Deck Method

This is my method for creating the deck of a boat or ship when the deck is based on a master deck section curve. All sections of the deck are a trimmed master deck section curve. All that is needed to begin is the sheer curve (edge of deck) and the master deck section curve, sometimes referred to as a master camber curve. The deck centerline shape is found as part of the process.

Deck DC 10.3dm (72.5 KB)

Start by creating or copying the master deck section curve at one end of the sheer curve. The curve in the example is a circular arc which is most common, but it can be any shape.

Rotate with Copy=Yes the master deck section curve 180 degrees in end view to create a temporary curve which will be used to find the deck centerline.

ExtrudeAlongCrv the temporary curve along the sheer curve to create a temporary surface.

Intersect the temporary surface and a plane along the center to obtain the centerline of the deck surface. An alternate method would be to project a centerline onto the temporary surface in top view.

ExtrudeAlongCrv the deck master section curve along the sheer curve to create an untrimmed deck surface.

Trim the deck surface with the sheer curve.

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Thanks David, I look forward to have a closer look.


 That is brilliant. I've played around with your method and I'm not sure why it works but certainly does and that inverted Extrude Along Curve seems to do the trick in finding that elusive deck CL which is needed to keep the constant section co-incident with the original sheerline. I have been doing my decks all wrong but now can use your method to keep the camber constant as it should be. The builders will love this! Thanks again!

Not sure why my formatting is going all weird but want to say that my old method of using Sweep 2 rails is very close to your resulting surface until you look at the radius of sections as seen here.

My method described above works for any shape master deck section curve. It does not have to be a circular arc.

Right David, thanks again. Now we can ponder ‘planar sheer vs non-planar sheer’! I do a lot of 3d modelling for Bob Perry and that is one of his favorite subjects. He will love your constant camber deck methodology but won’t really get it as he refuses to let me drag him into 3d Rhino. He said he fought the transition from hand drafting to 2d CAD and isn’t ready to do it again. Keeps telling me that the 3d stuff is why he keeps me around.

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I saw this method when you first posted it on Boat Design Forums some years ago. I use it now when I have need for a constantly cambered deck to follow the the sheer. I used to use a slower more tedious method but this works nicely. Thanks.

Any sheer curve (and any other 3D curve) which is not a planar curve will appear to have reverse curvature when viewed from some positions. That’s a fundamental of the geometry of 3D curves. the apparent reverse curvature matters depends on the desired aesthetics and where the reverse curvature can be seen from. One of the major advantages of designing hulls in 3D CAD such as Rhino is the ability to look at the 3D shape from any desired location. Design using traditional 2D drafting usually meant the shape of the sheer could only be fully understood from either a physical model, or from a batten during the build, assuming there was enough space around the build to back away far enough. Roger Long in another forum wrote about procedures used during lofting to “raise the sheer” at the ends so that the sheer in 3D looked like the designer intended when it was drawn in 2D,

Perhaps a method to create a planar sheer and related should be the topic of another thread.

Sure David, Joe and I await.