CG Question

[SacEsq]

Almost done with my Madcow Skipper. Instructions say the CG should be 32.25 from nose tip. I measured and marked, loaded a casing and motor bigger (heavier) than I anticipate using and put in the recovery as well. Balanced the rocket and its balance point is a good 3-4 inches further forward from the 32.25.

I am thinking this is due to making this zipperless with a baffle and splitting half way up the rocket.

Will this be a problem or is this what is referred to as "overstable" ?

Thanks

 

[azzie]

By moving CG forward, you are making it more stable so it won't be a problem. Yes it will be tad overstable which is OK.

You can download Rocksim design file from Madcow web site, load it in OpenRocket and play with CG/CP in different motor/design combinations. If you want to move CG back, just stick a bigger motor

-Alex

 

[Zeus-cat]

Overstable rockets are more prone to weathercocking; that means wind can push on the fins as the rocket is going up and cause the rocket to turn into the wind.

 

[Boosterdude]

What I don't understand is why they don't provide the CP instead of the CG. Isn't it more important to know where the CP is the CG can be based off the CP location?

 

[ClayD]

What I don't understand is why they don't provide the CP instead of the CG. Isn't it more important to know where the CP is the CG can be based off the CP location?

I believe it would be best to provide both. However, I can see why they would provide cg, as its what you actualy check for flight readyness. By providing the CG, they are including their recommended stability margin. CP then is secondary information.

Additionaly CP is a guess at best, and arguable about how CP is calculated. barromans, modified barrowmans, and other things like Virtual CP, dont always agree. Thus the CG, would be a measurement, that is based on real world testing by the manufacturers. Not, a number for something you may not be able to prove as accurate.

 

[SacEsq]

THANKS for all the replies and great discussion. Given that the current CG on this kit as built is only about 3 inches ahead of the stated CG I do not feel, based on the replies and other information I have gathered, that it will pose any problems for me.