Longitudinal Girders

[robert s hauser]

This question concerns the construction of the double bottom of the Olympics. In "Anatomy of the Titanic" mentions that there were 4 longitudinal girders on either side between the keel and the margin plate. The first problem to complicate things in my mind is the fact that I'm not exactly sure what a margin plate really is. From looking at several downward views of the Olympics double bottom that are no doubt familiar to Titanic buffs, I'm assuming this to be the outside edge to which those final triangular shaped wings are attached. You can see them on the ground around the bottom, and in some photographs you can see where about half of them have been added and extend outward from the floors. They seem to define the shape of the curvature where the bilge turns. Anyway, I've scrutinized these pictures to death but can't seem to see any evidence of 4 longitudinals. I can see the line of the keel, and 1 other line on each side, which seems to form a rectangular box shape outline within the double bottom (as seen looking down). Where are they? I thought I might get a clue from that cross sectional view that was famous as a publicity drawing, but there are actually 6 vertical lines on each side of the keel, so obviously thats not it. I'm curious as to how they were attached to the floors. It would seem that they would either have to be on the top, or the bottom, or be threaded thru a series of holes in the sides of the floors. Or were small sections put between each floor in a straight line? Sorry for the ponderous phrasology, but its hard to explain without a drawing. Thanks Rob

 

[Noel F. Jones]

Margin Plate:

"At the bilges the tank top may be either continued straight out to the shell, or knuckled down to the shell by means of a tank margin plate set at an angle of about 45 degrees to the tank top and meeting the shell almost at right angles.

This latter system was originally used in riveted ships in order to obtain an efficient, watertight connection between the tank top and the shell. It has the advantage, however, of forming a bilge space into which water may drain and proves to be most popular. If no margin plate is fitted it is necessary to fit drain hats or wells in the after end of the tank top in each compartment."

From Ship Construction for Marine Students (Stokoe), Reed's Marine Engineering Series, Sunderland and London, 1979 Edn.

"A longitudinal plate which bounds the double bottom at turn of bilge. The lower edge is fitted normal to the shell to which it is attached by a non-continuous angle bar; the top edge is flanged over horizontally and riveted to the tank-top plating."

From International Maritime Dictionary, De Kerchove, Van Nostrand Reinhold Company, New York etc. 1961 (Litton Educational Publishing)

Noel

 

[Cal Haines]

Rob,

You can see the intercostal plates in most cross-section plans. This link is to a boiler room section that shows them:

http://www.abratis.de/sources/pictures/pic/blue/xsection.gif

You can download this drawing (midships section) for a better view. (If your browser can't open the file, right click and save to disk then view with you favorite bitmap editor.)
http://copperas.com/titanic/Tit_sec.gif

The intercostals did not run from bow to stern. They ran parallel to the keel and drop off as the lines taper at bow and stern. They were 8'-11", 12'-5", 18'-6" and 24'-6" port and starboard of the keel.

The intercostals are hard to see in most photos. I don't think there are any in "Anatomy of Titanic" that show them. "Birth of Titanic" page 72 (photo H1332A, Olympic) shows them pretty well.

Cal