why does this 1986 steel Junk have holes in rudder?

This is fascinating stuff - thanks for all the great information everyone! I found this in a 2006 thread on junks in the boat design archives:

http://www.boatdesign.net/forums/archive/t-11449.html

It comes from an earlier wikipedia edit, now gone, so it may be questionable:

Somewhere in my surfing, but I forget where! sorry! I read that the combination of bow dagger plate and large rudder developed to allow a large clear space for cargo centrally, whilst still providing balanced lateral resistance.

Many, many great pictures of Junks on Karsten Petersen's Global Mariner website, mostly from the early and mid seventies:

http://global-mariner.com/index111ChineseJunks.html

Incidentally, the entire, splendid blue book on Vietnamese Junks can be downloaded free here, but no fenestrated rudders!

http://www.junkbluebook.com/

 

Heck - Alfa Romeo, the "worlds fastest super yacht"

and most of the canting keel yachts have them

http://www.gizmag.com/go/3164/picture/6741/

 

Foochow Pole Junk
http://www.tara.bz/index.asp?page=viewitem&ma=7