I had a similar problem with my kick-up rudder on my Potter 19. A while
back someone posted a web site that showed a upgrade someone had made on
a Macgregor 26, <http://www.mv.com/ipusers/whale/h1rcontrol.html>. I
used some of the same ideas. I placed a cheek block on the front
(transom side) of the rudder cheek plates and then added 3 turns of 1/4"
( approx. 6-7 feet) bungie cord in series with the rudder lowering
line. Now the lowering line goes from the cleat and is tied to the
coiled bungie cord. From the opposite side of the looped bungie cord
the line continues down around the cheek block to the tie point on the
rudder. When the rudder hits something it will pop up but then be
pulled back down by the bungie cord when the obstruction is cleared.
The tension on the rudder "downhaul" can be adjusted easily at the point
where the line is cleated. This may not be the clearest explanation
but the picture on the above web site should help. It is a cheap fix
that seems to work so far.
Dennis & Nancy Rieger
Potter 19, Hull 1066, Wanderer
Tijeras, New Mexico