How much weight should I add?

[SpartaChris]

Hello,

Is there an easy way to tell just exactly how much weight one should add to their nosecone for proper balancing? I have seen where people have added as litts as 1 oz. of noseweight or as much as 25 lbs. How does one know how much to add? Is it done by trial and error, or is there some kind of formula?

Thanks guys, I appreciate your help!

-Chris

 

[Justin Horne]

It all has to to with the relationship between the center of gravity and the center of pressure. for stable flight, the center of gravity(CG) must be ahead of the center of pressure (CP) by one body tube diameter, or caliber. Nose weight is added to make he CG move forward. If its less then one caliber ahead of the CP, the rocket is understable, and probably unstable. Nose weight moves the CG forward, making the rocket stable.

So how much do you need? 0-x. Where x is the amount you need. It all depends. Id suggest RockSim to find your cp. once you do that, find your cg with motor. If it's one caliber ahead of CP, you're good. If not, add nose weight.

Hope this helps
Justin

 

[loopy]

Make sure when you do that you're finding the CG with the heaviest motor you plan to use. That way, you're sure that it's stable no matter what you're loading into the back end. Some people with rockets designed to fly on a large variety of motors will create an adjustable weight system in their nosecones to help prevent overstability, and improve performance on the smaller motors the rocket will take. Overstability is not always a bad thing, but will tend to cause the rocket to weathercock more into the wind. If you do a search on adjustable noseweight I'm sure you'll find information on how that is done.

Loopy

 

[powderburner]

https://www.rocketryforum.com/showthread.php?threadid=3379&highlight=design+101

Does that help?

 

[gerbs4me]

on my cert rocket, when I stabilized it, I added weight to make it stable on a I212, so If I wanna use an H165, will it be ok to fly it? note that its not adjustable weight, I should make a new NC, and make it adjustable nose weight.

 

[Justin Horne]

Yes, it will. If the CG was far enough forward with lots of aft weight, all it will do is be farther forward with less aft weight. This means it will go more stable, actually.. There is such a thing as over-stable, but im sure you aren't there.. unless the I212 case was made of gold or something...

Just like loopy said. make it stable with the heaviest motor youll fly, and it were pretty much be stable on anything else.

 

[gerbs4me]

thanks for the info

 

[powderburner]

Originally posted by gerbs4me
If I wanna use an H165, will it be ok to fly it?

Gerbs, what is the weight and lengthwise c.g. of each motor in the loaded condition?

 

[loopy]

Gerbs, you should be fine. The only time I've seen people talking about adjustable weight in the nose is when they have a rocket that handles anything between like a high thrust I and like a K. HUGE weight difference in the motors.

Loopy