rust under foot

[simonsayssaysimon]

I've found a boat I'm happy with on a mooring I'm happy with. First warning sign though is the boat hasn't been blacked in 6 years which made me nervous.. but a survey and a blacking would solve this. Second warning sign (and this is the one that makes me think I should step away) is on inspection under the floorboards the steel below showed signs of quite heavy rusting. Is this normal?

Edited April 27, 2009 by simonsayssaysimon

[Berty]

I've found a boat I'm happy with on a mooring I'm happy with. First warning sign though is the boat hasn't been blacked in 6 years which made me nervous.. but a survey and a blacking would solve this. Second warning sign (and this is the one that makes me think I should step away) is on inspection under the floorboards the steel below showed signs of quite heavy rusting. Is this normal?

 

Hi,

 

My boat was build in 1984, and had paving slab ballast over roofing felt. On removing the felt there were some really bad patches of rust.

 

I had a survey done, and from an original spec of 6mm, the minimum tested point was 5.3mm, so 0.7mm over 25 years.

 

Steel inflates by a factor of 10 when it rusts, so lots of rusts doesn't necesarily mean lots of steel lost.

 

I scraped all the rust off, then greased the bilges and stuck the ballast back in. Hopefully it'll last another 25 years before needing any further attention!

 

So, in short, don't be too scared by rust, but *do* get a proper hull survey including ultrasonic thickness measurements. Ask your surveyor to do a few extra test points in any areas you suspect to be dodgy.

 

Finally, if you like the mooring, you can get a better boat much more easily than you can find another/better mooring.

 

Belt and braces approach:

 

Get the survey done and use it as a bargaining tool. Do not agree to a price before having the survey done, not even "subject to survey". Tell the buyer you will consider buying the boat, but that you require a full survey and valuation, and that you may make on offer on the basis of the result of the survey.

 

You should expect to meet the full cost of the survey, including getting the boat out of and back into the water, the cost of grinding off the paint down to clean steel for the thickness measurement and the cost of properly repainting it fit for going back in the water. You should meet this cost whether or not you decide to buy.

 

I imagine that's going to cost you in the region of £1000!

 

Note that I'm quite conservative when it comes to spending lots of money, and I don't like risk. Hence to me it was good value for money to get the survey done. I know a fair few people who are much less risk averse and they'll quite happily take a punt on a boat after they've done their own inspection, provided the price is right. These people usually know what they're on about though, and have several years experience of messing about in boats under their belts.

 

Hope some of that rambling is helpful!

 

Cheers,

Berty

[RLWP]

Hi,

... the cost of grinding off the paint down to clean steel for the thickness measurement and the cost of properly repainting it fit for going back in the water.

 

Cheers,

Berty

 

That's an unusual way of doing an ultrasonic hull thickness measurement. I haven't seen a surveyor remove blacking to do one before.

 

Richard

[paulcatchpole]

That's an unusual way of doing an ultrasonic hull thickness measurement. I haven't seen a surveyor remove blacking to do one before.

 

Richard

 

Dunno!

 

It was how it was done for us - use a grinder to clean an inch square patch of steel to bright and sparkly, then lube up and ultrasound.

 

Mind you, we owned the boat at the time, and it was to be reblacked in that week, so no problem there...

 

PC

[blackrose]

That's an unusual way of doing an ultrasonic hull thickness measurement. I haven't seen a surveyor remove blacking to do one before.

 

I have. I thought that's how measurements were usually taken?

[DHutch]

Sounds about right.

A lot of boats do rust inside, even ours which was shot blasted painted with good grade paint is showing some signs at the age of 18. So if your buying a boat of that age there will be rust almost certainly, but as said it might not be as bad as it looks, and assuming you keep it relativly dry in there it should get much worse, and there is a lot of material to go at.

 

However as said, unless you confident about what you doing a survey is the way to do. And that should include ultrasounding and the survayors thoughts on the rusting. Talk to him to, express your conserns, and get his take on the situation.

 

 

 

Daniel

[Gibbo]

That's an unusual way of doing an ultrasonic hull thickness measurement. I haven't seen a surveyor remove blacking to do one before.

 

I think you're being mischievous.

 

If the blacking isn't removed, and a gel applied between the clean steel and the sensor, then an ultrasonic thickness tester is nothing more than an expensive random number generator.

 

Gibbo

[sociable_hermit]

If it hasn't been blacked in 6 years, it makes me wonder why not, and what other jobs haven't been done. There might be very good reasons, but it's a question worth asking.

[Timleech]

I think you're being mischievous.

 

If the blacking isn't removed, and a gel applied between the clean steel and the sensor, then an ultrasonic thickness tester is nothing more than an expensive random number generator.

 

Gibbo

 

Not entirely true. There are some which work through the coating using 'multiple echoes',they work reasonably well.

 

http://www.cygnus-instruments.com/

 

Other more conventional types vary in their tolerance of imperfect surfaces.

 

Tim

[Gibbo]

Not entirely true. There are some which work through the coating using 'multiple echoes',they work reasonably well.

 

http://www.cygnus-instruments.com/

 

Other more conventional types vary in their tolerance of imperfect surfaces.

 

Tim

 

But have you actually tried them? I have. They're useless.

 

They might crack it one day, but the ones around at the moment are a joke. You actually have to know what the answer is before using it otherwise you could walk away stating that the hull is 2.1 metres thick. Pressing a finger on the other side of the steel affects the readings!

 

Gibbo

[paulcatchpole]

Sounds about right.

A lot of boats do rust inside, even ours which was shot blasted painted with good grade paint is showing some signs at the age of 18. So if your buying a boat of that age there will be rust almost certainly, but as said it might not be as bad as it looks, and assuming you keep it relativly dry in there it should get much worse, and there is a lot of material to go at.

 

Daniel

 

Below is what under our floor looks like - on a 30yr old boat, with a wet bilge, and having lost around 1.5mm average thickness over that time.

 

 

Not sure if I should be concerned about this or not - it's about as bad as I was expecting, and I'm not sure I can be bothered to lift all the floor in the boat to start doing something about it.

 

Interestingly, before the welding work, the internal welds between base and side were all that was holding the base on - so despite this all looking quite rusty, it must still have some intrinsic strength!

 

PC

 

But have you actually tried them? I have. They're useless.

 

They might crack it one day, but the ones around at the moment are a joke. You actually have to know what the answer is before using it otherwise you could walk away stating that the hull is 2.1 metres thick. Pressing a finger on the other side of the steel affects the readings!

 

Gibbo

 

Is this similar to the Ultrasonic CTGs which claim to show both clearcoat and topcoat thicknesses separately? I've heard mixed results of those too. I'm sticking with my 80s [bright orange] electromagnetic one, with analogue meters...

 

PC

[Timleech]

But have you actually tried them? I have. They're useless.

 

They might crack it one day, but the ones around at the moment are a joke. You actually have to know what the answer is before using it otherwise you could walk away stating that the hull is 2.1 metres thick. Pressing a finger on the other side of the steel affects the readings!

 

Gibbo

 

I think that 'knowing the answer before you start' is true to some degree with all ultrasonic thickness meters. Good surveyors do the ultrasonics after visual and hammer checks.

Yes I have tried one of the Cygnus meters, in fact I own one. I don't think it's any more easily confused than other types that I've used, provided you're within the proper range of the transducer. The one I have only goes down to 3mm, try measuring less than that & you get silly results so you need to know (not difficult with a hammer) that you're above 3mm. They do a transducer for thinner materials, I haven't even dared to ask the price and I have the feeling that it might be more troublesome.

 

Tim

[DHutch]

When EA was survayed for insurence and valuation the hull was linished back to bright at all points tested.

- Which was 1m spacing around hull at three points, 100 in on baseplate, 100m up on side, and at waterline. Or somthing like that.

 

To join in, these are the best of a few photos i took of emilyanne hull when we had some floorboards up to job in hand.

 

 

Under the back cabin, where it sometimes damp from rain geting in through back deck (lowest point of baseplate)

 

 

Under the main bilge, which is what most of it looks like. Bloody good for 17yo hull (photos taken a year ago)

 

Closer look at the above.

 

 

By the batterys, which are under the coal bunker, which can sometime be a source of dampness, as well as coaldust and assorted nastys, and areas it would have been very hard to get a good paint coat.

 

 

 

 

 

Daniel

[RLWP]

I think you're being mischievous.

 

If the blacking isn't removed, and a gel applied between the clean steel and the sensor, then an ultrasonic thickness tester is nothing more than an expensive random number generator.

 

Gibbo

 

Not at all. I have watched our hull being measured twice without any blacking being removed. Admittedly the last time was partly on worn bits that had no blacking left.

 

Are you seriously saying that a surveyor would attack someone elses property with a grinder so I can know the hull thickness. And leave loads of little patches to be blacked afterwards.

 

Richard

Edited April 27, 2009 by RLWP

[ditchcrawler]

I've found a boat I'm happy with on a mooring I'm happy with. First warning sign though is the boat hasn't been blacked in 6 years which made me nervous.. but a survey and a blacking would solve this. Second warning sign (and this is the one that makes me think I should step away) is on inspection under the floorboards the steel below showed signs of quite heavy rusting. Is this normal?

How old is the boat, an old one may only have a 5mm base plate where as a newer one could well be 10mm or thicker.

[Gibbo]

Are you seriously saying that a surveyor would attack someone elses property with a grinder so I can know the hull thickness. And leave loads of little patches to be blacked afterwards.

 

Yeah. Because they don't work unless you do so.

 

Have you heard of Ernie? That's what an ultrasonic gauge is without excellent contact to the steel.

 

Odd. I had a chance to take some photos of a boat with the blacking sanded off every 1 metre down the length of a boat for ultrasonic testing on saturday but I didn't bother as it seemed so routine to me.

 

Gibbo

[alan_fincher]

Gibbo,

 

I've no reason to doubt what you are saying.

 

However, I can say I see quite a lot of boats surveyed by different surveyors, and I don't recall any taking things back to the metal, (well not where we moor, anyway).

 

Most have the weed chiselled off, but the blacking is always left largely intact.

 

If that's no good, then there are quite a few surveyors taking the p*ss.

 

On our survey report the numbers were credible, and certainly showed little randomness. So either our surveyor had a device that wasn't troubled by the blacking, or he just made up some numbers he thought we would be happy with. Obviously I don't have to ask which of those two possibilities gets your vote.

[churchward]

That's an unusual way of doing an ultrasonic hull thickness measurement. I haven't seen a surveyor remove blacking to do one before.

 

Richard

Ours was done that way. The surveyor said it was the only way to get an accurate reading with the ultrasound equipment he was using he also put on some gel just like they use on a pregnant womens stomach again to make the device work effectively.

 

Gibbo,

 

I've no reason to doubt what you are saying.

 

However, I can say I see quite a lot of boats surveyed by different surveyors, and I don't recall any taking things back to the metal, (well not where we moor, anyway).

 

Most have the weed chiselled off, but the blacking is always left largely intact.

 

If that's no good, then there are quite a few surveyors taking the p*ss.

 

On our survey report the numbers were credible, and certainly showed little randomness. So either our surveyor had a device that wasn't troubled by the blacking, or he just made up some numbers he thought we would be happy with. Obviously I don't have to ask which of those two possibilities gets your vote.

perhaps there are differfent types of machine but ultrasound needs to be in contact with the bare metal normally and as I say above you should use the ultrasound gel also.

[Timleech]

Ours was done that way. The surveyor said it was the only way to get an accurate reading with the ultrasound equipment he was using he also put on some gel just like they use on a pregnant womens stomach again to make the device work effectively.

 

The older kit I used to have, still have but now more or less defunct, needed a squeaky clean smooth surface as well as couplant gel. Some newer kit using the same principle (single echo with a split transducer) is much more tolerant and doesn't need such a high degree of surface prep. The Cygnus that I have now will work OK with ordinary amounts of surface coating and within the transducer range. All need some couplant, Swarfega or grease can both work in the absence of the proper gel, but both have disadvantages.

 

Tim

 

Edited because I should have said that some thickness meters might give a reading through surface coatings but that reading won't be accurate unless it's the multiple-echo type of gear. Ultrasonic thickness meters work by measuring how long it takes a pulse of ultrasound to travel through the material, bounce off the far side and return to the transducer. If it's passing through a surface coating as well as the steel that will affect the reading to some degree which depends on the coating thickness and the sound velocity through the coating.

Edited April 27, 2009 by Timleech

[simonsayssaysimon]

How old is the boat, an old one may only have a 5mm base plate where as a newer one could well be 10mm or thicker.

 

Firstly thanks for all the replies. Berty your ramble was certainly useful. User photographs showing rust deposits on other boats also helped assure me that some rust is normal.

Visually under the floor seems dry with pretty badly rust bubbled bilge paint so without attacking it with a scraper it's hard to draw comparison to the pics. I guess the survey will be the only way to know just how bad it is.

 

I'm still a bit tentative to proceed but failing buying a new boat, I suppose rust comes with the territory. Or wait longer for a better maintained boat to come up within range.

 

The boat is from 93 and as a correction to my initial post the boat hasn't been blacked in thirteen years due to the owner's belief that the boatmen of old didn't do it. The engine has however been meticulously serviced.

[Queenofthenight]

Just had a lovely boat surveyed and one of the main things that needs doing is to "clean steel in bilges of loose scale, rust and coatings, treat with rust inhibitor and paint with suitable bilge paint."

 

My question is, does this mean that I will have to remove everything from the boat to complete the job? Kitchen and everything? Sounds like a huge pain in the arse-does anyone have any tips or advice?

 

Many thanks.

[Ex- Member]

Just had a lovely boat surveyed and one of the main things that needs doing is to "clean steel in bilges of loose scale, rust and coatings, treat with rust inhibitor and paint with suitable bilge paint."

 

My question is, does this mean that I will have to remove everything from the boat to complete the job? Kitchen and everything? Sounds like a huge pain in the arse-does anyone have any tips or advice?

 

Many thanks.

 

Hi Queen

 

 

If the bilges under the kitchen? need doing then the only of gaining easy assess would by removing anything that would obstruct such access. Basically if there's lots of rust in the bilges then moisture has or is gaining access there and the reasons for that I would want establishing. Are you sure the surveyor meant the boats entire under floor or just the bilge which is where the engine compartment generally is? and where any water ingress is supposed to end up.

 

If you give details of the boat, age, builder, style etc members will be able to advise further. The more info you impart, the better understanding of the problem and possible solution could be arrived at.

 

 

 

[Queenofthenight]

It's a 70's Norseman hull Hancock and Lane. The hull seems to be in good condition otherwise, which is good news for a boat that old!

[ditchcrawler]

Stareded reading this thread and thought Gibbo was back, then I sPotted the date

[Ex- Member]

It's a 70's Norseman hull Hancock and Lane. The hull seems to be in good condition otherwise, which is good news for a boat that old!

 

Hi again

 

you need to ascertain what your surveyor means. Is the area of rust in the bilge located @ the engine room????, or is there rust throughout the entire floor of the boat which can also be termed the bilge or bilges.

 

If the rust is only in the bilge in the engine area then although an awkward dirty job, it's perfectly doable. If under the floor of the boats cabins and as you stated "kitchen" which suggests it is, then you're looking a major work removing fitments and floors to gain access.

 

Other members may be more familiar with Norseman hull and the type of bilge arrangement though.