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U.S. Navy Training Film — Ship Hull Fundamental Lines & Sections

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  • Member since
    January 2020
U.S. Navy Training Film — Ship Hull Fundamental Lines & Sections
Posted by Space Ranger on Saturday, May 9, 2020 11:29 PM

This is a great tutorial for us landlubbers or those just getting into building ship models.

https://youtu.be/dTOmYgUP9TE

  • Member since
    January 2015
Posted by TheMongoose on Sunday, May 10, 2020 8:51 AM

At first i thought, ughh 20 minutes, really? Then I really got into it as I watched. Very educational. Although i did find the "port side looking aft" reference confusing as they say "port is now on your right side. Crying  it must have a meaning in how they orient stuff thats not in the film as i thought that would switch how you referenced where things are on the ship based on how you were looking at it but NO, it's still the left side of the ship just on your right side lol

thanks for posting, gonna save this reference!

In the pattern: Lots in my stash. But let's close out the SOD and do the 1/350 Enterprise I started a few years ago.

  • Member since
    January 2015
Posted by PFJN on Sunday, May 10, 2020 1:08 PM

Hi,

Eventhough I am a Naval Archtect by training, that was still an informative video for me, as some terms/concepts (specifically the A, B and C Divisions) seem to have changed between WWII and now.  Specifically I am not more familiar with ships being divided into Fire Zones, less tan or equal to 135ft in length, potentially leading to more than 3 main divisions.

Other than that the only things that stuck out to me was that, although the author mentions the fore and aft perpendiculars, he never specifically explains how they are defined (perhaps since it can be a little vague).

In general though, usually when first laying out a ship the Fore Perpendicular is "typically" set as where the stem of the ship intersects the "design waterline".  Unfortunately though, as a design progresses, sometimes the actual eaterline that the ship ends up sitting at is not the same as this "assumed" "design waterline".  Typically though you don't redefine a new "design waterline" since over the life of the ship (or even between sisterships) there will be issues that constantly cuase the actual operating waterline to vary, so in the end the "design waterline often typically just stays as your best 1st initial guess at something close to a warerline at where the ship will typically be operating, and the FP (or forward Perpendicular) remains as defined where the stem crosses that Design Waterline (or DWL).

However, occassionally on some ships it is possible that a decision is made to redesign the bow or something, leading to the FP not actually even being on the ship.  If I am recalling correctly one Naval Auxiliary that I worked on (the AFS class of ships) actually had its FP defined a few feet forward of where the DWL and Stem intersected because of reasons like this.

For the AP, or After Perpendicular, things can get a bit more confusing though, as on commercial ships it is often defined as coincident with the main rudder stock.  On many/most(?) naval ships though it is often defined as where the design waterline (DWL) intersects the stern (if I am recalling correctly).

In addition, during ship design, although the ship will eventually get divided up into Frame lines like shown in the video, before this happens it is often still necessary to know what the shape of the ship looks like, so the ship will often be divided into regularly Stations, that can make it easier to compare the shapes of different ships, etc.

In the US a ship is typically divided into 20 stations between the FP and AP, frequently with some half stations at the ends where the ship's hull may have more shape or curvature.  Typicvally in the US, for large ships, Station 0 is the FP and Station 20 is the FP, and anything forward the FP has a negative number and anything aft the AP is numbered 20.X (or something similar.  

In te US since these large ships are typically divided into these 20 stations you may hear reference to the ship's Frame Spacing, which really has no relation to it internal structure, but rather is just the distance beween the FP and AP divided by 20.

For smaller ships and boats in the US, as well as many ships of any size over seas though, the ship is typically only divided into 10 Stations, instead of 20, and often the umbering starts at the FP and moves forward, instead of the FP and moing aft.

Anyway, thanks for posting the video, I found it very informative.

Pat

1st Group Build

fox
  • Member since
    January 2007
  • From: Narvon, Pa.
Posted by fox on Sunday, May 10, 2020 1:33 PM

Thanks for the link. Great info. Brought back memories of finding pipelines at the Phila. refinery. Engineer asked me where a specific line came from and where it went. Walked around for a while and couldn't figure it out. Went over to the office and got the blueprints to look for it. After locating it, found out that it was disconnected at both ends but went back to older prints and found it. Tough engineer finally got a smile on his face and said "Good job kid". 

Jim  Captain

Stay Safe.

 Main WIP: 

   On the Bench:  Revell 1/96 USS Kearsarge - 70% 

I keep hitting "escape", but I'm still here.

  • Member since
    November 2005
  • From: Formerly Bryan, now Arlington, Texas
Posted by CapnMac82 on Sunday, May 10, 2020 6:52 PM

PFJN
In te US since these large ships are typically divided into these 20 stations you may hear reference to the ship's Frame Spacing, which really has no relation to it internal structure, but rather is just the distance beween the FP and AP divided by 20. For smaller ships and boats in the US, as well as many ships of any size over seas though, the ship is typically only divided into 10 Stations, instead of 20, and often the umbering starts at the FP and moves forward, instead of the FP and moing aft.

And, in H.I. Chappell's time, Forward Stations were lettered, either from Midships forward or from FP aft.  After Stations being numbered, typically in Roman Numerals.  It's decidedly quaint to see plans so marked.  That, and to see "futtock" planes rathe than "buttock" planes, too.

I remember seing this film in Naval Science 201, long, long ago.  And, even in 1979, we had rather a long classroom discussion on how, ships are designed differently from the way that they are built.  That the Stations in the Body Plan are what define the eventual actual frames when lofted.  The entire next class was on how one would loft a frame based on just the stations, waterlines and futttocks (and the Table of Offsets).  We had a brief diversion in the "why" of a Diagonal, too.

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