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 Author  Topic: 80' Elco PT foredecks - fabric-covered or open planking?
Drew Cook

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Drew Cook  Posted on: Jun 4, 2009 - 3:52pm
I have some observations and questions about the foredecks of the 80' Elco PTs that have bugged me for a while now.

In some vintage WWII photos, the foredecks appear completely smooth, with no signs of planking lines, as if the foredeck was covered by fabric. In other photos, the planking lines can be seen quite clearly, and are obviously present.

I seem to remember seeing some Elco plant construction photos, or maybe some film footage in the documentary "Giant Killers" where the foredeck was laid in two large, halved pieces placed side-by-side, which were, of course, smooth, with no planking lines.

What's the deal? Were some boats' foredecks left open-planked and some fabric-covered, or constructed of the two large side-by-side pieces?

Why the difference between the planked and smooth looks?


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alross2

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of alross2   Send Email To alross2 Posted on: Jun 4, 2009 - 5:58pm
Based on a review of plans, photos, and tech spec manuals, 103-196, 314-367, and 372-383 had planked decks; 486 on had the full-length plywood decks. Curiously, the earlier 77' types also had plywood decks, although their 70' predecessors had planked decks. None of the ELCOs had fabric-covered decks as a design feature.

On page 91 of Frank's b ook, there's a great shot of a plywood deck section being set in place. A little later, I'll put up a photo or two of the production line which includes hull 3474 (PT 339) which shows the planking.

Al Ross


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Drew Cook

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Drew Cook  Posted on: Jun 5, 2009 - 7:03am
Thanks, Al...that answers my question perfectly!


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Jeff D

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Jeff D   Send Email To Jeff D Posted on: Jun 6, 2009 - 5:21am
For games of PT Trivia you may need to know that the first 5 boats had 3/8" top decking and 5/16" under decking. After that the top decking was 5/16" and under decking 3/8", with 1/2" cellulose tape covering the under decking seams to prevent glue drips inside the boat.

This is according to a otherwise unmarked January 15th 1942 revised plan so any later changes would not be noted. The plan did not list the PT number ranges it is valid for either (most others do):

http://www.pt103.com/images/ptpics/ELCO_80ft_Typical_Deck_Fastenings_Decking_Sm.jpg



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Drew Cook

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Drew Cook  Posted on: Jun 6, 2009 - 7:04am
And thank you, Jeff...!


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alross2

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of alross2   Send Email To alross2 Posted on: Jun 6, 2009 - 7:08am
Great bit of info, Jeff! Always like to see drawings as supportive material.

Al


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Jeff D

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Jeff D   Send Email To Jeff D Posted on: Jun 6, 2009 - 6:29pm
Glad to help, although I have doubts about the plan Al. The drawings in the "First 5 boats" column are detailed with fastenings but the ones in the column for "Sixth boat and on" aren't. I would guess that the 103-107 drawings are correct since they show them as being changed. Here's the other detail drawings in the two columns:

http://www.pt103.com/images/ptpics/ELCO_80ft_Typical_Deck_Fastenings_Deck_Fasteners.jpg

I suppose the lack of detail could mean that the fasteners were similar and thus undrawn but the lack info usually found in the text blocks makes me wonder about the later boat details and if this plan was redrawn. I also wonder if they meant "First 6 boats" since some other design changes were made after the 108 not the 107.

Here's the plan's text section:





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Jeff D

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Jeff D   Send Email To Jeff D Posted on: Jun 8, 2009 - 4:28pm
This looks like more recent info, found at http://www.ibiblio.org/hyperwar/USN/ref/PT-Manual/MTBM-5.html#C2:

Motor Torpedo Boat Manual
February 1943

(A)The deck is of double-planked mahogany, 3/8-inch upper and 5/16-inch lower, with marine glue and airplane fabric between the plank layers. The planks are laid fore and aft, each lower plank acting as a batten for the upper planks and fastened throughout, with brass screws.

(B)The planking is double diagonal mahogany laid in the same manner as on the 77-foot MTB's. The total thickness of the topside planking is 3/4-inch, inner 5/16-inch, outer 7/16-inch. The bottom planking totals 15/16-inch; inner, 7/16-inch; outer, 1/2-inch. The fastenings to the main frames are Monel screws below the waterline and brass screws above and copper rivets or clinched nails are used for secondary fastenings. Due to the war requirements of copper, brass, and Monel, it is certain that, in production completed after the summer of 1942, all fastenings will be galvanized steel.

The later plywood decking, found at http://www.hnsa.org/doc/pt/specs/#pg19:

DETAIL SPECIFICATIONS FOR BUILDING MOTOR TORPEDO BOATS PT 565-624
31 March 1944

SECTION I-1.
DECK.
(Change)**** Line 33: "of plywood having 5/16" fir core with cross banding each side of 1/20 birch, and faced on each side with 1/12 mahogany." (Per BuShips ltr. 10 June 1944 PT565-62/S11-6 (516f) (Hull Change I-1-(1) Elco S.O. N3385 ****

Decking shall be single layer of mahogany plywood, approximately 9/16 inch thick, installed in general accordance with plan, BuShips No. PT486-S1106-411193, subject to development of satisfactory material.


SECTION G-1.
PLANKING.
Planking shall be mahogany in two layers, laid diagonally in opposite directions; total thickness of topsides 3/4 inch, inner 5/16 inch and outer 7/16 inch; and of bottom 15/16 inch, inner 7/16 inch and outer 1/2 inch. Planking shall be interlaid with aeroplane fabric and marine glue. Topside planking shall be fastened with bronze screws and copper nails; underwater portion aft to have monel screws and copper nails.



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