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electrolysis damaged wood under struts

Framing, planking and fairing. Repair, or reconstruction. If it's hull related, you'll find it here.

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keith colonna
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electrolysis damaged wood under struts

Post by keith colonna » Sat Nov 22, 2014 11:09 pm

My 1955 42' hull has damaged wood behind the struts, and shaft logs. That wood is a main structural member of the hull, not just a backing block. I am considering an epoxy repair. Anyone had experience with this?

boat_art
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Re: electrolysis damaged wood under struts

Post by boat_art » Sun Nov 23, 2014 8:05 am

I am very experienced with this. Over the last few years I have redone the bottom on my '56 Connie and I replaced the port side keelson for this very reason. See my topic '56 Connie 47' hull restore.
http://www.chris-craft.org/discussion/v ... php?t=7914
http://www.boatartgallery.com
1956 CC Connie 47'
1959 Caulkins bartender
1965 Cheoy Lee Frisco Flyer
1953 Chris Craft Holiday
1941 Chris Craft Deluxe
Plus 8-12 customer boats at any time
God don't count the days spent messing around in wood boats.

joanroy
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Re: electrolysis damaged wood under struts

Post by joanroy » Sun Nov 23, 2014 11:43 am

I replaced my shaft logs and redid my struts a few years back. The top 1/8 inch or so of the wood under my shaft logs was soft. The keelson is a big think chunk of mahogany so it still had plenty of structural strength. I scraped the layer of soft wood off and faired it with west system and micro fibers. Sanded it smooth and re bedded my new Buck Algonquin shaft logs with 5200 and fastened with bronze screws. That was seven years ago and it's still fine. The best way is what Boat Art suggests, but in my case the rot wasn't bad enough to justify replacement. To repair or replace is a judgement call that has to be made depending on the the situation.

boat_art
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Re: electrolysis damaged wood under struts

Post by boat_art » Sun Nov 23, 2014 5:27 pm

I did the exact same process to many of the other areas of the bottom on frames etc as Joanroy. Any parts that were threatened structurally had to be replaced. As he said, a careful decision on each part must be made.
http://www.boatartgallery.com
1956 CC Connie 47'
1959 Caulkins bartender
1965 Cheoy Lee Frisco Flyer
1953 Chris Craft Holiday
1941 Chris Craft Deluxe
Plus 8-12 customer boats at any time
God don't count the days spent messing around in wood boats.

jfrprops
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Re: electrolysis damaged wood under struts

Post by jfrprops » Sun Nov 23, 2014 5:45 pm

Keith,

There is a hybrid method to consider...leaving the old...cleaned up and maybe saturated....then....backing all that area with added new wood and gooped in...maybe thru bolts with sil-bronz carriage bolts from the outside to the in.......there is usually room on the inside of the hull to do such bracing and sistering....cutting out the old would be Pandora's box for sure....
I would avoid "picking that scab"....if at all possible.
John in Va.
1980 Fairchild Scout 30
19?? custom Argentine Runabout 16'
1954 Whirlwind deluxe dual ckpt 16'
1921 Old Town Charles River 17' (founding Captain, James River Batteau Festival)

boat_art
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Re: electrolysis damaged wood under struts

Post by boat_art » Sun Nov 23, 2014 6:17 pm

The problem with that is much of the rot can take place in inaccessible places. Plastering over can make things worse. Just be sure you get at all of it.
http://www.boatartgallery.com
1956 CC Connie 47'
1959 Caulkins bartender
1965 Cheoy Lee Frisco Flyer
1953 Chris Craft Holiday
1941 Chris Craft Deluxe
Plus 8-12 customer boats at any time
God don't count the days spent messing around in wood boats.

jfrprops
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Re: electrolysis damaged wood under struts

Post by jfrprops » Sun Nov 23, 2014 7:46 pm

I stick to my Pandora's principle.....seen too many boats picked and plucked all the rot out only to be left with not enough good wood to make a skiff. If this is a restoration .....you are surely right....if this is a patch job.....patch on I say.....

John in Va.
1980 Fairchild Scout 30
19?? custom Argentine Runabout 16'
1954 Whirlwind deluxe dual ckpt 16'
1921 Old Town Charles River 17' (founding Captain, James River Batteau Festival)

boat_art
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Re: electrolysis damaged wood under struts

Post by boat_art » Sun Nov 23, 2014 7:58 pm

On a 40' boat, one usually takes guests out for rides. These often include children. That thought alone was enough to make me do it right.
http://www.boatartgallery.com
1956 CC Connie 47'
1959 Caulkins bartender
1965 Cheoy Lee Frisco Flyer
1953 Chris Craft Holiday
1941 Chris Craft Deluxe
Plus 8-12 customer boats at any time
God don't count the days spent messing around in wood boats.

jfrprops
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Re: electrolysis damaged wood under struts

Post by jfrprops » Sun Nov 23, 2014 11:14 pm

Boat_art:
I suspect you have the resources to "do it right"....but sometimes there are viable and safe alternatives. Because of the aforementioned Pandora situation, I would rather add on and encapsulate assuming the whole hull area was not punky. Could wind up being stronger than the original.
It is always of interest to me how folks on this site react to non standard approaches? You are quite right to place safety first and I am sure you did not mean to suggest that would not?
I know you to be a professional at this...but it's not my first rodeo either....

John in Va.
1980 Fairchild Scout 30
19?? custom Argentine Runabout 16'
1954 Whirlwind deluxe dual ckpt 16'
1921 Old Town Charles River 17' (founding Captain, James River Batteau Festival)

joanroy
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Re: electrolysis damaged wood under struts

Post by joanroy » Mon Nov 24, 2014 6:20 am

All cruiser owners share the same problem. How far do I go with this and where do I stop? The things I consider are safety money and time. Keeping a cruiser alive is a whole different animal than restoring a typical runabout. It's all big, it's all expensive, and its all very labor intensive. It's important to me to be able to use my boat every summer so that dictates how much work can get done in the off season. I have about a month in the Spring to do all the usual maintenance and whatever repairs and improvements that time will allow. I think a big mistake a lot of do it yourselfers make is trying to do to much all at once ending up with an unfinished Boat In A Box. Sometimes knowing what not to take apart is more important than taking it apart and destroying originality. So make it as safe as money and time will allow, but, remember that our boats are antiques. Own and use accordingly.

jfrprops
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Re: electrolysis damaged wood under struts

Post by jfrprops » Mon Nov 24, 2014 9:25 am

Well said joanroy.....those are our challenges for sure....

John in Va.
1980 Fairchild Scout 30
19?? custom Argentine Runabout 16'
1954 Whirlwind deluxe dual ckpt 16'
1921 Old Town Charles River 17' (founding Captain, James River Batteau Festival)

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evansjw44
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Re: electrolysis damaged wood under struts

Post by evansjw44 » Mon Nov 24, 2014 11:12 am

I have to wonder about your use of the word electrolysis to describe the damage. Decay is decay almost always from fungus.
Jim Evans

wetpet
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Re: electrolysis damaged wood under struts

Post by wetpet » Mon Nov 24, 2014 2:50 pm

I have a 1967 48' connie. Been finding areas where the wood fiber is destroyed and I have tracked it back to electrical currents moving thru the wood with a ss fastener being the starting point.. The bad wood looks alot like dry rot but there are some other signs that tell you that this part of the boat is involved in electrical current. Had US Coast Guard Detroit Group on the boat for a day to try to track it down with no success !!

boat_art
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Re: electrolysis damaged wood under struts

Post by boat_art » Mon Nov 24, 2014 4:20 pm

I agree Jim, it is almost always wood rot fungus. However, electrolysis can accelerate it. On the bottom of mine I removed the original copper sheets which were originally used for the low frequency radio grounding and there was much evidence of electrolysis.
http://www.boatartgallery.com
1956 CC Connie 47'
1959 Caulkins bartender
1965 Cheoy Lee Frisco Flyer
1953 Chris Craft Holiday
1941 Chris Craft Deluxe
Plus 8-12 customer boats at any time
God don't count the days spent messing around in wood boats.

keith colonna
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Re: electrolysis damaged wood under struts

Post by keith colonna » Mon Nov 24, 2014 11:40 pm

Thanks Fellow CC cruisers for your feedback. What I have discovered is that my keelsoms are intact but the backing blocks are damaged in a 1" area surrounding the bolts...which are in very good condition. However, with nothing for the bolts to grip, the struts could virtually pull right through the bottom. My intended repair is to use Smiths Laminating Epoxy to create a "dutchman" which will replace the damaged wood and provide a wedge again the remaining block. The synthetic replacement will bond into the old wood and provide insulation against future electrolysis. This same technique is used by the US NAVY on their ships where dissimilar metals create unavoidable galvanic reaction. I also used this technique successfully on my rudder blocks 12 years ago without problem. For additional support I may also insert a bronze plate on top of the repaired block which will provide maximum strength for the strut bolts.
Attachments
main strut black port after removing electrolysis damage.jpg
before repair

joanroy
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Re: electrolysis damaged wood under struts

Post by joanroy » Tue Nov 25, 2014 4:52 am

That sounds like a good repair strategy. I would definitely go with the bronze plate for additional backing strength. Good Luck.

jfrprops
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Re: electrolysis damaged wood under struts

Post by jfrprops » Wed Nov 26, 2014 9:42 am

yep, I agree Keith, that is a good plan...

John in Va.
1980 Fairchild Scout 30
19?? custom Argentine Runabout 16'
1954 Whirlwind deluxe dual ckpt 16'
1921 Old Town Charles River 17' (founding Captain, James River Batteau Festival)

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evansjw44
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Re: electrolysis damaged wood under struts

Post by evansjw44 » Thu Nov 27, 2014 11:26 am

My two cents. I would pull the bolts, then set up a platform so I could use my router to make a clean rabbit cut. Then I would epoxy in new wood to fill the void. Maybe I would fabricate a plate to pick up the six bolts for added strength. I have no idea where to get a bronze plate. Maybe I'd get a strut with a similar bolt pattern and just cut the strut off and use the base plate.

On the electrolysis point. There are two kinds of corrosion that get tagged as electrolysis. Galvanic corrosion is the result of two disimilar materials (metals, usually) that are in electrical contact with each other. They swap ions causing one to erode. The other form of electrolytic corrosion is the result of stray currents passing through. Very often, the stray currents come from connecting the boat ground to the shore power ground. The current can also be from another boat or from the dock the the corroded part happens to be in the current path.
Jim Evans

keith colonna
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Re: electrolysis damaged wood under struts

Post by keith colonna » Thu Nov 27, 2014 10:25 pm

I can replace the wooden backing blocks to my struts...or I can reinforce/replace with Smith's epoxy products. Much of my wood is still OK, but what's gone is very gone. The Rot Doctor describes how using CPES followed by the laminating epoxy can reproduce the original dimensions of the wood with a superior substance which is all bound together and rot proof. As additional insurance from from the bolts pulling through, I am going to add a "top backing plate" to the repaired block. I can either use a sheet of roven wolving impregnating with Smith's laminating epoxy...or I can use "engineered plastics" such as UHMW (ultra high molecular weight) polyethelane or Delrin. To imagine this material think....synthetic cutting boards. See the attached spec sheet...this material exceeds all requirements for strength,chemical resistance and electrical isolation.
The source of my electrolysis is likely the commercial marina boat house. I do not stay connected to shore power and my 12 volt system is off except for a direct connection to my bilge pump. But other boats, tugs and liveaboards contribute a lot of stray current in the water I am sure.
Attachments
synthetic material for strut block backing plate.jpg

joanroy
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Re: electrolysis damaged wood under struts

Post by joanroy » Fri Nov 28, 2014 5:42 am

While we're on the subject, what's the general consensus on bonding. I know this has been discussed before, but I still don't know if bonding on a wooden boat is a good thing or a bad thing. Opinions seem to go both ways depending on who you talk to. How many of you salt water cruiser guys have bonding systems, and does it work?

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mbigpops
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Re: electrolysis damaged wood under struts

Post by mbigpops » Fri Nov 28, 2014 8:19 am

I would stay away from the Delrin solution as I think you would have more trouble keeping water away from the Delrin to wood joint than a wood to wood joint.

Mark
1953 CC Rocket Runabout "Rocket Man"

keith colonna
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Re: electrolysis damaged wood under struts

Post by keith colonna » Fri Nov 28, 2014 10:16 am

This won't be wet as it is inside the mostly dry hull...just serving as a top plate for the repaired strut block with the intent to distribute stress from the strut bolts across the entire top surface of the block. I would bed it down in some sort of compound and the Delrin may not stick to anything....perhaps the UHMW would be better. Another consideration is just a layer of roving woven fiberglass mat on top. Regarding "bonding"...I have read it is not recommended for wooden boats. I've just got everything zinced on my running gear

keith colonna
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Re: electrolysis damaged wood under struts

Post by keith colonna » Mon Dec 01, 2014 11:07 pm

strut block repair nearly complete as I have removed damaged wood, dried out solid section, soaked with Smiths clear penetrating epoxy sealer and filled voided area with layup epoxy resin giving new and better structure. I'll top the repair with a HDMW plate to hold it fast to the repair block. It's now stronger than wood and resistant to future electrolysis damage.
Attachments
s laminating epoxy.jpg

keith colonna
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Re: electrolysis damaged wood under struts

Post by keith colonna » Fri Dec 12, 2014 10:59 pm

CPES  soaking of excavated wood from block.jpg
strut block repair complete and all in awe.
Attachments
STB block with HMWD backing plate.jpg
port block with Smiths epoxy replacing electrolysis void.jpg

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