ification

[allrocketspsl]

they are sugar motors, i wouldnt call you a rookie and the reason you have never seen electrodes as sticks is because sticks are cheaper, lighter, safer, bio degradable the list goes on. if the motor is not lined up straight to the "stick" it will banana if your stick is bent it will banana if the motor doesnt produce enough thrust [coasting] after take off it will banana. if it loses fuel it will lose balance without sufficient thrust, you do have heavy motors[still using pvc right?]if your spear [stick] comes down and hits anyone i would go bananas.

sugar rockets fly quite well with a balanced body and no stick.

how well was it supported or guided before take off a launch tube going straight up to the motor may help if none of the above were problems

 

dan.

 

with your knowledge it seems your entering into the chanllenge,yes no? All

ps; I will admit i got to where people couldnt or thought my rockets were bp when they were sugar all along,sugar can be used in many ways!

[dan999ification]

with your knowledge it seems your entering into the chanllenge,yes no? All

ps; I will admit i got to where people couldnt or thought my rockets were bp when they were sugar all along,sugar can be used in many ways!

 

 

2 motors and a ring header not far off!

 

dan.

[THEONE]

If the nozzle throat it will not be exactly at the middle. the rocket will fly well and straight ?

[dan999ification]

If the nozzle throat it will not be exactly at the middle. the rocket will fly well and straight ?

 

 

it could be that, ive had engines that have had the nozzle off centre no problems for my small motors but it may be different for bigger and sugar, the nozzle not being dead centre doesnt worry me as much as the throat not being straight, that would send him off course even if you ligned evrything up and balanced it.

the way you joined the electrodes causes turbulance and may affect things also.

 

dan.

[THEONE]

it could be that, ive had engines that have had the nozzle off centre no problems for my small motors but it may be different for bigger and sugar, the nozzle not being dead centre doesnt worry me as much as the throat not being straight, that would send him off course even if you ligned evrything up and balanced it.

the way you joined the electrodes causes turbulance and may affect things also.

 

dan.

 

Yes Dan you have right thanks a lot for your precious help, i will try next time with a wooden stick and i will post the results

Edited August 22, 2011 by THEONE

[r1dermon]

Longer stick.

[THEONE]

Longer stick.

 

The balance point was round 24mm beneath the end of the nozzle... and the OD of the casing is 24mm

Edited August 23, 2011 by THEONE

[r1dermon]

the balance point is the center of gravity. you need to move it rearward in a rocket that is propelled from the head end in order to gain more stability. it's the opposite in a traditional rocket design with fins, where you want the center of gravity forward of the center of pressure...in a bottle rocket design, the Cg:Cp relationship is opposite.

 

 

 

Edited August 23, 2011 by r1dermon

[THEONE]

the balance point is the center of gravity. you need to move it rearward in a rocket that is propelled from the head end in order to gain more stability. it's the opposite in a traditional rocket design with fins, where you want the center of gravity forward of the center of pressure...in a bottle rocket design, the Cg:Cp relationship is opposite.

 

Can you saw me a figure please?

[dan999ification]

 

1. • 

Edited August 25, 2011 by dan999ification

[r1dermon]

the balance point is the center of gravity. you need to move it rearward in a rocket that is propelled from the head end in order to gain more stability. it's the opposite in a traditional rocket design with fins, where you want the center of gravity forward of the center of pressure...in a bottle rocket design, the Cg:Cp relationship is opposite.

 

 

 

 

dont listen to me...i didn't have my coffee this morning.

 

the CG/CP is the same relationship in any rocket design. the more forward the CG is, the better. with that in mind, the lighter the stick, the better (since a heavier stick would pull the CG back rearward). you need a light stick, with a high amount of surface area, like a square. the longer the stick, the more surface area it has. the stick stabalizes your header through pitch damping.

 

hope this helps. if your rockets are unstable, add a longer stick. heh.

[allrocketspsl]

dont listen to me...i didn't have my coffee this morning.

 

the CG/CP is the same relationship in any rocket design. the more forward the CG is, the better. with that in mind, the lighter the stick, the better (since a heavier stick would pull the CG back rearward). you need a light stick, with a high amount of surface area, like a square. the longer the stick, the more surface area it has. the stick stabalizes your header through pitch damping.

 

hope this helps. if your rockets are unstable, add a longer stick. heh.

 

one pounder use 4 foot stick 8oz three foot 4oz 3 foot 2lb 4 foot 3lb 4 foot(each 5/16 square)

[THEONE]

How you can find the CP ?

 

the CG/CP is the same relationship in any rocket design. the more forward the CG is, the better. with that in mind, the lighter the stick, the better (since a heavier stick would pull the CG back rearward). you need a light stick, with a high amount of surface area, like a square. the longer the stick, the more surface area it has. the stick stabalizes your header through pitch damping.

 

hope this helps. if your rockets are unstable, add a longer stick. heh.

 

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

 

What about the surface area ?

Edited August 27, 2011 by THEONE

[r1dermon]

think of it like a streamer, if you throw a ball with a streamer on the back of it, the streamer will correct the balls flight. the surface area of the stick acts like fins on a normal rocket, to correct the flight path. the further back the stick extends, the force placed on the stick is increased due to the leverage of the longer stick.

 

calculating center of pressure is very complicated and involves heaps of calculus. here you go. http://microgravity.grc.nasa.gov/education/rocket/rktcp.html

[THEONE]

I still can not understand how the stick and the rocket fins work... i thought the weigh of the stick makes it fly straight....

[Mumbles]

It may be a combination of drag and weight, but it's the drag that does the majority of the work. The stick acts just like a windvane. It wants to be in the place that has the lowest stress on it. A windvane and rocket stick if they are functioning properly will always want to face straight into wind/flight path. If you try to throw a rocket, it will straighten itself out. There is a toy popular in the US that really exemplifies this concept. No matter how uncoordinated you are, it's pretty much impossible not to throw it straight.

 

https://www.thegiftandgadgetstore.com/toys-sports/garden-and-beach-toys/nerf-vortex-mega-howler-whistling-football-orange__5010994520205.aspx

[OneEyeCharlie]

No matter how uncoordinated you are, it's pretty much impossible not to throw it straight.

With enough Bell's Oberon... nothing is impossible.

[Mumbles]

Valid point. Despite growing up in one of the boozier states in the union, even at the ripe old age of 7 I still wasn't throwing them back that often when I had things like that.