Awb stability

[roblpm]

Assuming anything after 2000 is an awb.....

I am on a cruise ship (don't ask) in the sports bar watching the end of the American football. We are between the Bahamas and Miami. I literally can't feel any motion at all! It's amazing. How do they do it?

 

[roblpm]

This ship was apparently the biggest cruise liner in the world when it was built in 2006

 

[Bajansailor]

Are you onboard the RCCL vessel Freedom of the Seas?
FREEDOM OF THE SEAS (Passenger Ship) Registered in Bahamas - Vessel details, Current position and Voyage information - IMO 9304033, MMSI 309906000, Call Sign C6UZ7

Re how you cannot feel any motion, she is a big ship - 156,000 gross tons - and she has a very effective stabilising system.
I have been on board her here (in Barbados) a couple of times in recent years on survey assignments, and she certainly is very impressive - although relatively small now when compared to the biggest RCCL vessels, which are (I think) around 220,000 gross tons now.

 

[Baggywrinkle]

I don't think it qualifies as an AWB .... ? ? ? ?

 

[Moodysailor]

Massive weight, and some of the best stabilising technology in the world. Stabilisers

 

[johnalison]

Our friends used to watch football on their satellite TV in the middle of the North Sea in their Island Packet. At least the aerial was stabilised but it wouldn’t make me want to buy the boat.

 

[Martin_J]

Although if you've got about £15,000 and sufficient electrical power on board, you could go to Osmotech and get a Seekeeper gyro stabiliser installed in your AWB.

Different technology to the fins but a little less obtrusive.

Osmitech install seakeeper-gyro-stabilizer

 

[roblpm]

Are you onboard the RCCL vessel Freedom of the Seas?
FREEDOM OF THE SEAS (Passenger Ship) Registered in Bahamas - Vessel details, Current position and Voyage information - IMO 9304033, MMSI 309906000, Call Sign C6UZ7

Re how you cannot feel any motion, she is a big ship - 156,000 gross tons - and she has a very effective stabilising system.
I have been on board her here (in Barbados) a couple of times in recent years on survey assignments, and she certainly is very impressive - although relatively small now when compared to the biggest RCCL vessels, which are (I think) around 220,000 gross tons now.

I was. Are you the cia.....? Anyway I am one step ahead of you now! You will never catch me....

I can't imagine being on something bigger! ?

 

[roblpm]

Massive weight, and some of the best stabilising technology in the world. Stabilisers

Yes amazing really. On my balcony I couldn't discern any movement between the balcony rail and the horizon. The sea was flat though.

 

[roblpm]

I don't think it qualifies as an AWB .... ? ? ? ?

I don't think it has an encapsulated keel? Skeg rudder? Doesn't smell inside. By a process of elimination it's not a MAB so must be an Awb. Although someone painted the hull blue.

 

[Koeketiene]

Assuming anything after 2000 is an awb.....

I am on a cruise ship (don't ask) in the sports bar watching the end of the American football. We are between the Bahamas and Miami. I literally can't feel any motion at all! It's amazing. How do they do it?

Many moons ago, I was invited to tour a US aircraft carrier (USS Enterprise IIRC).
An F15 pilot commented that things could get quite 'lively' in a storm. The deck could 'move' as much as 3 or 4 degrees.
How I laughed. I was XO of a minehinter at the time.

 

[capnsensible]

A submarine has to turn beam to sea to dive. A warning is given that the boat may roll heavily, and generally does. ?

 

[Bajansailor]

A submarine has to turn beam to sea to dive. A warning is given that the boat may roll heavily, and generally does. ?

Why is this? (Genuine question).
Are they worried about too much hull length possibly being cantilevered out of the water if they were to (eg) face into the waves, rather than having them on the beam?
Is it possible for them to submerge slowly while staying horizontal, or do they always have to put the nose down in order to do a dive?
If the latter, what is the steepest angle that they can dive at?

 

[capnsensible]

Why is this? (Genuine question).
Are they worried about too much hull length possibly being cantilevered out of the water if they were to (eg) face into the waves, rather than having them on the beam?
Is it possible for them to submerge slowly while staying horizontal, or do they always have to put the nose down in order to do a dive?
If the latter, what is the steepest angle that they can dive at?

The ballast tanks, filled with air on the surface need to be vented so they fill with water. They form the bow and the stern of most submarines. So it's easier to get them properly cleared of air and get that bow down angle......around ten degrees depending on the type....to dive under control. In calm seas it's not so bad, but in higher sea states in can be quite interesting and discovers anything not properly stowed. People, generally, don't like being fenders for mobile objects.?

Modern big boats need a good bit of propulsive power to drive them down too and you don't want to stick the stern out of the water.

It can be quite interesting at periscope depth for extended periods when Neptune is having a bad hair day too. ?

 

[Bajansailor]

I was. Are you the cia.....? Anyway I am one step ahead of you now! You will never catch me....

Well, I knew that she was built around 2006, and I went on Marinetraffic and saw that she was in the area that you mentioned, hence I guessed that she was a likely contender.
I shall have to report to the CIA boss that you gave me the slip.

Although someone painted the hull blue.

It is quite a nice very pale blue - this was done in dry dock during a massive refit that cost many millions just before Corona took off.

I visited her here in Barbados in October last year - here is a photo of her alongside at Bridgetown. The hull is pale blue, but the photo is a bit over exposed, and it is hard to tell.

 

[Bajansailor]

It can be quite interesting at periscope depth for extended periods when Neptune is having a bad hair day too. ?

What is the maximum wave height where you could stay just below the surface while still peering through your periscope at what is going on above?
In hairy conditions would you again be beam on to the waves, albeit underwater, or would you be trying to keep the nose pointed into them?
Would you try to generally keep the depth of the hull below surface fairly constant, or would she go up and down a fair bit if you are in big seas (eg 10 metre wave height)?

 

[matt1]

Yeah, c’mon Cap’n can you organise a zoom call for us all; I have a ton of questions like “what does it feel like going from the surface to underwater and losing the motion suddenly” “do submariners get seasick” “how do you know you aren’t surfacing under a yacht”

 

[roblpm]

Well, I knew that she was built around 2006, and I went on Marinetraffic and saw that she was in the area that you mentioned, hence I guessed that she was a likely contender.
I shall have to report to the CIA boss that you gave me the slip.



It is quite a nice very pale blue - this was done in dry dock during a massive refit that cost many millions just before Corona took off.

I visited her here in Barbados in October last year - here is a photo of her alongside at Bridgetown. The hull is pale blue, but the photo is a bit over exposed, and it is hard to tell.

View attachment 122678

What were you surveying? The tacos on board?

Yes the blue is a nice shade.

 

[capnsensible]

What is the maximum wave height where you could stay just below the surface while still peering through your periscope at what is going on above?
In hairy conditions would you again be beam on to the waves, albeit underwater, or would you be trying to keep the nose pointed into them?
Would you try to generally keep the depth of the hull below surface fairly constant, or would she go up and down a fair bit if you are in big seas (eg 10 metre wave height)?

Well that does stray a bit into if I told you I'd have to kill you territory. ??

It doesn't really matter what the sea state is......think oop north in winter, it can get bumpy. So as Ship Control, if the Captain wants to be at Periscope Depth for a variety of reasons, it was my job to make it so. To prevent the fin broaching (bad) so that someone might see you in high sea states required a 5h1t hot planes man and some, well actually a lot of mutual trust to catch the trim and not catch wrath of skipper. To prevent dipping the periscope under water (super bad) was even more sinful as you can't see things that may go bump.

Submarines do roll a lot under such conditions and can induce motion sickness in crew who are subject to the naval discipline act and generally get on with things despite feeling crap. Going deep again was a bit of a relief!

I had a ball. ???

 

[westernman]

Interesting figures for stability which any skipper should know for their vessel are:-

1) Down flooding angle (i.e. the maximum angle of heel before you are in deep dodo)
And the hatches and openings which need to be closed to ensure that you can get that far.

2) Angle of vanishing stability (i.e. the angle of heel after which you will continue to capsize rather than turn the right way up)

These figures are usually mentioned in the MCA stability book for the coded vessel.