Drydocking: Its HARDER Than it Looks!
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- Опубліковано 7 кві 2022
- In this video, we focus on drydocking. We look at the P Force and see how it has a critical impact on ships drying out.
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I think it is fascinating that, after thousands of thousands of years of sailing, high tech chemistry and sacrificial anodes, we STILL have to constantly battle the sea's corrosive powr and wildlife, and essentially scrub the same things off the hull with elbow grease as some phoenician did thousands of years ago.
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
Fascinating! I've never really thought about the process of dry docking apart from the 'oh, she is getting repairs/refits so she won't be available for survey this season'. Kind of cool learning a bit more about the logistics of actually getting a ship into drydock :D Thanks!
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.
I served on the USS Bremerton (SSN-698), a Los Angeles class fast attack submarine, during new construction an Electric Boat in Groton, CT. and at Pearl Harbor, HI. We spent the first 1-2 years going in and out of dry dock. Submarines have unique problems when entering dry dock. The worst time I had in dry dock was at Groton in the dead of winter with subzero temperatures. We would have to climb from the top of the sub into the bottom of the dry dock to ensure off-hull hose connections were not freezing once every hour.
Served on older boats, but yeah, same thing in 'rotton Groton' lol. And rig hoses to provide cooling water to key components.
Literally pushing 🅿️, great explanation on forces
Great video! Very interesting to visualize the forces involved. In helicopters we have a similar situation called dynamic rollover where one of the skids catches on an object during picking up/setting down, becoming the point the helicopter pivots around instead of the center of gravity. Once the helicopter body passes a certain angle - no matter the control inputs - the roll is irreversible and the helicopter rolls over.
That's really interesting. I hadn't thought about that before, but it makes complete sense.
I have seen Great Lakes freighters,, commonly as long as any blue water boat,, clean and repair their hull by differential ballast. Not in dry dock,, but along side a pier with a suitable depth of water. Water is pumped out of the ballast tanks on one end and pumped into the ballast tanks of the other end. The bow or stern may rise completely out of the water facilitating access to the submerged hull. When perhaps the bow is repaired , cleaned, painted,, then the process is reversed,, ballast pumped into the bow,, and ballast cleared from the stern tank,, and the stern comes up out of the water for service. I have watched it being done.
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.
There’s a major and obvious point missing in all this fascinating P Force talk and that’s the existence of more than a single longitudinal line of blocks along the vessel keel. No docking plan has a vessel with a single line of blocks and vessels of the size shown in the video will have 3 or 5 or even 7 lines of blocks where the hull is widest and flattest, the stern. No vessel will enter dock in perfect trim and it would be impossible for a ship to balance on a single line of blocks during docking let alone could the hull support such a point load.
Agreed! There are keel blocks along centerline, AND bilge blocks farther outboard that provide support from tipping over.
We've got to dry shock this singer Summer and have our hull re-blacked (2 part epoxy) new sacrificial anodes and whatever is blocking our now thrusters removed. Luckily we're not in brine or brackish water, and we're only 20m long wide beam barge. I love your videos, it makes things so clear. I know we've at least got edible growth on the hull as the water fowl like a nibble about 4am every day.
I'm sure they love the breakfast!
Cool.
I worked at a small dry dock for a few years, docking vessels of up to maybe 700 tonnes.
We would do a lot of the work manually and sort of winging it, but there hasn't been a serious incident at that dock for the last 35 years.
We used to adapt the blocking to every ship, so that it would land as level as possible. At the exact time that the ship touched down, we would fix the supporting beams around the hull. These beams were just telefone poles extending from the side of the drydock and jammed against the hull with wood wedges. The crew's job was to control the mooring lines, keeping the vessel straight and centered in the dock as it settled. We often docked two, three or sometimes even four vessels at the same time. As long as they had different drafts, you could concentrate on one at the time, but those were very busy days.
If it was a more complicated docking we would open the flood gates in the dock gate to let in water at the same rate as it was pumping out, this way we could keep the water in the drydock at a specific level while working with the support beams. Not optimal, since letting in water created a lot of strong currents that wanted to push the ships out of place. Turning off the pumps was not an option, they could only be started with a filled dock.
I have a book about the RMS Olympic and it contains pictures of her raised in her drydock. Those kinds of photos always amaze me
You do such a great job with your explanations and videos! Keep up the great work
I swear this was going to be one of those P-force memes. They scare me, or rather my inability to know what's real anymore thanks to them.
I liked (and understood) very much your explanation of how the contact of the ship's hull with the underwater block creates a rotational momentum that can capsize the ship.
Great video as per your excellent standard.
Thank you, regards...
Lovely video once more, Casual Navigation never fails to let the audience down :)
Thank you for these video's, i am currently studying to become a Maritime Officer in Rotterdam and i must say you do an exceptional job at explaining everything, i will totally suggest my teachers to use your video's in lectures!
Cheers from the Netherlands Rotterdam Mainport
Thanks FKMA. I'm glad they are useful for supplementing learning.
The best explanation of D/D stability considerations I've found...and great animations. (Liked & subscribed).
I spent years in dry dock in Houston and we always had two rows of columns. I don’t understand why anybody would try to balance a ship on a single row of columns.
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.
That block really do be pushin 🅿️
Thumbs up, you always come up with a great topic
Nice video, keep up the good work mates
Thanks!
I was watching a episode of world’s toughest fixes and they showed one of the specialized magnetic high pressure cleaning robots
One thing I did not understand about this is the trim aspect. Now, please correct me if I'm wrong but at least as far as I understand it, trim is mostly done via controlling the level of water inside the ballast tanks - at least at its core, I do know that it's not quite as simple given things like the free surface effect, but, even then I'd hazard a guess that this is not as important in the conditions that would need to be present for drydocking to be safe in the first place. Tangent aside though, what I wanted to ask is why the ship's crew, after having aligned the stern on the blocks and then having maneuvred the bow into its final position not begin to fill the bow tanks to achieve a neutral trim, hence reducing the maximum P-force asserted on the vessel as the bow comes into contact with the support blocks sooner. And, related to that, as the ship is refloated, why is it a concern to keep the trim towards the stern there instead of a neutral trim given that, during refloating, there is no need to align the ship anymore.
Sorry if this question is stupid but I simply couldn't make sense of this.
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
Commercial vessels real do be pushin P 😤💯
fr
Quick question: How do you get to the parts of the hull that are covered by the support blocks?
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.
From experience at see , watching your videos, I knew we would get a physics lesson and end on my favorite piece of equipment, the oops I just blasted the paint off washer. I have a small electric PW and a portable gas powered PW both of which are very satisfying.
Came down to the comments expecting it to be full of innuendos, was rather susprised to see there are some communities on youtube that aren't immature.
Wow! Thanks a lot! I'm impressed!
Here in Grecee our RO-RO ships go on dry dock every one year cruise ships go depending on the use condition etc so us Greeks we like to be somewhat clean Greek fan that wants to become a captain
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.
1:56 wow great animations on the rodder and the tug boat following!! such eye for details :O
Great explanation bro, thanks for the video!
Fascinating. Thanks.
Such educational content. So we’ll done 👏
3:39 There should be blocks placed on either side of the centre of mass, right? As shown, a single block will be unstable. With a block on either side and the ship rotating left for example, the left block will push more and the right block will push less, basically like a hull in water
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.
I'm not a mariner, nonetheless, I find this answers many of the abstract questions that have drifted about in my mind for many decades. Thank you for posting. I will endeavour to track down the other videos you have on the issues central to this video.
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) ;)
I'm new on this channel and this channel is really good this vids make me sleepy
Fascinating!
The real question is, when the first contact is made with the dry dock, why doesn’t the contact patch have a shape that supports the ship on left and right from capsizing?
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.
I tried dry docking with a friend and yeah you could say it was definitely hard :P
Our boat was only 50ft long, but we would always put it into dry dock to clean, repaint and fix it. Not far from us there was a movable floating dry dock for the ships that was use regularly it took ages for it to full up with water so the ships could enter the dock.
Never actually thought about the physics behind drydocking .immensely interesting as always. Honestly that bit kind of overshadowed the cleaning up of the hull for me.
I do love the physics too!
Dry dock for an extended period can have a damaging effect on a ship, the longer it is on blocks the greater the chance of the weight of its superstructure spreading the hull outwards as no longer evenly supported by water. The reason why historic preserved ships are kept afloat for as long as they remain water tight. Once in permanent dry dock a lot of tailored, fixed support needed and removal of excess top hamper, such as masts, yards and the rigging as has happened to HMS Victory and others.
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?
Apart from that, i love the videos. Do carry on!
Thank goodness they put blocks on the sides too and not just one row down the middle.
this suddenly explains why my canoe gets really tippsy when I beach one end and stand up to step out!
awesome, its pushing P 😎
Hi I have my boat in Cadiz at the moment a hundred meters from some big dry docks. Never thought about the complications however. Thanks
ahh first year physics we meet again. Fascinating video!
Having just left dry dock, as an engineer this is interesting information. I'd say from our side that dry dock is hugely about machinery - props and rudders off and cleaned, stern tubes emptied and inspected (and repaired, i our case). The fouling is very minor, and the big thing from deck side is a good shot blast and repaint.
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......
very interesting video
We need dry docking video 😍👍🏽
Great video as always but I'd like to say that your sound effects were excellent
Thanks Kanbei. I had fun adding these!
Plop plop! 😄
wow. i will have to rewatch this one, to understand the physics with the differenent center of gravity points, negative mass
Glad to have confirmed that my P-Force is as strong as my G-Force 😏
There was a Geico ad before this video. That gecko really went from selling me insurance to explaining how ships clean under their hull.
And here I was thinking its "just" driving into the dry doc, secure the ship and let the drydock operators worry about the rest... Learned a lot today, very informative and interesting as always!
Thanks Galen!
Wow, I hadn't considered the instantaneous p-force, I had mistakenly presumed it's presence would be gradual but this explanation totally makes sense. Dry docking seemed just risky for divers checking the positioning on the blocks but now I see the capsize potential is even greater - Thanks for sharing!
this happens on a smaller scale when launching or landing a kayak onto a steep bank. most of the stability comes from the center of the boat, where it is widest, so with the sharp and narrow stern on ground, and the narrow bow in the water, the boat is very unstable. it's put a few people into the drink.
Didn't understand lots of that, but very interesting anyway!
I would love more insight on dry docking
Great Video especially with the visualisation of the docking forces, but when talking about efficiency and cleaning the hull you should have mentioned the propeller, who has an even greater impact on the efficiency of the ship, often they are periodically cleaned and polished by divers to increase efficiency.
Oh yes, I did forget to mention propeller polishing. That will have to be a topic for another video.
To be fair, every time I entered a dry-dock, we immediately took berthing wires and the ship was eased in under control, specifically to keep it centred and fully supported. It doesn't seem particularly good practice to sit the ship on one block aft first, unless those wires are in place and in-hand around bollards or capstans.
The ship's centreline was matched to hanging plumb bobs fore and aft, then the lowering begins as side support timbers are readied. That way, the ship is centred onto all the blocks at pretty much the same instant, and the key frames are braced just as the ship hits them.
As a regular through the St. Lawrence Seaway, a lot of weed was lost in the fresh water, but cathodic protection was always pretty good and we'd only see a major build-up of weed on the waterline rubbing strakes, which were made of Elm beams encased in heavy rubber shrouds.
We also used a boot-topping paint that I never saw weed or animal life take to. Weird stuff, it was; even though you listed the ship to get a good deep waterline stripe of the stuff on the side, you could go into the water with your roller and it would still go on the hull.
That's pushin p
I feel the need to point out that I have never lived or worked anywhere near a body of water, yet somehow I am compelled to watch (and enjoy) every new episode. Keep up the great content!
You forgot to mention the fact that the Costa Concordia had a hole in it's hull the size of a bus that did play a role into it's capsizing.
3:29 He actually said, omg he said it... PUSHING P!!!!!
It's a rap slang that's trendy rn
There is a magic thing that happens whenever you dock at a freshwater ports up a river like my hometown Portland Oregon the Barnacles fall off
wow i love you're videos
You're
I'm
Haha.. Oops
If ships were drydocked with blocks under the keel only, your video would make sense. I have been under ships and boats in drydock. There are blocks across the width of the vessel as well as down the length. This is common practice on floating drydocks as well as graving docks.
pro tip. Mooring a vessel in fresh water really helps with steel preservation.
I like this video a lot. I am not an NA but I realized that this would happen and had difficulty explaining it when the MY Baden sank on launch in Anacortes WA.Knowing the name "P-force" will help and I didn't have the insight to combine the P and G vectors like you did here.
It's always important to keep the bottom clean :p
Some say having a healthy prostate is the key to p force
Reminds me of the careening scene in the wonderful series Black Sails
I used to clean My Boss's yacht by hand. Upside down with a scraper. One air tank would do it. 90 minutes. One time it was almost clean anyway..and I didnt want to come up early so sat on the bottom and played with a crab. Another time I found a £50 note drifting by. But diving under a super tanker was very very dangerous. As they are 75 m wide and you can easily get lost and so cannot surface.
I learned about the Costa Concordia from the Internet Historian.
me at 1 AM: "yeah, how DO they do that?" never thinks about it again
Just found your channel. Very interesting stuff. Could you cover some basics for smaller civilian ships at future? Other thing would be interesting to hear where have you learned all this, do you have some studies behind or all self taught?
I went to a maritime academy while training to become a ship's navigation officer. Most of the content is based on my experiences there and working in the industry over the last 10 years. I would like to include smaller boats too, but my knowledge of those is more limited.
Can you do more cruise ship videos?? Good video btw
Cruise ships do feature in some upcoming ones, but I like to keep the variety too.
In the Navy, we put submarines in drydock once in a while (for the same reasons). But ISTR we did it 'level'. Subs are quite a bit smaller and we went into 'floating drydocks' so the dock itself could trim as well.
While in dock, can the ship remove some ballast from aft so it 'lifts off' a little more easily? Just wondering.
3:55 - that's easily addressed by placing blocks across the width of the hull, which gives you the added benefit of also increasing your contact patch and reducing the force per cm2 of hull surface area. Alternatively, you can counter-ballast as you raise the ship, reducing the rear ballast and increasing the forward ballast until the entire hull is in contact with the blocks, then just drain all the ballast as you're draining the dry-dock. This will level the ship as you lower the water level (or raise the dock) and keep the upward force of the rear blocks low, so it doesn't cause a lateral imbalance.
Blocks go all the way to the turn of the bilge
Try dropping a 360’ tuna can full of squids in dry dock, it’s about 12-14 hour process .
I've enjoyed your videos and always found them interesting. You seem to have previously stumbled on a perfect presentation, because the "boings" of the force-vector arrows and the real human in this video were very distracting.
Thanks for making these videos for us.
i was searching a physics video and tis popped up and interesting
Right after I wake up, I have a strong P-force.
Another solution is coating your ship with Ecospeed which is 100% environmentally free so no antifouling is being used, it’s easy maintenance. Most growth washes off by sailing and when cleaning is required it can be both done underwater as in drydock by pressure washing the hull. On top of that. The Ecospeed has a 10 year warranty and being applied correctly it will outlast that easily!
Pushing 🅿️
Long ago there was a questionable practice (not very common though - fortunately) to clean the ship bottom from shells by humping the vessel over a sandbank. Pretty delicate operation all and all, and required vessel in ballast only, a well known spot and a reckless captain.
When successful, the vessel speed and fuel economy had a measurable improvement. When stuck, too bad.
Method not that much used today - I hope.
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.
It's alwasy better to have a clean bottom, when possible. So many benefits..
Hmmm, it’s almost like the blocks in a dry dock are the full width or even wider then the hull. Mix in the part about most commercial ships having a flat bottom, you really don’t get that much sideways lean, unless you’ve really messed things up.
One ship, two ships, not two ship’s. Be brave and add that “s” without an apostrophe. I believe in you.
My bad!
Cool.
All those vectors just to say that a ship that doesn't fall over when it's in the water does fall over when it's not. Good one.
Hey it's Easter holiday soon
In the early 1950's we bought a small cabin sailboat. At fall hauling, the growths and barnacles on the hull were huge and disgusting. Being a professional photographer, he took pictures. Next spring he used a different, I think copper based bottom paint. The following fall, much better. Took pictures again, sent his endorsement to the company and got some coin.
One thing I don't understand is how the anti-fouling paint is applied to the points where the hull is on the blocks.
it isn't, you have to wait until next time and put the blocks in different places
Interesting
How do they clean under the parts where the ship is resting on the blocks? Do the refloat and move it a bit?
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)
Actually most of drydocks requiring to enter dock with trim as less as possible. Second thing - as vessels are flat bottomed and block are planned to support full width - vessel will not be able to heel as long as it touches first pair of blocks. Did it many times, serving as a Chief Mate on gas tankers.
My pee-force is the strongest in the morning when it's pushing downwards. When I then start leaning towards one side, I need to stabilize myself by pushing against the wall. Maybe that would be an idea for ships too.
I would love to see a video on why certain ships (like the Disney Wonder and Disney Magic) received hull extensions that obviously jut out decades into their service.
Hey can you do a video on raising ships that have sunk as I am going to raise the britannic by making a watertight barrier around it and lowering the water level with pumps around the wreck then once the wreck is dry and treated so it dosing fall to dust it is uprighted and the hull repaired and other things in the debris field are collected it will be raise then taken back to Belfast for repairs, restoration, slight modernisation and reconfigured to be used as a ocean liner like it was ment to be used as but I want to know how meny ways there are to raise a ship including my way also how other ships were treated after emerging so they didn’t fall to dust
The amazing, futuristic ship maintenance technology of 2022: some concrete blocks to prop it up on.