Bottom Plates

[NB Willawaw]

One of the things that puzzles me (and there are many) is:

 

As bottom plates aren't blacked, why don't they corrode faster than they do ?

One forum contributor remarked recently that their 10mm bottom plate had only reduced to 9.8mm in 10 years (or something similar - sorry I forget the exact figures but I think I'm close).

You would think that bare steel permanently in water would rust quite fast.

Is it the absence of oxygen ?

[awatsonbcp]

if theres no oxygen at lower depths someone forgot to tell all the fish that live down there

 

alan

[James York]

The thing with rust is it looks much worse than it is. Quite a few mm of rust is equvilant to very little metal. This coupled with the relativley low oxygen levels at the lower depths means bottom plates corrode very slowly.

[John Orentas]

There are several reasons why the bottom plate is not usually paint protected.

 

1. It is such an horrible unpleasant job that people just don't bother.

 

2. Most of the paint would very soon get worn off anyway.

 

3. The corrosion does reduce with the depth of water, the worst rusting occurs at the waterline, the steel getting constantly wet and dry. The surface rippling action will inevitably oxygenate the water.

 

4. It is a relatively simple matter, and beneficial to have a heavier thickness of base plate though wear at the edges is a greater potential problem than corrosion. A 12mm untreated base will probably out-live your grandchildren.

[ChrisPy]

A 12mm untreated base will probably out-live your grandchildren.

<{POST_SNAPBACK}>

what grandchildren, John??

 

are you trying to tell me something?

 

I'll give one of the kids a good smack if it's true.

[wynd lass(nb.Black Pearl)]

lets face it Chris.....If you ain't got any at YOUR age .......

owwwww I see.....are they gay?

 

Just a joke...keep your hair on....

.......................................................................

Indeed John: infact It could easily be said a 10mmm bottom would see us and various children(if one has them) out?

Edited March 1, 2005 by wynd lass(nb.Black Pearl)

[bottle]

Wynd lass

 

Your signature cannot be right because we are all "mental" on this forum.

 

Those with boats, they keep spending on them and do not leave.

 

Those without boats, read all the warnings about cost etc. but we still want one.

[ChrisPy]

lets face it Chris.....If you ain't got any at YOUR age .......

 

<{POST_SNAPBACK}>

they're both old enough and wise enough ....... to know better !?

 

........... so far - no encumbrances. ........ but my 26yr old daughter is talking about getting a kitten. Is that a sign of broodiness?

 

oh and thank you for the respectful comment about my obvious age and maturity. it will not go unremarked. no offence taken - not half!! Yes, thank you v. v. much, my dear Winching Bird.

[wynd lass(nb.Black Pearl)]

Chris: (suck's in air before speaking) A kitten! that's the first sign of impending broodiness......before you know where you are the poor kitty will be dressed as a baby in a matinee jacket and matching mittens!

 

Re-Age: There's many a good tune played on an old violin.... as the saying goes...,..and I can't/will not recite the rest for fear of recriminations......

 

Winching Bird.........never been called that before, are you sure it isn't meant to be "whingeing Bird?" Chris..............

 

lol

[Richard Bustens]

Bird YES

 

Wingeing NO ( well probably )

 

Sarcastic, overbearing, annoying, cantankerous but extremely attractive YES.

[wynd lass(nb.Black Pearl)]

Richardo: Me sarcastic? Overbearing? annoying? cantankerous?

What's up with you dude? had a sense of humour bypass?

 

Its not my fault if you can't handle little meeeeee...........

 

lol

 

Not to mention a thick base plate(better mention that-keeping the subject alive)

[David Schweizer]

There are several reasons why the bottom plate is not usually paint protected.

 

A 12mm untreated base will probably out-live your grandchildren.

<{POST_SNAPBACK}>

 

I would have agreed with you John, until I had a discussion at the local Marina a few days a go. An utrasound survey on an ex-hire boat which is for sale has revealed that the bottom plate has reduced from 10mm to 4.5 mm in some places. particulaly on the outer edges adjacent to the rear swims. This would appear to have nothing to do with corrosion but with a deep hulled boat being constantly scraped along the concete chined sides and bottom of the K&A Canal between Trowbridge and Bath over the last seven years. When I worked a trip Boat in that same area we had the same problem and had to have new sacrificial chine plates welded on every two to three years.

[Richard Bustens]

O,O,O, I'm pretty sure i could handle you, with care of course.

[ChrisPy]

Richardo: Me sarcastic? Overbearing? annoying? cantankerous?

What's up with you dude? had a sense of humour bypass?

 

Its not my fault if you can't handle little meeeeee...........

 

lol

 

Not to mention a thick base plate(better mention that-keeping the subject alive)

<{POST_SNAPBACK}>

who's got a thick base plate ? wot, like: "how does my bum look in this?" ... .. now who are you insulting ?

 

......... oh, sorry, I'd forgotten all about the subject of this thread.

[John Orentas]

David.

 

A bit selective, the full quote is;

 

"It is a relatively simple matter, and beneficial to have a heavier thickness of base plate though wear at the edges is a greater potential problem than corrosion. A 12mm untreated base will probably out-live your grandchildren".

 

Non the less a hire boat plying a particular length of canal is surely a special case, the average hire boat will do 30 or so 'hard cruising' weeks in a year, the private boat would probably go perhaps 5 much more gentle weeks. That type of wear has always been a problem with ex hire craft and is something potential buyers should look out for, according to my simple arithmetic, a 7 year old hire boat may well have done the equivalent work of 50 years as private boat.

[Guest st170dw]

David.

 

A bit selective, the full quote is;

 

"It is a relatively simple matter, and beneficial to have a heavier thickness of base plate though wear at the edges is a greater potential problem than corrosion. A 12mm untreated base will probably out-live your grandchildren".

 

Non the less a hire boat plying a particular length of canal is surely a special case, the average hire boat will do 30 or so 'hard cruising' weeks in a year, the private boat would probably go perhaps 5 much more gentle weeks.  That type of wear has always been a problem with ex hire craft and is something potential buyers should look out for, according to my simple arithmetic, a 7 year old hire boat may well have done the equivalent work of 50 years as private boat.

<{POST_SNAPBACK}>

 

I must admit I am glad to hear that. My new boat doesn't have any anodes and at the age of 48 I was getting worried! I checked last week and it is still afloat. It was built last March.

 

Dave

Edited March 1, 2005 by st170dw

[David Schweizer]

David.

 

A bit selective, the full quote is;

 

"It is a relatively simple matter, and beneficial to have a heavier thickness of base plate though wear at the edges is a greater potential problem than corrosion. A 12mm untreated base will probably out-live your grandchildren".

 

Non the less a hire boat plying a particular length of canal is surely a special case, the average hire boat will do 30 or so 'hard cruising' weeks in a year, the private boat would probably go perhaps 5 much more gentle weeks.  That type of wear has always been a problem with ex hire craft and is something potential buyers should look out for, according to my simple arithmetic, a 7 year old hire boat may well have done the equivalent work of 50 years as private boat.

<{POST_SNAPBACK}>

 

Point taken, but what I was trying to indicate was that there are some conditions under which the bottom plate will apprently wear quite quickly. As a matter of interest my boat is an ex-hire boat and had done 19,000 hours in fifteen years when I bought it. The chines near the swims were getting a bit close to the welds which one would expect after that level of use, but there was no wear in the thickness of the plate, which is what has happened to the boat that I described in my earlier posting.

[Richard Bustens]

I think!

That it depends a lot on the chemicals in the water in a particular canal, so some boats on certain canals deteriorate at a faster rate than the same boats on another canal.

It would be handy to know which canals deteriorate the steel faster than others.

[nbtafelberg]

Hi All

 

I think the River Wey Navigation does especially with longer boats due to the fact there are a lot of metal moorings that scrrapppe your boat...

 

Now, where is that can of bitumen?

[NB Willawaw]

Thought you might be interested in this shot of a bottom !

 

http://www.nb-whisper.com/liftout/liftout-Pages/Image4.html

[Paul Evans]

Are we allowed one crack? That bottom's clearly not be treated to moisturising lotions!

 

But seriously, what are the lumps below the anode? Was it corrosion bubbling up or just frash water mussels/barnacles clinging to the shell?

[NB Willawaw]

From the other shots I saw of Whisper when she was lifted out of the Thames, I think they are fresh water mussels. There was even one on the weed hatch plate.

 

Mark

 

Are we allowed one crack? That bottom's clearly not be treated to moisturising lotions!

 

But seriously, what are the lumps below the anode? Was it corrosion bubbling up or just frash water mussels/barnacles clinging to the shell?

<{POST_SNAPBACK}>

[ChrisPy]

From the other shots I saw of Whisper when she was lifted out of the Thames, I think they are fresh water mussels. There was even one on the weed hatch plate.

 

Mark

<{POST_SNAPBACK}>

obviously one of the disadvantages of the new clean river water campaigns. Soon we'll be lifting out twice a year to refresh the antifouling like a salty type has to.

[nigel carton]

Paul,

 

definately fresh water mussels. They can be quite bad in some places on the cut. I bought a boat from Kingfisher marina on the GU, got out the water at Willowbridge for a blacking and the bottom was hanging with these little critters. What made things worse was it was August, and I didn't start work for a couple of days, the smell was unbearable. I managed to fill 12 bin liners.

[Paul Evans]

So the next question is, do fresh water mussels contribute to corrosion or do they, by providing a cover, protect the steel? Does anybody know of any research into this and what were the results?