Just wanted to know if there is a formula for determining the cg of any rocket.
In rc aircraft the starting point is around 33% of the wing width, measuring from the leading edge.
I presume you mean where you want the CG to be. Ideally, it should be one caliber (largest airframe diameter) ahead of your center of pressure (CP), which is similar to the neutral point (NP) in model airplanes.
The simplest (and most conservative) way to calculate the CP is the Cardboard Cutout method. Simply cut out a silhouette of your rocket in a piece of cardboard and balance it on a knife blade. The place where it balances is the CP at a 90 degree angle of attack. Because this is the farthest forward the CP can ever be, your rocket will always be stable if your CG is further forward than the CP.
Just wanted to know if there is a formula for determining the cg of any rocket.
In rc aircraft the starting point is around 33% of the wing width, measuring from the leading edge.
The absolute best way to determine the CG of a rocket is to install the heaviest motor you plan to use in it, and then balance the rocket on a straightedge.Just wanted to know if there is a formula for determining the cg of any rocket.
In rc aircraft the starting point is around 33% of the wing width, measuring from the leading edge.
Does this help answer any of your qstn?
https://www.rocketryforumarchive.com/showthread.php?t=3379
You gotta love tHe archive.... One of these days I'll have to check it out
And in the model airplane world 33% of the chord back from the leading edge is an approximation of where it should be, not necessarily where it is. Actually that's a bit aft for many airplanes....
John's answer is the way to go to find out where it IS for a given rocket. Some of the discussion about simulators and cardboard cutouts and cranking through the Barrowman equations sheds light on where it should be.
Some of the discussion about simulators and cardboard cutouts and cranking through the Barrowman equations sheds light on where it should be.
Just wanted to know if there is a formula for determining the cg of any rocket.
In rc aircraft the starting point is around 33% of the wing width, measuring from the leading edge.
And adding on a little bit to the end of Troy's post, c.g. location is NOT found through the use of Barrowman eqns or cardboard cutouts. Those tools are for estimation of c.p., or center of pressure.
Fair enough... I should've been more clear and was thinking in model airplane terms where one moves stuff around to get the balance point in the right place relative to the aerodynamic configuration of the airplane rather than in model rocketry terms where often the aerodynamic configuration may be in play as much as the mass distribution within it. But either way, correcting a tail heavy (or insufficient stability margin) situation can be done the same way - add nose weight. Using the CP calculations just suggest where the CG should be by using CP as a necessary reference point, which is what I was thinking.
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