Poured Concrete for Ballast

[Sheepshank]

Seems a waste to add concrete as ballast when a bit of extra baseplate steel would extend hull life. Quite bit more expensive though! Anyhow, poured concrete would have to go into the new build hull before fit out, wouldn't it? So some adjustable ballast would be required for final trimming after fit out. Perfect solution: bit more steel, some poured concrete and some paving slabs. Too easy, would have been thought of before......

[John Orentas]

Seems a waste to add concrete as ballast when a bit of extra baseplate steel would extend hull life. Quite bit more expensive though!

 

 

Yes, I specified a 12mm thick bottom-plate, it reduced the ballast problem by 50%.. If I were to build another I would use 16 or even 20mm steel. In the context of a new boat the extra cost is small

[Big Steve]

I agree. if I had the loot to specify a newbuild I would go for a extra thick baseplate/hull and do away with ballast altogether. My poured concrete job does have 1/2 a ton of bricks at the sharp end to trim it.

[DHutch]

We have a 10mm base plate, but then still 8 tonnes of (non poured) concreate spread evenly over most of the baseplate, in the form of 2" slabs.

- We've lost no steel off the the 10mm in 15 years, and having more than that to start off with, is just wasted money, if you ask me.

 

 

Daniel

[Hairy-Neil]

...... Probably where my asthma started.

 

Yeeesss. I too have issues with Perenial Rhinitis, Hay Fever and Asthma.........Ho hum.

 

If I were to build another I would use 16 or even 20mm steel. In the context of a new boat the extra cost is small

 

- We've lost no steel off the the 10mm in 15 years, and having more than that to start off with, is just wasted money, if you ask me.

Daniel

 

 

A friend's 'replica' tug hull was built with a 25mm base plate, as much to increase the cabin headroom without having problems of excessive draught or a top heavy appearance.

Edited October 2, 2007 by Hairy-Neil

[ChrisPy]

- We've lost no steel off the the 10mm in 15 years,

do you have a blacked bottom, Daniel?

[Gary Peacock]

If you just keep increasing the base plate thickness you will get some interesting welding issues arising.

 

From the CoP.

 

Where the thickness of two plates to be joined by welding are different, the difference between those two members’ should not be greater than a factor of 2; i.e. the thicker of the two plates shall be no greater than twice that of the thinner plate. e.g. 12mm bottom shell to 6mm side shell.

 

10mm or 12mm sides would be a bitch to work with. We are now using 8mm and that 2mm makes them a lot more rigid, in some areas this is a bonus in others it's a pain.

[carlt]

do you have a blacked bottom, Daniel?

[ChrisPy]

akshully it was a serious question.

 

I did originally write '..... black bottom' but then realised it would only elicit ribald comments from the oi-polloi, but it seems they can't be kept down, whatever words I use .............

[blackrose]

We have a 10mm base plate, but then still 8 tonnes of (non poured) concreate spread evenly over most of the baseplate, in the form of 2" slabs.

- We've lost no steel off the the 10mm in 15 years, and having more than that to start off with, is just wasted money, if you ask me.

Daniel

 

Do you mean no loss of steel from the inside? Unless it's been wet down there I don't see any reason why a baseplate would corrode from the inside.

 

If, on the other hand, you mean you've got no corrosion on the outside, then I'd like to know if your baseplate has been regularly blacked?

 

Here's a picture of the underside of my 2 year old unpainted baseplate taken last weekend. (Apologies to anyone who has already seen this picture on another thread and for taking this thread off topic). Now I know that anyone who says baseplates don't rust doesn't know what they are talking about. I'm a bit concerned about the small dark orange rust scabs.

 

Edited October 3, 2007 by blackrose

[ChrisPy]

Now I know that anyone who says baseplates don't rust doesn't know what they are talking about. I'm a bit concerned about the small dark orange rust scabs.

it will make a big difference if you are a salty sailor, Mike. The Tideway is not quite the same as the River Kennet.

[blackrose]

it will make a big difference if you are a salty sailor, Mike. The Tideway is not quite the same as the River Kennet.

 

But I only go out there a couple of times a year and I'm only in the tideway for a couple of hours each time. The rest of the time she's in non-tidal canal water.

Edited October 3, 2007 by blackrose

[Gary Peacock]

Do you mean no loss of steel from the inside? Unless it's been wet down there I don't see any reason why a baseplate would corrode from the inside.

 

If, on the other hand, you mean you've got no corrosion on the outside, then I'd like to know if your baseplate has been regularly blacked?

 

Here's a picture of the underside of my 2 year old unpainted baseplate taken last weekend. (Apologies to anyone who has already seen this picture on another thread and for taking this thread off topic). Now I know that anyone who says baseplates don't rust doesn't know what they are talking about. I'm a bit concerned about the small dark orange rust scabs.

 

 

There's nothing wrong with that bottom for two years it looks fine it probably looked like that after 6 months and wont look a lot different in 6 year!

[blackrose]

There's nothing wrong with that bottom for two years it looks fine it probably looked like that after 6 months and wont look a lot different in 6 year!

 

Thanks, that's reassuring but I'm still going to black it next time. Would pressure washing alone be sufficient preparation for the blacking - will it knock the rust off or do you have to grit blast first?

 

Do Legard Bridge boats have their baseplates blacked?

Edited October 3, 2007 by blackrose

[Guest]

There's nothing wrong with that bottom for two years it looks fine it probably looked like that after 6 months and wont look a lot different in 6 year!

I was looking at a thirty seven year old bottom a bit earlier, and it looked just fine.

 

Our previous boat was/is close to 14 years old, and the bare bottom (ooer) plate looked fine when hauled out. It had a few orange blisters like the photo and a little surface rust,but it was very minimal.

[Gary Peacock]

Thanks, that's reassuring but I'm still going to black it next time. Would pressure washing alone be sufficient preparation for the blacking - will it knock the rust off or do you have to grit blast first?

 

Do Legard Bridge boats have their baseplates blacked?

 

Not the fresh water ones the salty ones can be done but we can't do it, the HSE boys have a field day about working under 30 plus tons of boat!

 

I would just wash it then black it, to get it blasted first would cost a bit and in all honesty on a fresh water boat I wouldn't really bother doing it at all. How many springers with 6mm bottoms from new are still going strong without rotting through.

 

One place to keep an eye on is under the counter plate (I know there is a proper Rosie and Jim name for this plate but I have forgotten it!) this should be the same thickness as the base plate, but recently a cost saving was spotted and some hulls now use some very thin plate here, unlike the baseplate this is often exposed to the air can be a site of rapid corrosion if the blacking fails!

Edited October 3, 2007 by Gary Peacock

[blackrose]

Not the fresh water ones the salty ones can be done but we can't do it, the HSE boys have a field day about working under 30 plus tons of boat!

 

I would just wash it then black it, to get it blasted first would cost a bit and in all honesty on a fresh water boat I wouldn't really bother doing it at all. How many springers with 6mm bottoms from new are still going strong without rotting through.

 

One place to keep an eye on is under the counter plate (I know there is a proper Rosie and Jim name for this plate but I have forgotten it!) this should be the same thickness as the base plate, but recently a cost saving was spotted and some hulls now use some very thin plate here, unlike the baseplate this is often exposed to the air can be a site of rapid corrosion if the blacking fails!

 

I'm pretty sure my counter's only 6mm (the baseplate is 10mm), but I blacked it well last time and even had an anode welded on each side of the counter. I couldn't see any signs of corrosion last weekend.

 

By the way, I gave all the anodes a scrub with a wire brush while she was out. I'd never heard of this before but I just thought why not?

Edited October 3, 2007 by blackrose

[magnetman]

The Uxter plate? I was bothered when i saw a boat in dock with a thin plate here, just where corrosion is likely, seems like poor design.

[blackrose]

The Uxter plate? I was bothered when i saw a boat in dock with a thin plate here, just where corrosion is likely, seems like poor design.

 

Uxter plate? I'd always thought it was just called the counter. Anyway, if the sides are only 6mm and part of them are always on the waterline why does the uxter have to be any thicker? My uxter is about 3" below the waterline.

Edited October 3, 2007 by blackrose

[Gary Peacock]

The Uxter plate? I was bothered when i saw a boat in dock with a thin plate here, just where corrosion is likely, seems like poor design.

 

That's the word sorry I was just been lazy and didn't feel like thinking too much about it!

 

It's not about poor design it's about cutting costs the base plate is normally the most exspensive bit of steel in the hull if you can shave off £300.00 or so per hull it's worth doing.

 

Unfortunately some started doing this, a lot of others scoffed about it then started doing it too and slowly it seems to be becoming very common practice.

 

Another one to keep an eye out for with baseplates is:-

 

When is 10mm not 10mm plate? Answer when it's 8mm plate!

[blackrose]

Another one to keep an eye out for with baseplates is:-

 

When is 10mm not 10mm plate? Answer when it's 8mm plate!

 

Well if a builder specifies 10mm and then gives you 8mm they are clearly in contravention of trading standards.

 

Mine is definately 10mm.

Edited October 3, 2007 by blackrose

[Gary Peacock]

Uxter plate? I'd always thought it was just called the counter. Anyway, if the sides are only 6mm and part of them are always on the waterline why does the uxter have to be any thicker? My uxter is about 3" below the waterline.

 

The prop wash can be a bit heavy on blacking here and because a lot of air is often pulled under the counter they quite often rot here, another common failure in this area is that it used to be a common practice to drain the deck Via box sections through this plate where the thin wall of the box section introduced a week point in the hull that couldn't be blacked at all.

[smileypete]

One place to keep an eye on is under the counter plate (I know there is a proper Rosie and Jim name for this plate but I have forgotten it!) this should be the same thickness as the base plate, but recently a cost saving was spotted and some hulls now use some very thin plate here, unlike the baseplate this is often exposed to the air can be a site of rapid corrosion if the blacking fails!

Pour an inch or two of concrete on then!

 

Some galv reinforcing mesh and cement fibres too for good measure...

 

Seriously though, places like this are a good place to add weight with thicker plate, provided the stern doesn't sit too low.

 

cheers,

Pete.

[Timleech]

The prop wash can be a bit heavy on blacking here and because a lot of air is often pulled under the counter they quite often rot here, another common failure in this area is that it used to be a common practice to drain the deck Via box sections through this plate where the thin wall of the box section introduced a week point in the hull that couldn't be blacked at all.

 

It is, as others have said, the Uxter plate, and absolutely nothing to do with Rosie & Jim (cringe)

 

I see a lot of nb's out of the water for blacking & other work, very few suffer serious external corrosion in this area.

What is very common, though, is serious internal corrosion from, as you say, leaking deck drains, also just from condensation which collects & can't drain away.

Actually a cement wash might be a good way to protect this area

Bilge areas of barges are/were often protected in this way from new.

 

Tim

[thomasthetanker]

If you add more ballast, the boat sits lower in the water so you get more headroom in the cabin