Bottle Rocket B

[fishman100]

I'm relaxing on the couch after a 4-hour building session, so we can launch on Wednesday. 15-20 seconds on rockets we launched a couple weeks ago, only they landed on the roof of the school. We had to wait until the next day to get them down. Hopefully these new ones me and my twin are just finishing will do a bit better. (And avoid the roof...oops.)

15-20 seconds already? You're off to a great start!

[Saturiea]

I have a strong feeling that the times this year at state and the national competition will only be 10ish seconds less then last years.

[skillfullparrot7]

I launched mine once already, and it went really high, but came down in a nosedive. It was still about 7 seconds, so I can't wait to see how it does when fixed.

[gmui]

Did anybody start launching yet? What kind of times are you getting?

I honestly don't think anyone has tested yet, and if they have it's most likely a crude prototype (i.e. not something they would bring to a competition).

We actually tried to launch a couple rockets my son and I made with the Aquaport launcher we recently got (thanks to the advice of this forum). As expected, it was our first attempt to make and launch rockets so we didn't have great success - but it was fun and got my son and his friend / partner excited about it. He's already made a better one that we'll try to launch this weekend.

Our rockets didn't go high and our times were only about 5 seconds, but they did at least backslide!

For round 2, my son added a stronger cone with a rounded nose cone on his original bottle / fin base and tried launching it again yesterday. Original launch was with 75 psi and got 3-5 seconds. Yesterday he got 14.2 and 14.5 seconds for 2 launches so he's definitely on the right track. Main thing to look at now is to get it to fly straighter / higher (it veered off on the way up) and to examine the video of its descent. On those two topics, does anyone have any methodologies for ensuring that the cone is attached exactly straight on the bottle? And for the descent, the rocket did backslide in general, but we noticed that it was twirling on the way down. Is that normal / ideal? If not ideal, can anyone explain how to improve that behavior on descent?

[fishman100]

I honestly don't think anyone has tested yet, and if they have it's most likely a crude prototype (i.e. not something they would bring to a competition).

We actually tried to launch a couple rockets my son and I made with the Aquaport launcher we recently got (thanks to the advice of this forum). As expected, it was our first attempt to make and launch rockets so we didn't have great success - but it was fun and got my son and his friend / partner excited about it. He's already made a better one that we'll try to launch this weekend.

Our rockets didn't go high and our times were only about 5 seconds, but they did at least backslide!

For round 2, my son added a stronger cone with a rounded nose cone on his original bottle / fin base and tried launching it again yesterday. Original launch was with 75 psi and got 3-5 seconds. Yesterday he got 14.2 and 14.5 seconds for 2 launches so he's definitely on the right track. Main thing to look at now is to get it to fly straighter / higher (it veered off on the way up) and to examine the video of its descent. On those two topics, does anyone have any methodologies for ensuring that the cone is attached exactly straight on the bottle? And for the descent, the rocket did backslide in general, but we noticed that it was twirling on the way down. Is that normal / ideal? If not ideal, can anyone explain how to improve that behavior on descent?

One system I heard (but we never tested due to the shape of our nose) of was to roll the rocket on a flat surface and see if the nose/bottle wriggles. If it rolls in a straight line without any bumps (think of rolling a soda can on the floor) then the nose is straight. If it does wriggle, then add tape, etc. to straighten out the nose.

IDK exactly what you mean by "twirling" but if the fins are spinning then that's a good sign.

[Saturiea]

We actually tried to launch a couple rockets my son and I made with the Aquaport launcher we recently got (thanks to the advice of this forum). As expected, it was our first attempt to make and launch rockets so we didn't have great success - but it was fun and got my son and his friend / partner excited about it. He's already made a better one that we'll try to launch this weekend.

Our rockets didn't go high and our times were only about 5 seconds, but they did at least backslide!

For round 2, my son added a stronger cone with a rounded nose cone on his original bottle / fin base and tried launching it again yesterday. Original launch was with 75 psi and got 3-5 seconds. Yesterday he got 14.2 and 14.5 seconds for 2 launches so he's definitely on the right track. Main thing to look at now is to get it to fly straighter / higher (it veered off on the way up) and to examine the video of its descent. On those two topics, does anyone have any methodologies for ensuring that the cone is attached exactly straight on the bottle? And for the descent, the rocket did backslide in general, but we noticed that it was twirling on the way down. Is that normal / ideal? If not ideal, can anyone explain how to improve that behavior on descent?

Not totally sure what you mean by twirling, but if it was twirling you may want to add small amounts of clay (and by small I mean really small increments) to the side opposite the twirling and it should help stabilize.

Second thing is you may want to check the rules regarding air pressure used.

Third building it strait is a hard thing to do one way I have seen is using a door frame as an alignment tool as well as visual alignment.

[Lady Epidemic]

The way we use is to stand the bottle up exactly straight, have one person on the floor hold it straight and slowly spin it, while someone else watches from a distance and straightens the unattached nosecone if anything looks off. Then, when everything looks perfect, put your hands in a ring around the tip of the nosecone, and watch it spin. It should stay in the exact center, and rotate perfectly. After that's done, attach it to the bottom with a small strip of tape. Do the hand-rotate thing again, and if it still looks good, tape it all the way around. Takes about 15 minutes until you get the hang of it, but well worth the extra seconds.

[gmui]

Thanks for the straightening advice. We'll have to try it out for the next one. By "twirling", yeah, I mean that on descent, the rocket is spinning along the long axis. I guess that's a good thing? We'll see how the rocket does tomorrow. My son has to "try-out" to get to compete with the water rockets on his school team. I guess it's the most popular event and the school will only enter 2 teams.

[fishman100]

Thanks for the straightening advice. We'll have to try it out for the next one. By "twirling", yeah, I mean that on descent, the rocket is spinning along the long axis. I guess that's a good thing? We'll see how the rocket does tomorrow. My son has to "try-out" to get to compete with the water rockets on his school team. I guess it's the most popular event and the school will only enter 2 teams.

If the rocket is spinning like the one in this video then that's a good sign.

Not totally sure what you mean by twirling, but if it was twirling you may want to add small amounts of clay (and by small I mean really small increments) to the side opposite the twirling and it should help stabilize.

Second thing is you may want to check the rules regarding air pressure used.

Third building it strait is a hard thing to do one way I have seen is using a door frame as an alignment tool as well as visual alignment.

Agreed. I think the max. air pressure is 60 PSI.

[Glopy19]

What launchers will be used at the competition?

[space scientist]

What launchers will be used at the competition?

The most common launcher that you will see is the Aquaport one that was previously mentioned on this thread, but you may occasionally see other types of launchers (like the NERDS one that was previously mentioned on this thread or a homemade launcher).

On a side note, do you go to Woodcreek Junior High School (I want to know what active members on the board are in the same school as me.)?

[jma]

Is the bottle neck opening internal of the 1 litter smaller than the 2 litter? Does anyone have any problem of fitting the 1 litter into the launcher? I used the homemade one and the 2 litter fit perfectly but the 1 litter doesn't. I can fix my launcher but I just want to make sure I don't have the same problem on the competition day. I used the safeway cola and fruit flavor sparkling water bottle.

[Saturiea]

Nozzle size is extremely variable between bottles. So sticking to the 2.2cm opening specified by the rules is best. Get a set of calibers to check the inside diameter and if it is not 2.2cm don't use it. The variability is strong between bottles, for example Dr. Pepper work, but Diet Dr. Pepper are a bit too small. So just check before you build with a set of calibers

[jma]

Thank you Saturiea. I will get a set of calibers.

[Glopy19]

What launchers will be used at the competition?

The most common launcher that you will see is the Aquaport one that was previously mentioned on this thread, but you may occasionally see other types of launchers (like the NERDS one that was previously mentioned on this thread or a homemade launcher).

On a side note, do you go to Woodcreek Junior High School (I want to know what active members on the board are in the same school as me.)?

I go to Colleyville Middle school.