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 back 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 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 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 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 is 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 both so

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