You're right, this is a very dry subject, but your genius is that you managed to make an 11 minute video about it that I, a complete layman who has nothing to do with naval architecture, found truly engaging.
The not so silent killer example of weight control and stability: The Swedish warship Wasa who sank on a few minuts into its maiden voyage in 1628 after a breeze made it unstable...
Watching this, I think of the SS EASTLAND in 1915. The tourist ship was already unstable and then after the TITANIC disaster, more lifeboats, davits and all of the accompanying equipment were installed high up on the ship to comply with new safety requirements. It flipped over. The large crown on board added to it.
Yes! Finally someone who feels the same way about Weight Control like I do. It is often a lonely voice that is constantly beating the warnings of proper weight control from early design to shipyard construction, but boy does that lonely voice suddenly gets the attention of everyone when shit goes wrong (often at the shipyard, let's be real). Of course, one weight engineer doesn't get praise when shit goes right. But that's the way it is for us weight engineers - we can take pride in seeing that for any of the problems that occur, weight control is not one of them. It takes a special person to do weights because this person has to be okay with doing a boring job, while having the people skills to get people do their part all the way from the executive level to the shipyard worker level thru whatever-method-will-motivate while being one hell of a project manager. I love it. And I love being a marine engineer.
oh boy do me and my friend Taki know the pain of this well...he had a shipyard convert an old 110 meter ferry (Taygetos of 1979) into a 132 meter Cruise ship in the 1980s but the yard tampered with the plans and increased its weight and other features that made it a hazard that couldn't be fixed, in the end he was forced to sadly give up on the project in 1996 and sold it in 1998, sadly it was scrapped after never being completed in 2004 (though to be fair...that ship was cursed from the beginning and I could go on and on for about an hour of all the misfortunes that happened to it...)
Funny you should mention a cursed ship, I was on board a 70 foot yacht, as soon as i set foot on it I knew it was wrong. On a test sail one of the main stays snapped and almost took one of the crew out, then back at Port the next day the whole bank of batteries just blew all their tops off, the complete lids ( I have never seen this before) it also had a weird smell below decks and looked like a scene from a terror movie, the owner then chained it to the dock to stop it being repossesd, the boat gave me the very strong impression that it would try and kill you at its first chance. Almost all electronics gave wrong readings and the analogue gauges were just gave weird readings. I think it was sold very cheaply and then sunk not long after.
The main tool I know of is called ShipWeight shipweight.com/ There are other tools as well, integrated into full ship design suites. But many companies still use their own proprietary spreadsheets.
For give an electronics guy with a very rusty knowledge of mechanics, but is centre of gravity the only problem? You always hear that the ship rotates around the centre of gravity, and I say, what about the constants. And even if that is true, what if the axis of rotations are not lined up with the ship? My reaction is fear. I have never had to study those xy, zy .... moments only xx, yy, zz, but they seem important to me when we talk design of wave-piercing vessels (or any vessel with an uneven weight distribution), and the loading of cargo vessels.
The two major concerns are weight and center of gravity. You mentioned the momentum factors: moments of inertia (Ixx, Iyy, and Izz) and the cross products of inertia. First, there are two different levels of risk associated with these. The weight and center of gravity affect vessel safety and cargo capacity. Get those wrong, and the vessel may not enter service. Less important are the momentum factors. Get those wrong, and it only really impacts seakeeping, with consequences for crew comfort. Crew comfort is important, but I'm sorry to say that most vessel owners consider it secondary to cargo transport. And most of the cargo we carry on a ship can easily handle a bumpy ride. Secondly, we rarely need to worry about the cross moments of inertia (Ixy, Ixz, Iyz). Because most ships are long and skinny, this results in very little coupling between the different motions. For example, roll motions do very little to influence vessel pitch. The hydrostatic forces involved mean the vessel roll, pitch, and yaw operate on completely different scales of impact. Because of this we see very weak interaction between the motions. And the cross moments of inertia only become relevant with strong interactions between the different motions.
You're right, this is a very dry subject, but your genius is that you managed to make an 11 minute video about it that I, a complete layman who has nothing to do with naval architecture, found truly engaging.
Nice to hear someone talk about my profession as a senior weight engineer as important. :)
The not so silent killer example of weight control and stability: The Swedish warship Wasa who sank on a few minuts into its maiden voyage in 1628 after a breeze made it unstable...
Watching this, I think of the SS EASTLAND in 1915. The tourist ship was already unstable and then after the TITANIC disaster, more lifeboats, davits and all of the accompanying equipment were installed high up on the ship to comply with new safety requirements. It flipped over. The large crown on board added to it.
i just found this channel man its awesome for a naval architecture student!! thank you!
This should be a mandatory lesson for staff in design companies and shipyards.
Yes! Finally someone who feels the same way about Weight Control like I do. It is often a lonely voice that is constantly beating the warnings of proper weight control from early design to shipyard construction, but boy does that lonely voice suddenly gets the attention of everyone when shit goes wrong (often at the shipyard, let's be real). Of course, one weight engineer doesn't get praise when shit goes right. But that's the way it is for us weight engineers - we can take pride in seeing that for any of the problems that occur, weight control is not one of them. It takes a special person to do weights because this person has to be okay with doing a boring job, while having the people skills to get people do their part all the way from the executive level to the shipyard worker level thru whatever-method-will-motivate while being one hell of a project manager. I love it. And I love being a marine engineer.
Very interesting, educational, and entertaining video(s).
Thank you. Stay safe.
Thanks for sharing, your videos are always super informative
True for people, true for ships/yachts, and true for aircraft. As they say, we gain by the pound, but only lose by the ounce!
oh boy do me and my friend Taki know the pain of this well...he had a shipyard convert an old 110 meter ferry (Taygetos of 1979) into a 132 meter Cruise ship in the 1980s but the yard tampered with the plans and increased its weight and other features that made it a hazard that couldn't be fixed, in the end he was forced to sadly give up on the project in 1996 and sold it in 1998, sadly it was scrapped after never being completed in 2004 (though to be fair...that ship was cursed from the beginning and I could go on and on for about an hour of all the misfortunes that happened to it...)
Funny you should mention a cursed ship, I was on board a 70 foot yacht, as soon as i set foot on it I knew it was wrong. On a test sail one of the main stays snapped and almost took one of the crew out, then back at Port the next day the whole bank of batteries just blew all their tops off, the complete lids ( I have never seen this before) it also had a weird smell below decks and looked like a scene from a terror movie, the owner then chained it to the dock to stop it being repossesd, the boat gave me the very strong impression that it would try and kill you at its first chance. Almost all electronics gave wrong readings and the analogue gauges were just gave weird readings. I think it was sold very cheaply and then sunk not long after.
I wonder if a triple hull ship would be good to cross the Pacific
I also struggle with weight control. About 25 lbs over right now!🍕🍔🥨😃
But you're still lightning quick, and in not just talking about being quick when smashing a large pizza either!!!
What is the best software for weight analysis on boats and yachts
The main tool I know of is called ShipWeight shipweight.com/
There are other tools as well, integrated into full ship design suites. But many companies still use their own proprietary spreadsheets.
For give an electronics guy with a very rusty knowledge of mechanics, but is centre of gravity the only problem?
You always hear that the ship rotates around the centre of gravity, and I say, what about the constants. And even if that is true, what if the axis of rotations are not lined up with the ship? My reaction is fear. I have never had to study those xy, zy .... moments only xx, yy, zz, but they seem important to me when we talk design of wave-piercing vessels (or any vessel with an uneven weight distribution), and the loading of cargo vessels.
The two major concerns are weight and center of gravity. You mentioned the momentum factors: moments of inertia (Ixx, Iyy, and Izz) and the cross products of inertia. First, there are two different levels of risk associated with these. The weight and center of gravity affect vessel safety and cargo capacity. Get those wrong, and the vessel may not enter service. Less important are the momentum factors. Get those wrong, and it only really impacts seakeeping, with consequences for crew comfort. Crew comfort is important, but I'm sorry to say that most vessel owners consider it secondary to cargo transport. And most of the cargo we carry on a ship can easily handle a bumpy ride.
Secondly, we rarely need to worry about the cross moments of inertia (Ixy, Ixz, Iyz). Because most ships are long and skinny, this results in very little coupling between the different motions. For example, roll motions do very little to influence vessel pitch. The hydrostatic forces involved mean the vessel roll, pitch, and yaw operate on completely different scales of impact. Because of this we see very weak interaction between the motions. And the cross moments of inertia only become relevant with strong interactions between the different motions.
Just calculate what 1 cm more length on every weld seam will do to the weight, lol
You are awesome!
true a silent killer indeed
to bad old dougy with the SV seeker never saw this. Although to be honest he knows everything already some I'm sure he wouldn't have listened anyways
Perhaps you would be kind enough to give Mads, at rebuilding Athena a consultation?
You may save his and his SO's life/lives among others.
wow
i have to do weight control every day when i gotta go take it out to pee