Pitting on 30 year old boat - how much is too much? (opinions on recent survey welcome)

[Troyboy]

If it has taken 30 years for 2mm pits to develop then assuming it continues at that rate it will rust through in 60 years time. If it was mine I would wire brush the rust off and then treat with Vactan before applying quality blacking . I would then repeat the process every two years .With luck the Vactan will slow up any future pitting . I'm not sure how insurers arrived at a figure of 4mm minimum steel thickness for comprehensive insurance particularly as I believe some some boats start off with 4mm steel albeit not newly built narrowboats. 

[blackrose]

8 hours ago, thingsweregood said:

Which dry dock did you do this? I'm currently emailing a bunch of dry docks to get quotes for both them grit blasting/applying 2 pack, and costs if they just do the grit blasting and I apply epoxy myself.

 

It was a DIY dock called Harvington on the River Avon in Worcestershire - probably no good for you

[BWM]

3 hours ago, thingsweregood said:

I had a chat with him, he was really lovely but yes, up in Nottingham. Boat is gloucester, but I'd be ideally living around the London area most of the time. There's a yard in Bradford on Avon which has ok pricing for grit/epoxy, but nightmare to get there on the Severn/estuary through Bristol, or 2 weeks trip one way from London. Gah!

It's not too bad a journey from Gloucester to Nottingham, the route planner quotes 48 hours - would be good to get any major work out of the way so you can forget about it and get on with enjoying your boat, a great way to get to know it too!

[blackrose]

1 hour ago, Troyboy said:

If it has taken 30 years for 2mm pits to develop then assuming it continues at that rate it will rust through in 60 years time. If it was mine I would wire brush the rust off and then treat with Vactan before applying quality blacking . I would then repeat the process every two years .With luck the Vactan will slow up any future pitting . I'm not sure how insurers arrived at a figure of 4mm minimum steel thickness for comprehensive insurance particularly as I believe some some boats start off with 4mm steel albeit not newly built narrowboats. 

 

Yes, assuming the corrosion continues at the same rate it will rust through in 60 years time. However, assuming my maths is correct, in 10 years time the sides will be down to 3.33mm at the bottom of the pits and the boat will potentially be uninsurable. 

 

After grit blasting a good epoxy will fill those pits and stop the corrosion.

2 hours ago, Phoenix_V said:

It is important to get the primer on quick if shotblasting I note that the p and S Marine price for blasting only includes the 1st coat of primer leaving you to do the rest which is less critical, though I suspect that arrangement may indicate they do it outside which isn't optimal

 

If you use a proper epoxy you don't need any primer. Epoxy is the primer and you don't need to get it on that quick. Many are surface tolerant and can even go over a degree of flash rusting.

Edited May 6, 2021 by blackrose

[dmr]

1 hour ago, Troyboy said:

If it has taken 30 years for 2mm pits to develop then assuming it continues at that rate it will rust through in 60 years time. If it was mine I would wire brush the rust off and then treat with Vactan before applying quality blacking . I would then repeat the process every two years .With luck the Vactan will slow up any future pitting . I'm not sure how insurers arrived at a figure of 4mm minimum steel thickness for comprehensive insurance particularly as I believe some some boats start off with 4mm steel albeit not newly built narrowboats. 

 

Using Vactan as a primer for blacking is not standard practice, maybe its not a good idea? If it was a good idea it would be standard???

 

The boat has pitted due to the limitations of blacking, so if the blacking is just replaced then the pitting will continue. It is generally believed that epoxy stops the pitting dead.

There is some debate about the economics of shot blast and epoxy, but if the boat has a lot of pitting there is no debate....epoxy is the way to go ?

 

.................Dave

[Mad Harold]

14 hours ago, Bee said:

I would be pretty happy with that sort of corrosion.  What, though, is a 'hairpin??? Last time I went to London I was looking at HMS Belfast and wondering when that great lump of a thing was docked? It seems that narrowboats that sit in fresh water corrode faster than any other steel ship that floats in salt water. Its a puzzle.

Could it be due to the electric worms found in most marinas?

14 hours ago, Bee said:

I would be pretty happy with that sort of corrosion.  What, though, is a 'hairpin??? Last time I went to London I was looking at HMS Belfast and wondering when that great lump of a thing was docked? It seems that narrowboats that sit in fresh water corrode faster than any other steel ship that floats in salt water. Its a puzzle.

Could it be due to the electric worms found in most marinas?

[David Mack]

13 hours ago, BWM said:

It's not too bad a journey from Gloucester to Nottingham, the route planner quotes 48 hours

It quotes 62 hours for me from Gloucester Docks to Sheet Stores Basin (where Paul Barber is based), using the Canalplan default values.

[Bee]

1 hour ago, Mad Harold said:

Could it be due to the electric worms found in most marinas?

Quite possibly. Certainly some of the more recent cases of really rapid corrosion must be down to that. I think some of the problem is historical, when I first came onto the canal there were lots of wooden boats, as they disappeared steel boats replaced them in their thousands and at the time people thought that steel would last forever. The underneath was never painted, docking was very infrequent and bitumastic was the only stuff used. Therefore many older boats started life with minimal protection. Hopefully as better maintainence and paint become the norm boats will last longer. Narrowboats are built using very thick steel compared with most boats and really should last much longer than they do.

[blackrose]

17 hours ago, Bee said:

Last time I went to London I was looking at HMS Belfast and wondering when that great lump of a thing was docked? It seems that narrowboats that sit in fresh water corrode faster than any other steel ship that floats in salt water. Its a puzzle.

 

It's not really such a puzzle. Most canal boats are painted with bitumen which isn't very good and many are not painted often enough so they corrode. You think HMS Belfast was painted with Bitumen? 

 

Bitumen was originally used because that was the best thing available for wooden boats at the time and it continued to be used because it was cheap and easy and traditionalists liked it. That's continued even though there are much better, harder wearing, longer lasting paint systems available these days. 

 

In short bitumen is crap. That's probably why they call it "bitcho" ?

[thingsweregood]

Bit of an update for anyone invested in my saga: I've agreed to a price with the owner, reduced from original asking, so I'm happy with where we landed.

 

Now I need to... learn how to operate a NB, figure out how to run the electrics and plumbing and not fry my batteries on day one, somehow figure how to get her up the River Severn and onto the canal system (anyone know any boat movers in that area? I won't be attempting it by myself!)

 

Officially one of you lot now ?

 

 

[Alan de Enfield]

25 minutes ago, blackrose said:

 

It's not really such a puzzle. Most canal boats are painted with bitumen which isn't very good and many are not painted often enough so they corrode. You think HMS Belfast was painted with Bitumen? 

 

Bitumen was originally used because that was the best thing available for wooden boats at the time and it continued to be used because it was cheap and easy and traditionalists liked it. That's continued even though there are much better, harder wearing, longer lasting paint systems available these days. 

 

In short bitumen is crap. That's probably why they call it "bitcho" ?

 

 

A lot of offshore boats and other commercials (and even some leisure boats) use a product called Copper coat which gives protection for ~30 years, it is expensive but hey ho you probably only do it once in your boating life time.

 

• Effective in warm and cold conditions, at any depth, in any tidal or current conditions and in fresh or salt water
• Works perfectly and is stable on fast and slow moving or static parts of any size and complexity
• Delivers enhanced performance on coated components to enable much smoother ongoing operation between moving parts
• Creates a cleaner, smoother surface with lower friction and drag for better performance with lower energy requirements and greater longevity
• Eliminates growth in heavy duty situations such as canal walls and tide turbines as well as highly technical commercial equipment with strict operating parameters
• Easy to apply on a wide range of surfaces including GRP, iron, steel aluminium and concrete
• Protects against scour on foundations due to higher abrasion resistance than coatings designed to work in ice flows
• Prevents MIC (Microbial Induced Corrosion), a major problem on transition pieces and monopiles

 

[David Mack]

18 hours ago, Bee said:

Last time I went to London I was looking at HMS Belfast and wondering when that great lump of a thing was docked?

According to Wikipedia HMS Belfast was docked at Tilbury in 1982 and at Portsmouth in 1999, and was not expected to need docking again until 2020. 

[Phoenix_V]

49 minutes ago, David Mack said:

According to Wikipedia HMS Belfast was docked at Tilbury in 1982 and at Portsmouth in 1999, and was not expected to need docking again until 2020. 

do you think they used bitumen or epoxy

 

[David Mack]

1 hour ago, Phoenix_V said:

do you think they used bitumen or epoxy

 

According to a 1997 paper ( https://maritime.org/conf/conf-wenzel.htm), the work planned for 1999 was:

 

"As it is not thought likely that the hull will require any significant repairs, the work to be undertaken whilst in dry dock will be limited to:

Cleaning and blasting of the entire hull, both above and below the waterline

Checking of all hull blanking plates, bilge keels and packing in propeller and rudder shafts

A comprehensive ultra-sonic survey of hull plating thicknesses

Remedial work, if necessary

Application of epoxy coatings, concluding with the reinstatement of the ship's Admiralty Disruptive Camouflage above the waterline."

Edited May 7, 2021 by David Mack

[Phoenix_V]

3 hours ago, David Mack said:

According to a 1997 paper ( https://maritime.org/conf/conf-wenzel.htm), the work planned for 1999 was:

 

"As it is not thought likely that the hull will require any significant repairs, the work to be undertaken whilst in dry dock will be limited to:

Cleaning and blasting of the entire hull, both above and below the waterline

Checking of all hull blanking plates, bilge keels and packing in propeller and rudder shafts

A comprehensive ultra-sonic survey of hull plating thicknesses

Remedial work, if necessary

Application of epoxy coatings, concluding with the reinstatement of the ship's Admiralty Disruptive Camouflage above the waterline."

so there you are it is official epoxy coatings last 20 years, do you think they waited for a dry day and maybe put more than just the 2coats ?

[Bee]

Well if HMS Belfast comes up for sale on E Bay I will be happy to rely on the sellers hull survey

[ditchcrawler]

1 hour ago, Phoenix_V said:

so there you are it is official epoxy coatings last 20 years, do you think they waited for a dry day and maybe put more than just the 2coats ?

But how many locks has it scraped through in the past 20 years

[Phoenix_V]

1 minute ago, ditchcrawler said:

But how many locks has it scraped through in the past 20 years

and did they paint the base plate

 

[blackrose]

9 hours ago, thingsweregood said:

Bit of an update for anyone invested in my saga: I've agreed to a price with the owner, reduced from original asking, so I'm happy with where we landed.

 

Now I need to... learn how to operate a NB, figure out how to run the electrics and plumbing and not fry my batteries on day one, somehow figure how to get her up the River Severn and onto the canal system (anyone know any boat movers in that area? I won't be attempting it by myself!)

 

Officially one of you lot now ?

 

 

 

There are a couple of people on the forum who move boats for a living, but if you put a post in the crew swap section with likely dates, departure point and destination you may get some volunteers to help you in return for cups of tea and sandwiches.

 

I've had help from forum members moving up the GU and along the K&A because I was on my own and due to the sheer number of locks and it was much appreciated.

 

Up the R Severn from where to which canal?

Edited May 7, 2021 by blackrose

[blackrose]

9 hours ago, Alan de Enfield said:

 

 

A lot of offshore boats and other commercials (and even some leisure boats) use a product called Copper coat which gives protection for ~30 years, it is expensive but hey ho you probably only do it once in your boating life time.

 

• Effective in warm and cold conditions, at any depth, in any tidal or current conditions and in fresh or salt water
• Works perfectly and is stable on fast and slow moving or static parts of any size and complexity
• Delivers enhanced performance on coated components to enable much smoother ongoing operation between moving parts
• Creates a cleaner, smoother surface with lower friction and drag for better performance with lower energy requirements and greater longevity
• Eliminates growth in heavy duty situations such as canal walls and tide turbines as well as highly technical commercial equipment with strict operating parameters
• Easy to apply on a wide range of surfaces including GRP, iron, steel aluminium and concrete
• Protects against scour on foundations due to higher abrasion resistance than coatings designed to work in ice flows
• Prevents MIC (Microbial Induced Corrosion), a major problem on transition pieces and monopiles

 

 

Isn't that an antifouling? 

[Alan de Enfield]

Just now, blackrose said:

 

Isn't that an antifouling? 

 

It is, but it is also an abrasion resistant coating that offers better abrasion resistanace that ice-flow coatings.

It also prevents the spread / growth of MIC

 

'Blacking' is also an antifouling, prevents zebra mussels etc from adhering to the boat.

[blackrose]

It never stopped then from sticking to mine! Absolutely covered in them once when I pulled it out for reblacking.

[Alan de Enfield]

6 minutes ago, blackrose said:

It never stopped then from sticking to mine! Absolutely covered in them once when I pulled it out for reblacking.

 

I dropped a spanner in the marina and got the magnet to hoik it out - it caught a metal step (that had been kocked in some time before) and when we pulled it up it was absolutely solid with mussels, when we had the boat reblacked there was not a single mussel on it. Maybe it was a different 'blacking' to the type you used.

[ditchcrawler]

I saw a boat lifted at Debdale for blacking, the base plate was thick with mussels but the side were clean.

[cuthound]

13 hours ago, ditchcrawler said:

I saw a boat lifted at Debdale for blacking, the base plate was thick with mussels but the side were clean.

 

So if the baseplate is covered in mussels would they prevent corrosion,  or would you still need to black it? ?