The Clamcleat® CL257 Auto-Release cleat provides the neatest and best solution to the problem of how to lock-down a rudder blade yet allow it to flip-up if it hits the bottom or a solid obstacle in the water. The cleat holds ropes securely yet will release them immediately when the cleat is overloaded.
Once tripped, it can be easily reset in seconds by just pushing the cleat back down into its base. The CL257 is fitted with an adjustable cam so that the release tension can be set to suit the boat and local conditions. The cam is adjusted until the rudder blade is held down reliably under maximum sailing conditions. The CL257 will then be set so that the least strain is put on the rudder if it hits an obstacle.
The CL257 can be fitted to virtually all lifting tillers and can also be used to protect centre boards. Fitting instructions are included with every CL257 and are also in the Downloads tab.  Above images show how to rig for 2:1 advantage or with different sized ropes.
Technical Details
 
Metric
Imperial
Rope Diameter
 
4 - 6mm
5/32 - 1/4"
Material
 
Aluminium & Acetal
Aluminium & Acetal
Hole Centres
 
36mm
1 3/8"
Length
 
68mm
2 5/8"
Width
 
22mm
7/8"
Height
 
28mm
1 1/8
Bolt Size
 
M4
#8-32. 5/32"
Screw Size
 
4.2
No 8
Weight
 
31gms
1.1oz