Hull Thickness

[DannyC]

Thanks everyone

[blackrose]

50 minutes ago, Alan de Enfield said:

Overplating is not something that should be undertaken lightly.

It will probably cost more to do than you will achieve in increased selling price as most folks, would consider a cheap non-overplated boat that requires overplating is a better option than one already done. The standard of overplating and the condition below the overplate will be unknown and not be able to be seen forcing folks to consider the 'worse case' that it has been poorly done to cover up problems and make the boat saleable.

I would NEVER buy an overplated boat.

 

You may find the attached article (written for surveyors) about the "dangers of overplating" of interest.

 

 

The dangers of overplating.docx

 

I had a 45' Springer 2/3 overplated about 20 years ago by a coded welder. Cost me £2k which was a good price, but in hindsight I should have just walked away.

 

 

[Mad Harold]

This subject has been discussed quite comprehensively previously.

It's true that 10,6,4mm steel thickness has become the yardstick that is applied to narrowboats.

Popsie built 1978 was originally 6,5,3mm thickness.At the last survey,[2007] the base plate measured 4.2 to 5.8mm,and the sides 4.1 to 4.9mm.

Some rust pitting was also noted.

The surveyor's recommendations were to have the rust pitting spot welded,monitor the hull every other season,and keep the hull sides well coated to prevent further pitting.

The boat is comprehensively insured on the strength of this survey, and I suppose one could extrapolate the measurements to guess when the boat may need overplating,but am I worried ?   No.

[MtB]

Bear in mind there are two separate issues at play here, which get conflated and confusing. 

 

1) Insurance.

2) Structural integrity

 

 

You have to have third party insurance to get a licence. Any boat can have third party insurance, you just have to pay the money.

 

Most folk however, actually prefer comprehensive insurance, so if their boat is a total loss or gets damaged in any way, the insurance pays out. For this the insurance companies demand either a boat less than 25 years of age, or a survey showing hull thickness of 4mm or more. This is where the concept of 'failing' a survey and a boat 'needing' overplating originates. IF the boat is over 25 years old and IF you want comprehensive insurance, you NEED a survey report showing 4mm hull thickness. Surveyors will generally rather arrogantly translate this into "the hull is less than 4mm, it need overplating" with no further explanations. This seems to have happened to you. 

 

The structural integrity of a hull is a different matter. Hulls only sink when the steel thickness somewhere gets down to zero and lets the water in. Most boats still float matter how thin the baseplate or hull sides. There is a very wide spectrum of ability in welders and my suspicion is a lot of boats get overplated in a very slap-dash manner as the welder knows the boat will still be float if his workmanship is not watertight. I suspect there are a LOT of overplated boats cruising around with random lumps of steel covering up the thin bits in a non-watertight way. i.e. the gap between the hull and the overplating is full of water. The original corroded hull is still doing all the work of floating and the owners have that warm fuzzy feeling of smugness that their boat has been overplated, insurance issued and everything is right in their world. In reality their boat may as well not have been overplated. It would still be floating just the same.

 

 

 

 

[Horace42]

2 hours ago, Alan de Enfield said:

Overplating is not something that should be undertaken lightly.

It will probably cost more to do than you will achieve in increased selling price as most folks, would consider a cheap non-overplated boat that requires overplating is a better option than one already done. The standard of overplating and the condition below the overplate will be unknown and not be able to be seen forcing folks to consider the 'worse case' that it has been poorly done to cover up problems and make the boat saleable.

I would NEVER buy an overplated boat.

 

You may find the attached article (written for surveyors) about the "dangers of overplating" of interest.

 

 

The dangers of overplating.docx

Sorry to harp on it, but what happens down the line -  eventually someone will end up with an unsaleable rust bucket - what do they do - how are these boats disposed of ?

 

[Alan de Enfield]

4 minutes ago, Horace42 said:

what do they do - how are these boats disposed of ?

 

 

One of the several places around the country who 'specialise' in such vessels, one example :

 

http://www.boatwrecks.com/power.asp

 

 

 

32ft Steel hull narrow boat with wooden superstructure and BMC diesel inboard engine. This vessel has suffered flooding damage throughout. Lying Leighton Buzzard

[Horace42]

22 minutes ago, Alan de Enfield said:

 

One of the several places around the country who 'specialise' in such vessels, one example :

 

http://www.boatwrecks.com/power.asp

 

 

 

32ft Steel hull narrow boat with wooden superstructure and BMC diesel inboard engine. This vessel has suffered flooding damage throughout. Lying Leighton Buzzard

That's interesting - but they all seem to be for sale, not scrapped - none of them are stated to have damage due to sinking (ecause of advance rusty hulls) - except perhaps the 3rd one - the Springer, that has suffered internal flood damage - that without explanation could have been due to rainwater - leaky prop-shaft - open weed hatch - duff pump, that sort of thing. 

So we are still left with disposal issues. No mention of whatever finally happens to rusty steel narrowboats.

[Alan de Enfield]

5 minutes ago, Horace42 said:

No mention of whatever finally happens to rusty steel narrowboats.

They are all bought from Whilton by Wannabe Londoners and then they sink on the way.

[Mad Harold]

1 hour ago, Mad Harold said:

This subject has been discussed quite comprehensively previously.

It's true that 10,6,4mm steel thickness has become the yardstick that is applied to narrowboats.

Popsie built 1978 was originally 6,5,3mm thickness.At the last survey,[2007] the base plate measured 4.2 to 5.8mm,and the sides 4.1 to 4.9mm.

Some rust pitting was also noted.

The surveyor's recommendations were to have the rust pitting spot welded,monitor the hull every other season,and keep the hull sides well coated to prevent further pitting.

The boat is comprehensively insured on the strength of this survey, and I suppose one could extrapolate the measurements to guess when the boat may need overplating,but am I worried ?   No.

I made a mistake. The hull survey was 2017 not 2007.So in 40 years it has lost 1.8 from the base, and .9 from the sides,the base probably more due to erosion than corrosion. I stated before,that in my opinion many boats are unnecessarily overplated.