Trajectory B/C

[starpug]

My trajectory device is a ballista, we finished it and it works. The only problem is that it isn't the most accurate or repeatable in its shots, and we need an answer to this madness. Does anyone out there have a solution? We're asking our coach, but we wouldn't like to bother her too much... Someone MUST know!!!

Gonna need a little more info then that in order to help you.

[scifipi]

Hmm, problems... I'll figure out how to explain it then I guess.

[Draylon Fogg]

what type of ball are you using? because the amount of drag could be the problem...

[cypressfalls Robert]

what type of ball are you using? because the amount of drag could be the problem...

hacky sacks are the worst possible choice for projectiles...

[Draylon Fogg]

well that depends on the machine you are using

[zyzzyva980]

hacky sacks are the worst possible choice for projectiles...

I disagree. The plastic practice golf balls- the ones that look like whiffle balls- are absolutely terrible. Because they are so light and have holes, they are easily blown off course. This can be magnified by the fact that trajectory is often held in a gym, and most gyms have fans that turn on at inopportune moments. We tested this type of projectile once and because you could never tell if it was to hook left or right we abandoned the idea altogether. Hackysacks are usually heavier and harder to force off course. But it really does depend on the machine you are using.

[cypressfalls Robert]

yea I never thought about those balls before, but when i say hacky sacks I say this because they aren't aerodynamic and, etc.

[Balsa Man]

The only problem is that it isn't the most accurate or repeatable in its shots,

Per my earlier post - if you've got the ball....how do I say this...going back with the string; pull the string back further, and how ever you have it set up, the ball is going back, too, we found that pretty erratic. Also, rails to guide it at least for a few inches- big help.

The plastic practice golf balls- the ones that look like whiffle balls- are absolutely terrible

Don't know about the ones with holes, but the hollow plastic ones without holes, that look just like golf balls, are working great. With enough wind, the low mass would be a problem. The plus with a lower mass is lower energy needed, so easier to control the input precisely.

[cypressfalls Robert]

here's a picture

[Draylon Fogg]

plus you dont need aerodynamics as much as you need the right string tension and the right mass of the projectile.. yes they help but not that much.