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Westerly Discus 33ft Half Model by jonny.amy - 1:24 - SMALL

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Welcome to my Build Log on the my "commission" build of a Westerly Discus 33. The Westerly Discus is a popular cruising yacht design of the late 1980's with hundreds being built by Westerly Marine Construction of Hampshire (UK) until liquidation in early 2000. The Discus 33 was designed by John Laurent-Giles, who drew two design iterations, sloop rigged, and ketch rigged, both with either a fin keel or bilge keels.


For more information on the Discus 33, follow the links below:




Why call this a "commission"? This is strictly not a commission as I will not be paid for this build, but my family will be giving this to my Grandfather for his 80th Birthday in January 2017, as he is in the process of selling his yacht Giselle due to ill health. Although the deadline is still 10 months away, I will be trail-blazing to some extent, and will in theory be building this as a 3D model in AutoCAD 2014/2016 and DelftShip (free), exporting the 3D model as an .STL file and then getting it 3D Printed. As this is a gift, the quality of the finish has to be on point, so if the 3D Printing is not up to scratch I will be producing a Laser Cut Plank on Bulkhead model instead. At this point, I will use Delftship to model the hull to the highest accuracy and then produce a cutting plan for all bulkheads, and planks.


The final deliverable will be as follows:

  • Half Hull - Westerly Discus 33 Sloop with Bilge Keels, mounted of decorative board
  • Build Log - Bound Book - contents comprised of 3D model development photo's, 3D Printed Model Building, Fairing, Painting and Finishing.

Now, the Legal aspect of this build-log. I have purchased the AutoCAD** drawings from the Laurent-Giles Archive, and have been given express permission to build ONE and ONE ONLY half hull model. I am free to manipulate the AutoCAD files as I require to produce a 3D model of the yacht, on the basis that the drawings and resultant 3D model are used to build one model as a gift or for personal use, and are not to be replicated in any way.


** The AutoCAD file that has been purchased is a rework of the original hand-drawn line drawings. This drawing shows all the Waterlines, Shearlines, Buttocks, Keel & Rudder Profiles, Stations, Coahroof Profiles, and the Mast Position. I would have been happy doing this, but this has saved me countless hours on getting the line drawings in AutoCAD from paper copies of the drawings.


With this, I'd like to thank Barry van Geffen of Laurent-Giles Archive for producing excellent quality CAD drawings for me to use in the production of this model for my Grandfather.


Build Information:


The model will follow the basic principles of building a Half Hull model. The Starboard side of the hull will be built up from the plans, in to a 3D model where I will commission a local 3D Printing Company to print the model in three sections, Bow, Midships, and Stern. This will be because of size limitations for printing. At a scale of 1:24, the model will be 430mm in length, and have a maximum beam of nearly 100mm.


The Bow, Midships, and Stern pieces will be printed as 5-Sided Cube, with bolt holes for alignment, and finally bolted together with an M8/M10 bolt with a corresponding nut epoxied in to place. If the epoxy is strong enough for the task, then I might just epoxy the pieces together? These decisions are to come in due course.


Finally, the model will be faired and painted to match my Grandfathers yacht. The fittings such as winches, mast, boom, kicker, blocks, stanchions, and deck hatches will either be scratch built or bought from a reputable source.


I will post Part One of the Build Log later on.






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  • 2 weeks later...

Hi all,


Sorry for the lack of updates on this build log, I have had a couple of busy weeks decorating our flat to keep the Admiral happy. I'll do a quick update on how I started this project...


Obtaining the CAD Drawings:


The ball started rolling on this project after I took the Admiral on holiday in July 2015 to Jersey (Channel Islands, UK) to meet my fathers' side of the family. This was a holiday for her, a chance to see where I came from, and where the family name Amy comes from. We stayed with my Grandfather in his lovely apartment overlooking the English Channel (with a great view of St. Malo on clear days through binoculars). Lucy has never been sailing before, so my Grandfather took us out on his yacht the aforementioned Westerly Discus 33, and mentioned he was selling the yacht at the end of the season. Shortly after the holiday was over, and we were back to reality. 


Fast-forward to Christmas time 2015, in the festivities I sat down with my father, and over a pint (or three) we hatched a plan on a meaningful 80th birthday present for my grandfather from us three kids and our father (including our respective partners). It was suggested that a scale close to 1:24/1:25 would be a suitable size for the model, and that a Half Hull model would be best for his apartment. 


A Plan of Action was then devised.... I would build the model, either using traditional "bread-and-butter" or PoB building methods, or to produce a 3D CAD model (I am very fortunate that this sort of thing is in my job description), and investigate the processes of 3D printing and finally finishing off the model with fixtures and fittings. In the mean-time, my father would locate an exceptional piece of wood to build the display board, finish it with gilded beading, and then most importantly, obtain the CAD Drawings.


To start off with, a quick internet search found very little in the drawing department, but fortunately, we found the Laurent Giles Archive website, and made contact with them. It is with great luck that Barry van Geffen was more than happy to supply us with the drawings for this model. The CAD drawings were delivered to me in mid-February 2016.




From this, I built up a 3D wire-frame model to add mesh surfaces to. The image below is of the 3D wire-frame model.




Unfortunately that's all for now folks as I have to get back to work....


The next part of my build log will be about the set backs I've come across with the mesh modelling in AutoCAD, and my attempts to around the issues I have come across.







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Hi All, thanks for the likes and comments.


Mark - I hope it will make a nice model, I just have to get my head around 3D ship modelling in AutoCAD!!!


Walter - I have a hard drive full of photos of the yacht so looking at those isn't an issue. The real issue is the logistics of getting to the yacht as it is in the Channel Islands (about 100 miles off the UK South Coast) which would require a flight there and back (or ferry) and will cost a small fortune, but I've been in contact with an owner of a Discus 33 of the same 'vintage' and have the option to carry out a survey if required.


iMack - I am a CAD designer by trade, so this is mostly second nature to me (I plan to get a detailed description of the set backs I have encountered so far on here tonight of tomorrow). I thought my knowledge of 3D AutoCAD and 3D design packages would be beneficial to creating a highly detailed 3D printed model of the yacht. I know the concept of scratch building is to "do it all from scratch", but I wanted to obtain the highest quality from this model.


Cheers for now,


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Problems with 3D Modelling:




In my attempt to 3D model the yacht in AutoCAD I have come across a few problems that have left me a bit stuck on the 3D modelling aspect of this project. Firstly, the choice in method of 3D modelling, either extruding the bulkheads a certain depth, lofting other a 3D wire frame, or laying a mesh over the 3D wire frame.


Option 1 - Extrusion of Bulkheads - This option is the easiest option. Taking the 2D drawing supplied, I copied the bulkheads over to a new 3D drawing sheet, where I then converted each bulkhead profile in to a Polyline. This the allowed me to use the "EXTRUDE" command to pull the bulkhead out to the depth required (at this scale, 28mm). The issue with this is the extrusion is square along the extruded Y axis, so a step between each bulkhead is then created in the X axis. This poses a problem in accuracy. The transition from bulkhead to bulkhead would require trimming, using the "SLICE" command to keep the transition from bulkhead to bulkhead as close to the design drawings as possible. This proved to be difficult as the high internal volume of the yacht has meant that a knuckle and hard chine following the Shear Line on the topsides (allowing for additional space below) does not allow this drawing command to give a precise cut on each face of the bulkhead. 


The images below show this problem at the three central bulkheads towards the bow.


Extrude Bulkheads.bmp


Extrude Bulkheads_2.bmp


Sliced Bulkheads.bmp


Option 2 - Loft Bulkheads over Wire Frame - This option seemed to be the most logical. The Lofting command breaks a surface down in to a number of workable points on one face. This then applies those workable points on to the new face. The example I've shown below shows a square lofting in to a circle.




In this instance, the face of the square is broken in to 20 workable points which are then copied up to the new face (the circle) and then applied to the new face in the automatically calculated positions. This works in principle from say a square to a circle, but didn't work in practice on the hull.

I found the issues with the lofting from bulkhead to bulkhead were that the program automatically optimised the lofted points without user interference. This meant the lofted surfaces were "too square" in shape and did not conform to the voluminous shape of this complex hull form. 


I then decided I would try to Loft from the water lines, using the 3D mesh, but again, this did not conform to the voluminous shape of this complex hull form. 


That's it for now, and time is marching on - I'll edit this post later on with my other options.






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Problems with 3D Modelling Pt. 2:




So I left off with Options 1 & 2 giving very little in a way of usable 3D model, now I will discuss the other limitations I faced in the design process.


Option 3 - Laying a mesh over the 3D Wire Frame - This option was a step in to the unknown for me, as I have never modeled meshes for "yacht design" before. I read around on the internet for advice, but there was very little available in regards to meshes in a complex surface form, such as a hull. Each website I looked at eventually suggested lofting complex surfaces in programs such as AutoDesk Inventor, 3DS Max, and Rhino, but ultimately, because this is project on a budget and time schedule I was not prepared to download another free trial and try to learn the software whilst working on the deliverable 3D model.


With this I tried to lay the mesh over the 3D wire frame I had built in AutoCAD previously. The wire frame model was imported in to AutoCAD as DXF file (AutoCAD reference file) and the number of mesh parts was calculated. This was achieved by calculating the number of intersection between the waterlines and stations on the model. With 15 Stations and 11 Waterlines, I calculated that 165 Mesh Panels would be required. I ran the AutoCAD mesh command, setting the mesh length to 15 panels, and mesh width to 11 panels. I imported the mesh to the drawing datum point (X,Y,Z - 0,0,0), and started manipulating the mesh to fit on the wire frame. This worked fairly well around the Shear, Knuckle (Chine) and Flatter surfaces around the bow, but as I pulled the mesh elements around the waist of the hull, I found the computer started to struggle to align the flat surfaces to the voluminous hull shape.


I will continue the discussion on design limitations with DelftShip, AutoDesk Inventor, and Bentley Microstation, in the pursuit of perfection.




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  • 2 weeks later...
  • 1 month later...

Hello Chaps,


It's been a while without a post on the Westerly Discus... Home life and work have been incredibly busy over the last month or so, and with the nicer weather and lighter evenings, it's been very hard to sit down at the laptop and work on the Discus after work when I could be out enjoying the nice weather with the dog.


Problems with 3D Modelling Pt. 3:




So I left off discussing the problems I was having AutoCAD to produce a comprehensive 3D model of the yacht, specifically modelling the bow and stern with accuracy, so whilst talking with my boss about the problems I had encountered, he suggested using DelftShip, a free 3D design package used to design Ships Hulls (my boss spent 20+ years in the Ship Building Industry as a Draftsman) and with gave me a brief run down of how it worked (admittedly he hasn't used the program in a number of years). So following the sound advice that had been imparted on me by him, I went home and downloaded the free version of DelftShip.


The first piece of advice I was given by my boss was to import the lines drawing (provided by Barry van Geffen) in to DelfShip as a .dxf file, but in the free version, this is not possible, so I had to try to create a copy of the hull based on the basic hull shape generator built in to the program. This would have been a suitable method of producing the hull shape if I had a Table of Offsets to work from, but unfortunately, I did not think I would have this issue whilst I was in contact with Barry from Laurent Giles, meaning I had to try to recreate an accurate Table of Offsets from the drawing provided. Upon further investigation in to the functions of DelftShip, I found that I could input a Table of Offsets in to DelftShip and produce a hull shape from that. Unfortunately, I found that this did not work on my version of DelftShip.


This drew an end to my investigation in to the feasibility of 3D modelling the hull in DelftShip.


Autodesk Inventor:


After this, I decided I would search the internet for the best method of 3D modelling a yacht. I found an number of Autodesk users describing 3D modelling of yachts and ships in AutoCAD Inventor. Reading further in to yacht design with Autodesk Inventor, I found that it could be done, and the design could be manipulated to produce a 3D printing file.


Taking in to account that Inventor is completely different kettle of fish to AutoCAD, I decided I would take this slowly and start building a cube, and adding chamfers, fillets, fittings and penetrations to the faces. After a bit of time, I thought I had cracked it, and I decided I would try to model the yacht in Inventor. Once again, I severely underestimated the complexity of the hull shape and soon came to the realisation that I did not have the skills required to model such a complex hull form in Inventor.


Bentley MicroStation:


Feeling rather down-trodden with this realisation, I decided I would try one last 2D/3D design package that would allow me to utilise a Civil Engineering design package to create the hull form. In MicroStation there is a Topographical Modelling module that can be used to produce a 3D model of hillsides/slopes/mountains using topographical "slices". 


Treating the hull like an upturned hill or slope, I prompted the command to loft between the waterlines of the hull. I found this worked, but the lofted panels between each waterline were very triangular and primitive. 


Laser Cutting:


At this point I wasn't confident I could 3D print this model, so I investigated Laser Cutting the design based on the waterlines. I manipulated the CAD drawing to include a 10mm offset on each waterline and found a number of local companies capable of Laser Cutting the model out of 5mm thick MDF. At this point I sent the laser cutting files out for inquiry and soon had a number of responses from the companies. 


Upon receiving the initial quotes (average price in excess of £250) from the Laser Cutting companies, it was decided that Laser Cutting the waterlines was too expensive and the required work outweighed the cost of laser cutting. 


This left the project dead in the water for a week or two until it was suggested by my Father to try using Google SketchUp. I have not used SketchUp in the past and have always been dubious of the quality of the 3D modelling capabilities of the software. Willing to try anything at this point, I decided I would give it a go, and downloaded Google SkecthUp 2016.


I can safely say now that I was wrong to have the misconceptions about validity and modelling capabilities of SketchUp. This is very good 3D modelling package and with a fairly small learning curve, it allows the user to build high quality 3D models with a great deal of accuracy.


That's it for now folks. I'll post more this evening with some photo's of the 3D model.





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