USCG requiring steel hull replacement- how about repair?

[Sean M]

I have 1986 steel hull paddlewheeler. COI for 150 passenger plus crew. Some waterline down steel panels have minor pitting on 1/4 steel. Coast guard saying panels need to be removed and replaced. Is there any other options? Not really interested in cladding etc. but would be interested in some type of epoxy, slick or "fill weld". Thanks.

 

[bajansailor]

Welcome to the Forum Sean.
I have a feeling that there is more to this story than just "Some waterline down steel panels have minor pitting on 1/4" steel".
How did the Coastguard arrive at this conclusion?
Was it a simple visual inspection, did they scrape off some areas of paint, did they do any ultrasound thickness testing?
Is the pitting on the outside of the plating only, or on the inside as well?
Can you post any photos of the paddlewheeler, and some close up photos showing typical pitting?

 

[Sean M]

Welcome to the Forum Sean.
I have a feeling that there is more to this story than just "Some waterline down steel panels have minor pitting on 1/4" steel".
How did the Coastguard arrive at this conclusion?
Was it a simple visual inspection, did they scrape off some areas of paint, did they do any ultrasound thickness testing?
Is the pitting on the outside of the plating only, or on the inside as well?
Can you post any photos of the paddlewheeler, and some close up photos showing typical pitting?

The Coastguard seems to want to kind of 'pass off the buck' when it comes to taking responsibility for any type of hull wear and tear.
The boat had to be pulled out of the water for its 5 year inspection. They did a straight visual inspection but it was obvious there was a small amount of pitting; no audio testing was done. The engineers at the boat yard agreed the hull was structurally sound but they cannot overall the coast guard regulations. Because about 80% of hull had some pitting, the yard recommended replacing the the entire hull at quite a costly expense.
There was no oxidation, intrusions or pitting on the inside whatsoever.
Ill try to post some pictures shortly.
Thanks.

 

[bajansailor]

They did a straight visual inspection but it was obvious there was a small amount of pitting

Because about 80% of hull had some pitting,

I am baffled - is 80% of the hull a 'small amount'?

Re this pitting - has (most of) it occurred since the last haul out / bottom paint job was done?
If so, then I would assume that there is no paint in the pits.
More likely the pits have gradually accumulated over the years (?) and they have been painted over?
How deep are the pits typically? And what diameter - 1/4", 1/2"or even 1"?
When was the last time you blasted the bottom back to bare metal? Did you use any high build primers to coat the hull (and fill the pits) then?
You mention a steel thickness of 1/4", which I am assuming is the thickness of the side shell plating - is the bottom shell plating the same thickness?

 

[Sean M]

The boat measures 65 ft. x 24ft.
I believe a lot of the pitting happened before the last haul out but perhaps the inspector was more lenient that time. Now its an issue.
One of the old owners attempted to paint over the pitting and use the boat dockside only therefore if appears the pits are under the paint but they weren't. The pits are problably an 1/8th in diameter with the largest maybe being a quarter as seen in pics.
Boat yard believed sandblasting to bare metal was a waste of time and money because it was in fact in the steel.
Never used high build primers to my knowledge.
Side shell and bottom shell are both believed to be 1/4 but may be 3/8.
Thanks for your time Bajansailor.

 

[Sean M]

Some more pictures

 

[TANSL]

In my opinion, asking to change entire plates is exaggerated because the appearance is not so bad as to undertake such a huge job, maybe remove some more damaged area. It would also be unwise to give a definitive answer without having seen the ship. However, it all depends on the current thickness of the plates. If their thickness is greater than the regulation, which happens many times because the designer has taken some margin, it would not be necessary to change them. A sandblasting and a good paint scheme would suffice. Then it would be convenient to put sacrificial anodes to protect the entire hull.

 

[DCockey]

They did a straight visual inspection but it was obvious there was a small amount of pitting; no audio testing was done.

Who is "they" - USCG members/employees or somebody else such as boat yard employees? Those are two different situations.

However, it all depends on the current thickness of the plates. If their thickness is greater than the regulation, which happens many times because the designer has taken some margin, it would not be necessary to change them.

Good point.

Not really interested in cladding etc. but would be interested in some type of epoxy, slick or "fill weld".

The USCG regulations are concerned about structural integrity, not cosmetics. Epoxy or other fillers on the surface of steel will not restore structural integrity.

 

[gonzo]

Epoxy is a cosmetic repair. You have a structural defect. The regulations are clear about what percentage of plating loss of section is acceptable. If the loss is past the limit, replating is the only solution. What kind of yard has several engineers in staff? Also, you need to quantify what you call "minor pitting". Ultrasound measurements will give you average readings over the transducer area, and a micrometer will measure the actual depth of the pits. Can you post what those are?

 

[fallguy]

It is all out of my wheelhouse, but the one picture looks pretty bad to me.

I have to ask a question.

Is there a way to prevent such horribles?

 

[Rumars]

The coast guard did a visual inspection and condemned your plating? Do they have x-ray glasses now or what? Where is the inspection report and what does it say? And you don't know exactly what thickness the plating is on your own boat?
Sorry but the entire thing doesn't sound plausible at all.

Fallguy, the way to prevent such horribles is to keep up on the coatings. If the coating is breached one needs propper rust removal and recoat.

 

[Ike]

Epoxy is a cosmetic repair. You have a structural defect. The regulations are clear about what percentage of plating loss of section is acceptable. If the loss is past the limit, replating is the only solution. What kind of yard has several engineers in staff? Also, you need to quantify what you call "minor pitting". Ultrasound measurements will give you average readings over the transducer area, and a micrometer will measure the actual depth of the pits. Can you post what those are?

As most on this forum know I am a retired Coast Guard Engineer but I worked mainly with recreational vessels. But what they may not know is that years ago I worked in a ship yard and one of my many jobs was doing audio testing on hulls for their annual survey. In the Coast Guard, I was not a marine inspector but have some training in that field (just enough to be dangerous). What Gonzo said is true. Marine inspectors have a lot of latitude and a lot of authority, but their decision can be appealed if you provide evidence that replacing the plating is not necessary. Hire a commercial marine surveyor; One who has experience with audio testing and surveying passenger vessels. preferably one who does American Bureau of Shipping (ABS) surveys. They won't be cheap. Have them examine the vessel and prepare a report for the Coast Guard. If the USCG finds the report does not support replating the hull, then they will give you an alternative solution. I looked at the photos. I have seen that kind of pitting on ships hulls. If the pitting is too deep (I don't recall the percentage) then the plate has to be replaced, and it is quite extensive. Had it been me I would have ordered audio testing, but then that's just me. The inspector may have seen hundreds of hulls like this.

 

[Will Gilmore]

I can't really see well, from the pictures, but does most of the worst pitting seem to be near the waterline? You may be able to justify replacing only the worst areas, unless the pitting is equally distributed everywhere.

Beyond that, inspect for stray current from your boat and from the marina.

-Will (Dragonfly)

 

[fallguy]

Isn't the boat awful close to the ground for anyone to be running a sounding device? Maybe the inspector gave you worst option to put the burden to prove your hull is worthy for so many souls onboard on you.

i.e. raising the hull for sounding work, etc

I find it at least a bit odd that anyone would expect the government to prove the vessel is safe for passengers when they have seen many boats with 1/4" plate and have a good idea about pitting depths.

What did the last inspection say? Probably recommended getting it coated? Just curious.

Good luck on the repairs and finding some way to reduce the corrosion. I am also curious if you are docked in brackish water.

I googled the boat and she is a beauty.

 

[rangebowdrie]

Is there a way to prevent such horribles?

Yes, and just adding zincs can be counter productive.
An active cathode system can give a steel boat much better protection.

inspect for stray current from your boat and from the marina.

Without doubt, a friend of mine does consulting and inspection work that specializes in corrosion control. I have seen pics of tests showing several amps of currant leakage in shore>boat systems.