John G. Alden Malabar VI, in 1:12 scale

Here we have the start of an R/C schooner project. The design is done in Solidworks CAD and then the parts are cut on a laser cutter. Each of my designs has a few new twists and improvements on the previous one but there is always room for improvement. Please feel free to use the Contact Page to send constructive criticism, from a modeller’s perspective, or from a fellow Solidworks user. Please note that I have never built one of my designs so anything I’ve learned in designing these models is learned from you, the builders. I’m just the guy with the software.

First thing is to establish the scope of the project and make sure the dimensions are correct, or pretty close, anyway.

Actual boat, from http://mitmuseum.mit.edu

  • LOA: 52’ 3”
  • Design number: 248
  • LWL: 38’
  • Beam: 12’
  • Draft: 7’ 4”
  • Year Designed: 1925
  • Builder: Hodgdon Bros. E. Boothbay, ME. http://hodgdonyachts.com/
  • Designer: John G. Alden
  • Launched: 1925
  • Still Existing or scrapped: n/a

Scale model dimensions, at 1/12 scale

  • LOA: 52 ¼”
  • LWL: 38”
  • Beam: 12”
  • Draft: 8 ½” (including 1 ¼” allowance for stability)

Next is to establish the actual design criteria:

Standard Equipment:

  • Topsides identical to the drawing.
  • 10% more volume below the waterline.
  • Four keels of 1/8” each to allow for ¼” slot for removable ballast keel. This gives the total width of the keel at ½”.
  • Double number of stations seen on the drawing
  • 3/16th “ offset for hull planking
  • Inside keel to support rabbet plank. This is to be discussed as the project evolves. I’m not sure if this will work for this keel.
  • Bulkheads are 1/8” birch plywood.

Phase Two:

  • 1/16th” sheet of plywood for the deck opening pattern, with slots for frames, and cleat and shroud positions drawn in.
  • Complete set of deck structures. TBD

 

Starting Point – The Original Plan Sheets

Here we have a look at the starting point of the design. These plans are in 1/48 scale and have half the bulkheads we eventually want to have in the model.
 

Fig.1 – Page 1 of 2
 
 

Fig.2 – Page 2 of 2
 

 

Modifying the Underwater Shape

The drawings were then chopped up so the area below the waterline could be tweaked for R/C modelling. The drawings are inserted into Solidworks on separate planes so they can be stretched separately. As noted in the builder’s requests the keel was lowered by about 1 1/2″. When the frames will be sketched, the discontinuity will be smoothed with a long spline.
 

Fig.3 – Cropped bow view
 
Fig.4 – Cropped side view
 
Fig.5 – Cropped bow view – below the waterline
 
Fig.6 – Cropped side view, below the waterline
 

 

Inserting the Drawings into Solidworks

The drawings are now inserted in the software and stretched to fit the dimensions for 1/12 scale. Note the keel is also lowered by the requested amount. The first sketches are then created.
  The drawing is inserted on a plane parallel to the sketch plane. It’s important to insert the sketches on planes where they cannot be edited by mistake.
Here’s a good angle showing the five sketches inserted outside the sketching volume. They are close enough that you can get an impression of the 3D even before starting.
The original drawing has too few bulkheads for such a large R/C model. With the outside dimensions established, internmediate bulkheads will be created at the new vertical lines.
Next is one of the most critical tasks in the development of the model is the design of the sheer. This is a 3D combination of two curves, the deck curve in the top view and the same curve from the side view.In Solidworks, I use the Projection feature to develop this curve. In this picture, the sheer is the swoopy blue line. The two curves that make up the Projection are tweaked until the sheer is just right. This is a tedious and repetitive task but is what starts to bring the model to life.

Note that the keel has already been extruded in this picture.

The completed keels can be seen here. In order to create a centerboard well, the keel is divided into six parts. The idea, at this point, is to make sure the centerboard well reaches above the waterline.

 

Building Up the Bulkheads

At this point the general shape of the frames is created. Note that certain details will be added in later phases of the construction. I’ve found it’s much easier to do one thing at a time than to try and incorporate all details on a frame in one shot. As compared to modelling in wood, in CAD one does not have to worry about creating a mess of half-made parts. Parts can be “assembled” and disassembled with a couple of clicks.Another thing that is important is to make sure the notches in all the parts are connected to the keel, and that the keel is well-connected to the general sketch for the keel. It’s always possible that requirements change as the project progresses. Understanding robust parametric modelling is an asset at this point.
 

Fig.7 – Frames B1 to B9
Fig.8 – All Bulkheads

 

The Design is Modified, and Improved

OK, well, here’s why you really need to know your Solidworks. As you can see, the design requirements were considerably improved in this new keel design suggestion. I really like it and, because all the notches in all the parts are connected to each other, and the original lines are drawn as sketches outside the work area, presto, in a few keystrokes, we’ve changed a good deal of the work. I think it looks much better.
 

Fig.9 – A Very Good Suggestion
Fig.10 – The Improved Keel Shape

 

Some Mechanical Manipulations

I like to add features to the model one step at a time. Over the years, I’ve learned that working this way makes it easier to make changes later on. Yes, when things do explode (in Solidworks that means seeing a whole bunch of red in your feature tree) I feel it makes it much easier to do trouble-shooting as the sketches in each group of extrusions, or cuts, are simple. If you create complex sketches and try and hook them all together then it becomes a nightmare to trouble-shoot the correct frames while trying to remember the strategy that was used in the original design.
  In this image, we see that all the bulkheads have been opened up and a deck is defined.
Next, the supports for the T-rail are added.
Basically, the boat is ready to go at this point. All the bulkheads are created, they are opened up, and the T-rail pieces are designed.

 

Fine Tuning to Simplify Assembly

Next is to work on the preparation for assembly. There is no drawing that shows the line from the rudder shaft through to a position where it would make sense at the wheel. In fact, after drawing in the shaft according to the line drawing of the hull, it was evident that there is an inconsistency somewhere, as can be seen by Fig. 11.

The dark, rough, lines you see in the picture are from the original drawing. As you can see, if you project the line for the end of the hull upwards, it doesn’t line up with the wheel in the wheelhouse.

The thin, clear, lines show the way the parts are being constructed.

Note the detail at the bottom of the enlarged rudder in Fig. 12. Some people like to use the wooden foot to attach the shaft, others like to cut off the foot and add a steel plate to attach the shaft instead. Since I am not sure what will happen at the construction level, I have decided to allow material for both eventualities; the rudder is made large enough to use a steel plate, and the foot is large enough to support the shaft. In the latter case, of course, the rudder would have to be reshaped at construction.

Fig. 13 shows a detail of the top of the rudder. The rudder is made up of four sections; two large sections, a slightly smaller middle section, and a thin cap. These form a space for the rudder shaft.

Fig. 14 shows the realigned keel and rudder. Again, it’s nice to have good parametric design.

 

Fig.11 – Shaft angle on drawing
 

Fig.12 – Rudder end options
 

Fig.13 – Rudder shaft detail
 

Fig.14 – Steering aligned

 

Space for Steering Servo

I share the building process with clients using a 3D viewer, where they can manipulate a Solidworks file in 3D. This leads to some interesting observations and allows for in-line improvements. Here we see a space created to ease the installation of a steering control.
 

Fig.15 – Builder’s suggetions
 

Fig.16 – Steering fixed

 

Final Details and Some Discussion about 2D and Solidworks

Fig. 17 shows an interesting step. The frames are opened to allow bilge water, if there is any, to flow freely towards a bilge pump.

The next pictures show specific Solidworks uses. All parts are inserted on a blank sheet, in 1:1 scale. Note the tiny, tiny, part numbers. On an 11″ section, they’re not so tiny but, since every line is accounted for by the laser-cutter, and adds cost, it’s useful to reduce lines wherever possible.

As for Solidworks itself, the easiest way I’ve found to do this is to insert forty or fifty identical, complete, drawings, and then use the “select bodies” feature. Note that we designed this as a multi-body part, not as multiple parts in an assembly. This is a faster way to design certain types of assemblies but is not easily compatible with manual fabrication or digital storage. The entire structure is saved as a single entity.

Note also, that the each body had the property added in the Feature Tree Cutlist. This allowed me to pull that data into the drawing to get the part numbers. See fig. 18 for a screen shot of the use of Body-Properties.

Once the data is entered in the Body Property, it is easy to retrieve it for the 2D. Fig. 19 shows the menu to retrieve data and Fig. 20 shows a detail of the 2D. Note the red font used for the numbers.

 

Fig.17 – Bilge openings
 

Fig.18 – Body Properties
 

Fig.19 – Item Numbers
 

Fig.20 – Example of frames 2D

 

Parts Cut

Parts are cut and ready for assembly. There are two things I am pleased with here. The little etched numbers look really good and will certainly simplify the construction as the middle of the boat has several frames that are quite similar.
 

Fig.21 – Cut Frame
 

Fig.22 – Frame under construction

 

Assembly Progress

She’s out of the build board!

Malabar has already been turned over and is being prepared for some deck construction.

 

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