Introduction: How to Draw a Radio Control Sailboat Hull to Make With Laser Cut Wood on Autodesk Inventor. I Made It at Techshop

About: I am an auto safety engineer. In my spare time I like sailing and radio control airplanes and boats.

The purpose of this instructable is to go through the process of how to create a 3D model of a boat hull that will be used to create a radio control sailboat.  This part will go through the process of creating the model in CAD so that the parts can be laser cut and assembled easily.   This was created using Autodesk Inventor Pro 2013 from TechShop Detroit.  The boat is going to be a simple 20 inch long, hard chine design that will be constructed of balsa and plywood.

There is a part 2, of this instructable with the steps of building the boat.  It is:


Step 1: Draw the Side View

Step one is to draw the side view of the boat.  draw a few vertical lines to use as references for loft sections on the other view.  This will be where you draw the cross sections to loft it into a 3D solid.  To make this a little more challenging I set the deck so that it's not on the standard XY plane, but sloping a little instead.  

Step 2: Draw a Top View

The next step after drawing the side view is to draw a top view.  In this case because my deck isn't orthogonal, I am drawing off a work plane that is on the plane of the deck and not the global XY plane.  You will draw horizontal lines across where you will be making the loft sections.

Step 3: Make Cross Sections.

Next draw cross sections at each of the section lines you created in the prior views.  To make this come out looking normal, I kept the chine angles constant throughout all of my sections.  My hull side is at 80 degrees to horizontal and hull bottom is at 85 degrees to vertical.  That way when matched to the top view and bottom view splines it will make nice smooth sides.  For the lofting to work, without too much hassle.  Only have the hull bottom and hull side as normal lines.  Keep everything else as construction lines so that the loft process will ignore them.  It's easiest to loft if you have similar shaped sections everywhere.

Step 4: Create the Loft

After your cross sections are completed but before you loft, you need to add a 3D spline curve to the corner of the chine edge.  This will be 1 rail of the spline along with the deck edge and keel edge of the boat.  The loft tool in Autodesk inventor is not the easiest or most straightforward tool to use and it doesn't always pick the sections you would like.  Sometimes you have to go back and fiddle with what is and isn't a construction line in the individual sections.  With some persistence, you'll eventually get it.  After you successfully loft the hull side, you will then reflect it it about the global XZ plane (this assumes that X is fore and aft, Y is lateral and Z is vertical directions).  Then you create patch surfaces to fill in the transom and deck.  After that you use stitch surfaces to turn it into a solid.  Then you have your boat hull.

Step 5: Shell the Hull So You Can Make the Internals

After you have a solid for the hull, next step is to shell it so you have hull sides and an open top.  I shelled to 1/16inch thickness since I plan on sheeting the hull sides with 1/16" balsa sheet.  

Step 6: Draw the Keel and Extrude

Next I draw the keel.  I created the sketch on the global XZ plane.  I extruded it to 3/16" thickness in symmetrically about the plane.  It is important to extrude each new part as a new solid so that you don't affect the hull soild and to make it easy to turn into parts for creating the drawing file to laser cut in the end.  

Step 7: Draw and Extrude the Rudder

Sketch a rudder and extrude it in a similar manner as the keel.  The rudder was made 1/8" thickness.  The only part that really needs the stiffness of the 3/16" ply is the keel and it may be okay as 1/8" also but for this I did 3/16".  Remember to extrude as a new solid.

Step 8: Draw the Longitudinal Former

Next I sketched the longitudinal former and extruded it.  It is extruded as 3/16"inch also to  match the keel.  The  keel will be inserted into the notch in the former when it's assembled.  Draw the former along the hull inner surface.  Using the cutaway view and also project cut geometry is essential for drawing this former and all the other internal boat parts.  It will allow you to see all the notches you created in other parts.  For this I draw an 1/8" thick notch approximately every 2 inches.  This is where we will add bulkheads at.  2 inches seems to be a good distance that will give good form to the sheeting in the finished boat.  As always, extrude it as a new part and extrude symmetrically about the global XZ plane.

Step 9: Create Bulkheads

Create bulkheads by sketching on the notch surfaces in the longitudinal former.  I created all my bulkheads by drawing only one half, then extruding and mirroring.  Make sure each bulkhead is a new solid.  I created a notch at the chine corner to run a 1/8" x 1/4" balsa stick.  I didn't model the stick because there really is no need and the time to draw sections and loft it would add a lot of work.  Just know it's going there in the physical boat when you build it.   Extrude the bulkhead in the direction so that it's fitting in the notches in the longitudinal former.  You need to create a bulkhead at each notch.

Step 10: Draw the Deck

The deck is drawn after all the bulkheads.  You will draw it on a work plane 1/8" below the top deck surface of the boat (my deck is made of 1/8" plywood) and extrude it up.  This allows you to use project cut geometry to catch all the top edge of the bulkheads and draw notches around them.  This will allow you to assemble the boat by putting all the notches into the longitudinal former and deck. I only sketched half of it and mirrored it after extruding it.  The deck needs to go over the mast step (base of the mast) and also the transom and bow where you will attach rigging.  

Step 11: That's It for Sketching

So essentially that's it for sketching the hull, keel and rudder.  There are several miscelaneous pieces that were also created such as a set of doublers to form the keel box and rudder tube box.  There was also a couple of small pieces created under the mast step to support it by the bulkheads.  These were created in the same fashion as the bulkheads, longitudinal former and deck.  

Step 12: Create and Assembly of Parts

The next step is to turn your one part with several solids into many parts.  This is done so that when creating the drawing you can put in a base view for each part and have it only containing one part instead of all the parts.  Use the "Make Components" button under the manage tab.  Then select all of your solids to create the assembly of parts.

Step 13: Make a Drawing to Use for Lasercutting

The next step is to create a drawing.  This drawing will be used to feed a laser cutter.  You will create a new drawing and delete the title box and border because you don't want to cut them.  Create a base view of each part you now have and place it on the drawing.  For the deck since it is not orthogonal, you will need to place a custom view aligned to the surface plane of the deck. This will place it on the drawing so it can be cut.  For this project I created 3 drawings.  One for each thickness and type of wood.  In my case I have drawings for the following:

1/8" Plywood shown below
3/16" Plywood
1/8" Balsa