Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 05-12-2013, 14:44   #16
cruiser

Join Date: May 2007
Location: Brisbane AUS
Boat: Cowther 43 - Hunter 40.5
Posts: 1,006
Re: Stainless Rudder Stock Needs Replacing In Foam Core Rudder?

Quote:
Originally Posted by minaret View Post
No Sawzall needed, just use a cutting disc to split it open. It's easy, I've done many.

Believe me, a solid shaft is not overkill. That thin walled pipe was never OK, and you wouldn't be here now if they'd built it right in the first place. Solid shafts are standard on boats of any degree of quality. Tab welds also tend to fail much faster on material like this.


Silicon bronze would be a poor choice of material, too soft and easy to bend.
Solid shafts I am sure are standard on many boats, but are they 87mm in diameter on a 40 foot boat? I would rather loose the rudder than rip the ass end of the boat off when hitting a large unmovable object. The corrosion started on the outside. Does corrosion suddenly not appear if the shaft is solid?
__________________

__________________
dennisail is offline   Reply With Quote
Old 05-12-2013, 14:46   #17
cruiser

Join Date: May 2007
Location: Brisbane AUS
Boat: Cowther 43 - Hunter 40.5
Posts: 1,006
Re: Stainless Rudder Stock Needs Replacing In Foam Core Rudder?

Thanks Ann. Will do.
__________________

__________________
dennisail is offline   Reply With Quote
Old 05-12-2013, 14:49   #18
Senior Cruiser

Cruisers Forum Supporter

Join Date: Nov 2005
Location: Tasmania
Boat: VandeStadt IOR 40' - Insatiable
Posts: 2,317
Images: 91
Re: Stainless Rudder Stock Needs Replacing In Foam Core Rudder?

If it were my decision, I'd be building a new rudder entirely. I'd use a duplex stainless (Aquamet 22, or maybe 2205) rather than 316.
__________________
Weyalan is offline   Reply With Quote
Old 05-12-2013, 15:13   #19
cruiser

Join Date: May 2007
Location: Brisbane AUS
Boat: Cowther 43 - Hunter 40.5
Posts: 1,006
Re: Stainless Rudder Stock Needs Replacing In Foam Core Rudder?

Do you have any links to data that compares 2205 to 316? I am not finding that much which is easy to interpret.

From these links it seems superior in every way. Corrosion resistance is MUCH better and it is stronger.

Grade 2205 for High Corrosion Resistance and Strength

Stainless Steel - Grade 316 (UNS S31600)

http://www.ljstar.com/technical/pdf/...05over316L.pdf
__________________
dennisail is offline   Reply With Quote
Old 05-12-2013, 15:26   #20
Marine Service Provider

Join Date: Sep 2008
Location: Victoria B.C.
Boat: CS27
Posts: 1,349
Re: Stainless Rudder Stock Needs Replacing In Foam Core Rudder?

Quote:
Originally Posted by dennisail View Post
Solid shafts I am sure are standard on many boats, but are they 87mm in diameter on a 40 foot boat? I would rather loose the rudder than rip the ass end of the boat off when hitting a large unmovable object. The corrosion started on the outside. Does corrosion suddenly not appear if the shaft is solid?
Corrosion will still appear, assuming the same alloy is used. But the amount of corrosion that will allow a hollow shaft to break is not an issue on a solid shaft as there is so much more meat there in the first place.
__________________
mitiempo is offline   Reply With Quote
Old 05-12-2013, 16:37   #21
Senior Cruiser

Cruisers Forum Supporter

Join Date: Nov 2005
Location: Tasmania
Boat: VandeStadt IOR 40' - Insatiable
Posts: 2,317
Images: 91
Re: Stainless Rudder Stock Needs Replacing In Foam Core Rudder?

The reason I suggest replacing the rudder completely is based on an interesting experience we had with our yacht a few years ago:

Competing in a 300 nutical mile offshore race, our rudder snapped off, about 200 miles into the race, in less than ideal circumstances (not that losing a rudder is ever "ideal").

We had pulled the rudder out of the boat prior to the race and had it inspected by a local well-respected shipwright. The rudder shaft looked absolutely fine. When the rudder broke, the shaft snapped about 75mm (3") inside the blade. It was obvious from the stump of the shaft that there was quite extensive corrosion and damage to the shaft inside the rudder blade, even though the exposed part of the shaft looked fine. Hence my recommendation to replace the whole shooting match.

Duplex 2205 is quite a bit more expensive than 316, but in the total cost of a new rudder, the material cost is relatively insignificant.

I replaced the prop shaft on our boat a few years back - again I changed from 316 to 2205.
__________________
Weyalan is offline   Reply With Quote
Old 05-12-2013, 20:02   #22
Resin Head
 
minaret's Avatar

Cruisers Forum Supporter

Join Date: Aug 2007
Location: Seattle WA
Boat: Nauticat
Posts: 6,848
Images: 52
Re: Stainless Rudder Stock Needs Replacing In Foam Core Rudder?

Quote:
Originally Posted by mitiempo View Post
Corrosion will still appear, assuming the same alloy is used. But the amount of corrosion that will allow a hollow shaft to break is not an issue on a solid shaft as there is so much more meat there in the first place.


And, a hollow tube is subject to buckling; solid shafts are not. This means a solid shaft will take orders of magnitude more force to fail, and when it does fail (barring corrosion), it will bend. A tube will not bend much at all, instead it will buckle. Failure will occur much, much sooner, and in a far more catastrophic way. Totally unacceptable build method for an offshore boat. Just take a piece of bar and bend it till failure (you will have to twist it in loops), then take a larger piece of tube and bend it till failure. The difference will be blatantly obvious.
__________________
O you who turn the wheel and look to windward,

Consider Phlebas, who was once handsome and tall as you.
minaret is online now   Reply With Quote
Old 05-12-2013, 20:16   #23
cruiser

Join Date: May 2007
Location: Brisbane AUS
Boat: Cowther 43 - Hunter 40.5
Posts: 1,006
Re: Stainless Rudder Stock Needs Replacing In Foam Core Rudder?

Minaret, you are right of course. When you compare stocks of the same diameter. If the tube is made with a much larger diameter as mine is, the size makes up for the fact it is not solid. A tube is stronger than a solid round bar of the same weight, so a tube can therefore be made lighter at the same strength if it has a larger diameter.

Weyalan. The whole shaft would be replaced, so what happened to you could not happen to me even if I rebuilt the rudder.
__________________
dennisail is offline   Reply With Quote
Old 05-12-2013, 20:22   #24
Resin Head
 
minaret's Avatar

Cruisers Forum Supporter

Join Date: Aug 2007
Location: Seattle WA
Boat: Nauticat
Posts: 6,848
Images: 52
Re: Stainless Rudder Stock Needs Replacing In Foam Core Rudder?

Quote:
Originally Posted by dennisail View Post
Minaret, you are right of course. When you compare stocks of the same diameter. If the tube is made with a much larger diameter as mine is, the size makes up for the fact it is not solid. A tube is stronger than a solid round bar of the same weight, so a tube can therefore be made lighter at the same strength if it has a larger diameter.

Weyalan. The whole shaft would be replaced, so what happened to you could not happen to me even if I rebuilt the rudder.



Choose to believe what you like. All I know is that solid 3" rudder shafts are quite common in your size range. A thin walled 3 1/2" tube isn't even in the same ballpark.
__________________
O you who turn the wheel and look to windward,

Consider Phlebas, who was once handsome and tall as you.
minaret is online now   Reply With Quote
Old 05-12-2013, 20:27   #25
cruiser

Join Date: May 2007
Location: Brisbane AUS
Boat: Cowther 43 - Hunter 40.5
Posts: 1,006
Re: Stainless Rudder Stock Needs Replacing In Foam Core Rudder?

Thanks Minaret, your opinion has been noted. Whole yachts made fully of metal are also common in my size range.
__________________
dennisail is offline   Reply With Quote
Old 05-12-2013, 20:35   #26
Marine Service Provider

Join Date: Sep 2008
Location: Victoria B.C.
Boat: CS27
Posts: 1,349
Re: Stainless Rudder Stock Needs Replacing In Foam Core Rudder?

Quote:
Originally Posted by dennisail View Post
Thanks Minaret, your opinion has been noted. Whole yachts made fully of metal are also common in my size range.
True, but most often with solid rudder shafts.
__________________
mitiempo is offline   Reply With Quote
Old 05-12-2013, 20:42   #27
Senior Cruiser

Cruisers Forum Supporter

Join Date: Nov 2005
Location: Tasmania
Boat: VandeStadt IOR 40' - Insatiable
Posts: 2,317
Images: 91
Re: Stainless Rudder Stock Needs Replacing In Foam Core Rudder?

When we had our new rudder built, the naval architect we consulted told us that we should definitely use solid round bar, not tube.
__________________
Weyalan is offline   Reply With Quote
Old 05-12-2013, 20:49   #28
Registered User

Join Date: Feb 2008
Location: Kauai, Hawaii
Posts: 44
Re: Stainless Rudder Stock Needs Replacing In Foam Core Rudder?

If it were me I'd use a Fein tool to split the fiberglass shells apart, and then a sawzall to work the foam inside. Much more control with the Fein tool. I'd use schedule 80 316 stainless pipe for the shaft, it has a thicker wall. The Aquamet 22 is a great choice if you do not have to weld to it. Be sure to use only epoxy to put it back together, and be sure to glass at least the leading edge with 17oz biax or similar. Be good to go!
__________________
drewke07 is offline   Reply With Quote
Old 05-12-2013, 20:58   #29
cruiser

Join Date: May 2007
Location: Brisbane AUS
Boat: Cowther 43 - Hunter 40.5
Posts: 1,006
Re: Stainless Rudder Stock Needs Replacing In Foam Core Rudder?

Quote:
Originally Posted by Weyalan View Post
When we had our new rudder built, the naval architect we consulted told us that we should definitely use solid round bar, not tube.
What are the dimensions of your rudder and rudder stock? Was the old stock tube or solid.
__________________
dennisail is offline   Reply With Quote
Old 05-12-2013, 20:59   #30
cruiser

Join Date: May 2007
Location: Brisbane AUS
Boat: Cowther 43 - Hunter 40.5
Posts: 1,006
Re: Stainless Rudder Stock Needs Replacing In Foam Core Rudder?

Quote:
Originally Posted by mitiempo View Post
True, but most often with solid rudder shafts.
Makes sense to me. But I dont need a shaft 10 times as strong as the rear of my boat which will lead to sinking if I hit something big.
__________________

__________________
dennisail is offline   Reply With Quote
Reply

Tags
core, rudder

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 19:49.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.