And the ocean itself is salty liquid hate.

The ocean is one beautiful lovecraftian beast kid.

This 'battle' is going to be our destruction.

The thing is that chemistry and sience general can solve most problems but it's always a matter of cost. You probably could built a layer of Teflon coating around the hull and never had to scrub it again. Buts it's just way more economical to just scrub it from time to time

They didn't have power tools

When I learned it, I was surprised how much maths and physics was involved, but it made it really interesting to learn!

@@CasualNavigation Sorry, but its a really easy task, if you know how to place the blocks beneath the ship. If you have ever put a sailboat on a trailer, you know its not hard.

@@petersizen3897 If you've ever put a sailboat on a trailer, you understand how to dry dock a multi-hundred ton container ship. Basically the same thing. Makes sense, good to know.

@@mrnicomedes have you ever heard that there are wave pools where they test scaled down ships? Basically the same thing.

@@CasualNavigation that’s the reason why there isn’t just one middle line of blocks. Side blocks will counter the rolling movement. Apart from distributing the weight over more blocks these blocks ensure that the ship will not capsize.

Served on older boats, but yeah, same thing in 'rotton Groton' lol. And rig hoses to provide cooling water to key components.

I believe the great lakes freighters don't have the same environmental restrictions. They're not gonna pick up an invasive Asian species, and then blast it off in a European port, because they're contained to one area I believe. But I may be wrong.

I’m a Mate on a Great Lakes freighter, and you’re both correct. If we have to do repairs on either end, you can trim the ship by the head or stern by removing the ballast from the opposite end, albeit the Chief Mate calculates and carefully considers the moments and stress beforehand. It’s common for bow thruster repairs FWD or rudder/propeller repairs AFT. Vessels operating solely on the Great Lakes have minimal restrictions on discharging ballast because the water is considered homogeneous (as of writing no law requires ballast to be exchanged, the EPA only requires a record of ballast exchange to be submitted). In the early 2000’s Salties (foreign-going vessels) brought over many invasive species including the Zebra Muscle which reeked havoc on local marine life, particularly bad on Lake Erie. Now, vessels coming into the system are required to perform a ballast exchange or make use of filtering equipment before entering inland waters. In my experience dry-docking, the process was a large-scale event but relatively simple. Wooden blocks hung over the wall of the dry dock between the ship’s hull to gauge the transverse distance and a spotter gauging the longitudinal distance by a marker, held in place by the ship’s mooring wires until she was stable on the blocks. Vessels require a dry-dock every five years but can apply for an extension if suitable.

@@thomas1910 Thank you. Being a rag bagger I have seen all the processes you describe. Refreshing to get the straight information. I routinely sail under the Bluewater Bridge,, port has been either Sarnia or Port Huron. It made learning the requirements of the big boys , channel, berthing, stern swing, current under the bridge,, rules of the road,,,, almost from the first time I ventured out on to Lake Huron an absolute. I have often been the last guy out with sails hoisted in late November and dodged ice in the spring. My hat is off to you guys, professional and skilled, and never seen an exception to that.

@@thomas1910 thanks for the reply. I'm not a seaman but I have to deal with invasive species control in coastal boundaries as part of my job so I was just basing it off of that. Thank you for explaining how it works.

That's really interesting. I hadn't thought about that before, but it makes complete sense.

I'm sure they love the breakfast!

Agreed! There are keel blocks along centerline, AND bilge blocks farther outboard that provide support from tipping over.

Yeah I was wondering why they don't just have two sets of blocks. I know whenever you have a question that has the word "just" in it, there's a reason why you don't "just" do that. Maybe there's still something, idk.

It depends on the size and hull-form of the ship, what you're docking for, and where your openings are, but it should be remembered that the ship was (probably) built sitting on its keel with the frames sharing the load along the perpendiculars. In my experience, the chosen yard for docking hangs a plumb bob at the inner end of the dock matching the dock - and the ship's centreline, then once the ship's in, another is suspended across the dock behind the stern. The ship is trimmed and lowered slowly, as timber supports are readied to hold the ship upright from the dock wall terraces. If you know the middle of the dock, you 'just' need to middle the ship on the plumbs as its lowered to get the keel on the blocks.

@@ginskimpivot753 yeah I don't think anybody's using Timber on an 800 ft long cargo ship for cribbing but I hear you in theory

@@markvickroy6725 Oh, timber's used extensively, but every ship has unique requirements. Timber is cheap, convenient to cut, shape and use quickly, and where wedges are employed and used arbitrarily to fill gaps and apply further bolstering, they will float out and not cause issues when the dock is refilled. For the blocks on the dock bottom, timber will yield and equalise - or share- the load - much like a fence-post lowered onto 4 different pillows in a line on the floor. With large flat-bottomed vessels, particularly carriers, terrace timbers wouldn't be needed, but anything with a deep-V hull-form needs side support which cannot damage the side by virtue of being harder or as hard as the material it supports. These timbers are usually wedged in place as the hull settles down on the blocks, so that when the dock is filled later, the force they exert - always in an upwards direction from terrace to vessel - automatically reduces as the ship rises.

Usually you'll have an odd number amount of rows, either 3 or 5. At the bow and stern the keel blocks (middle row) will be the longest, making the representation in the video quite accurate actually.

My guess would be that it's easier to account for the forces keeping it trimmed to the stern on the way down. Even if it's technically better to retrim as you drain, if it also increases the chances of human error when the other process is good enough it's not worth it. Just a guess. I'm not really sure. No clue why they don't change trim once they're down.

My experience was that when going into dry dock, u will be asked to maintain minimum ballast because tanks need to be emptied for the inspection. Any extra water in the tanks means delaying the schedule, which in turns cost extra money. That’s why u only pump out the water, not in. Also, it’s considered a bad practice not pumping out ur ballast in time when ur ship is sitting on the blocks, because u’ll cause extra stress on the ship’s structure, which is totally avoidable. As for re-floating, u’ll also be asked to calculate the minimum amount of ballast u need. The yard will pump water into ur tanks as per ur calculation, and charge u. As far as i can remember, we only maintain even keel cuz we were just a handysize bulker, pretty light when emptied. But i figure the method mentioned in the video is more controlled compare to just float the whole ship at once with an even keel.

Any weight in the ship needs to be supported by the hull which is outside of its normal "supportive" water surroundings, so you need the weight to be kept to a minimum. As for leaving drydock, you can aim for zero trim if you want, but it is normally easier to control the ship if it lifts off gradually, and you know which end is going to lift first.

@@CasualNavigation @Tung-Chiao Wu Ah, many thanks for both your answer, yeah, reading it now and actually thinking about it this makes complete sense. Thanks for enlightening me :)

Every ship has a docking plan from the builder's that shows the proper locations for the blocks and the acceptable stresses. Adding ballast could bring these stresses up too high. As stated before usually they want the tanks dry so they can perform work, so adding water is counter productive. Also the ships crew has nothing to do with the positioning of the ship. Once the ship enters the dry dock the dock master assumes responsibility for the vessel. They use winches from shore to position the ship and divers to verify its right

Technically, the drydocking period is 36 months for inspection of the bottom, but with a possibility to replace one of those by an afloat survey before 15 years of age. Passenger ship have shorter period of time between bottom surveys.

In another few years in the next dry dock session

Shipbuilder/repair here, you don’t. At least not this time around. You can see the area the last blocks were when you go down the dry dock; sometimes the blocks are laid super close to the last blocks so some areas aren’t even cleaned the second go around.

Answers are below for large ships. For small boats like mine you shift the supports after you put the first coat on. The blocks under the keel are placed so I can get every thing but a very small bit. That part gets painted when the boat is in the slings off the ground just before it is launched. You lie on your back under 13000 lbs. of boat and hope the slings don't decide to part at that moment and paint. The paint gets all of maybe an hour to dry if they stop for lunch before launch. Needs a day for full cure but you do what you can. Next time you have the blocks in a different spot. Not perfect. Big ships use paint we are not allowed to use and it can go longer between repainting and be effective. Most recreational anti fouling lasts 1-3 years and that third year is not very effective.

Speaking from someone who worked in a shipyard many years ago, you can't during the same dry docking session. Simply has to wait for the next dry docking and hope the blocks are placed in slightly different locations.

@@alwaysbearded1 Small boat anti fouling paint is lucky to last 6 months, it is crap, a ripoff, and causes high boat emissions, if a diver doesn't clean the bottom every month, or less in high growth environments.

Correct. There are more blocks in drydock, but they don't exert an even righting lever until the ship is resting on them all.

thought the same doing it with a single block is just asking for trouble and running face first into a brick wall put a block on each side so it physically cannot capsize

The stern block is often narrow because of clearances of screws and rudder. the principal blocks forward are usually full width. The instability is until the hull lowers and rests upon more than just the narrow stern block. The narrowness,, and the restrictions of screws and rudders is also why the stern must be aligned first and most carefully.

In general, the aft section of a ships hull is intricately profiled such that it is only possible to have the ship "touch down" on the centre line first. There are of course rows of blocks off of the centre line but they won't make contact until the ship is sitting level and all of the rest of the blocks make contact at the same time. Another thing to keep in mind is that the ship would not capsize by 'falling off' of a centre line block. The forces generated throughout the procedure would act on the ship to turn it around its own centre of buoyancy.

@@frogandgauge Thanks but (as mentioned) how high P force can increase the centre of gravity height? Thanks.

What I was thinking. Must be cheaper to do it the more dangerous way, as usual.

Not even that, if the bottom of a ship is flat then why not just have the blocks be wider than the ship? That way it simply can’t tilt.

This is good practical information that I will use if I find myself dry docking a mega ship.

If it's someone else's mega yacht you really don't have to be too fussy, think of it as practice. It only starts to really matter when it's your own mega yacht. (You know this) ;)

The driving force for dry dock is hull aspects for Special Survey. Rudders are a hull item, not machinery. Majority of machinery items except the tailshaft can be acheived in the water, and even the tailshaft if done right.....

@@skippyguy3 The rudders themselves are hull, but the stocks, sealing, carrier bearings are definitely machinery. There's no reason to do a tailshaft survey in water; if you have to replace a seal while wet, you've got bigger problems. I mean, it can be done, but it shouldn't be outside of a leak. I wouldn't say that the driving force of a dry dock is hull; it's obviously a huge part of it, but any ship side valve comes under machinery, plus there's definitely going to be a lot of engine work to do that is not feasible in water or during constant running. The big ones for us engine side are shafts, CPPs, rudder bearings and rams, fan flaps and motor balancing. The ETO has a whole other bunch of issues, switchboard cleaning and such. After that we dealt with TMs and replacing sections of shell. Mind, the yard messed up the coating, so we sent weeks skimming the bilge tank and recoating it ourselves.....

@stevestoker incorrect. Rudder stocks are a class hull item, not machinery. Check your classification rules if you are in doubt......

I wouldn't be surprised if it turns out to be more complex with wooden ships too, no idea about the particulars of ships but with wooden foundations under the water level they seem to be fine as long as they stay wet. If they end up becoming dry that's when the trouble starts, are any similar things at play with the exterior of the hull when that's no longer exposed to salt water? Changing dimensions depending on water content also come to mind, always fun with doors in houses with seasonal change of humidity but similarly no idea how this affects a massive wooden construction going from wet to dry and changing load distribution. Provided a steel structure can take the load would I be correct that it should hold up better over time compared to wooden ships if you can prevent enough corrosion and maybe timely repair/replace/reinforce some specific things?

Thanks FKMA. I'm glad they are useful for supplementing learning.

I do love the physics too!

Thanks!

Thanks Galen!

Thanks Kanbei. I had fun adding these!

Plop plop! 😄

Oh yes, I did forget to mention propeller polishing. That will have to be a topic for another video.

Blocks go all the way to the turn of the bilge

it isn't, you have to wait until next time and put the blocks in different places

Well old wooden sailing ships would be beached at high tide and allowed to roll to the side as the tide went out. You had only a few hours to get work done (including 'paying' the seams with oakum and tar. ;) ) Of course, they were a lot smaller and crews were actually larger.

fr

I can 100% confirm that there are vessels that make the initial landing on keel blocks alone. Once the vessel is resting on the keel blocks, bilges blocks are brought in to keep the vessel from tipping. We calculate the draft at instability where the P force will make the vessel unstable so we know when to haul in the side blocks.

My bad!

Yes except they float/refloat takes a lot of effort so they just leave it for next time and hope the blocks line up differently in however long the time between cleanings is. (Presumably a year or two)

I'm no expert, but I imagine that those kinds of structures can only accommodate ships that fit those blocks. So you'd need several kinds of blocks to cover various hull contours, and they would have to be removable, and so on.

@@etherealessence Well they could at least make the blocks wider

@@gregorpajdlhauser2850 if it were that simple, I'm sure it would have been done already. There are most certainly physics problems that we just simply don't know about, let alone understand.

We do make side blocks like this (half U-shape on both sides) on some ships. But it has to be very precise. To help manage the dry docking we use mooring lines thrown from the ship to keep the ship from drifting and helping keep it stable when lowering the water level.

@@MrCMStud Interesting

I guess so, it's just that the liter of water has to spread all over the wetted surface area of the ship so it'll be ridiculously thin, to the point where it might break apart into droplets

@@dsdy1205 Yea surface tension and at some point molecular size might change things, but excluding those isn't it totally counter-intuitive given the weight difference? :-)

@@foolwise4703 Well, it makes more sense once you realise that the perfectly hull-shaped vessel is holding everything up, at least that's how I explain it to myself

Cruise ships do feature in some upcoming ones, but I like to keep the variety too.