yes we got a little off track
Frondeur wrote on Sep 13
th, 2018 at 7:35am:
Now I'm coming to what was the point of this post: pouch alignment can't be perfect, and the glande has, with its own properties, the ability to more or less realign itself. And now I'm getting lost, so what follows is just guesses:
for a projectile to realign itself , it needs to has it's CP(center of pressure) behind it's CM(center of mass).
the spin means the projectile has angular momentum and will only keep the axis of rotation stable like a gyroscope.
so if CP is behind CM you can throw with or without spin and the shot will realign itself eventually.
if CP is in front of CM then you got to think it over and experiment.
the first thing i would consider about making an aerodynamically stable bullet would be to keep the CP as close to CM as possible (or add fins to move it behind CM)
then add spin (how much? i don't know)
for retaining the kinetic energy at long range you'll need:
small surface area (thin projectile)
high mass for that area, means long projectile , too long and thin will be destabilised easily. also high density material
for lowering drag you need a boat tail ,it seems that the nose shape doesn't change the drag a lot.(conical vs ogive vs parabolic but it changes CP and CM position= stability)
you could add dimples so the drag lowers at lower reynold numbers, or have an overall mass which you can throw fast enough that you get into that area.
interesting read:
http://www.aem.umn.edu/people/faculty/flaten/Rocketry_Remote_Lessons_Fall_2017/B...
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Questions about clay glandes shapes (Read 3327 times)
