Quadrant - keyway/clamp friction/set screw?

[Nekton73]

Recent posts regarding cable steering and quadrants got me looking at my own setup again and considering its age and how it has been implemented. I'm interested in peoples experience and opinions with the various designs that join quadrants to rudder stocks.


My own boat has an old Edson cable steering system. The quadrant is clamped to the rudder stock and a couple of bolts have been tapped through the quadrant to act as set/grub screws. The rudder stock has been drilled/dimpled so that the end of each bolt has a shallow depression to lock into.





I've seen quadrants with keyways, which seems a much more reliable way to ensure the don't slip under load, and others, including autopilot arms, that just rely on clamping force with no key or set screws.


Would it be worth it to consider having a keyway cut into my stock and quadrant, just for the peace of mind? The stock is 1.25" diameter. Does cutting a keyway into the shaft pose any strength concerns?

[donradcliffe]

The short answer is yes to the first question. The second depends on the diameter and thickness of the rudder shaft.

[Lepke]

Usually installations w/o a keyway have dimples in the shaft and the set screw has an end that fits the dimple. It looks like your quadrant also clamps the shaft. The bolt you're using should have a locking nut, too. If you're not having slipping problems...
The shaft and quadrant have to be removed from the boat to be machined. There are services that can do some machining aboard, but they're more expensive.

[Don C L]

This is on your Grampian 30, right? I would think the set screw and hole/dimple in the shaft is adequate. I might check the set screw but judging by the mark on the shaft there has been no slop in there. It would be nice to have a locking nut but it looks like you don't have room for one there. Certainly a keyway would be stronger, but IMO the set screw is up to the strains posed by a rudder on a 30 foot boat. JUst my $.02

[Nekton73]

Yes this question is about my Grampian 30, and the pic is of my quadrant showing the set screw/bolt. There is matching bolt on the other side.


I just made the red index mark myself because I recently experienced some slippage on a gusty day with my spin up and after realigning the steering I wanted something to reference.



I'm unsure if the slip was due to the bolt backing out over time, or may have been my own fault due to poor installation. I removed the rudder a couple of years ago to repair where it goes through the cockpit sole and may not have been precise about ensuring the bolts seated into the dimples when I reinstalled. I did make absolutely sure this time by colouring the dimple with the same red paint so that it is visible through the bolt hole when properly aligned. The bolt is now definitely seated in the dimple.


I will add a locking nut to the bolt though, easy enough to do and thanks for the suggestion. Also appreciate the opinion that the current setup should be strong enough for this size of boat. I thought so too but the recent slip made me want to ask for other thoughts.