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NoBozo · 09-06-2009, 06:48 PM

I can only believe from that underwater picture .. that that structure such as you described as amidship would be a "Spreader" of some sort to bring support to the derrick from a more aft... or more advantageous angle....Via cables.

BUT there is no evidence of such a support in the Dago picture. I had a problem with the Dago picture..in that there was no apparent aft support for the derrick...hence I speculate the derrick was a tripod..which would "Self Support". BTW: And I am just speculating here....if the "spreader" were in use on the Dago..the "HOG" in the hull would perhaps have been less severe. A kind of balance of forces which would have diminished the tendancy to hog.

The "donkey engine" winch cable which would be used to lift the pile to vertical, would run horizontally along the deck of the barge foreward....and turn UPward via a sheave/pulley at the base of the tripod.

Another picture of the Dago from a different angle would answer some of the questions as to what type of derrick was onboard.

NB

PS: #1: I have not to date... been able to decipher side scan sonar pictures.

PS: #2: My first experience with SCUBA was in 1961 or so. I dove off a small island in Greenwood Lake, NY and went down to "whatever depth" it was, and was unable to dive deeper than an ICY layer of water. I think Wetsuits were not invented yet. I could actually stick my finger into the layer...it was ICEWATER. I think today we recognise this as a Thermocline.

09-06-2009, 06:48 PM	#10
NoBozo Senior Member Join Date: Jun 2008 Location: Portsmouth. RI Posts: 2,231 Thanks: 400 Thanked 460 Times in 308 Posts	I can only believe from that underwater picture .. that that structure such as you described as amidship would be a "Spreader" of some sort to bring support to the derrick from a more aft... or more advantageous angle....Via cables. BUT there is no evidence of such a support in the Dago picture. I had a problem with the Dago picture..in that there was no apparent aft support for the derrick...hence I speculate the derrick was a tripod..which would "Self Support". BTW: And I am just speculating here....if the "spreader" were in use on the Dago..the "HOG" in the hull would perhaps have been less severe. A kind of balance of forces which would have diminished the tendancy to hog. The "donkey engine" winch cable which would be used to lift the pile to vertical, would run horizontally along the deck of the barge foreward....and turn UPward via a sheave/pulley at the base of the tripod. Another picture of the Dago from a different angle would answer some of the questions as to what type of derrick was onboard. NB PS: #1: I have not to date... been able to decipher side scan sonar pictures. PS: #2: My first experience with SCUBA was in 1961 or so. I dove off a small island in Greenwood Lake, NY and went down to "whatever depth" it was, and was unable to dive deeper than an ICY layer of water. I think Wetsuits were not invented yet. I could actually stick my finger into the layer...it was ICEWATER. I think today we recognise this as a Thermocline.