I have a backpack with rip-stop material that is quite beaten up from scrambling over granite boulders. What are some good materials for patching the holes, what kind of thread should I use, and how should I sew the patches to the holes? I am looking for solutions that make the patched areas at least as sturdy as the rest of the pack, if not more sturdy. I have come across some pretty general tutorials online for how to patch backpacks, but I am more interested in tried and true methods from avid outdoorsmen/women.
I believe that the best material is the same as you backpack is made of, though you may want something tougher if you are planning more scrambling over granite boulders.
There is a plenty of Cordura varieties which will meet your requirements. Make sure to choose waterproof Cordura (with a waterproof glistening film on one side, which will be the inner side of your patch).
Keep in mind, that when it comes to applying force (not friction), the least sturdy part counts, so technically you can't make it more sturdy than original material. To make it equally strong as it was before, you should
The patch should obviously be bigger than the hole and maybe you'll want to overstitch the edges of both the hole and the patch to prevent them from raveling out.
Oh, and please use a thimble to push the needle and prepare some pliers to pull it out, if you are sewing manually: cordura is really hard.