Fair existing rudder?

[ebb]

Experience tells us that covering planks with frp is not a good method. Water will still
get in and the encapsulation will delaminate because solid wood expands & contracts.

Some wise guy will come along and tell you that if you really soak the old DRY wood
with multiple coats of laminating epoxy and then cover the result with 3 or four layers
of 8 or 10 oz woven glass -- stapled on with monel staples -- you may have a chance
for success. You might have to take a wrap or two around the shaft with the cloth,
and you have very little room to make that possible -- but somebody's probably done
it! You are attempting to immobilized a system that has swelled and shrank a 1000
times before.

You will be adding, depending on technique, considerable extra weight and thickness.
You have to add enough glass to cancel the swelling of the wood. This may not actually
work. That's why you have to staple the cloth to the wood, this also may not be enough.
Getting the epoxy to grab onto the old wood is a problem. You will have to depend on
the shell you are creating. You'll need good epoxy, good technique, and there's always
the possibility that the rudder blade will just not like what you are doing to it!

Epoxy isn't the wonder cure-all plastic its cracked up to be. Imco there a 50-50 chance
you'll have trouble with it living under water as part of a plank rudder, and that's having
good luck on your side.

A dried out rudder looks a lot worse than one that is fresh out of the water. All it needs
is a good soaking to swell planks and cracks closed again. A rudder can be renewed by
cleaning and a little sanding, if dry some one part primer coats and bottom paint.
Fair, no plastic.


Success with depend on the condition of the rudder parts you are encapsulating.
Covering rudder won't fix mechanical problems with old age. In the Manual,
in Section E, pg170, we have a drawing of the A/C rudder with dimensions. In the
short list of 'NOTES', it reveals that the original rudder stock (shaft) was "MADE OF
NAVAL BRONZE". Naval bronze is actually naval brass. It is a 40% zinc alloy.
This alloy self destructs in the right conditions, the zinc acting as anode to cathodic
copper, in saltwater electrolyte. Corrodes and becomes porous. Manual warns this
happens to the stock around the waterline inside the rudder tube, where it cannot
be seen unless you drop the rudder.
Page 170 rudder drawing does not show the strap gudgeon in the middle of the
lower half of the stock. It cannot be left out of a fully realized rudder. Grounding
can lift the rudder out of its heel socket -- the gudgeon acts as a guide, insures that
the shaft will reseat itself.

Silicone bronze will probably last 4000 years in your boat. And since all available bronze
fasteners, allthread and rod happen to be 600 series silicon, there can be no galvanic
metal corrosion in an immersed rudder put together with this incredible durable stuff.

It's possible that a new rudder, that includes bronze, epoxy and fabric, is in your future.

There are as many ways to fabricate a new rudder as there are owners. Because of
experience, rudder dimensions, and materials, imco there are criteria we have to stay
within keeping the bronze shaft. Which so far, almost everybody seems to have done*.
Other materials like stainless steel are verboten for underwater use. I would also stay
away from manganese bronze which has 25% zinc in it. It's a handsome bronze for
on-deck yacht fittings.

IN CASE YOU WANT A NEW RUDDER
One inch diameter 655 silicon bronze rod is readily available and not too expensive. 655
bronze sheet for welding gussets is harder to find. You can design your new rudder to
use smaller diameter rod (like the original bolts & screws) to hold the blade rigidly to the
shaft, but instead of solid wood planks use marine ply, and/or pvc foam, and frp. It's
possible to make a composite rudder with a full length shaft without a prop cutout -- and
maybe possible to include the prop cutout without having to bend the shaft you see in the
original, essentially by simply leaving a 16" length of 1" rod (3lbsft) out of the middle of
the 6' shaft. Depends on quality of materials and design. Haven't done this myself, and
will not leave the dogleg out on a no-fiberglass new 3-plank mahogany rudder.

You'll have the rudder stock prepared by a machineshop, who will reduce the diameter
of the bottom end to seat in the heel fitting, cut in a keyway up top for the tillerhead,
and precisely make blind threaded holes** along the shaft at various locations for the
smaller diameter rods that join the blade to the shaft.
** not to push your design, let's say ebb's suggestion here is that 3/8" 655 allthread is
a less expensive way to sub for the original bolts and screws noted on page 170 in the
ArielAssociation Manual. It's my opinion that blind 3/8-16 holes in the 1" bronze stock
positioned of course on the blade side are less likely to weaken the shaft, and are
protected by the composite construction of a Meranti ply and epoxy/glass rudder blade.
Built this way the rudder can not be taken apart... but imco easier to maintain!
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~

*There is a 22page thread here in the archive called rudder discussions.
It is the best thread you'll ever find that talks exclusively about our A/C rudder.
Answers all your questions -- you'll meet a whole bunch of folks in the same boat as you.
HOW TO GET THERE
Currently you'll find 'rudder discussions' near the top of the sticky list of threads on the
lead page of theTechnical section.... DIVE IN!