Have you noticed how boats both large and small
tend to be painted a different color under the water?
Most often it is red,
but actually nowadays you can get almost any color you like.
The reason for it goes back to the earliest days of sailing ships.
In those days wooden sailing ships would slowly plot around the world,
a combination of their slow speed and rough hull
made them an ideal breeding ground for underwater growth.
Just take a look under a pier,
you will see the sort of growth these ships used to suffer.
We’re talking barnacles worms seaweed and things like that.
这里我们所说的是藤壶 蠕虫 海藻之类
So what’s the issue?
Well, all of these things have negative impacts on ships over time.
You get the obvious of things,
like damage to the hull itself, due to worms and the actual growth.
Then you get issues, like the additional weight that they have to carry around and reduction in maximum speed,
还有其他问题 比如 由于船只额外负重
due to the extra drag.
Of course on sailing vessels that dragon weight would impact their ability to sail upwind,
which would yet further reduce their efficiency.
What you need
is a way to stop marine life from growing on the bottom of the hull.
And this is where antifouling comes in.
Antifouling fairly obviously is just a system designed to reduce fouling
by animal and plant life on the underwater sections of a boat or a ship.
Early solutions were to place copper sheets on the hulls of ships.
The Cutty Sark is a great example of this.
And I’ll link to the greenwich maritime museum below
if you want to see more about that.
The primary purpose of the copper sheets was actually to
stop worms eating their way through old wooden hulls.
A secondary benefit though is that
the copper would reduce the growth of plant life.
Of course, as wooden hulls were a place by iron, worm issues did reduce,
当然 随着木质船体被铁质船体所代替 蠕虫问题确实减少了
but they’ve never been eliminated.
Just look at the leisure industry today,
and you’ll still see plenty of wooden hulls around.
And of course, regardless of its construction material,
we still have the same old issue of drag,
caused by the growth of plant life is probably more important.
Now to keep that under control
what were the cost of fuel and efficiency savings on long passage.
We still need antifouling to stop a combination of
worms barnacles and weed from growing on the underside of hulls.
But instead of using the old technique of copper sheets,
we now use a form of paint instead.
That antifouling paint works on the same principle
and actually still uses copper as a biocide.
Though is mostly cuprous oxide,
now mixed in with the paint rather than copper sheets.
It’s the natural red color of those copper oxides
that’s led to the traditional red color of antifouling.
Modern antifouling systems can be broken down into two broad categories: hard and soft.
Soft coatings are designed to wear off over time
continuously exposing fresh biocides as the outer layer of the paint wears off.
Hard coatings on the other hand are designed to be a lot more durable,
they’re meant to last a lot longer.
As the biocides are released,
the durable layer of paint remains.
But of course the biocides contained in the outermost layer do get used up.
Both systems work on the same principle:
they gradually release biocides commonly based on the chemical element copper.
The difference is that soft coatings slowly allow the paint to flake off as well,
as you can imagine there are environmental considerations to think of.
No matter what way you look at it,
antifouling releases via cites and possibly paint into the environment.
That is one reason a lot of ports don’t allow cleaning of hulls.
They don’t want the extra dose of biocides and paint released by the scrubbing process.
So what are your other options？
The cleaners one is to simply use
normal hardware and paint on the other side of the hull.
But that will result in a lot of aquatic growth.
That’s fine on a small boat that
you can pull out the water and clean quite often.
But is not so great on a container ship running around the world.
What would happen if for example a container ship
picked up some seaweed in Asia and carried it into the Baltic Sea?
Where it takes hold and overtakes some of the native species.
Similar things have happened and do actually continue to happen.
Though it’s not so much from hull growth
because of antifouling is more of an issue for a ballast water,
but that’s a topic for another video.
So aside from just using no antifouling,
what could you do?
There is talk of systems that slowly use some sort of jelly from the hull.
The theory is that as the growth attaches to the hull,
the using jelly seeps off and takes the growth away with it.
I’ve never seen it in use,
but if anyone has let me know in the comments below cuz,
it’d be fascinating to look into.
Otherwise there are some silicon based paints that make it hard
for barnacles and things to stick to the hull itself.
Unfortunately these don’t actually stop the growth,
but it makes it easier to clean off.
Send that most ports don’t allow cleaning anyway,
not only because of the historical antifouling issues,
but also they don’t want to clean off species
that are not native to the harbor itself.
The last thing they want is to be overcome by
some sort of invasive weed from the other side of the world.
Anyway, hopefully you’ve enjoyed today’s video
and have liked learning about the paint on the bottom of the hull.
For more content like this every other Friday,
be sure to subscribe right here on the channel.
Until next time thank you for watching and good bye!
下次见 谢谢观看 拜
Have you noticed how boats both large and small