Reply
 
Thread Tools Display Modes
 
Old 10-31-2015, 09:00 AM   #1
Guru
 
angus99's Avatar
 
City: Signal Mtn., TN
Country: US
Vessel Name: Stella Maris
Vessel Model: Defever 44
Join Date: Feb 2012
Posts: 1,385
Angry Pitted Rudder Shafts

I bit the bullet and had the yard remove and clean up the steering gear. There are no signs that water has ever leaked past the packing, but there had been leaks at the base of the bronze shaft logs, which had been "fixed" with a filet of caulk around the joint between the flange and hull, visible in the first two photos below. That kept the water out but obviously did not solve the problem. Miraculously, there is no rot in the wood reinforcing the hull penetrations and most of the gear cleaned up beautifully after bead blasting. That's the good news.

The bad news is some significant pitting on the steering shafts as you can see from the lower photos. I'd appreciate any knowledgeable recommendations about my options. It looks awful, but these are very robust shafts. I don't want to lose a rudder, but is that what I'd be risking if I have them reinstalled as is?

If I opt to get them fixed, is a prop shop the best option? Can anyone recommend a good shop in the northern Chesapeake who does this work well? (I'm not even going to ask about cost.).









__________________
Advertisement

angus99 is offline   Reply With Quote
Old 10-31-2015, 09:38 AM   #2
Veteran Member
 
City: New Bedford, MA.
Country: USA
Join Date: Oct 2015
Posts: 55
shaft repair

You have a simple shaft repair there. Being that the shafts are bolted to the rudders and easily removed, it is a Shaft repair, not a rudder repair. The shafts also seem to appear to be of sufficient mass to allow removal of the damaged area , build up , and machining. The mass works to your benefit as the larger mass will lessen the effect of heat input. Sorry don't know any shops in your area. TurnWright on Cape Cod could certainly do it. " I'm not affiliated with TurnWright, Although he did build the shaft and rudder on my Nauset".
Attached Images
 
__________________

Gurryman is offline   Reply With Quote
Old 10-31-2015, 09:38 AM   #3
Senior Member
 
City: louisiana
Country: usa
Join Date: Aug 2014
Posts: 207
That certainly is more than surface pitting. I would be concerned that corrosion has occured between grain boundaries well beneath the surface. You would have to have a machinist turn down the shaft, build up, machine down the shafts. I would suspect the cost of fabricating new shafts (that will not be suspect in the future) may be in the range of a questionable repair. If you are in Penn. you will likely be able to find an oilfield machine shop that will take on the job for a very fair price as they are looking for anykind of work to keep their crews employed. I would certainly get a few bids on new builds.
rardoin is offline   Reply With Quote
Old 10-31-2015, 11:00 AM   #4
Guru
 
Phil Fill's Avatar
 
City: Everett Wa
Country: US
Vessel Name: Eagle
Vessel Model: Roughwater 58 pilot house
Join Date: Oct 2007
Posts: 2,919
The pitting might be caused by galvanic action beteen the bronze and SS over time. So might want to added a bonding wire to the ruder shaft or a shaft zinc. Ss is rated less than bronze or brass. As for a repair might just use an epoxy to smooth out the area and check it next time you pull.
Phil Fill is offline   Reply With Quote
Old 10-31-2015, 06:34 PM   #5
Guru
 
angus99's Avatar
 
City: Signal Mtn., TN
Country: US
Vessel Name: Stella Maris
Vessel Model: Defever 44
Join Date: Feb 2012
Posts: 1,385
Thanks for the replies. I got to see them for the first time this afternoon and no way are they going back on the boat as they are. The yard is investigating different techniques, including sleeving and "spraying" steel on them and machining back to original specs. They said new ones would be $800-900 each.
angus99 is offline   Reply With Quote
Old 10-31-2015, 06:47 PM   #6
Guru
 
City: Sydney
Country: Australia
Join Date: Jul 2015
Posts: 1,352
Quote:
Originally Posted by angus99 View Post
Thanks for the replies. I got to see them for the first time this afternoon and no way are they going back on the boat as they are. The yard is investigating different techniques, including sleeving and "spraying" steel on them and machining back to original specs. They said new ones would be $800-900 each.


Ask about hard chrome and grind to build the shafts up .I personally don't like steel spraying as it can delaminate when ever it want to .
gaston is offline   Reply With Quote
Old 10-31-2015, 07:04 PM   #7
Guru
 
psneeld's Avatar
 
City: Avalon, NJ
Country: USA
Vessel Name: Freedom
Vessel Model: Albin 40
Join Date: Oct 2011
Posts: 15,913
Had the best marine machine shop in the Cape May, NJ area (home to large sporty fleet and commercial vessels) flame spray my shaft 4 years ago.


3 round trips to FLA and back, 3 years r in salt water and all seems fine, Just repacked the stuffing box...shaft seemed fine and packing looked great.
psneeld is offline   Reply With Quote
Old 10-31-2015, 07:05 PM   #8
Veteran Member
 
City: New Bedford, MA.
Country: USA
Join Date: Oct 2015
Posts: 55
"The Yard" is going to charge you double what ever they spend to repair them. Send photos and shaft dimensions to Keith Fenner at TurnWright, He will be able to give you a fairly good idea what a repair would cost. These are not high speed shafts and not a difficult repair.

What is the shaft diameter?
Gurryman is offline   Reply With Quote
Old 10-31-2015, 07:42 PM   #9
Guru
 
boatpoker's Avatar
 
City: Port Credit
Country: Ontario
Vessel Name: DIRT FREE
Vessel Model: Benford Fantail 38
Join Date: Sep 2012
Posts: 2,011
It is unlikely this kind of corrosion could be galvanic, more likely stray current. Get your electrical system checked by an ABYC Certified Corrosion Analyst.

CORROSION PHOTO ALBUM - Take a look at the photo in the far right column, 9th row. It is an x-ray of a 1mm pit on the surface of a prop shaft ,inside the shaft was a 1.5cm cavity. Sorry, IMHO your shafts are done.

PS. I am an ABYC Certified Corrosion Analyst.
__________________
If you can live with the consequences, go for it - wg
Y'am what I y'am an' thats' all that y'am - Popeye
As God is my witness, I thought turkey's could fly. Mr.C
boatpoker is offline   Reply With Quote
Old 10-31-2015, 08:23 PM   #10
Guru
 
psneeld's Avatar
 
City: Avalon, NJ
Country: USA
Vessel Name: Freedom
Vessel Model: Albin 40
Join Date: Oct 2011
Posts: 15,913
Quote:
Originally Posted by boatpoker View Post
It is unlikely this kind of corrosion could be galvanic, more likely stray current. Get your electrical system checked by an ABYC Certified Corrosion Analyst.

CORROSION PHOTO ALBUM - Take a look at the photo in the far right column, 9th row. It is an x-ray of a 1mm pit on the surface of a prop shaft ,inside the shaft was a 1.5cm cavity. Sorry, IMHO your shafts are done.

PS. I am an ABYC Certified Corrosion Analyst.
Sure it's not just crevice corrosion from stagnant water under the packing?

pic courtesy of Cox Engineering.


It does look pretty bad either way, Rudder shafts? If the shop could either x-ray or turn to good metal...but then the cost of new may not be much further. Prop shafts...probably new is the deal unless those could definitely be x-rayed and certified. Unless the shop has different techniques I'm not familiar with.
Attached Thumbnails
Click image for larger version

Name:	P1010966.jpg
Views:	105
Size:	54.9 KB
ID:	46127  
psneeld is offline   Reply With Quote
Old 10-31-2015, 09:14 PM   #11
Guru
 
Capt.Bill11's Avatar
 
City: Sarasota/Ft. Lauderdale
Country: USA
Join Date: Apr 2014
Posts: 5,422
Quote:
Originally Posted by psneeld View Post
Sure it's not just crevice corrosion from stagnant water under the packing?
+1

And I bet they are repairable.

http://highseasyachtservice.com/wp-c...Corrosion1.pdf

Of course since they're rudder shafts they would probably go another 10-20 years as is.
Capt.Bill11 is offline   Reply With Quote
Old 10-31-2015, 09:47 PM   #12
Guru
 
angus99's Avatar
 
City: Signal Mtn., TN
Country: US
Vessel Name: Stella Maris
Vessel Model: Defever 44
Join Date: Feb 2012
Posts: 1,385
Thanks, again, guys. I'll get a proper hands-on evaluation, x-Ray or whatever it takes before deciding to repair or replace.

Gurryman, I appreciate the lead. Will probably give Turnwright a call Monday. The shaft is 2.75" in diameter.

Wallace, in rereading my survey, the stbd rudder assembly had no attachment to the bonding system and the port assembly had excessive resistance. I haven't verified it with the yard yet, but I'm betting the stbd post is the one with the worst corrosion. Most of the damage is confined to the area that would have been in the packing gland--in constant contact with salt water and, I assume, no oxygen. On the other hand, the zincs on both rudders are eroding at about the same rate. The galvanic isolator was checked during the survey and reportedly OK.
angus99 is offline   Reply With Quote
Old 10-31-2015, 10:10 PM   #13
Guru
 
boatpoker's Avatar
 
City: Port Credit
Country: Ontario
Vessel Name: DIRT FREE
Vessel Model: Benford Fantail 38
Join Date: Sep 2012
Posts: 2,011
Quote:
Originally Posted by psneeld View Post
Sure it's not just crevice corrosion from stagnant water under the packing?
I agree that is possible but only if the boat sat for years without the shaft moving thereby allowing stagnant water to be held against the shaft.
Either way it's not repairable in my opinion.

If you look at the photo immediately to the left of the x-ray photo you'll see that it is of a broken shaft. The shaft broke from crevice corrosion when the boat was moved for the first time on over 10years. Take a look at the pitting on the unbroken part, it is less severe than the OP's
__________________
If you can live with the consequences, go for it - wg
Y'am what I y'am an' thats' all that y'am - Popeye
As God is my witness, I thought turkey's could fly. Mr.C
boatpoker is offline   Reply With Quote
Old 10-31-2015, 10:26 PM   #14
Guru
 
cappy208's Avatar
 
City: Cape Cod
Country: USA
Vessel Name: Slip Aweigh
Vessel Model: Prairie 29
Join Date: Oct 2013
Posts: 1,131
Reading your posts it appears you have twin screw. If so then you have another rudder to get home on. So do the flash, replate and machine. But remember that this issue is cumulative and will require full repair soon.
cappy208 is offline   Reply With Quote
Old 11-01-2015, 12:38 AM   #15
Guru
 
Capt.Bill11's Avatar
 
City: Sarasota/Ft. Lauderdale
Country: USA
Join Date: Apr 2014
Posts: 5,422
Quote:
Originally Posted by cappy208 View Post
Reading your posts it appears you have twin screw. If so then you have another rudder to get home on. So do the flash, replate and machine. But remember that this issue is cumulative and will require full repair soon.
Heck, on a twin screw boat they could both fall off and you could get to a dock just fine.
Capt.Bill11 is offline   Reply With Quote
Old 11-01-2015, 01:28 AM   #16
Guru
 
Northern Spy's Avatar
 
City: Powell River, BC
Country: Canada
Vessel Name: Northern Spy
Vessel Model: Nordic Tug 26
Join Date: Feb 2012
Posts: 2,668
Looks like regular old pitting corrosion (as much as one can tell from a photo). Here is what would generally be required to repair each shaft.

Remove shaft from rudder. Chuck shaft up in lathe. Skim cut material away from corroded area, until defect is visually gone. (More you remove, the more weld you have to deposit). 0.125-0.200" will probably clean it up. If machinist goes more than SAY 0.250-0.300" consider machining new shafts. Be sure to chamfer or radius transition. Conduct Liquid Penetrant Inspection (LPI) of affected area to check for cracks or pits. Skim cut again if required. Weld metal build up with GTAW (tig), distributing heat evenly. Ensure weld cap is adequately proud to nominal diameter. Machine back to a few thou above nominal. Buff with emory and crocus cloth to nominal, achieving a finish of around 4 micro" Ra. LPI final repair to check for indications.

The tough part is picking the filler material for the weld. It is probably an austenitic stainless steel (300 grade). 316 on 316 is appropriate, 304 on 304, etc. Many welders will choose 309 for an unknown SS. The problem with that is that it has no molybdenum, which arguably makes it more susceptible to crevice corrosion and pitting later on.

You could see if any fab shops have the ability for Positive Material Identification with an XRF gun. It's possible, as the price on these guns have gone down a lot recently.

This is a very common repair methodology. Consider seeking out a pump repair shop or other industrial fab shop. Easy peasy.
Northern Spy is offline   Reply With Quote
Old 11-01-2015, 06:22 AM   #17
Guru
 
psneeld's Avatar
 
City: Avalon, NJ
Country: USA
Vessel Name: Freedom
Vessel Model: Albin 40
Join Date: Oct 2011
Posts: 15,913
Quote:
Originally Posted by Northern Spy View Post
Looks like regular old pitting corrosion (as much as one can tell from a photo). Here is what would generally be required to repair each shaft.

Remove shaft from rudder. Chuck shaft up in lathe. Skim cut material away from corroded area, until defect is visually gone. (More you remove, the more weld you have to deposit). 0.125-0.200" will probably clean it up. If machinist goes more than SAY 0.250-0.300" consider machining new shafts. Be sure to chamfer or radius transition. Conduct Liquid Penetrant Inspection (LPI) of affected area to check for cracks or pits. Skim cut again if required. Weld metal build up with GTAW (tig), distributing heat evenly. Ensure weld cap is adequately proud to nominal diameter. Machine back to a few thou above nominal. Buff with emory and crocus cloth to nominal, achieving a finish of around 4 micro" Ra. LPI final repair to check for indications.

The tough part is picking the filler material for the weld. It is probably an austenitic stainless steel (300 grade). 316 on 316 is appropriate, 304 on 304, etc. Many welders will choose 309 for an unknown SS. The problem with that is that it has no molybdenum, which arguably makes it more susceptible to crevice corrosion and pitting later on.

You could see if any fab shops have the ability for Positive Material Identification with an XRF gun. It's possible, as the price on these guns have gone down a lot recently.

This is a very common repair methodology. Consider seeking out a pump repair shop or other industrial fab shop. Easy peasy.
Thanks for the expertise.


Nice to know exactly what goes into the time between dropping off the shaft and breaking out the credit card...and why it cost more than a Big Mac.
psneeld is offline   Reply With Quote
Old 11-01-2015, 06:57 AM   #18
Art
Guru
 
Art's Avatar
 
City: SF Bay Area
Country: USA
Vessel Model: Tollycraft 34' Tri Cabin
Join Date: Feb 2011
Posts: 7,981
Quote:
Originally Posted by Northern Spy View Post
Looks like regular old pitting corrosion (as much as one can tell from a photo). Here is what would generally be required to repair each shaft.

Remove shaft from rudder. Chuck shaft up in lathe. Skim cut material away from corroded area, until defect is visually gone. (More you remove, the more weld you have to deposit). 0.125-0.200" will probably clean it up. If machinist goes more than SAY 0.250-0.300" consider machining new shafts. Be sure to chamfer or radius transition. Conduct Liquid Penetrant Inspection (LPI) of affected area to check for cracks or pits. Skim cut again if required. Weld metal build up with GTAW (tig), distributing heat evenly. Ensure weld cap is adequately proud to nominal diameter. Machine back to a few thou above nominal. Buff with emory and crocus cloth to nominal, achieving a finish of around 4 micro" Ra. LPI final repair to check for indications.

The tough part is picking the filler material for the weld. It is probably an austenitic stainless steel (300 grade). 316 on 316 is appropriate, 304 on 304, etc. Many welders will choose 309 for an unknown SS. The problem with that is that it has no molybdenum, which arguably makes it more susceptible to crevice corrosion and pitting later on.

You could see if any fab shops have the ability for Positive Material Identification with an XRF gun. It's possible, as the price on these guns have gone down a lot recently.

This is a very common repair methodology. Consider seeking out a pump repair shop or other industrial fab shop. Easy peasy.
Why Gilligan... Had you performed that process to the SS Minnow's UW shafts maybe Thurston Howell could have gotten back to land, become even richer and bought you and The Skipper a brand new tour boat. I had no Idea you knew sooo much about metallurgy.

Art is offline   Reply With Quote
Old 11-01-2015, 07:10 AM   #19
FF
Guru
 
FF's Avatar
 
Join Date: Oct 2007
Posts: 16,530
Rudder shafts are usually specked with a huge safety margin.

Turning 1/8 or 1/16 off them will not change their service life.
FF is offline   Reply With Quote
Old 11-01-2015, 07:16 AM   #20
Guru
 
angus99's Avatar
 
City: Signal Mtn., TN
Country: US
Vessel Name: Stella Maris
Vessel Model: Defever 44
Join Date: Feb 2012
Posts: 1,385
Quote:
Originally Posted by Northern Spy View Post
Looks like regular old pitting corrosion (as much as one can tell from a photo). Here is what would generally be required to repair each shaft.

Remove shaft from rudder. Chuck shaft up in lathe. Skim cut material away from corroded area, until defect is visually gone. (More you remove, the more weld you have to deposit). 0.125-0.200" will probably clean it up. If machinist goes more than SAY 0.250-0.300" consider machining new shafts. Be sure to chamfer or radius transition. Conduct Liquid Penetrant Inspection (LPI) of affected area to check for cracks or pits. Skim cut again if required. Weld metal build up with GTAW (tig), distributing heat evenly. Ensure weld cap is adequately proud to nominal diameter. Machine back to a few thou above nominal. Buff with emory and crocus cloth to nominal, achieving a finish of around 4 micro" Ra. LPI final repair to check for indications.

The tough part is picking the filler material for the weld. It is probably an austenitic stainless steel (300 grade). 316 on 316 is appropriate, 304 on 304, etc. Many welders will choose 309 for an unknown SS. The problem with that is that it has no molybdenum, which arguably makes it more susceptible to crevice corrosion and pitting later on.

You could see if any fab shops have the ability for Positive Material Identification with an XRF gun. It's possible, as the price on these guns have gone down a lot recently.

This is a very common repair methodology. Consider seeking out a pump repair shop or other industrial fab shop. Easy peasy.
Brilliant!!! Thanks a ton, Spy. Pump repair specialists (minus the "marine" inflator) will be the first place I look. It will be immensely helpful to walk into a shop and have some idea of what to expect. I will post the outcome of this little drama when I have it fixed.
__________________

angus99 is offline   Reply With Quote
Reply

Thread Tools
Display Modes

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





All times are GMT -5. The time now is 04:21 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012