Rocket with Gardena nozzle is extremly unstable

[Sitell]

I just finished building my first water rocket/rocket launcher. I use a Gardena quick release mechanism and everything should work fine but... the rocket is very unstable. Immediately after lift off it starts turning and continue to spin until depressurized.

Is the problem that the nozzle/area is small and therefore making the bottle very sensitive for tilting directly after launch?

Do one generally need guides when using small diameter nozzles?
I really hope anyone can help me out!

/karl

[rockets-in-brighton]

I just finished building my first water rocket/rocket launcher. I use a Gardena quick release mechanism and everything should work fine but... the rocket is very unstable. Immediately after lift off it starts turning and continue to spin until depressurized.

Is the problem that the nozzle/area is small and therefore making the bottle very sensitive for tilting directly after launch?

Do one generally need guides when using small diameter nozzles?
I really hope anyone can help me out!

/karl

To be of any help we need info ans pictures of the rocket itself. Is it theoretically stable ie CG & CP in the correct relationship? are the fins securely attached? Have you used a sim to work our the correct amount of water... And so on. As much info as possible please.

[thampson]

Karl,

If you just launch the bottle as it is in the pictures, it will definitely tumble. You need to move the centre of pressure back towards the bottom of the bottle to make it stable. I doubt it has anything to do with the nozzle itself. It looks ok from the pics.

Add some fins to the bottle. Here is an post showing how to build a removable fin assembly you can then tape to your bottles ...

http://wrocket.hampson.net.au/?p=198

There are many ways to add fins to a bottle, we find this method easy as you can move it from wrocket to wrocket

Good Luck
-todd-

[thampson]

Here is the next article where we used PL Premium glue instead of wire to attach the fins ... If you can get a hold of this glue, its a better way to attach the fins

http://wrocket.hampson.net.au/?p=556

-todd-

[Jelo]

As Todd mentioned above, lauching your rocket like that will make it tumble and will slow it down extremely fast.

try putting a nose cone on top of that bottle, and some good fins.
I made a post all about fins and the physics involved, explained in very simple terms:
http://www.wra2.org/forum/viewtopic.php?f=3&t=764
go check it out

Also, i use a 5mm thick wooden stick about a meter long attachet to the launcher to guide the rocket in the right dirrection at take off. it is easily attached to the rocket by using a wide straw glued on the side of the rocket body. hope that helps

[air.command]

I just finished building my first water rocket/rocket launcher. I use a Gardena quick release mechanism and everything should work fine but... the rocket is very unstable. Immediately after lift off it starts turning and continue to spin until depressurized.

Is the problem that the nozzle/area is small and therefore making the bottle very sensitive for tilting directly after launch?

Do one generally need guides when using small diameter nozzles?
I really hope anyone can help me out!

/karl

Hi Karl,

I agree with what the guys have already said. In addition to that, in a dry normally stable rocket you are also partly correct that a Gardena nozzled rocket can be more unstable during the thrust phase of the flight compared to a full bore nozzle. There are two reasons for this:
1. The acceleration is slower so it takes a while for the rocket to get up to effective speed for the fins to start working.
2. The rocket retains water for longer and therefore has a heavy mass near the tail for a part of the flight.

For these reasons it is a good idea to use a guide rail with your rocket.

Is the bottle your rocket or is it just a stand-in for the photo?

- George

[Jelo]

i know this sounds realy random but has anyone ever flown a rocket or r/c plane and got attacked by an animal?
i landed my plane in grass and my neighboor's cat jumped on it thinking it was a bird

[Tim Chen]

i know this sounds realy random but has anyone ever flown a rocket or r/c plane and got attacked by an animal?
i landed my plane in grass and my neighboor's cat jumped on it thinking it was a bird

Once when we launched our rocket the sound spooked a horse in the neighboring field and he jumped a fence and ran around for about 30 minutes before the owner could catch him!

[Jelo]

poor horse... my first high altitude rocket landed on my dog's head, not to mention the parachute didnt open...i supose thats why he rolls on the floor and starts barking franticly everytime i prepare a rocket...

[thampson]

We had a magpie (http://en.wikipedia.org/wiki/Australian_Magpie) have a go at our water rocket car at our last launch .. it landed nearby and walked straight up to it .... we were clapping and making noise to scare it away as I didnt want it to make on hole in it with its beak ...

It then hopped right over the middle of the car and just stood there beside it looking at it .... i had to stomp on the ground near it to get it to fly off .. lucky it wasnt pressurized at the time

-todd-

[Sitell]

Is the bottle your rocket or is it just a stand-in for the photo?

- George

The bottle is actually the rocket, or what I first thought could be the rocket. After reading your comments (thanks a lot, a really appreciate it) I realize I will have to add fins and some guides. When I first tested the rocket it never ever came higher than about two meters (2 m) even with 100 psi. It started to spin directly after launch every time...
Today I also bought some "threaded lamp rod" for making Robinsons couplings. (But first I should get it above two meters with one bottle!)

/karl

[U.S. Water Rockets1]

We had a magpie (http://en.wikipedia.org/wiki/Australian_Magpie) have a go at our water rocket car at our last launch .. it landed nearby and walked straight up to it .... we were clapping and making noise to scare it away as I didnt want it to make on hole in it with its beak ...

It then hopped right over the middle of the car and just stood there beside it looking at it .... i had to stomp on the ground near it to get it to fly off .. lucky it wasnt pressurized at the time

-todd-

If you ever watch our appearance on Mythbusters (Episode #42) you can see the launch video from our ground camera on one of our past world record launches. If you look closely, a small bird is seen flying along the water in the background just as the rocket launches. The sound of the rocket taking off (or the motion of it shooting up so fast) startles the poor bird which proceeds to turn straight into the lake. The bird splashes into the water and then reverses course and flies off in the opposite direction. If you ever see the show, look for the bird!

[Jelo]

If you ever watch our appearance on Mythbusters (Episode #42) you can see the launch video from our ground camera on one of our past world record launches. If you look closely, a small bird is seen flying along the water in the background just as the rocket launches. The sound of the rocket taking off (or the motion of it shooting up so fast) startles the poor bird which proceeds to turn straight into the lake. The bird splashes into the water and then reverses course and flies off in the opposite direction. If you ever see the show, look for the bird!

that must have been pretty funny (exept for the bird) i landed my rc plane and a robin landed on it just a second after...i put the throttle to max, poor robin had a hearth attack (not realy, just flew away)

[bl4ck_4nt159]

Where i can find gardena in indonesia?

[ninja_iga]

Where i can find gardena in indonesia?

hi!
greetings from Malaysia.

you can try the hardware stores, usually the gardening section.

look for Gardena or similar clones, try to get the European brands as the materials are way better.
i cant recall the names now, but there's at least 3 brands other than Gardena, which are compatible with each other