Wednesday, June 13, 2012

The Riveted Hull.

"Full Away!"  And the order 'steady as she goes' is being repeated back as we see that rudder slowly responding to the command.  Where were we?  Right!  Thought I'd lost you at my last post the Back End.  But let me draw your attention to the most obvious - rivets!  They're all along the hull of the MV Doulos, it is the aesthetic part of her that cannot be hidden but only to marvel.


ship rivet construction

www.doulos1914.blogspot.my


Like the stern design of the Medina, so was the use of rivets on the construction of this ship.  Fastenings used in traditional wooden boat building, like copper nails and clinch bolts, work on the same principle as the rivet but were in use long before the term rivet came about.  Hence, that technology 'overlapped' into the steel and iron industry - those 'nails' just got bigger.



Doulos rivets
www.doulos1914.blogspot.my

A rivet is a permanent mechanical fastener. Before being installed a rivet consists of a smooth cylindrical shaft with a head on one end. The end opposite the head is called the buck-tail. On installation the rivet is placed in a punched or drilled hole, and the tail is upset, or bucked (i.e., deformed), so that it expands to about 1.5 times the original shaft diameter, holding the rivet in place.

Because there is effectively a head on each end of an installed rivet, it can support tension loads (loads parallel to the axis of the shaft); however, it is much more capable of supporting shear loads (loads perpendicular to the axis of the shaft). Bolts and screws are better suited for tension applications.  It is said that the older-riveted ships were more 'flexible' in rough seas than the modern welded hulls.

Old ship construction using rivets

These are original riveting done when Medina was laid to keel in 1914.
You are looking at it in present times, how exciting! -  provided by www.ssmaritime.net

Plate section replaced on the Doulos

"Me" and Joe Saemala (Bosun). There was a little 'hole' we found this bilge section. We had it cut out and welded on with a new plate.  You can see the original construction using rivets in this photo. - www.doulos1914.blogspot.my


The story of the picture 'above' was that one day a few of us including myself was assigned to 'needle gun' the bilges in Hold No.1.  In other words to clear the area of rust, prepare the area concerned with coats of primer.  I was using the needle gun on a particular spot of thick rust and managed to remove a big chunk of it - there I noticed a dark, wet patch on the hull.  Sea water!  Mind you the Doulos was tied-up in port - that's the sea a few inches the other side of that steel plate!  "Oops!!"  I left that job for another.  We had it 'patched up' during dry dock in Hong Kong not long after that incident.  You can clearly see the rivets in the photo of the 'cutout'.


Hall of Names.  'Medina', just above the line and 'Franca C', behind the name 'Doulos'.  www.doulos1914.blogspot.my


The three names of the ship from 1914 to 1977.  The name 'Roma' was not found here unfortunately.  It may have been 'painted' on the hull and replaced after that (we'll never know, but probably is), unlike the other 'three' which was welded on the hull.



The hull of the 'Medina' (MV Doulos 1991).  Hull thickness was astounding, it 'passed 'many certifications all through the years to continue sailing.  www.doulos1914.blogspot.my


Today, in heavy steel fabrication, welding has almost completely replaced riveting as a means of making connections.  Welds require less preparation of the metal, do not reduce the effective cross-section, and take a minimum of space.  The miracle repeated itself year after year, one certification passed and then another - "Fit for service!"  The dock certifiers found that the thickness of the hull was still the same thickness of when it left Newport News in 1914!  Now that's a WOW!




Friday, June 1, 2012

The Back End.

One of the many 'interesting' features of the Doulos is the stern.  For those who are unfamiliar with nautical terms, the stern is the opposite of the bow.  No offense, we're all learning.  We have read in my other posts that the hull design dates back to the 1900's.  Not much have changed since the days it was built, except that more decks have been added and that the original bridge structure, raised higher.  The hull structure, Bridge, the propeller shaft and other fittings were the originals from the days of the Medina - the rest were added progressively during her years as a cruise liner.

Sister ship of Titanic

The Olympic, sister ship of the Titanic.


In the picture above, most ships were built with the 'counter stern' design.  Other names for the counter stern include a "elliptical stern," in reference to its very long counter and "cutaway stern." The counter stern began use during the age of sail, but remained very popular for both merchant and warships well into the nautical age of steam and through the first eight decades of steamship construction (roughly 1840–1920), despite the fact that the design left the rudder exposed and vulnerable in combat situations, therefore the design gradually was replaced with the cruiser stern.



Counter stern of a ship

The 'Counter stern' of the SS Medina. - provided by www.ssmaritime.net



Old Stern design

The deck where the two lines run through the 'fairlead' is the hull of the Medina. 
- provided by www.ssmaritime.net



Notice the hull plating riveted together in a longitudinal pattern and the four 'round eye' plates on the curvature of the stern (near the rudder post) , the same pattern as in the picture of the RMS Olympic, the sister ship of the RMS Titanic.  I cannot imagine enough to say again and again about the existence of such a living historical 'champion of the seas'.  Through the years, she has picked up bits of technological upgrades of between 1914 to 1977 and some upgrades again after that - all on the same hull.

Counter stern SS Medina

Another view of the stern - www.doulos1914.blogspot.my


Those 'bollards' on the deck in the picture below probably dates back to the days of the Medina.  They look old and pretty worn and weathered!

Old Medina stern

1990. ME on the winch controls at Aft Mooring stations. - www.doulos1914.blogspot.my

Do not be left at the back end, but do come up forward to share any thoughts, or extra information if you have; in any case, anything that you've learnt so far.  Cheers!!