Concerns about hull thickness

[Damo]

Hi,

 

We recently purchased our first boat, built in 1983 by an unknown builder. I have been browsing this forum for some months and following the advice given here we had a full survey carried out. The surveyor took hull thickness readings at various points and the original 6mm plate seemed to be largely in very good condition. He then measured the worst of the pitting that he could identify and subtracted this from the ultrasound readings. The worst occurrence of pitting was on the underside and resulted in a thickness of 3.8mm.

 

The surveyor told us that this was fine and that insurance companies weren't concerned until the thickness was less than 50% of the original. Based on the age of the boat, and the current rate of corrosion, he felt that we had many years ahead of us before we had to be concerned by this.

 

I am not in any way wishing to cast doubt on the credibility of our surveyor (he came highly recommended by another surveyor) but from what I have read on this forum a lot of people seem to have a much more pessimistic view about hull thicknesses and insurance and I am starting to become a little worried that we may not have purchased very wisely despite our best efforts to do things "properly".

 

I am sorry for the long-winded post and I'm not even sure what I am asking really... maybe just hoping for some reassurance that we haven't made a huge mistake and bought a boat that will very soon require thousands of pounds of work or be uninsurable and unsellable!

 

Lastly, since the worst affected area was on the underside and nobody seems to recommend blacking that is there anything we can do to arrest the problem as much as possible?

 

Thanks for any advice.

[Naughty Cal]

Not much help now but you should have had a survey before buying.

[RLWP]

Hi,

 

We recently purchased our first boat, built in 1983 by an unknown builder. I have been browsing this forum for some months and following the advice given here we had a full survey carried out. The surveyor took hull thickness readings at various points and the original 6mm plate seemed to be largely in very good condition. He then measured the worst of the pitting that he could identify and subtracted this from the ultrasound readings. The worst occurrence of pitting was on the underside and resulted in a thickness of 3.8mm.

 

The surveyor told us that this was fine and that insurance companies weren't concerned until the thickness was less than 50% of the original. Based on the age of the boat, and the current rate of corrosion, he felt that we had many years ahead of us before we had to be concerned by this.

 

I am not in any way wishing to cast doubt on the credibility of our surveyor (he came highly recommended by another surveyor) but from what I have read on this forum a lot of people seem to have a much more pessimistic view about hull thicknesses and insurance and I am starting to become a little worried that we may not have purchased very wisely despite our best efforts to do things "properly".

 

I am sorry for the long-winded post and I'm not even sure what I am asking really... maybe just hoping for some reassurance that we haven't made a huge mistake and bought a boat that will very soon require thousands of pounds of work or be uninsurable and unsellable!

 

Lastly, since the worst affected area was on the underside and nobody seems to recommend blacking that is there anything we can do to arrest the problem as much as possible?

 

Thanks for any advice.

 

 

Listen to your surveyor. What you have is a hull that is largely in good condition that will give you years of service before you have to do anything about it. It has localised pitting that is up to 2.2mm deep which isn't a problem.

 

If you want reassurance, your surveyor has given it to you after looking at the hull. How can we improve on that from sitting at a computer miles from your boat??

 

Richard

 

You'll be fine.

[Liam]

Not much help now but you should have had a survey before buying.

 

They did.

[ChrisPy]

Listen to your surveyor. What you have is a hull that is largely in good condition that will give you years of service before you have to do anything about it. It has localised pitting that is up to 2.2mm deep which isn't a problem.

.............. and if there are just a few localised deep pits it may be worth identifying them and filling them with weld metal before the next blacking.

[Naughty Cal]

They did.

 

Thats not how it reads

[Timleech]

Lastly, since the worst affected area was on the underside and nobody seems to recommend blacking that is there anything we can do to arrest the problem as much as possible?

 

Yours sounds like a case where painting underneath would be a very good idea. In particular, make sure any major pitting is painted (or welded if it's bad enough, but remember that will ruin any remaining paint on the inside at those spots).

That way, if you get more pitting it should be in different places.

 

Tim

Edited August 10, 2009 by Timleech

[Liam]

I have been browsing this forum for some months and following the advice given here we had a full survey carried out. The surveyor took hull thickness readings at various points and the original 6mm plate seemed to be largely in very good condition. He then measured the worst of the pitting that he could identify and subtracted this from the ultrasound readings. The worst occurrence of pitting was on the underside and resulted in a thickness of 3.8mm.

 

Sounds like it to me

Edited August 10, 2009 by Liam

[Damo]

Not much help now but you should have had a survey before buying.

 

We did, but I can see how it's not clear from the post.

 

If you want reassurance, your surveyor has given it to you after looking at the hull. How can we improve on that from sitting at a computer miles from your boat??

 

Richard

 

You'll be fine.

 

Thanks Richard, I guess all I was hoping for was confirmation that if the surveyor said it was fine, it was fine! No need for a second opinion etc. so I am reassured! I realise that it sounded like I was asking the impossible

 

and if there are just a few localised deep pits it may be worth identifying them and filling them with weld metal before the next blacking.

 

Yours sounds like a case where painting underneath would be a very good idea. In particular, make sure any major pitting is painted (or welded if it's bad enough, but remember that will ruin any remaining paint on the inside at those spots).

 

Ah, right, that's exactly what I hoped. I didn't know it was acceptable to spot-weld pits, I thought the whole area needed over-plating. I have a lot to learn... the first of which is not to over-react and panic every time I read about hull problems

[RLWP]

Ah, right, that's exactly what I hoped. I didn't know it was acceptable to spot-weld pits, I thought the whole area needed over-plating. I have a lot to learn... the first of which is not to over-react and panic every time I read about hull problems

 

When we first had our hull surveyed there were pits in the sides of the hull - that scared us quite a bit. I suggested to the surveyor that we had them spot welded and his opinion was it could get rid of the pits, but it could affect the surrounding steel and cause that to pit more quickly. His opinion was to black them over and keep an eye on it. That's what we do.

 

Welcome to the trials and tribulations of boat ownership. There has to be some payment for all of those fantastic experiences you know.

 

Richard

Edited August 10, 2009 by RLWP

[Naughty Cal]

Welcome to the trials and tribulations of boat ownership. There has to be some payment for all of those fantastic experiences you know.

 

When you say some you really mean a lot

[timboharticus]

I had my bottom overplated and up to the waterline for about £6.5k some time ago.

 

The main reason being to satisfy the surveyor/ insurance company.

 

In your case I would black it regularly , say every 2-3 years including bottom and keep anodes in good nick.

[Andy Woods]

Been living on an 80's boat with a 6mm hull with pitting for the last 7 years....

No problems whatsoever!

Black it every couple of years, painted the underside of the base plate once ....just for fun..

Saw a similar boat having the bow chopped off to lengthen it and the quote from the guy with the cutting gear was " this old steel is as hard as nails ".

[Matthew Dowson]

You only need to worry when the waters coming in! On my brothers old Northwicher you could nearly see the outside from the inside at some points.

Edited August 13, 2009 by Matthew Dowson