I used to own one of these. On a tiller boat, the leverage near the pivot point is just too high to try to brake the swing by some friction-increasing thing closer than where you hand normally rests. You will need to rig a lashing of some sort. Davis Instruments sells a thing that locks to a line run from the gunwales called a Tiller Tamer, but looking at the pictures I just rigged my own:
Tiller-Tamer™
A line run between the jib sheet blocks on the gunwales with a loop formed so it can be slipped over the end of the rudder to hold it steady to raise sails, grab a beer, or whatever. In either case, you will not want to leave it in place while sailing, so you need to make it easy to detach and throw below.
Not that it matters, but what year H216 do you have? The cassette Vara rudder, or the hung off the back rudder?