The difference ballast makes

Discussions about rockets, construction materials, adhesives, nozzles, nosecones and fin design.
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bugwubber
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The difference ballast makes

Post by bugwubber »

Does having the proper ballast improve rocket performance? Yes, yes it does.
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HK-A_2014330_1459.png (152.48 KiB) Viewed 86 times
Same 2 liter rocket at 100psi, 1st launch with less ballast, 2nd with more.
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Re: The difference ballast makes

Post by Water Rocket Expert »

Wow twice the height! I can see how that would make a difference. Even just adding weight to a soda bottle without fins makes it go higher. What is your best speed for a 2 liter rocket. Mine is 74 mph. That isn't great but it still is fast!
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Re: The difference ballast makes

Post by bugwubber »

Water Rocket Expert wrote:Wow twice the height! I can see how that would make a difference. Even just adding weight to a soda bottle without fins makes it go higher. What is your best speed for a 2 liter rocket. Mine is 74 mph. That isn't great but it still is fast!
Registered 176fps on another launch yesterday. So about 120mph.
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Re: The difference ballast makes

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Where on the rocket did you put the ballast? I have never thought about adding weight.

It does make perfect sense. The extra weight has more kinetic energy which keeps the rocket going for a longer period of time. Why didn't I think of this before?!
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Re: The difference ballast makes

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DogLover wrote:Where on the rocket did you put the ballast? I have never thought about adding weight.

It does make perfect sense. The extra weight has more kinetic energy which keeps the rocket going for a longer period of time. Why didn't I think of this before?!
The most effective location is the nosecone. Back in my pyro days, I remember tying a string to the rocket and swirling it in the air to make sure it flew right. There was some kind of clay that came with the kit that could be smeared onto the inside of the plastic nosecones that would add weight so it balanced on the cg mark.

Keep in mind this is for a single bottle (short) rocket. A long rocket might not need any additional weight.
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Re: The difference ballast makes

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Weight is better for distance, but can be used for height. A big rock is going higher than a small rock if you throw it, but too big and it is going lower. You see.
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Re: The difference ballast makes

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bugwubber wrote:The most effective location is the nosecone. Back in my pyro days, I remember tying a string to the rocket and swirling it in the air to make sure it flew right. There was some kind of clay that came with the kit that could be smeared onto the inside of the plastic nosecones that would add weight so it balanced on the cg mark.

Keep in mind this is for a single bottle (short) rocket. A long rocket might not need any additional weight.
Ah, ok this makes sense. Thanks.
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Re: The difference ballast makes

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Water Rocket Expert wrote:Weight is better for distance, but can be used for height. A big rock is going higher than a small rock if you throw it, but too big and it is going lower. You see.
If the rocks are made from the same material (same density) and both are thrown at the same speed, then the question ultimately comes down to which rock has a better aerodynamic shape. The idea of putting weight on a rocket is to increase the average density so that the rocket has more momentum than a less dense rocket but not so much mass that the top speed is reduced.

The batter comparison is throwing a baseball vs. throwing a wiffle-ball.
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Re: The difference ballast makes

Post by rstaff3 »

Yup, there is such a thing as 'optimal mass'. Lighter is better for speed but you often have to add mass to a rocket to optimize altitude.
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Re: The difference ballast makes

Post by Jamie5335 »

Thats great information you have collected their bugwubber. Many say to make rockets as light as possible and avoid the use of a recovery system as this adds weight- but from what you have shown, it looks as if a recovery system on top of the rocket could act as ballast, as well as recovering the rocket in style via a parachute!

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