> Judy
>
> You've brought up another problem that is significant to Potters---broken
> rudders. With P-15 rudders (and maybe P-19 rudders, too; I don't know) they
> tend to break when water gets into the plywood cheeks of the rudder head
> where the pivot bolt goes through the rudder head and the rudder blade
itself.
> Even though the outside of the rudder head is kept varnished, water can
get
> into the plys along the pivot bolt.
>
> When I purchased my gunter it came with a broken rudder. A friend
> fabricated a new rudder head and blade for me out of marine plywood and WEST
> epoxy. I bought bronze bushings to fit the thickness of the plywood and
> overbored the hole in the rudder head and the rudder blade. Then I took an
> elliptical rasp (on an electric drill) and made the holes bigger in the
> interior of each piece of wood. Then I epoxied the bushings into the rudder
> pieces so that the bolt will turn in the bushing and the epoxy will seal the
> bushing into the plywood. So far, it has worked.
>
> Someone else on the Potter web (this is all in the archives a couple of
> years ago) suggested that the pivot bolt hole in the rudder pieces should be
> overbored and the complete hole filled with epoxy, which is then allowed to
> cure. Then bore the pivot hole out to fit the bolt, which would be in an
> epoxy bushing.
>
> It would be better to make this modification, whichever variation you
choose,
> before the plys get saturated with water and the whole assembly is
weakened.
Hi Tom,
When I think about it, it's easy to see that your idea has a lot of merit. I
think the idea of a bushing makes perfectly good sense. The advantage, which
you point out, is that this would prevent deterioration of the water barrier
inside the hole, with the bushing taking the wear-and-tear.
It made me think about other rudders I have disassembled. I copied the design
of the kick-up design of the one piece rudder on a Laser when I built a dinghy
for my daughter to learn to sail in. The laser rudder has a nylon bushing
(available at any hardware store in different diameters) in the hole for the
pivot. When the nylon bushing gets worn, you just push it out and replace it.
The thru bolt holds it in place.
With a design like that, you could put a water barrier coating inside the
oversized hole and expect years of service without problems.
I like the idea of using nylon rather than metal for the bushing for at least
two reasons. First, there's a large difference in the expansion coefficients
between the wood of the rudder blade and the metal. This might be a problem
*if* your design depends on firmly bonding the metal bushing to the wood. The
bushing would break away from its bond when it expanded and contracted with
swings in temperature.
The other problem with the rudders is that you point out they're made of
plywood, which brings up a whole slew of special design considerations in a
marine environment. Even marine grade plywood. Water seeps in through dings
in the moisture barrier and separates the laminates. The dings you can hardly
even see will do your rudder in.
I would start by considering the following solution: coating the whole rudder
blade in an epoxy moisture barrier, and THEN wrap the whole thing in at least
two layers of glass to protect the underlying moisture barrier. My high-tech
friends would probably use kevlar cloth rather than glass cloth to make the
rudder bullet proof (literally). There may be other solutions better than
wrapping it in glass, but that's the best I have to offer.
One other important point as I think about this is the whole issue of
repairing stressed wood and the causes of failure of the part. There are
several dimensions to this problem. One about the materials chosen for the
part (wood, either laminated or solid), and the second is about the mechanical
design of the rudder itself and the physics of sailing (aha! now we can talk
about sailing <grin>).
On materials: If the rudder blade is failing, then its structural integrity
is already compromised, even if it hasn't broken completely yet. Any repair
you to the failed part had better take care strengthening not only the
immediate area, but also the surrounding area. The ideas we've been
discussing go a long way towards arriving at a solution to this problem.
On mechanical design: I don't know much about the design of the P14/15
rudder, but I gather it pivots around a single bolt like the rudder on the P19
I own. Weather helm puts a lot of stress on the rudder and tiller. Extreme
weather helm can break a brand new tiller (ask Maurice about that!) and I
imagine it can break a weakened point on a rudder blade as well.
So part of the responsibility for tiller/rudder failure is on the sailor. The
old saw of "reef when you first think of it, don't wait until it's too late"
applies to exactly this sort of situation. If you don't trim your sails to
reduce their power (outhaul, cunningham, vang, backstay and finally putting in
a reef or whatever means you have at your command) or change your course when
you should, you are stressing the rudder. Over time, the wood weakens,
finally failing at exactly the worst possible moment.
If you're wrestling with your tiller like a pro-wrestler on TV, working up a
sweat, and heeling way over, you need to change how your boat is trimmed.
Heeling and weather helm go hand-in-hand.
If you're a big strong guy, saw a foot or two off your tiller so you can't put
enough leverage on the tiller to break it. This is pretty drastic, I know,
but I'm a little more than *half* serious about this. (Being a 110 pound woman
has its advantages when it comes to learning to sail. You males can cover your
mistakes with brute force, I have to use my brains <grin>) This will force
you to sail according to what the wind demands, not your own preconceived
notion about how it ought to work. Hold the tiller with two fingers, thumb
and index, whenever possible and your boat will tell you when it wants you to
change something on the trim.
There's a delightful book _First You Have to Row a Little Boat_ by Richard
bode, about a boy learning to sail and the practical and philosophical lessons
he learns in the process. There's an episode where "The Captain" saws his
tiller in half without so much as a "by your leave" and simply says by way of
explanation "it was too long anyway." Then he teaches the boy sail with just
two fingers on the tiller. You don't have to actually saw your tiller in half
to be a better sailor ... but you get the idea.
Judith Blumhorst, DC
HMS18/P19 Fleet Captain, Potters Yachters
WWP-19 #266 "Red Wing"
SF Bay, CA