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How do I create a shape from a series of cross sections?


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I'm trying to build a cedar strip canoe in Vectorworks using the same techniques that would be used in the real world. I do not want to take the time to try and create and add each curved 1/4" x 3/4" strip to the forms. I have the station molds created and mounted to the strong back, and I have created top view and side view profiles which I extruded and intersected solids. How do I take what I have and create an accurate plug (the shape of the boat as one solid object) of the boat?

 

1170374303_ScreenShot2022-01-25at8_50_58AM.thumb.png.3071ccd5cf5a148d41087de64aee0a93.png166088237_ScreenShot2022-01-25at8_51_41AM.thumb.png.f194c3960fee1393d4d8bc28ba7a32ec.png

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If you extract a NURBS curve from each of your “formers” and then use the Loft Surface tool in the first mode. You can select the create solid option when you have selected the profile curves.

 

That should give you the main body of the boat. The bow and the stern segments can be made using extracted NURBS from the profile and each leading edge and then as long as they are connected, you can use the Create Surface from Curves command to give you what you need.

 

Then you need to add them together and hopefully all will be well! (Hopefully!)

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11 minutes ago, markdd said:

If you extract a NURBS curve from each of your “formers” and then use the Loft Surface tool in the first mode. You can select the create solid option when you have selected the profile curves.

 

That should give you the main body of the boat. The bow and the stern segments can be made using extracted NURBS from the profile and each leading edge and then as long as they are connected, you can use the Create Surface from Curves command to give you what you need.

 

Then you need to add them together and hopefully all will be well! (Hopefully!)

Thanks. I will give that a try.

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  • Vectorworks, Inc Employee

@Bruce Kieffer  I have tried from time to time to model boat hulls in Vectorworks and always had an issue at the bow and stern...you may want to try rebuilding your NURBS curves so that they do have the same number (and as few as possible) control points...honestly, I haven't tried it in a while... another trick is to only model HALF the hull and then mirror it over the the other side...another trick is to use as FEW stations as possible and still get the hull shape you're after...

BTW, this is something Rhino does very easily and can produce some very good hull shapes (along with everything else on a boat) - here's an example of a design I'm working on...  I haven't tried Blender yet but since it's open-source (free) it might be worth looking into...

 

Wes

 

 

G47 reach.jpeg

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Hi @Bruce Kieffer

 

Looks like you’re on the right track….. I’ve found as @Wes Gardnersuggests that keeping the vertex counts of the profile curves the same is the biggest way to get smooth results. The results you are getting look pretty good from here….

 

NURBS were conceived for just this kind of use so it would be gratifying if you felt that you were getting what you need.

 

 

Edited by markdd
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Benson S. is helping me with this too. He did a loft from polylines created with equal # of vertices, and his lofted shape looks real good. He split his shape down the keel line rather than across the beam as I have been doing. I think his way is better. I have more work to do.

Screen Shot 2022-01-27 at 2.52.03 PM.png

Edited by Bruce Kieffer
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  • Vectorworks, Inc Employee

@Bruce Kieffer ... yes, mirroring side-to-side is certainly the methodology that seems to work best!  Looks good!  You may also want to have a go at projecting waterlines, station/section lines and buttock lines onto the hull shape to insure a good fair hull that has no bulges or hollows like in the lower wireframe drawings...  BTW, this was designed in Rhino and then cleaned up in Vectorworks for presentation...

 

Wes

G45RS V2Profile.jpg

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I'm using a canoe a plan I produced for a magazine in 1991. That plan defines the shapes of the molds. That makes it very difficult to recreate a solid version of the canoe in Vectorworks. I was talking with Bryan G. tonight and I realized that this would be so much easier to start lofting the canoe shape, and then create the mold shapes.

1151501242_ScreenShot2022-01-27at10_18_40PM.thumb.png.8a33a4bfdbdf5488c8087477336b9f0c.png

 

This is baby me back then!

2127318854_ScreenShot2022-01-27at10_23_59PM.thumb.png.f992f46cf7b42ea8cece884ee46bd2ed.png

Edited by Bruce Kieffer
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Using lofting of cross sections can be a nightmare in most NURBS based programs, and VW simply doesn't handle NURBS editing very well either, compared to most standard 3D CAD programs. No disrespect intended. VW's inability to nudge control points, and why you can't edit any number of control points in any number of objects at the same time remains a mystery. In my professional boat design program, I can easily tweak 500-1000 NURBS objects at the same time using a random selection of control points, and get an instant update of the lines drawing at the same time. 

 

Given the use of VW, you my consider using the following method: 1/ Generate some curves along the length of the boat, say three. 2/ Loft them into a a surface. Convert it into an interpolated surface having four by four controls in the grid (or thereabout) . 3/ Adjust the shape so that it looks reasonable. 4/ Add sectioning to see what the shape looks like. 5/ Repeat step 4 & 5 until the sections get close to the original cross sections 6/ Extract the cross sections to generate the updated buck shape cross sections. 

 

 

Skärmavbild 2022-01-28 kl. 10.38.58.png

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3 hours ago, Claes Lundstrom said:

Using lofting of cross sections can be a nightmare in most NURBS based programs, and VW simply doesn't handle NURBS editing very well either, compared to most standard 3D CAD programs. No disrespect intended. VW's inability to nudge control points, and why you can't edit any number of control points in any number of objects at the same time remains a mystery. In my professional boat design program, I can easily tweak 500-1000 NURBS objects at the same time using a random selection of control points, and get an instant update of the lines drawing at the same time. 

 

Given the use of VW, you my consider using the following method: 1/ Generate some curves along the length of the boat, say three. 2/ Loft them into a a surface. Convert it into an interpolated surface having four by four controls in the grid (or thereabout) . 3/ Adjust the shape so that it looks reasonable. 4/ Add sectioning to see what the shape looks like. 5/ Repeat step 4 & 5 until the sections get close to the original cross sections 6/ Extract the cross sections to generate the updated buck shape cross sections. 

 

 

Skärmavbild 2022-01-28 kl. 10.38.58.png

Great. This is what I'm saying. It would be easier to start by creating a boat shape, then create the mold shapes to match the boat shape you created. I did it the reverse only because I wanted to build my canoe in Vectorworks. Super hard to do.

 

@Claes LundstromYour steps do give me a few ideas. Thanks.

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