Bottle Rocket B

[rishj09]

My coach said that cones will break after one flight..... so we use small water bottles all the way up to the top.

I've seen a few rockets with water bottle/cup nose cones (there's one in the Image gallery, IIRC) and those tended to have a lower time than those built with another material, such as the wrapping paper.

The nose cone will break depending on a variety of factors; CG and CP (which ultimately affect the flight of the rocket), wind, landing, etc. If your rocket is made of a fragile material then it's more susceptible to breaking than a sturdier material, but a heavier material for the nose cone will shift the CG. Also if the rocket nosedives then yes the cone will most likely break (our rule was if the nose cone was still intact upon a nosedive, then it's too strong).

How are you connecting the water bottles? Tape? Are you experiencing stability problems with your nose cone?

We use tape.... and our rockets get about 15 sec per flight

[mtheleman]

I think the homemade launcher we used at home was not sealed as tightly as the one at the tournament( I heard a pop sound and the rocket went up very fast).

As long as your homemade launcher will get up to 60psi and hold it for a few seconds, you should be okay. Our launcher usually makes a popping sound. The key is to launch in many different weather conditions while keeping the other launch variables (PSI) the same.

[jma]

I think the homemade launcher we used at home was not sealed as tightly as the one at the tournament( I heard a pop sound and the rocket went up very fast).

As long as your homemade launcher will get up to 60psi and hold it for a few seconds, you should be okay. Our launcher usually makes a popping sound. The key is to launch in many different weather conditions while keeping the other launch variables (PSI) the same.

My launcher actually gave us very good results but my concern is that it is not reliable. While we got very good results at home, we got a very bad score at the tournament. We are trying to figure out what was wrong so we won't get the same problem at the state tournament. I am listing all the possible problems that I can think of here and I really appreciate any opinions or ideas.
1. Bottle nozzle was small ( I used Safeway 1 litter soda). I think when the nozzle is fixed too tightly ( the popping sound was from the launcher at the tournament), it will take more power to push the rocket off the launcher therefore there is not much energy left to push the rocket higher. It only went up for less than 2 sec., then it went down.
2. The nosecone was not strong enough. 1 of our nosecones was made from 1 layer of thin mylar film and another one was a long plastic tube from home depot ( we cut part, between the 2 ends, of the tube out and covered the tube with laminate plastic to make the nose lighter). I saw that the tube bent on it way up.
Both of my rockets have 3 fins, they are made by manila folder and plastic sign. I used programs on the computer to calculate CLA and CP and both of the rockets have CG in between CLA & CP ( not in the middle though).

We are unsure what the problem is. I wish we could afford the commercial launcher. Does anyone have an extra one that you want to sell?

[fishman100]

My launcher actually gave us very good results but my concern is that it is not reliable. While we got very good results at home, we got a very bad score at the tournament. We are trying to figure out what was wrong so we won't get the same problem at the state tournament. I am listing all the possible problems that I can think of here and I really appreciate any opinions or ideas.
1. Bottle nozzle was small ( I used Safeway 1 litter soda). I think when the nozzle is fixed too tightly ( the popping sound was from the launcher at the tournament), it will take more power to push the rocket off the launcher therefore there is not much energy left to push the rocket higher. It only went up for less than 2 sec., then it went down.
2. The nosecone was not strong enough. 1 of our nosecones was made from 1 layer of thin mylar film and another one was a long plastic tube from home depot ( we cut part, between the 2 ends, of the tube out and covered the tube with laminate plastic to make the nose lighter). I saw that the tube bent on it way up.
Both of my rockets have 3 fins, they are made by manila folder and plastic sign. I used programs on the computer to calculate CLA and CP and both of the rockets have CG in between CLA & CP ( not in the middle though).

We are unsure what the problem is. I wish we could afford the commercial launcher. Does anyone have an extra one that you want to sell?

1 layer of mylar and the plastic tube/laminate doesn't sound sturdy enough, especially if you saw the nose cone bend as it made its way up. Try using multiple layers of the mylar/plastic tube, etc. It shouldn't add too much weight but it will make the cone sturdier.

Did they use the Aquaport launcher at the tournament? If so, then try to use a bottle with the same size nozzle as a standard 2-liter bottle, because they fit perfectly onto the Aquaport (and if you're correct about the nozzle being too small, then that will solve your problem).

[jma]

Fishman100,
We don't know what type of launcher they used at Regionals, but I know it's not the Aquaport Launcher. Thank you very much for your help.

[jgrischow1]

We can't seem to get above 10 seconds and I am wondering if anyone has any ideas. Yes, I have read this thread, last year's thread, the wiki, and Googled for hours.

We are using a 1 L bottle and about 425 mL of water.
Our nose cone is a long plastic tube, about 5 ft long and 1.5 in diameter.
Our fins are made from plastic folders and folded and taped for rigidity. They are trapezoidal, with bases of 3 in and 5 in and a height of 3 in.

We have two main problems that I see:

Height: The rocket doesn't seem to be going very high.
Delayed backslide: It falls the same way it came up (i.e. the opposite of a nosedive) for awhile before turning and backsliding.

My ideas:

Make the rocket lighter. Take away some tape, shorten the rocket?
Add weight to the tip so it goes up straighter and/or turns to backslide sooner (but we tried this a little and got some nosedives at the end of the backslide)?
Change the fin size/shape?
I don't think we have time to significantly alter the design of the nose cone to, say, paper. Our regional is Saturday.

Any ideas? Thanks.

[Balsa Man]

Well, 10 seconds is not that bad....
Your list of things sounds about right.....
Your comment about not going very high makes me womder about launcher problems; is it homemade or commercial; is the nozzle right (not too tight, or loose/leaking); are you getting full pressure?
Why I wonder is that back a couple years ago, with C-Div (Egg-o-Naut- running 1 liter and parachute) we were getting close to 4 seconds of climb (so around 8 sec when parachute failed to deploy and it did a lawn dart. With any backsliding, that would get well over 10 sec.... You also can probably get a bit more with a bit more water; we were running 450-500ccs.
Good luck

[jgrischow1]

Well, 10 seconds is not that bad....
Your list of things sounds about right.....
Your comment about not going very high makes me womder about launcher problems; is it homemade or commercial; is the nozzle right (not too tight, or loose/leaking); are you getting full pressure?
Why I wonder is that back a couple years ago, with C-Div (Egg-o-Naut- running 1 liter and parachute) we were getting close to 4 seconds of climb (so around 8 sec when parachute failed to deploy and it did a lawn dart. With any backsliding, that would get well over 10 sec.... You also can probably get a bit more with a bit more water; we were running 450-500ccs.
Good luck

Thanks Balsa. I think our launcher is OK. It is an Aquaport just bought this year. I don't see any leaking or tightness issues. The gauge reads 60. We will see.

[fishman100]

We can't seem to get above 10 seconds and I am wondering if anyone has any ideas. Yes, I have read this thread, last year's thread, the wiki, and Googled for hours.

We are using a 1 L bottle and about 425 mL of water.
Our nose cone is a long plastic tube, about 5 ft long and 1.5 in diameter.
Our fins are made from plastic folders and folded and taped for rigidity. They are trapezoidal, with bases of 3 in and 5 in and a height of 3 in.

We have two main problems that I see:

Height: The rocket doesn't seem to be going very high.
Delayed backslide: It falls the same way it came up (i.e. the opposite of a nosedive) for awhile before turning and backsliding.

My ideas:

Make the rocket lighter. Take away some tape, shorten the rocket?
Add weight to the tip so it goes up straighter and/or turns to backslide sooner (but we tried this a little and got some nosedives at the end of the backslide)?
Change the fin size/shape?
I don't think we have time to significantly alter the design of the nose cone to, say, paper. Our regional is Saturday.

Any ideas? Thanks.

If your rocket is not going very high, you might be encountering stability issues. Do you see the rocket "wobbling" as it ascends? If so, then you need to make the rocket more stable.
Check to see where the CP/CG is; that might be affecting the flight of your rocket.

This applies for all rockets; make sure you minimize the amount of resistance on your rockets. A poorly taped nose cone that has air bubbles in it, etc. will decrease the time of your rocket!

[Balsa Man]

Yup, for good stability, you want CP- center of areodynamic pressure- aft of the center of gravity. Bigger fins will move it aft; bit more drag, but if you need stability...