Recently bought boat advice

[douglas_ferguson1]

Good morning all,

 

I'm a longtime reader of the forums but this is my first post!

 

I've just completed the purchase of a 57 foot trad stern narrowboat, I am over the moon as I have wanted one since the age of 18, that was a fair amount of time ago!

 

To cut a long story short, I completed the survey, which was undertaken by a guy named Will Flannery, whom I cannot recommend enough!

He found that there were some minor pits which would need addressing, I contacted the boat yards welder who advised puddle welding should do the trick.

There are a fair few around the water line, but they aren't deep enough to cause an issue... yet.

 

The boat has recently been blacked so this will require dressing it back to expose the pits so they can be filled in.

 

My question is, is it okay to locally re-black the immediate area around the welding? Or is it more advisable to remove the coating and redo it once welding work has been completed?

 

Any advice would be greatly appreciated.

 

Doug

 

 

[Alan de Enfield]

If the pitting is not sufficient to cause concern - why not wait until the Spring / Summer of 2018, have the welding done and re-blacked at the same time ?

 

Now is not a good time to apply blacking, it is too cold and damp and it will just 'fall off' so time, money and dry-dock wasted.

[douglas_ferguson1]

The reason for me asking is that we have decided to have (some) of the interior refitted (a benefit of having a yacht carpenter as a father).

 

We will also be undertaking some other minor works which are more cosmetic than anything else, the boat was previously a weekend cruiser whereas we will be living aboard.

 

The boat is presently on hard standing to make our lives easier for the refit, we are getting a heavily discounted hard standing rate until Feb 17, as we know the owner of the yard so I just saw it as a good opportunity.

Keeps it categorised as preventative maintenance rather than required maintenance.

[dmr]

Any really deep pits will need welding but there will almost certainly be lots of less serious pits. Accepted wisdom is to shot blast and apply a two pack which should stop the pitting dead.

If a boat already has suffered pitting then i think its crazy not to use two pack.

 

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

[Neil2]

There is a contradiction between "minor pits" and "need addressing".

 

Normally if a surveyor identifies minor pitting on a hull it's just a case of maintaining a good regime of hull protection and the rot can be kept at bay almost indefinitely.

 

What would cause concern is anything that might cause a problem in the immediate future, let's say pitting that penetrates the hull enough to reduce the steel thickness below 4mm though this is debatable. If this is what your surveyor is referring to, then the only sensible way ahead is blasting the hull back to bare metal and go from there. Blacking hides a multitude of sins, until you remove it you can't tell how extensive pitting is, or what remedial work is needed.

 

 

[douglas_ferguson1]

There is a contradiction between "minor pits" and "need addressing".

 

Normally if a surveyor identifies minor pitting on a hull it's just a case of maintaining a good regime of hull protection and the rot can be kept at bay almost indefinitely.

 

What would cause concern is anything that might cause a problem in the immediate future, let's say pitting that penetrates the hull enough to reduce the steel thickness below 4mm though this is debatable. If this is what your surveyor is referring to, then the only sensible way ahead is blasting the hull back to bare metal and go from there. Blacking hides a multitude of sins, until you remove it you can't tell how extensive pitting is, or what remedial work is needed.

 

 

Apologies, not always the best at getting my paint across!

 

Evidently, from what the survey advised, the boat appears to be a custom build completed by Evans and Sons, consisting of 15mm base plate, 8mm lower sides (below waterline) and 6mm cabin side.

 

The pitting around the waterline is generally in the region of 0.5mm (these will not be addressed), however one area went to 2.7mm, I argued the toss as it seemed to me more of a dink rather than a pit but none the less it is there and I would like to address it.

 

All measured points showed over 5.3mm, so to say the pitting is negligible is probably a fair point, however given my "newbie status" I am unsure whether this is something i need to consider doing now or wait until next blacking is due.

[Stilllearning]

Apologies, not always the best at getting my paint across!

 

Evidently, from what the survey advised, the boat appears to be a custom build completed by Evans and Sons, consisting of 15mm base plate, 8mm lower sides (below waterline) and 6mm cabin side.

 

The pitting around the waterline is generally in the region of 0.5mm (these will not be addressed), however one area went to 2.7mm, I argued the toss as it seemed to me more of a dink rather than a pit but none the less it is there and I would like to address it.

 

All measured points showed over 5.3mm, so to say the pitting is negligible is probably a fair point, however given my "newbie status" I am unsure whether this is something i need to consider doing now or wait until next blacking is due.

 

Have you asked the boatyard welder what he/she thinks of this "dink"?

My immediate feeling, not having seen the hull, is to either go down the easy route and just black the hull and wait a year or two before doing anything, or to take the hull back to bare metal and two pack it while you have the boat out of the water and easily accessible.

[OldGoat]

Is two pack less 'dependent' on the outside temperature (I have no experience of this stuff). Remember it's quite expensive - so that may be a limiting factor.

[nikvah]

Could you ask your surveyor for his advice as he is probably still familiar with your boat after the recent survey?

[Neil2]

It's fairly important you establish whether this is a "dink" or a rust pit.

 

Even on a heavily built boat like this, evidence of pitting that deep would give cause for concern ie where else on the hull might similarly be affected, (even the best surveyor can't examine every square inch) and what has caused it.

 

Also, I know it's received wisdom that the waterline is the most vulnerable area but I don't subscribe to it. What did the surveyor say about the condition of the baseplate and the area around the chines? I'd be very surprised if there was evidence of pitting at the waterline and none at all lower down. Unless the blacking has really deteriorated and given the amount of diesel floating around the canals these days, that's possible.

 

 

[Stilllearning]

It's fairly important you establish whether this is a "dink" or a rust pit.

 

Even on a heavily built boat like this, evidence of pitting that deep would give cause for concern ie where else on the hull might similarly be affected, (even the best surveyor can't examine every square inch) and what has caused it.

 

Also, I know it's received wisdom that the waterline is the most vulnerable area but I don't subscribe to it. What did the surveyor say about the condition of the baseplate and the area around the chines? I'd be very surprised if there was evidence of pitting at the waterline and none at all lower down. Unless the blacking has really deteriorated and given the amount of diesel floating around the canals these days, that's possible.

 

I think the surveyor said the baseplate was 15mm, so no need to worry about that for some time to come.

[Bee]

!5mm. That's awfully thick. However, like Neil2 I am not convinced that the waterline is the most vulnerable and if it is I think its just good old fashioned 'rust'.

I think pitting can be anywhere and its pitting that normally causes the problems. If you have some welding done then you will need to scrape off the burnt area, then apply some sort of matching covering. After that it depends on your budget, if its out of the water then its a missed opportunity not to paint it so you can pressure wash it then slap a few coats of the same stuff on or go the whole hog and shotblast it and use expensive epoxy stuff. Personally I would pressure wash it, then see what the existing paint is like. If its good then I would use the same stuff again and resign myself to hauling it out more frequently, say every 3 years or so. It doesn't matter what is on it so long as it stays on.

[MtB]

Even really deep pitting can be held at bay with a big enough bilge pump...

 

 

But seriously, 2.7mm pits in 8mm steel don't need addressing in my opinion. But a second survey in two or three years to see if they are still getting deeper would be a good idea.

 

Pitting is regarded as often being caused by electrolytic action when a boat is in a marina connected to shore power. Was this the case, and/or will it continue to be the case?

 

If yes do you have a galvanic isolator you know works?

[Neil2]

Even really deep pitting can be held at bay with a big enough bilge pump...

 

 

But seriously, 2.7mm pits in 8mm steel don't need addressing in my opinion. But a second survey in two or three years to see if they are still getting deeper would be a good idea.

 

Pitting is regarded as often being caused by electrolytic action when a boat is in a marina connected to shore power. Was this the case, and/or will it continue to be the case?

 

If yes do you have a galvanic isolator you know works?

 

This is what was going through my mind - though it's no big deal structurally, you do wonder what has caused a fairly deep pit so has the surveyor checked the hull for stray DC current and/or has the boat been connected to shore power without isolation.

 

One of my abortive purchases a few years ago was a boat that looked fine until it was slipped and then it turned out to be rotten as a pear. The surveyor identified stray 12v current as the cause, it's terrified me ever since.

[Sea Dog]

My question is, is it okay to locally re-black the immediate area around the welding? Or is it more advisable to remove the coating and redo it once welding work has been completed?

 

Any advice would be greatly appreciated.

 

Doug

 

Hi Doug,

 

Welcome to the forum and happy new boat!

 

It's now the wrong time of year to be blacking as the steel is too cold. It's not going to be the right time until after February either, so I'd certainly not be looking at removing or replacing any more blacking than was absolutely unavoidable. Defer whatever welding work you can til next time she's out for blacking.

 

Alan de Enfield said similar early on, but I thought it worth reiterating about the blacking question since most of the other advice is about pitting. Personally, I'd be looking to do any patch to the blacking on an unseasonably sunny and warm day followed by a warm, cloudy night. Good luck finding that!

[Bee]

The problem with pitting is that ALL of the erosion/wasting/call it what you will seems to be happening in those small places. If the rest of the steel has a covering of paint the pits seem to occur in the bits without paint, that is what it seems to be anyway, once a pit starts it keeps on going, surrounding steel may be still ok. I have read that stray currents can occur between, for example, bits of steel where there may be a little bit of dissimilarity within the steel itself. I don't think that fresh (ish) water is a particularly good electrolyte so the best thing to do, as ever, is to keep it all painted. Epoxy is best but B&Q white gloss would probably work so long as you keep the steel covered. Others will disagree with some or all of this but I've seen an awful lot of corroded steel I think it's right.