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Rudders are not isolated
sickleave
#1 Posted : Sunday, June 07, 2009 11:41:49 AM(UTC)
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What happens if your rudders are not isolated (Stainless Steel).
They are sealed and painted with bottom paint, except for surface under the piece of Aluminum Anode on each, which is working.
Shafts on Rudders is bare where they go up through boat bottom.
I have new bronz or brass packing glands but they are isolated with Rubber Hose.
They are proably grounded through the steering cable.
What does this do to charge on hull, I have always been low, but anodes are working and no signs of crosion (other than all Anodes).
I have some extra pieces of anodes on trim tabs (some magnesium).
With the extra Magnesium on boat the Aluminum does not react as fast.
No matter how clean Anodes are I never get above .6 or .7 volts.
Gauge has been Calabrated, I put in a known Voltage from a Calabrated Source.
Drive Shafts are isolated.
SICK LEAVE, Bob
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Barkleydave
#2 Posted : Monday, June 08, 2009 12:07:54 AM(UTC)
Barkleydave

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Bob,

A couple of points.
1. Since you are in the GL and the water is fresh and cool galvanic corrosion will be less than in warm high sediment, bracish or salt water. Your readings will tend to be lower in fresh than salt.

2. The non-isolated rudders will defelt your readings down and will add the disimular metal to the bonding grid.

3. Since your rudders have a strong barrier coat there is very little SS surface area exposed to electron transfer.
If your rudder coatings fail then your readings will drop further (often rapidly) and will expose your rudders will become anodes.

4. Your packing glands are isolated to some extent. Since the bronze glands may be grounded through the steering cable the effect would be minimum if any since they are not submerged. I would pay attention at the point of any bronze to SS contacts for evidence of corrosion.

Since you haul every fall and have not observed corrosion of the hull..in my opinion I would not be concerned.

safe boating,
dave

None
sickleave
#3 Posted : Saturday, June 20, 2009 4:25:28 PM(UTC)
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Thanks I will try to isolate them. This may be reason for low reading
I had low reading when rudders were steel and same since I changed ti Stainless Steel
SICK LEAVE / Bob
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