As some of you may already know, I like to experiment with my Pocket Cruiser. This has led to many different modifications during and after building my boat some of which have worked out to my satisfaction and some less so. One area of my boat that has seen a flurry of experimentation is the rudder. Now, before I go any further, realize that I am not a naval architect but a rank amateur so fair warning!
My first experimental rudder
was created in the flurry to finish my boat in time for the BYYB Northeast
Regatta on Lake George, NY. Given limited time in which to fit out my
boat, I decided to go 
with
a simpler “friction” type rudder than the one in the plans.
My design was based in part on foggy memories of a Wayfarer sailboat I
had owned over ten years ago. I started with 3/8th plywood which I laminated
together to create the blade. I then made the pivot out of overlapping
pieces of 3/8th inch plywood with a bolt through the middle. The friction
of these two pieces of ply rubbing against each other would, in theory,
keep the rudder blade down. I used a hickory axe handle for the tiller.
Confused? well, that is probably a good thing since a strong gust on Lake
George broke off the business end of the rudder at the swivel joint. While
watching the bottom half of my rudder drift away in the wake of my now
rudderless boat I realized that 3/8th inch plywood is probably not strong
enough for the stresses placed on it by my boat.
My second rudder was made using borrowed tools from a Lake George resort and a beautiful length of mahogany purchased at considerable expense from a local exotic wood lumberyard. This rudder was a simple raked affair that reached a below water depth of 30 inches. There was no way to raise the rudder so when I approached shore I had to take it off. Pintles and gudeons helped with this operation. This rudder was rugged enough to withstand some high winds and accompanying weatherhelm. The pocket cruiser is a beamy boat and, as the boat heels, the curve on the leeward hull digs in and wants to turn the boat towards the wind, hence the increasing weatherhelm which can get rather tiring for the helmsman and make reefing a necessity in controlling the boat.
A few sailing sessions after Lake George convinced me I needed a way to shorten the rudder for sailing in the shallower lakes near my home. The obvious and easy solution was to go with the Stevenson’s proven design. Of course, I never stick with the obvious and easy solution. I decided, with the encouragement of a lot of books about Catboats, that I wanted to make my pocket cruiser look more like a proper catboat and that meant a barn-door rudder. One advantage of the barn-door rudder is it can operate in shallow depths without the complexity of being able to kick-up.
More reading of books and internet material informed me that several
experts and armatures blamed barn door rudders for the heavy weather helm
catboats can have in high winds.
Unfortunately, this was spoken like gospel with no explanation as to why
this was the case. Bolger suggested that the problem was the amount of
water that slipped down underneath a shallow rudder, like the barn door,
rather than traveling off the trailing edge which ultimately reduced the
effectiveness of the steering surface. Bolger recommended the addition
of wings to the bottom of shallow draft rudders to redirect the water
off the trailing edge. Armed with this information, I made my barn door
rudder complete with wings made out of aluminum L channel at the bottom
of the rudder. In cross-section, my new rudder looked like an inverted
T. This rudder was 2 foot wide and extended six inches below the bottom
of the transom which led to some problems I will describe later. Below
is a diagram of the rudder including the dimensions and components—
This new barn door rudder worked well in steering the boat but the excessive weather helm was still there when the wind picked up. So, I just shrugged my shoulders and sang the mantra of the catboat sailor, “reef early and reef often.” One unintentional but incredible benefit of the barn door rudder came due to its width. Basically, it was long enough that I could scull my catboat around. So, when coming into dock, I could lower my sails and then use the rudder to bring the boat in without having to start the motor. Also, I was able to help my boat tack when loss of momentum threatened to leave me in irons. For those of you not familiar with being in irons, it is when your boat gets ‘stuck’ pointing dead into the wind. Since you have no forward momentum you can’t steer the boat to get it unstuck. However, if your boat has the equivalent of a fishtail on the back, you can help the boat through the turn.
Well, life with my new rudder wasn't all rosy. The advantage of the simplicity of a non-kick-up-rudder came with a big problem; when the boat is shallow enough the rudder can hit bottom. One incidence with a dragged anchor and a beach resulted in the weight of the boat resting on the rudder. This put pressure on the pintles and gudeons damaging both them and the transom. After fixing the damage, I once again went to the drawing board.
The simplest solution, the one I took this time, was to cut off 2 ½
inches off of the bottom. In the picture above, that would be cutting
right above the unpainted aluminum L channel. I thought this wouldn't
make a difference but my experiences sailing my boat summer of 2004 proved
me very wrong. In choppy water not enough of my rudder stayed in the water
to give me 
control.
When the wind started blowing and the boat started heeling, I found I
didn't have enough rudder to counter weather helm and control the boat.
On several occasions, some during the mega-mess, I pulled the rudder hard
over only to have the boat not turn! The boat even had bad manners in
light air. So, I learned through experimentation that you can have too
shallow of a rudder. So, I headed back to the drawing board one more time.
Before building my next rudder I sat down and contemplated everything I had experienced with and read about rudders. I came to the realization that rudders are simply levers in the water with the attachment point to the transom being the pivot point of the lever, the tiller being one arm of the lever and the rudder being the other arm of the lever. Yes, that physics class in high school was coming back to haunt me. So, pull out your thinking caps and follow along. For sake of discussion, refer to the figure shown below. The stock rudder four our boats is the deep but narrow rudder called for in the plans. The barn door shows the added length aft of the transom for the barn door rudder. As I said above, consider the attachment point of the rudder to the transom as the pivot point, the tiller as one arm, and the rudder as the other arm of the lever. With a lever you get your force by having the pivot point closer to the load and further away from the part you push down on. Basically, the longer the part you push down on is in relation to the part that lifts the load the more force you have.
Think of a seesaw for a moment. A seesaw is basically a lever but with the pivot point located right in the middle of the lever. When I go to do seesaw with my six year old I can catapult him a couple blocks away with my weight and he has no hope of raising my side of the seesaw off the ground with his weight. He would have to weigh the same as I do to be able to do that. Now, what if I take the pivot point of the seesaw and move it towards me? That will give me less leverage with my weight and gives my son more leverage with his weight. At some point, he will be able to lift my mass off the ground. If you think of energy, his side (the longer side of the seesaw) may move 3' but my side (the shorter side) will only move one third that distance. Basically, if you lift my son (who may weigh one third or less my weight) 3' you are expending the same energy as lifting my heavier body 1'.
Now, returning to the rudder. If my tiller arm is the same length as
my rudder is past the transom then I have zero leverage. As I make the
tiller longer relative to the rudder (or make the rudder stick out a
shorter distance relative to the tiller) I give myself leverage. Basically,
I am moving the pivot point towards the rudder or load bearing part of
our setup. Again, if you think of it as energy expended. The end of a
long tiller will move a much greater distance than the end of a high-aspect
narrow rudder giving the helmsman more force to counter weather helm.
Conversely, a wide barn door rudder extends much further beyond the transom
reducing the leverage of the tiller meaning you have to use more muscle
to counteract weather helm. So, in short, a narrower rudder relative to
the tiller will give you more force reducing the pull of weather helm.
That is why barn door rudders are said to increase weather helm, though
they aren't really increasing weather helm, just reducing the leverage
you have to fight weather helm.
Now Pat Mellema, in an effort to reduce apparent weather helm on his weekender, experimented with a balanced rudder. Again, refer to the figure below. The stock weekender rudder, as well as my barn door rudder, both have the pivot point at the leading edge of the rudder. This means that when we push the rudder right, the mass and force of the water rushing past the rudder wants to push the rudder to center resisting the turn. If the boat wants to turn, in the case of weather helm, the water will rush past the rudder making it want to turn as well. Thus, we feel resistance in the tiller and/or have to pull the tiller over a bit from center to resist weather helm. With a balanced (or semi-balanced rudder) part of the rudder extends past the pivot point. So, when we turn the aft part of the rudder right the forward part of the rudder goes left. The water rushing past puts pressure on the right side of the rudder aft of the pivot point and on the left side of the rudder forward of the pivot point. Basically, the part of the rudder forward of the pivot point assists the helmsman. Pat said he had fingertip control on his tiller regardless of the amount of wind.
Now that the theory was in place it was time to put it in practice by
making a new rudder. I decided to make a kick up rudder this time to enable
easy and damage free beaching. I also decided to make the extension drop
down like a dagger board (see chart below) rather than pivot down primarily
because the aspect of the rudder wouldn’t change even if I had the
extension only partially dropped. 
Well,
this decision proved to be a disaster. First, it took me three tries to
get a workable barn door upper part of the rudder. Once I finished this
and started playing with the extension I found that I couldn’t keep
it from getting off-track and jammed. So, I threw up my hands and (temporarily)
gave up on the idea of a kick up rudder.
With the Erie fleet Pymatuning outing only a week away I decided to experiment with shape by making a new fixed barn door type rudder. My first requirement was to make the rudder deeper than my current not-very-functional barn door rudder. My second requirement was to make the rudder a bit narrower so I would have more leverage with the tiller. My final requirement was to somehow add a balancing component to the rudder so that I could turn the force of the water into a tool to resist weather helm with. So, I came up with the rudder you see in these pictures complete with wings on the bottom to help with the flow of the water and to protect the vulnerable plywood if and when a grounding would occur. The bit of the rudder that is under the keel made taking the rudder off and putting it on a bit difficult but the solution was to make it stand off from the keel by an inch and to turn the rudder when putting it in. Of course, the downside to this design is a lot of vulnerable rudder extends beyond the bottom of the keel.
I glassed my new rudder on Thursday, put all the hardware on it Friday morning, and headed off to meet the other Erie fleet folks at Pymatuning with my new unpainted experimental rudder. I did also stick my old barn door rudder in the boat just in case. Friday night we launched our boats but I didn’t get a good test of my rudder due to absence of any wind. We did have an enjoyable time admiring the water, stars, and full moon out that night. Saturday, we sailed for six hours and I went out for a wonderful evening sail with Bushfire Bob.
However, the true test of my new rudder came on Sunday with a steady
wind blowing rather brisk at times combined with some moderate wind-driven
waves. Prior to this new rudder I would have to let out my sail on the
gusts or contemplate putting a reef in my sail in order to keep my arm
from being pulled out of my socket. Anytime the boat heeled weather helm
put a lot of pressure on the tiller making me feel like I was on the edge
of loosing control. This sensation was worse when heading downwind on
a reach since I was unable to let out the sail to spill wind. With this
new rudder, however, I felt I had perfect control of the boat in all conditions
giving me the desire and the ability to push her for all she is worth.
The rudder has a nice balanced feel and the tiller requires very little
force 
to
turn the rudder regardless of the wind conditions and\or the heel of the
boat. In fact, I sheeted in and had my pocket cruiser heeled over at a
greater angle than I ever before during this sail just for the fun of
it. Complete feeling of control throughout the whole sail! I just can’t
describe with any accuracy the difference the rudder made in the sailing
characteristics of the whole boat; it was like having a brand new boat!
The design of the rudder was able to overcome many of the annoying sailing
characteristics I had ascribed to the beamy hull of the Pocket Cruiser
that I thought were previously incurable and gave me a wonderful sailing
sensation as well as the ability to point higher than I ever had before.
The final measure of my happiness with the change is the grin on my face
right now as I remember the wonderful sailing sensations. What a difference
a rudder makes!
My newest and, by far, best rudder!
Back Yard Yacht Builders
A non-commercial association of amateur boat-builder enthusiasts.
All our wooden boats are Stevenson designs.