I suggest you have a look at Ray Jardine's website (www.rayjardine.com). He sells kits for the ultralight backpacking crowd; but he has some good tips on sewing and machine setup. He's also a very interesting guy who has pretty much done it all (backpackpacking, through-hiking, climbing, treking, ski touring, kayaking - the list is impressive!!!). I sewed one of his backpack kits and had no problems but I did have to hand crank as another poster suggested above. Unlike many things, you can always do-over by carefully ripping the stitches out (get a seam ripper).

There's a vast amount of information on the web on sewing nylon (Cordura)... you might want to google kite-making.

Good luck and be patient and like many tasks in life sewing can be a mental exercise... if you think the machine will beat you it probably will!!!