Bob Blick wrote: > Does anyone know what the rule of thumb regarding center of > gravity on a model rocket? Specifically, if you want to add > telemetry to a model rocket, is it OK to put it in the nose, or is > it better to keep the weight low in the fuselage? Bob: A crosswind (or any airflow with a lateral component, relative to the rocket) is going to act at the rocket's center of pressure. That force, though, will make the rocket pivot about its center of gravity. If the CP is behind (i.e., lower than) the CG, the rocket self- corrects: It tends to point itself into the wind. If, on the other hand, the CP is in front of of the CG, the effect of a crosswind is amplified and the rocket tumbles. It's for precisely this reason that modern mid-engine sports cars have most of their body area (as viewed from the side) toward the rear. In the old days, when engines were mounted up front, it was easy to keep the CP behind the CG; in fact, it was almost impossible NOT to. Now that the CG has moved so far back, designers must go to a lot of trouble to maximize the area at the rear of the car. The integrated wing at the rear of an NSX, for example, performs practically no function in terms of aerodynamic downforce. What it DOES do, however, is provide an excuse for the vertical wing SUPPORTS on the fenders, which add a fair amount of area to the place where it does the most good: as far behind the CG as possible. The C5-and-newer Corvettes do the same thing, although (to my eye, at least) the huge ass on a new Corvette looks substantially less elegant than the NSX wing. Anyway... The answer is: Put the weight at the nose. -Andy === Andrew Warren - fastfwd@ix.netcom.com === Fast Forward Engineering - San Diego, California === http://www.geocities.com/SiliconValley/2499 -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu