Belegarth

Is it allowed for swords to taper down their length? If so, is there any particular method for achieving this?

It should be totally possible to build a tapered blade that passes provided you build it to the specifications in the BoW and it can get through the safety check.

As far as construction goes, I'd start by making a normally shaped sword with extra padding on the blade like this:
(Tip)
| | | |::| | | |
| | | |::| | | |
| | | |::| | | |
| | | |::| | | |
| | | |::| | | |
| | | |::| | | |
(Handle)

Once that was finished I'd trace the taper on the flat of the blade and then use a bandsaw, or a hacksaw to trim it down:

(Tip)
....| |::| |
....| |::| |
.../| |::| |\
..| | |::| | |
..| | |::| | |
./| | |::| | |\
| | | |::| | | |
| | | |::| | | |
(Handle)

You'd need to use enough padding in the initial construction so that the sword will hit safely at the least padded point once it is trimmed down. This method would waste a lot of foam, but it's really straightforward. If you have more patience and less foam, you can probably come up with a design where you build the taper in from the get go.

Which direction?

It's still got to pass the 2.5" rule at the tip, so you need an extra-wide base to begin with if you go this route. Plus, it still has to pass the hit test at the tip.


If you mean tapering the foam so that it gets thinner in the flat-to-flat direction from the spine to the edge, that's fine, just, again, be aware that a regularly built sword that passes before tapering is unlikely to pass after tapering due to reducing the compressive resistance of the padding layers.