I wouldn't try it, have you ever left your clothes to soak in a washing machine too long? The stuff stinks. Just go on ringside.com, or your fitness store and look for an unfilled heavy bag. Ringside sells them for $40, and it's more much more durable then a homemade heavy bag. The stuffing is easy to come by. If you can't get any rags or shredded cloths like what they throw out at a place that makes clothes, you can just go to thrifty store, or a salvation's army outlet and fill a cart with the cheapest clothes that they have. Then you can remove all the buttons/zippers and cut them up and fill your heavy bag with the rags.

If you want to add some weight to your bag without making a lot of rockhard spots, you can use a durable plastic bag with sand in it and place it at the bottom of your heavy bag.

Then if you want to make the most of your bag you outta a long chain/rope and tie it to something so that the bottom of the bag is at about waist level. This would be a little easier on your joints, and a swinging heavybag makes you move a lot more.