Should I pursue this project?
 

My friend has a huge heavy plastic tarp that came apart at the middle "seam". She asked if I could fix it. Since it was a heat set seam instead of stitched I'm hesitating on trying it. If it were canvas I might attempt it but have concerns about the plastic.

Has anyone done anything like this? And any suggestions?

I would like to help her out if I can.

I think if you sew it, it will cease to be a functional tarp as the needle holes will probably leak. If she uses it for hauling leaves it will probably come apart again fairly quickly. I don't think it will be worth the effort. I think you are better off sending your friend to Harbor Freight
http://www.harborfreight.com/lawn-garden/tarps.html

I agree with feline fanatic.

Gota' love that Harbor Freight!!

Sounds like a good project for duct tape to me. I agree that the holes from stitching will allow moisture through.

Not to mention a perforation line for a tear.

and the thread my rot

use outdoor thread and cover with a few layers of duct tape,,,otherwise, harbor frt. is a good choice.

If it can fix space ships a tarp is nothing for Super Duct Tape!

Tape of some sort - no sewing - (in my opinion)

duck tape, duck tape, duck tape