Hogging and sagging! - Ships Nostalgia
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Hogging and sagging!

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  #1  
Old 4th March 2008, 21:52
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Mervyn Pritchard Mervyn Pritchard is offline  
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Hogging and sagging!

A chap postd this video clip on another forum which i frequent. It is very dramatic and clearly demonstrates the distortion in a vessel's hull due to stress in heavy swells

http://www.youtube.com/watch?v=NE_ri...eature=related

- Merv.
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  #2  
Old 4th March 2008, 22:00
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Will have to show my wife this she thinks Im joking when I tell her ships "bend"
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  #3  
Old 4th March 2008, 22:00
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Thanks for that Merv. Glad that's all behind me.
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  #4  
Old 4th March 2008, 22:36
K urgess K urgess is offline
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I would've been VERY worried if I hadn't seen that sort of movement.
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  #5  
Old 4th March 2008, 23:11
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Had a lot of hogging ang sagging on lake boats as they are long and narrow compared to a convenional ship. Especially the one I sailed overseas. Also a problem in the spring on the "lakes" as we got hot days and the water temperature was cold. This caused the boat to hog and could cause it to become overdraft and not be allowed Seaway transit.
Used sprinklers on deck to keep it cool and its not an uncommon sight to see a dozen sprinklers all in action at the same time. Started before sunrise till dusk.
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  #6  
Old 5th March 2008, 09:53
John Cassels John Cassels is offline  
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Nothing really strange here. This sort of movement ( inclusing the torsion
bending ) was pretty common in the '60's and '70's.
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  #7  
Old 5th March 2008, 10:18
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Lying straddled across the River Nene for a tide or more, resulted in Rowbothams 'Tillerman' being permanently sagged by about 2.5 inches. The explanation for the discrepancy on the deadweight summary was always sag.
Bruce.
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  #8  
Old 5th March 2008, 14:25
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Very good demonstration for someone like me who has never seen it.

Brian
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  #9  
Old 7th March 2008, 21:52
Jeff Taylor Jeff Taylor is offline  
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It's hard to get used to the silence on a new welded ship after all the creaking on a riveted hull. Even with all the felt strips behind the paneling the old Queens used to make quite a racket in even a moderate sea.
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  #10  
Old 7th March 2008, 22:16
Bill Davies Bill Davies is offline  
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Nothing special here. Try a ULCC in ballast then you will see something.
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  #11  
Old 8th March 2008, 00:44
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Are you not glad the shipyards have qualified welders and a Quality program .

Cheers Derek

PS Best place to see the Hog and Sag is on an oil tanker . Just stand at the aft end of the "Catwalk " and look forward . Ballast condition is best to see the large deflections .
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  #12  
Old 8th March 2008, 01:45
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Quote:
Originally Posted by Derek Roger View Post
PS Best place to see the Hog and Sag is on an oil tanker . Just stand at the aft end of the "Catwalk " and look forward . Ballast condition is best to see the large deflections .
If you look at this picture here you will see two metal plates on the catwalk about a foot deep these are to allow the catwalk to bend in relation to the deck and the railings have a gap here too. It is surprising how little sea you need to see the movement.
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Last edited by captkenn : 8th March 2008 at 01:50.
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  #13  
Old 8th March 2008, 02:15
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The Sealand Venture had tunnels on each side of the cago holds with the fuel oil piping and other services. The expansion bellows on the fuel oil line would crack and the openings would be big enough around to accomodate the cadet's finger.

The Cadet wouldn't understand why you do not put fingers in holes or cracks on a ship until I had a pencil in one of the cracks and had the cadet hold the dumb end of the tape and pencil while I measured the pipe line to be replaced. The pencil did not finish the measurement task and we were not in heavy seas no rolling or pitching.
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  #14  
Old 8th March 2008, 08:21
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The view from the bar (officers lounge) window on Oloibiri - a VLCC - was quite dramatic. The window faced forward and the focsle could be seen clearly rising and falling several feet relative to the manifold - the thwartships cargo pipes which were at half length.
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Last edited by R798780 : 8th March 2008 at 08:34.
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  #15  
Old 8th March 2008, 12:12
K urgess K urgess is offline
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VLCCs going round the Cape were an interesting sight in the swell.
A sort of whiplash action between the bow rolling one way and the accomodation rolling the other.
Plus the bend in the hull moving aft from the bow just like the wave that caused it.
The early VLCCs were long and thin so it was very noticeable. ULCCs tended to be broader and squatter.
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  #16  
Old 8th March 2008, 13:22
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Anyone who has sailed on any of the Norwegian-type steam, Empire tankers, including the 'Esso Cheyenne' and the 'Esso Appalachee', ex 'Empire Coleridge' and 'Empire Dickens' respectively, will probably remember the extraordinary flexible movement of these vessels when underway in ballast conditions. The bouncy motions accompanied by rhythmic squeeking from deck joints and the flying bridge with every turn of the slow propeller, was felt most when standing aft. The view from the break of the poop past the centrecastle to the break of the Focsl'e was quite dramatic.
Bruce.

Last edited by price : 8th March 2008 at 13:25. Reason: spelling mistake
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  #17  
Old 8th March 2008, 13:23
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Alway fun to replace a pipe on deck after repairs. It either didn't fit being too long and you had to somehow get those flanges far enough apart to drop it in, or there was a huge gap between the flanges that you used long pieces of threaded stock to pull the flanges up enough to put the regular bolts in. The OBO I was on, we could never keep the fire main from cracking on the foscle. The bending and twisting would crack the pipe in the Tee.
In a sea, the bow would wave to you.
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  #18  
Old 9th March 2008, 20:17
Bill Davies Bill Davies is offline  
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I can remember a Cape Size Bulk Carrier which sailed Dampier in 72 for Port Talbot with an 18 inch recorded Hogg . Apparently, the 2/off (ex Brenda Silver) got friendly with the man in the ship loader and passed him 'coldies' on a heaving line. No.9 was loaded to such an extent that the cone of ore exceeded the hatchcoaming and had to be flatted with shore & ship labour. Ship sailed with Forepeak and midship DBTks /TSTks ballasted.
Understand from several who were on board at the time that 18" was conservative.
British Steel were very happy with that ship. Might be because she always had a good out-turn.
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  #19  
Old 9th March 2008, 20:29
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It is reported that many a Chief Officer deliberately hogged a ship on its maiden voyage, as the hog stayed with the vessel to an extent for the rest of its life. Certainly, the two PSNC ships I sailed on had a similar permanent hog, allowing the vessel to load a little more than she would if the hog wasn't there.
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  #20  
Old 12th March 2008, 11:08
gas_chief gas_chief is offline  
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I did one trip on a bulker as a 3rd mate. The mate there told me that the best way to get the max cargo, was to load as much as possible fore and aft and reserve the midships hatches for the last. This ended up hogging the vessel to the max before during the first few passes and then bringing her down midships; but thanks to the mean of mean of means of the midships draft being used for the draft survey, she was always safely loaded.

I gave never sailed as a mate on bulkers, so do not really know if the above actually works.
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  #21  
Old 12th March 2008, 12:46
Dave Wilson Dave Wilson is offline  
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A lot of these practices were borne out of incompetence rather than design.
I have been instrumental in manageing dozens of Panamax/Cape Size in my time and would say practices eluded to above may have resulted in in the catastrophic loss record of this type of vessel. Combine above with alternative hold loading and you can get a feel for the situation.

Dave
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  #22  
Old 19th March 2008, 14:33
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I agree with Dave Wilson as to the incompetence aspect. The ship I referred to in my earlier post was about 250,000t dwt. The hatches on this ship were secured by hatch pins, but not tightened. You could see the gap between the packing and the compression bar in many places around the coaming! Main reason given for this was that the ship was on a regular Brazil to Rotterdam liner run. I brought up the question of seaworthiness on board, and boy did I get cold stares from everybody on board.

If we seafarer's do not take the issue of seaworthiness seriously, why blame the builders?

Well that was my last trip on a bulker. Had enough of that!
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  #23  
Old 21st March 2008, 01:04
Bill Davies Bill Davies is offline  
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Gas_Chief,
Blaming the builders is easy and always sits better than admitting to human error of those onboard. My post #18 in this thread was only half the story.
In order to protect the Master & Ch.Mate who were BOTH ashore at the time of the incident the 2/mate was not reported but went on to take the sister ship on her maiden voyage on his next trip only to put the that ship aground in the English Channel. Asleep in the wheelhouse chair rotten drunk. The German Master, a dear friend of mine, knew nothing of the former history but ended his seagoing career a 'wrecked' man. One of Brenda Silvers 'A' team.
Lost his Liberian License but kept his UK Certificate and went on to First Mates (FG) around 74. Tragedy.
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  #24  
Old 21st March 2008, 20:11
Bill Davies Bill Davies is offline  
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Gas_Chief,
Just re read my post last night and think it sounds ambiguous. The statement One of Brenda Silvers 'A' team.
Lost his Liberian License but kept his UK Certificate and went on to First Mates (FG) around 74. Tragedy.
refers to the scouse 2nd Mate who caused the accident. Brenda Silvers ran a manning agency in Liverpool

Hope that is clearer.

Bill
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  #25  
Old 21st March 2008, 21:40
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"Asleep in the wheelhouse chair rotten drunk. "

Is this documented evidence? Or hearsay? Or someones personal opinion?

Anything but documented evidence should not be posted. If this is documented, then it is a sad reflection on the Officer in question
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