: Maybe a standard understern would be the most simple to make and
: less problems than a retractable. Maybe also less weight. Does
: anyone use greenland paddles with surf skies? I have been
: thinking maybe a TNR surf ski. I have been playing with the
: design with the kfoundry software. Nice boat.
The comment about the composite tube glassed into the boat is right. It's simple and light and as long as the top end is above waterline it doesn't leak (with a reasonably close fit or an O-ring fitted somewhere).
My rudders on the TNR break off once or twice a season when I paddle over shallow rocks but the boat can take it. The TNR actually has a flat transom that is intended for a retractable rudder for some river runs (Fraser River). Look at Nick's Mystery photos for an example of a do it yourself retractable.

In the 2010 US surfski championship video you can hear Dawid Mocke run over a rock. That would be one tough rudder. He went on to win.
Mine would have been gone.

I've only seen wing blade paddles used with surfskis BTW.