My first proper big project was the Kingdom Keyblade from Kingdom Hearts. If you don't recognise the name, it's this;
Cool font though.
First, I took a couple images and made a full scale cardboard model. In fact, weapon makers rule number one; ALWAYS make a cardboard model first, even if you know what it'll look like. It lets you figure out how you'll do it with the more costly materials, rather than waste them away. I made my cardboard model (and thus my full one), 85 cm long, and it'll be more evident in a minute.
The cardboard model's on the right.
I then bought from a hardware store (B&Q, I think it was) some PVC piping in 32 and 40mm, each 1.5 metres tall. I cut the 40mm into a 22mm piece, and cut through it lengthways. The blade prototype on the left shows this, as this allows the Crown Blade piece to slot into it, and the extra space of the 22mm piece can fit onto the 50mm piece from the 40mm pipe. The bottom of the 32mm part has two slots cut into it, so that it fits into the handguard piece. At the bottom of the post there'll be 1:1 drawings for the two wooden parts, so it might make more sense there.
Now, you can see how the slots work. For the blade not to fall off, I had to put four screws in place, two in each side. Upon reflection, a thinner Crown Blade would've been better, as the balance would've been great. So, now you can see the one 32mm pipe section in place, as the handle. I had a 13 cm part cut out, and more slots at the ends. To get it in snuggly, I brashly decided to use a hammer to get it in place. At least it worked...? Only now, I realise that the only useful place for glue is at the tip, for the two PVC parts to fit and the Crown Blade together.
You can now see how the slot works, and it's quite a good fit.
Both finished Keyblade models. The cardboard model is still useful here, as it can be used as a final comparison. At the bottom of the cardboard model is a ruler, so you can use it to find the height and measurements (it's a metal 30cm ruler with no pointless edges).
Once I had the parts individually, I primed the plastic pieces (except for the handle, as it was already black) with a PVC Primer so that the paint would stay on. I put about 5 or six coats on, just to be sure. I then painted the Crown, it's hold, and main staff section silver. I then duct taped the handle so it wouldn't be painted gold. Once the handle guard was gold, I attached the two main sections to make the full blade, then made the mid-point gold, with the help of lots of duct tape. Once the tape came off, and a quick touch-up here and there, it was done!
For the hexagons in the Crown Blade, use the points to make them into circles. Hexagons aren't on the real Blade, and are more of a pain to get right.
For the Handle guard, use this twice mirrored to make the whole piece. An A4 sheet wouldn't have fit the whole thing, so I made half of it. The handle line is just for reference.
I'm sure that there are better ways of doing this, but in no way am I unhappy with this. I hope to see other people's versions, and I hope that I helped any Kingdom Hearts fans out there.