It is so frustrating. You see grape clusters just 4 weeks from picking then like locusts on the prairie the descend upon the vines and start poking holes in grapes.
As the grapes go thru verasion the smell changes and attracts birds. Netting is virtually the only best defense. Even with netting, which will only last 3-4 years the birds sit on top and poke thru getting what they can. They will search out weaknesses and exploit them.
Shotgun blasts, tin foil pans, owl silhouettes, hawk sounds, cats only are temporary.
For my trellis/arbor I sewed 3 pieces together and erected. Had I not have done that I would have nothing by now.
Trim your cap back so grapes can get more sunlight then net. Put a few stones or boards on to keep wind from blowing out of place on ground.