Is there a 2D program that will replicate whole moulding?

[Jaager]

This is for a bucket list project that is a long shot at best.

Is there a 2D drawing or CAD program that includes the following functions?

The ability to select and place a compass center and use it to scribe an arc between two points on the circumference.

Draw a spline curve using three or more points -  probably a least squares fit  curve function.

The program would ideally be a hobbyist level cost or a cloud subscription sort of critter.

The 16th and 17th century ship designers mostly used a straight edge,  compasses - large and small,  and flexible battens.   
This limited quiver of tools is why those hulls had a similar shape.  Most current drafting programs seem to totally ignore these old methods.

 

[Kevin-the-lubber]

I’m not sure if I’ve understood what you’re asking for but from the description think this is probably standard fare in any normal CAD package. You can certainly draw points and use them to create arcs and splines in Fusion 360, which has a free hobby licence, and I expect the same is true for FreeCad. There’s a thread running on this forum called “an attempt to create a hull…..” or similar, in which we’re talking about various CAD packages, and the methodology of hull drafting, that you might find helpful.

[Jaager]

The programs that I have explored have arcs, but the function involves starting with two defined points on the circumference and connecting them.  This is no help for whole moulding.

Whole moulding - the center and one point on the circumference are the beginning  data that is input .    

Modern programs allow the center to be derived, but not used as a beginning.

I suspect that it is necessary to work thru the exercises in Anthony Deane's book to understand the tools needed.

The key curves on the profile i.e. main wale, etc.  have centers than are far above what paper is needed by a plan in its finished shape.   The one or two drawings of ships being drafted that have come down to us (M. Baker) show the draftsmen using large flat tables.  Which would be uncomfortable - backache and spasms - but a near vertical board would need to be impractical in height.

A computer would be much easier -  but what is needed is a function that starts with:  define center -  define point on circumference  - draw arc. 

 

Least squares fit curves are not a favored method either  as far as my past examinations have found.    What is needed is a math formula that simulates what a long thin wooden batten does to connect three points.  The math formula used to smoothly connect three points in the drawing programs that I have examined show far less restraint in possible solutions than an actual wooden stick would allow.

[Per Rise]

Try InkScape. It's free to use, and You can find a lot of instructional videos on Youtube.

 

link: Download Inkscape 1.1.1 | Inkscape

[Egilman]

On 11/25/2021 at 2:58 AM, Jaager said:

The programs that I have explored have arcs, but the function involves starting with two defined points on the circumference and connecting them.  This is no help for whole moulding.

Whole moulding - the center and one point on the circumference are the beginning  data that is input .    

Modern programs allow the center to be derived, but not used as a beginning.

Brother, you've been looking at the wrong software's..... Most 3D cad software has all this capability your looking for built in and then some... Try Free Cad or Tinker Cad... Rhino has an affordable subscription I've been told and we have a thread on how to do hulls in it beginning to explore the process in a bit...

 

EG

[Dr PR]

Jaager,

 

CAD programs have many different ways to draw arcs and circles. All have the ability to set a center point, another point on the radius, and then set the length of the arc with a third point. You can set the center and radius points and define the angle. Other arc functions allow setting three points and generating the common arc or circle, set two points on the arc and a third for the radius, draw an arc tangent to a line, etc.

 

Spline curves are universal, but it can be difficult to create a specific "French curve" or similar variable radius arc. But if you know the geometric definition of the particular curve you can generate a sequence of points and connect them with a curve.

 

I use a program called DesignCAD 3D MAX that sells for about US$95 (there is a 2D version for about US$65). It has an excellent user forum (probably the most important thing for starting a new program) that is free, and the program does not have recurring subscription costs. It has the best user interface I have seen in any program. BUT - it is a CAD program, and all CAD programs have a pretty steep learning curve.

[Jaager]

@Egilman  @Dr PR  Thank you for the direction.   I think it was DesignCAD 3D  - the V. 1.0  or so that clued me to the realization that, although I may be able to generate a hull, I could not use it to take a cross section at any Z (point along the keel) and get a frame outline.  I was desperate to find a way to avoid hand plotting 200 plus frame outline shapes.   I have come to understand that a 3D modeler can do this.  But, by then I has found an entirely different and much more efficient and much faster way to reach my goal.    What my bucket list objective is to replicate one the Anthony Deane's 1673 first rate liners using the directions in his Doctrine.   I got a ways into it long ago when the first modern edition  was published.  This was on Mylar.  A key that I missed  at the time was  how many cross sections were drawn.  I thought that it was done for every station.  What I could not determine was which parameters were adjusted for each interval.  It turns out that I totally misunderstood the process.  There were only 3 cross sections during the design stage.  

The bow and aft sections could even be "slud" to get a sharp or blunt entry  and a lean or abrupt run aft.   Battens were used to get the run.  Diagonals and ultimately a model (with a framing style that simulated diagonals) were used to "prove" the hull shape.  No flats and no hollows.     There is no 3D needed.  It sounds like DesignCAD 2D is a way.  That is if it allows for the really huge circles whose arcs define the wales, decks and other construction curves needed.     I recommend following Deane's exercises as way to gain some understanding of the old hull design techniques and why all those strange lines that are not a part of actual wood shapes are on those old plans from the 18th century.  Essentially all of the 17th century ones did not survive time.

At my present age, this project is mostly a fantasy, but it is a comfort to see that it is a possibility using electrons instead of graphite.

 

[Kevin-the-lubber]

I may still be misunderstanding (I'm good at that) but, in case it's helpful. you can easily get cross-sectional sketches using Fusion 360. https://knowledge.autodesk.com/support/fusion-360/troubleshooting/caas/sfdcarticles/sfdcarticles/How-to-create-a-sketch-of-a-cross-section-of-a-3D-Model-in-Fusion-360.html

 

So, if you created the basic hull shape in F360 with just a few stations you should be able to slice this any number of times along the keel and get precise cross-sectional 2D sketches at each station. You'd need to add dimensions to each sketch manually (F360 will calculate the dimensions but you have to tell it which points to measure on each drawing) which might be a bit of a slog but not nearly as much as doing this on paper. And of course you can then fiddle with dimensions and detail at each station to create new profiles and loft again using these for a more accurate hull.

 

I imagine you can do the same or similar in other CAD programmes. Egilman, I don't think you can really do this in TinkerCad, it's extremely limited in the splines department and Jaager, as Dr PR says, whatever you use, the learning curve is going to be long and steep so it's well worth browsing the market before you commit. As I've implicitly plugged F360 I should add that it's very good on the whole (and free) but can drive you up the wall when it's not, and lofting is one area where it can be, shall we say 'playful'. Not always, mind, sometimes it's a dream, but sometimes it's not.

[allanyed]

IF I am understanding you correctly Turbocad allows you pick the center, then a point on the arc, then the second point to complete the arc.  They call it an arc center and radius function.   Unfortunately, TC is not free but TC 2019 for beginners is cheap and may suit.

Allan

 

Edited December 2, 2021 by allanyed

[Nirvana]

Another program to consider which also can be found as a free version is Sketchup, can do 2point and 3point radius.

[Dr PR]

DesignCAD 3D MAX can easily generate unlimited cross sections of a hull in the X, Y or Z planes (section lines, water lines and butt lines).

 

The "Contour Line" function (Draw/Lines/Contour Line) will generate  cross sections lines in any plane at any position. You set a point on the plane and tell the Contour Line function to generate an intersection line with the hull and an imaginary plane that passes through the point in the X, Y or Z plane. The transverse contour line through a hull is the shape of the frame. Basically it is the same thing as drawing a plane that intersects the hull and using the "Draw/Lines/Surface Intersection" tool, but without having to create the intersecting plane.

 

I just create a series of points at the desired spacing along the length of the hull, create a contour line at one of them, then move the cursor to the next point and use the "F3" "Repeat" function key to repeat the Contour Line function, and so on down the line of points. But if it is something you do often you can write a BasicCAD macro program to determine the length of the hull, divide this into some number of equal spaces, and generate the contour lines for each section automatically.

 

Contour lines are also extremely useful for fairing the curves of a hull. I create waterlines (horizontal plane intersections) at various elevations and then look at them length wise. If there is any slight kink in what should be a smooth hull surface it is readily evident, and easy to locate the point on the hull that needs fixing.

 

For modern hulls where you have a Table of Offsets it is fairly easy to generate a CSV (comma separated variable) text file from the offset data and feed it into the program to automatically generate all of the curves. However, the engineers or draftsmen often made "typos" when they were entering thousands of numbers from calculations into the tables. These are usually single unit errors (1/8ths, inch or foot) that cause very noticeable bumps and dips in contour line waterlines generated on the hulls, and then corrections are easy.

 

Here is an example of water lines and butt lines generated with the DesignCAD Contour Lines function for a Cleveland class cruiser hull:

 

Edited December 2, 2021 by Dr PR