How do shuttle manufacturers adjust speed?

they don't, from what I've seen.

they just make shuttles, fire them across a distance (with everything constant) and the shuttles select themselves. the natural deviations in weight (cork, feathers, glue, etc) make up the shuttles speed...

 

Some good bird manufacturers will have their own prefference.They usually manufacture the birds in the standard,and they add a lil bit more glue to make the heavier birds.Usually,it's the glue that adds the weight.So,if u wanna add some weight on a bird,just put some glue.=).If it's too heavy,just flip a lil on the end of the feathers.

 

So i'm guessing slower birds have more glue, and faster birds have less?

 

i tried to put some power glue on the bird,n it flew faster..so i guess it works..

 

Other way round.
And it's not really about how fast they go, but about how they slow down.
Heavier shuttles decelerate less than lighter shuttles.

 

Ah I get it then, so if I had a slow bird and wanted it to go faster, just add some more glue?

 

yeap..or u can even try to stick in a small nail on it.It's kind of dangerous though,since i'm afraid when u smash,the nail flew n kill ur opponent.Lol..I tried it though,but no accidents happend.But i suggest u not to try it.Just add some glue,like power glue..