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 Author  Topic: ELCO 80' Decking Types
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: Apr 10, 2010 - 5:16am
While going over Dick's ELCO drawings I came across decking types used on the 80' boats:

Boat Number / Construction / Dimensions

103-108
Mahogany planking, 2 layers laid fore and aft
Inner layer 5/16", outer layer 3/8"

109-196, 314-367, 372-383, 487-497, 546-563, 731-760
Mahogany planking, 2 layers laid fore and aft
Inner layer 3/8", outer layer 5/16"

486, 498-545, 565-624
Plywood
9/16"

Notes:
Coaming sits on lower layer of planking on plank decked boats.
Coaming sits on top of plywood on plywood decked boats.
Planked boats have a layer of marine glued airplane fabric between layers.

Information is based on ELCO type section drawings.



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David Waples

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of David Waples  Posted on: Apr 10, 2010 - 5:36am
Interesting that they reversed the size of the planking after the 108 boat. I wonder what drove that change. Cost or quality? Jeff, does it specifiy the width of the planking?
Dave

David Waples

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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: Apr 10, 2010 - 10:13am
Good question about the width, one my rather scatter-brained self didn't think of. I checked assorted drawings and didn't find an answer. I'll post if I run across them. The closest I found was an upper layer deck planking drawing for the 731-760 boats that shows joint locations. It didn't give widths but scaling the drawing comes up with a width of about 5.5".

My guess is that the thicker layer should go down first for strength. Maybe a carpenter put a foot through the thinner layer while laying it down...




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Frank J Andruss Sr

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of Frank J Andruss Sr   Send Email To Frank J Andruss Sr Posted on: Apr 10, 2010 - 10:55am
According to my ORIGINAL ELCO HULL CONSTRUCTION Manual, here is what is says:

Bottom Innr Skin 7/16" x 6" Outer Skin 1/2" x 6"
Sides inner Skin 5/16" by 6" Outer Skin 7/16" x 6:
Transom Inner Skin 1/2" x 6" Outer Skin 9/16" x 6'
Deck Inner Skin 5/16' x 6" Outer Skin 3/8" x 6"
Deck 5/8" Mahogany Plywood
--------------------------------------------------------------------------------------------------------------
There are of course many other measurements within this RTU Manual but too numerous for me to copy unles you guys want something specific............


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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: Apr 10, 2010 - 3:19pm
Cool, thanks Frank. That book scanned would be great at the hnsa web site... hint hint.



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  djwhite

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Post a Reply To This Topic    Reply With Quotes     Edit Message   Posted on: Apr 16, 2010 - 7:39pm
I may give away my age here but thats ok.

Does anyone know if the plywood was made of 4 foot by 8 foot panels overlapped?

Or were there perhaps longer pre-made pieces that might have been wider?

The only reason I ask is that a 2 by 4 in the 40's was exactly that 2" by 4" , not the 1 3/4" by 3 1/2" we have now days.

Denny


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BobPic

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Post a Reply To This Topic    Reply With Quotes     Edit Message   Posted on: Apr 17, 2010 - 12:49pm
I would think the finished ply construction would be the same strength whichever thickness was outside. Jeff may be right, it was chosen to facilitate construction, to get the stronger panels on first to provide a better work surface. I might add that since most damage (in our case) was to the skin layer and it was easier to form and work with a thinner ply, it might have influenced the decision.
I didn't understand djwhites question. A lot of people interpret Plywood to mean the 4X8 panels available to the construction industry. Some PTers protest that the boats were NOT plywood. But if you use the dictionary definition of plywood (layers of wood with cross-grain plies) then we can accept that they were indeed plywood, but djwhite's question I think assumes plywood refers to convetional 4X8 sheets. I never saw such plywood used anywhere in the war. Our plywood was built up of mahogany planking laid in a ply configuration. Hence his question is moot.


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  djwhite

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Post a Reply To This Topic    Reply With Quotes     Edit Message   Posted on: Apr 17, 2010 - 5:04pm
I certainly was not around during the war years, so please excuse my ignorance. The only plywood which I am familiar with is the 4 by 8 foot sheets sold today.

That is why I was asking the questions I asked. Is the 6 inch wide double planking with marine glues fabric between the layers considered "plywood" for the decking? As the later PT boats are listed in Jeffs' listing

If so, how is it visably different than the earlier PT boats which are shown as having the two plank with different thicknesess?

Part of my question was wanting to know if there were longer sections maybe such as two feet wide by ten feet long or was there some other configuration.

I finally received my tax refund so I am ordering our moderators set of Elco plans, so maybe I won't have quite so many stupid questions.

Please explain this to me as I have become very confused and I am not a long time boat person.


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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: Apr 17, 2010 - 11:30pm
That's something I didn't know, that lumber dimensions used to be accurate. Now I suppose it's the dimension before final finishing, snd bordering on false advertising in my book because the only logical reason would be to have the consumer suck up the trimmings from the rough cut. It sure makes things more difficult.

Bob, there sure was a LOT of plywood used on PT boats. It looks like ELCO made a lot of it up themselves. And I'm sure a lot of time was saved using a single layer (another thinner doubler layer was added around areas needing extra strength) of ply over a double planking.

Denny, the drawings show different sizes were used, up to 144" length. Max of 68 x 96" for the 577-624. The main layout was two center sections with two wing sections with butt joints along the center line and along each wing piece. Scarphs were made on the fore to aft section joints. One of the YouTube videos shows a bunch of workers at the factory carrying a really long section, maybe they made up the scarphed sections before laying them on the boat? The planked decks are not considered plywood.



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David Buck

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Post a Reply To This Topic    Reply With Quotes     Edit Message     View Profile of David Buck   Send Email To David Buck Posted on: Apr 18, 2010 - 3:46am
Hi, just a note that Frank J. Andruss, Sr. new book Building the PT Boats on page 91 has a very good photo showing the workers at Elco with an outside section of Plywood Decking ( not plyed wood ) about to lay it down on the decking frames, this section runs just about the full length of the Boat (allowing for the centre sections ). This section of Decking would have been made inhouse just as Elco made many of the special timber parts for the Boats.

Hope this helps a little .

D.buck

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