There are a lot of tutorials online about making PVC weapons, and a lot of good ones at that. The problem I've had with most of them is that you end up with more of a club than a blade shape when you're done, or they use fancy (i.e. expensive or hard to aquire) cores and foam. So I'm recording what I've found to be the best of both worlds. I'm not claiming that this idea is unique, or even that i'm the first person to make a PVC weapon this way. But I haven't found anything online that indicates they wrote about it if they did. If you've seen/done something else like this, please let me know about it in the comments.
Step 1: Tools and materials
1 piece of 3/4" schedule 80 PVC conduit, equal to the finished length of your weapon, minus about 2 inches for stabbing tip. (You can find it at electrical supply stores. You don't want the schedule 40 stuff they sell at Lowe's and Home Depot because the dowels won't fit right, and because it's weaker.
3/4" oak dowel(s) the same length as your PVC. I've only found them in 3' lengths, which seems to be no problem. Just use more than 1.
1" schedule 40 (repeat, forty) PVC conduit for your crossguard.
1 3/4" PVC end cap for a pommel. (That's just what I use, you may want to make your pommel out of foam so you can bash people with it. I don't, and I don't think it's a very good idea.)
1" pre-slit polyethylene foam pipe insulation. It's sold in 6-foot lengths. a rule of thumb for how many to buy is 1 for every 18 inches of blade.
Double-sided duct tape.
Regular (single-sided) duct tape.
Boiled linseed oil.
A drill, and a 1" hole saw. It's that little white thing in the picture, and you need it to make your crossguard.
A box-cutter/utility knife. Make sure it's the kind with the break-off blades, so you can extend it all the way. You're gonna want a fresh blade for it.
Leather work gloves.
You'll also need some way to heat your PVC. Some people pour boiling water over it, some people use a blowtorch, and some use purpose-built heat guns, which are basically a hair dryer on steroids. I use a torch. (A word of warning: If you use a torch, do your best not to singe the PVC, because those fumes are toxic. Keep your torch well back from your PVC, and wear breathing protection. And DO IT OUTSIDE. That goes for the PVC cement too. Remember, manufacturers' warnings are there for a reason. Always read and follow them.