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 Author  Topic: PT 761 Class
Andy Small

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Andy Small   Send Email To Andy Small Posted on: Mar 3, 2018 - 10:49am
While at the Naval War College last month, I found information leading me to believe that the PT 761 Class of Elco's were significantly different from the previous models as far as superstructure goes. The first image is my sketch of what the the day cabin and chart house (with raft)/cockpit configuration probably looked like. Bridge stretched across the boat and the cockpit area protected with aluminum armor. This area was slightly elevated above the boat's deck by about 6 inches. Don't have any info on the forward right .50 call tub other than it was farther aft. Other info mentions that these were going to be equipped with SO-5 radars (second image), most likely mounted on the top of the slope of the day cabin, so significantly higher that the previous mounting. Also, they were going to be equipped with W-100s. You can see a few superstructure similarities with PT809.

So, was wondering if anyone out there had any late war Elco plant images showing this final class of boats being built? Seems a shame that so little seems to be known of this final class of PTs.

jQECc.jpg

PT 761 Class Sketch

jQOt3.jpg

SO-5 Radar


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Andy Small

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Andy Small   Send Email To Andy Small Posted on: Mar 4, 2018 - 7:45pm
Guess there's not much out there? Here is the only photo I know of showing the forward chart house of PT767 (cropped from Chip Marshall's collection). You can really see the difference from the previous design. The two late 45 drawings showing the chart house and trunk cabin (day cabin) are from the Naval War College collection. Unfortunately don't have any photo of the starboard side. Hoping somebody has another Elco construction photo from the Aug-Sep 45 time frame.

jQqQt.jpg

PT 767

jQWsT.jpg

Elco Drawing 3580

jQyfw.jpg

Elco Drawing 3584


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Andy Small

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Andy Small   Send Email To Andy Small Posted on: Apr 12, 2018 - 9:45pm
Here's my first crack at the PT761 Class profile based on the data I've collected to date. I used portions of John Drain's PT 593 to expedite.

jhpg5.jpg


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  TED WALTHER

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of TED WALTHER   Send Email To TED WALTHER Posted on: Apr 14, 2018 - 8:42pm
Andy;
That is a good looking "first effort"!! To bad more can't come to light about this design modification, I hope you find more.
Take care,
TED


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Andy Small

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Andy Small   Send Email To Andy Small Posted on: Apr 15, 2018 - 11:01am
Thanks Ted! Actually hit a good amount of pay dirt during my research visit this past week, but unfortunately no outboard profile drawings so I had to piece items together. Starboard, turret and trunk setup as well as most of the armament drawings were located. Engine room setup of the PT613 Class and PT761 were the same and seem to be configured to eventually use the W50 and W100s. Did locate the 761 plywood deck configuration and the plan view of the superstructure. Sensor information and location is only available through Elco/BuShips correspondence.

What I found interesting was that the 761 class drawings, for the most part, were dated earlier than the 613 class drawings. Looks like 761 class items were applied as mods to the 613 class as Elco/Navy looked to apply these items to production boats due to the end of the war and termination of the 761 build. Lastly, I like how the 761 shows the direct progression from all the original Elco PTs to the post war PT809.


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  TED WALTHER

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of TED WALTHER   Send Email To TED WALTHER Posted on: Apr 15, 2018 - 4:24pm
Andy;
I hope you can post all this. You are correct, externally, I can see 767(761 Class) as the gap bridge between 613 class and the 809. It all makes sense now, I have always wondered where the 809 design originated, to me, it appeared to come out of thin air. She was at our pier at SBR-2 in 1991-92, Walking on her deck and looking at her, she was a real stretch from the 80 Elco design, I was familiar with.
Take care,
TED


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Andy Small

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Andy Small   Send Email To Andy Small Posted on: Apr 23, 2018 - 8:32am
Frank posted some of Chip's photos of PT613 (National Archives) and I went ahead and did a comparison of the deck layout of the PT613 class from the previous factory weapons configuration. This was the same layout for the PT761 class. Thought it interesting that the forward turret doesn't have the cutout.

jh5cM.jpg

Also posted an update of my PT761 sketch.

jhNUJ.jpg



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Will Day

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Will Day   Send Email To Will Day Posted on: Apr 23, 2018 - 1:40pm
Wonder if they were already flirting with the idea of a 40mm bow-mount, hence the weight shift aft...

Will

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  TED WALTHER

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of TED WALTHER   Send Email To TED WALTHER Posted on: Apr 23, 2018 - 3:42pm
Will
That is a good possibility.
Andy;
As you noted most forward weight was shifted aft, including the torpedoes that are out of the photo. PT 613 was the first to have these modifications, and the remaining RON 42 boats. Good eye noticing that the ,50 mount doesn't have the indentation, I never noticed that on the last 10 boats, now I can see it, especially in the turn over photos of PT 620 (as ROKN PT 27), to the South Korean Navy in 1952.
Keep up the search!
Take care,
TED


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  Andy Small

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Andy Small   Send Email To Andy Small Posted on: Apr 28, 2018 - 3:02pm
Might have found some info on the whole shifting the ordnance aft. A 2 Aug 45 Board of Inspection and Survey letter, subject: PT613 preliminary trials to the SecNav stated No more weight should be added to increase the trim by the head, as on starboard turns particularly at high speed, there is now a tendency to dip forward. I also was interested in the new 20mm location and it seems that was another hot topic with a request that the forward arrangement of weapons be re-studied and that the new position of the 20mm was now inadequate (too near side of vessel). Big problem with shifting stuff aft is it makes it hard for a boat to turn since you need the bow or a fin to build the turning moment. So in a 31 Oct 45 letter from the Supervisor of Navy Yard, NY, PT's 613, 616, 617, and 618 were to have a horizontal fin installed. I assume this would have been similar to the one installed on the Elco Planes boats such as PT487. This info was from the Naval War College Archives.


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