Kick-up Rudders:
Problem and a Solution
by John O'Neill


Bolger Cartopper and many, many other "kick-up" type rudders are held in the down position by rudder cheek friction achieved via a sufficiently tight pivot bolt. The bolt needs a fair amount of tension to prevent the rudder from creeping up under sail (most rudders float!), resulting in a rudder that:

  1. Slowly creeps up and becomes hard to operate if there isn't enough tension
  2. Won't kick-up easily at any time

Problem number one has caused me near capsizes downwind in stiff breezes several times, and hard steering on any number of occasions. It's also caused the loss of a good wrench, dropped in the drink while trying to tighten the bolt.

Problem two has twice caused me to fully capsize in the mud-bottom waters I sail. As those are the only two times I've fully capsized my Cartopper, that's not a good record.

Each instance was downwind in a stiff breeze at low tide when the rudder grabbed a (hidden) mudbank, stopping or slowing the boat, causing the light boat to instantly and dramatically slew sideways and careen wildly over. Sickening quantities of muddy water then pour over the gunwale no matter what extreme contortions I undertake to prevent it, causing angst, dismay, wet drawers and loud, unconscious emanations from my vocal chords - and that's the easy part.

Cartopper is an open boat; capsize is never a wholly fun situation - even at the best of times. At the worst of times it can be downright dangerous.

This Cartopper sailer is making lots of leeway in the mud using a pre-modified, kick-up rudder - one that ain't doing any kicking up . . .


A spring-loaded ball-detent device that keeps the rudder down until the spring pressure is overcome, allowing the rudder to fully kick-up. (Ball detents can be had commercially, I have since learned, but they are easy enough to scavenge together).

Basically my device is a short piece of threaded pipe capped at both ends. The ‘inside' cap has a hole drilled through it just slightly smaller than the diameter of a ball bearing. The ball bearing (I used 9/16") is placed inside the pipe and sticks through the cap hole, with a spring holding it firmly in place. A second, closed cap is then screwed on the other end, compressing the spring (and allowing for pressure adjustment by varying how far it's screwed on).

A hole big enough to accept the inside cap is drilled through one rudder cheek, in way of the edge of the rudder fin (for maximum leverage). The ball detent assembly is mounted on that cheek, with the inside cap (and thus the ball bearing) facing the pivoting rudder.

On the rudder fin itself is mounted a metal plate with a hole (large enough to accept the ball bearing) drilled through it, and positioned so that the ball bearing fits in the hole when the rudder is fully down.

The assembly holds the rudder down, firmly and positively, but when sufficient force is applied to overcome the spring pressure, up pops the rudder. (Tighten the pivot bolt just enough to keep everything in place; no more is needed.)

To make it work there needs to be either enough space between the rudder cheeks to allow for rudder, metal plate and ball, or, lacking clearance, the plate is let into the rudder flush and a groove is routed in the rudder to allow clearance for the ball as the rudder is raised and lowered.

In practice I've found that when the rudder does kick-up, it doesn't kick up enough to allow loss of all steerage. Instead it bobs up and down floating high on the water but with enough remaining submerged to allow directional control.

While I was at it (and thinking that it might come in handy during the "sea trials" of my new ball detent device) I rigged up a loop of line to raise and lower my rudder from inside the boat. The line is rigged with a mechanical advantage purchase on the "raise" side to more easily overcome the spring pressure. I was concerned that I might have to rig the same on the "lower" line, but in practice the momentum of a quickly lowering rudder easily overcomes the spring pressure.

When the ball engages there is a loud, satisfying "clunk," letting you know that yes, the ball is engaged!

Reefed for a blustery day with a pre-modified, kick-up rudder that's already kicking up - when it's not supposed to! Later that same day, between a big gust, an unexpected jibe, a helmsman inexperienced with the boat (my brother) and a rudder not as responsive as it should have been, this brother and that boat took a not-so-nice, unscheduled dunking. (Picture taken by me, from my other Cartopper.) Personally I blame the entire incident on his stubborn insistence on not bringing in that red fender, "because it gets in the way." Well bro', you went and spoiled the picture, and aren't paybacks a b----?

How it works:

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pic 1: That bronze, handle-looking thing is the ball detent assembly. Most of the bright-finished wood, by the way, is birch plywood, except the tiller which is ash. The strange-looking piece on the underside of the tiller was supposed to guide the tiller raise/lower lines, but proved unnecessary. The block is rigged to get mechanical advantage for raising the rudder, handy for achieving the initial movement needed to get the ball out of the detent. After that, if you keep pulling, the rudder comes up like a reverse guillotine. Make sure, when you're showing it off to your politely appreciative wife, leaning over to more closely examine your handiwork in the garage, that that fast-rising fin doesn't try to cut her head off! (Learned the hard way.)

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pic 2: An example of a metal plate (in this case brass) for mounting to the pivoting rudder. The center hole is sized to accept the ball bearing. Once it is mounted, drill slightly into the rudder with the same size bit to allow room for the ball to fully seat.

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pic 3: Here you can see the outline of the mounting block surrounding a hole in a rudder cheek, through which you can see the brass plate mounted on the rudder fin itself. The green stuff is marine grease which I loaded up into the threaded pipe (probably overkill for a dry-sailed Cartopper, but with the grease inside when the detent engages it emits a satisfyingly solid mechanical sound, like the door closing on a Rolls Royce!). Note the "stop sign" outline inside the hole, achieved with epoxy which set around the wax-coated inside pipe cap. It keeps the assembly from turning - and between the interference fit it provides and the mounting block (which only has a loose fit on the pipe) everything is kept solidly in place. As an aside, probably the most nerve-wracking operation in the procedure was drilling that fat hole through my varnished rudder cheek. Measure twice and cut once (the woodworkers mantra)? No way. The center of this hole was measured about 8 times before I got up the nerve to start the drill!

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pic 4: The thing itself, ball bearing in cap hole and all that. The screws used for the mounting block are of two different sizes. The lower one short, to screw into the ½" cheek ply, behind which is empty space, the other longer, to screw through the cheek into the solid fir spacer block the cheek is mounted to.