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How to design ships in Fusion 360 and 3D print them


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I'm going to be starting the USS Baltimore (C-3) so I thought I'd create a thread where I can share some techniques on using Fusion 360 for creating a model of a ship and the design considerations for 3D printing that I've developed over a couple years as I progress through the design....  The Baltimore is a nice mix of areas that are easy and some harder spots so it's a good example to use. 

It's also a pretty historic ship - built domestically in the US using plans bought from Armstrong-Witworth.  Baltimore was an improvement on it's predecessor (USS Charleston). It was laid down in 1887 and was one of the first US Navy ships with the more powerful and efficient, and at the same time it did away completely with sails which were still often provisioned on other ships of it's time.  The Baltimore was one of the ships involved in a diplomatic crisis between the US and Chile during the Chilean civil war.  During the Spanish American war Baltimore was second in line behind USS Olympia during the Battle of Manila Bay.  As a side note it seems the plans for the Baltimore were originally drafted by Armstrong for bid on work for the Spanish Navy who eventually turned down Armstrong's design in favor of one from JG Thompson - who produced a ship for Spain which was christened the "Reina Regente" which tragically sunk with all 420 hands after 7 years in service.....

 

Here's a few details of the USS Baltimore:

 

Length: ~336ft
Beam:  ~48.5ft
Screws: 2
Speed: 19knts
Main Armament: Four 8" guns
Secondary Armament: Six 6" guns
Type: Protected Cruiser

 

First thing I do gather as much information on the ship – photos are of great importance since a lot of the detail areas of the ship you won’t find in drawings that are available.  I was lucky enough to find a series of drawings that included the hull lines on the Baltimore in either the library of Congress of the National Archives (I can’t remember which – since I grabbed them about 2 years ago).  I also downloaded every photo I could find from the Navy History and Heritage archives which is a good supplement to the library of Congress and the National Archives. The plans that were available were old blueprints – actually blue!  And the lines for the hull were hard to discern so I converted the images to black and white and tweaked the hue and contrast so it was a little easier to see things:

 

Original1252223033_23-6897105-cruiser-baltimore11.thumb.jpg.12c29adb17733cc149cbd0296d4a2d97.jpg

Cleaned up:1327624299_Enchanced-BaltimoreDrawings.thumb.jpg.010fe80013dda2f4e75d817f6017612d.jpg

 

Before I go any further, I want to mention that for creating ships in Fusion360 I use the metric system since the 3D printer that I use is basically a metric system machine with movements in fractions of millimeters and a nozzle size of 0.4mm so that particular dimension (0.4mm) is somewhat of a constraint in the design process (i.e. I cannot print something that's only 0.2mm wide)

 

The next step is converting the ship measurements into millimeters (length and width) and creating a box in fusion that I'll use to start designing the hull, but before I actually do that I'm usually checking multiple sources and, not surprisingly, I got different from different sources and usually no clear definition of what the measurement actually is (i.e waterline length, parallel to parallel, or length overall).  Since two sources (one of which was the "Dictionary of American Naval Fighting Ships" published by the Department of the Navy) concurred that the length was 335' and beam of 48'8" that is what I'm going  with. After conversion to millimeters at 1/72 scale it comes out to 1418.2mm long and 206.0mm wide....so now I draw that box in fusion 360 on the X plane in Design/sketch mode using a "center rectangle" on the origin and put a line down the middle lengthwisefusion1.thumb.png.6e49db6936b9fbf278021a819c5e2453.png

 

Next I switch to the Z plane and use the "p" key to project a point on both ends.  I use these points to draw vertical datum lines that will be used to define the aft and foremost ends of the hull:
fusion3.thumb.png.fe8ca759a986bbb3185bd7d35b1f81bc.png

 

These lines help a lot when sizing and centering images that you want to trace.  This is where things will get a little tricky - so were going to start with a side view of the ship and insert it into the design and scale it up and down it until the ends of the bow and stern are just touching the vertical datum lines and the highest point of the bow is touching that middle line that runs down the center of the rectangle.  (To insert, position, rotate, and size an image on a plane in fusion 360 you would used the "insert canvas" while in the "Design Mode").  So I've done that and have it zoomed in to show the bow position:

fusion4.thumb.png.a1d93d43150c180f6571f56ca346c550.png


From here, we're going to do a couple of different things. Firstly, you'll want to look and the hull profile lines and write down the station numbers because you'll be needing those later!   On the Baltimore there's 23 unique station numbers (going from 1.5 to 21.5) as below:

fusion5.thumb.png.56c6cdf62bf7c35d1a8a7da90bc9ae2a.png

 

Next is where it starts to get fun (maybe...) - were going to trace the side profile of the hull using the design/sketch mode in Fusion 360.  An in the case of the Baltimore we'll draft a line along the all the rails and decks  (which you can see named in the picture above) even if they are incomplete. We also need to draw the vertical lines for the stations of the hull profiles.  One mistake I use to struggle with was using a straight spline when tracing curved features of the hull, especially the bow.  Splines by themselves can work but once you complete a spline it becomes harder to correct.  These days I use "sketch points"  and draw splines from sketchpoint to sketchpoint, and its a bit easier to make adjustments if I didn't quite get things right.  Here's close of up some sketchpoints (in white) I'm using to define the bow:fusion6.thumb.png.65d83d518e5b6f280129434570bc2768.png defining 

 

And here's where I am basically ready to move on to the next step and add the lines that define the shape of the hull (which I'll be using the vertical lines to do):

fusion7.thumb.png.c2a403c1eec8ea650dec6a60d6055a29.png

 

 


 

 

 

 

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Picking up where I left off,  I've created a construction plane at the station which is nearest to the middle of the ship using the "plane at an angle" and specifying 90° for the angle so I can look from bow to stern and sketch and size the canvas for the station lines.  I've trimmed the image already and inserted it as a canvas on that plane & I've also dropped vertical lines down on either side (using project to pick up the edges of the rectangle that I created in the beginning which represent the max beam of the ship:

fusion8.thumb.png.4de6fad39c7b827b34468fe71ab5f1d3.png

 

Looking straight down the the center now - there's a couple of things I noticed - The scanned image of the hull shape shows some very slight skewing which really isn't unusual or a problem but the horizontal lines that I drew to see if I could intersect the position of the three rails is off by about a millimeter or so. Not a bid deal - and usually you have to decide what is going to be the authority when there's some discrepancies, especially when you might be using drawings from different sources.  In this case I'll be using the drawing of the side profile as the authority since the differences are really small and it's typically easier to compensate the hull shape lines to meet the requirements of the side profile.  but if the difference is large the drawings of the hull shape should control. 

 

I've got red circles where the horizontal lines should be intersection of the bearth deck, gun deck, and underside of rail to the outside hull line - I'll actually be using multiple horizontal lines to create points at every station to make rails that follow the shape of the hull from the bow all the way to the stern which will help maintain a smooth surface and more accurate hull shape. 

fusion9.thumb.png.51b86db35c388bf81fa352ea8af65bfa.png

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On 5/29/2021 at 11:15 PM, Haze Gray said:

This is where things will get a little tricky - so were going to start with a side view of the ship and insert it into the design and scale it up and down it until the ends of the bow and stern are just touching the vertical datum lines and the highest point of the bow is touching that middle line that runs down the center of the rectangle.  (To insert, position, rotate, and size an image on a plane in fusion 360 you would used the "insert canvas" while in the "Design Mode")

I know I'm kinda late to the party here HG, but for future reference....

 

One of the dimensions of a ship is very important to describing the shape of the hull, it's a basic dimension and is usually synonymous with Waterline Length, but not always...

 

LBP, Length between perpendiculars. It can be calculated or, it's usually marked on the profile drawings...

 

When inserting a drawing as a canvas in Fusion 360 it installs it on the plane you selected, once done you close it and it shows up in your design tree on the left side of the screen. there will be a folder labeled "Canvasses" open it and right click on the drawing you just installed and it brings up a menu, one of the selections is "Calibrate" what that does is put your canvass in a mode that will scale it to whatever length you want it at keeping the aspect ratio constant...

 

You mark one point on the drawing, then another point on the drawing at the end of a known dimension... Fusion 360 enlarges/scales the drawing for you to the dimension you specify...

Once that is done, you again right click on the drawing in the Canvas folder and select edit, you can then move it to line up whatever index point on the document you wish to use with the origin....

 

The point of this little operation is you now have a drawing in accurate scale on a known dimension, you can take dimensions directly off the canvass within Fusion 360 cause your drawing is now indexed.... everything you draw or sketch out will be in scale with the blueprint....

 

A big huge timesaver to having to constantly do the math.... Let the blueprint be more than just a guide for overdrawing/tracing, let it do the job it was drawn for, convey the actual data....

 

EG

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I didn’t know that (calibrating the sketch), useful. One thing I wish I could do in F360 is annotate sketches. Is there a way? I haven’t found one myself. The kind of thing you’d add in a box on paper drawings. As far as I can see, the ‘notes’ function is good for adding info about the version, but not what I’m describing here. Even on my potty little stern section I have literally hundreds of sketches now and, as I work through finalising everything for printing, even though everything is named, it can be really hard to remember why I’ve put this or that line ‘there’, or what I used as the reference for ‘that’ sweep path etc. It’s always possible to figure it out but adds hours to the project.

 

One thing I’ve learned (the hard way of course) which I would certainly try to apply to any future complex f360 projects, is to write an end to end workflow plan at the beginning. Very boring, but it will probably save me hundreds of hours. Of course it’s not the writing that’s of value, it’s the thinking it through. I have about 60 components on the stern section, all inter-related and I developed these in a logical ‘woodworking’ sequence. Turns out that’s not necessarily the best sequence in f360. As I tidy up now, I’ve been surprised to find myself moving (now derived out) components to quite different places in the timeline, because they need to happen before or after this or that other component. If I’d written a plan I would perhaps have foreseen this, though I probably needed to learn the lesson first! I probably haven’t explained this very well but suspect very experienced users will nod sagely and know what I mean.

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Egilman's  description of calibrating the drawing to known dimensions is a very good writeup.  One challenge that may present itself is when you don't have perpendicular lines to calibrate.  Since I do a lot of older ships where the plans are rough and don't show reasonable detail down the the individual frames or the only available reliable measurement is LOA (length over all) or the two extremes of the ship are at different elevation (stern high and bow low) drawing a calibration line at an angle won't get you the right size. I've also found that (for me) it's hard to draw that calibration line perfectly horizonal which can impact accuracy. 

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12 hours ago, Kevin-the-lubber said:

I have about 60 components on the stern section, all inter-related and I developed these in a logical ‘woodworking’ sequence. Turns out that’s not necessarily the best sequence in f360.

Yeah I'm kinda wrapping my head around this as well... The order of features you add can have a dramatic effect on workflow for just a single component... And the more complex the component the the more complicated it becomes....

 

As far as a note feature for sketching? there is none, and there is a request in their support forums to add it... But it's not getting a lot of traction....

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8 hours ago, Haze Gray said:

Egilman's  description of calibrating the drawing to known dimensions is a very good writeup.

Thank you, being a newbe myself I was afraid I would get it wrong....

 

8 hours ago, Haze Gray said:

One challenge that may present itself is when you don't have perpendicular lines to calibrate.  Since I do a lot of older ships where the plans are rough and don't show reasonable detail down the the individual frames or the only available reliable measurement is LOA (length over all) or the two extremes of the ship are at different elevation (stern high and bow low) drawing a calibration line at an angle won't get you the right size. I've also found that (for me) it's hard to draw that calibration line perfectly horizonal which can impact accuracy. 

Agreed, scans of blueprints/drawings are notoriously distorted.... Working with scanned or microfilmed BoGP's I soon realize they are only as good as the skills of the original photographer.... Then there is the automatic issue of lens distortion, then age deterioration... Lots of issues to deal with to convert them into useable drawings...

 

Back when I started out with 3D in Maya then Blender, there was a tutorial I found on prepping drawings for use in 3D design software... There is a lot of issues to fix especially in scanned naval drawings, given their size they are difficult to scan accurately.... But that is how I was introduced to Gimp and how to fix and correct drawings which is a huge rabbit hole itself... (no time for that here, too big a subject)

 

Most of the time coming up with perpendicular or parallel lines is impossible.... 

 

The most accurate line we have is the keel line....

 

My method of getting a straight scale loa measurement in fusion 360's calibrate function is to use the edit canvas feature to move my first point I want to measure from to the origin, then close and move the canvass to match the vertical origin line to the left side of the screen... Then I activate the calibration function and measure horizontally from the point I want to calibrate to, to the edge of the screen... you can get awful close to horizontal this way.. (within a very small window of deviation) Once calibrated to size/length, you then open the edit routine again and move the calibrated drawing to where ever you want it... It even works for drawings where the stern is inches higher than the stem..... 

 

Use the edge of the screen for your base ruler and move the point you want to measure from to it.... Then you can make the first calibration point anywhere along that line vertically.... it's like drawing a vertical baseline except it's a virtual one... 

 

Or you can add a vertical line to the drawing in PS or Gimp to use as a base line...

 

There are several different ways to do it my friend...

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