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Question for Boat designers - opinion wanted.
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* October 05, 2009, 09:45:04 AM
I've done most of my lofting work on the floor using battens. In Turbo CAD which (spline by control points, spline by fit points or bezier) do you use for frame layout. I've been using beziers for buttocks, wls,etc.

Thanx,
Ed


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* October 05, 2009, 09:50:38 AM
#1
I think it's largely a matter of personal preference. I prefer Spline by Fit Points; and I always expect that editing the curve will be necessary after it's first drawn.

Henry H

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October 05, 2009, 10:01:19 AM
#2
I have a question Henry. Based on your experience as an engineer, do you think that the 3D boat hulls that can be designed in TurboCAD would really cut the mustard in the real world? As you know the user is really at the mercy of the loft tool and to get it to create a smooth hull one must really tweak those profiles - often quite a ways off from what seemed appropriate in the 2D design. Can you comment?


* October 05, 2009, 10:40:35 AM
#3
Before we get too far off - a little clarification. I am drawing set of plans to build a POF (Plank on Frame) model of an 1841 Whaler, the Charles Morgan.
My question revolves around development of the individual frames. The major lines were taken from a table of offsets and drawings from the Mystic Seaport.

Ed

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* October 05, 2009, 11:53:13 AM
#4
Before we get too far off - a little clarification. I am drawing set of plans to build a POF (Plank on Frame) model of an 1841 Whaler, the Charles Morgan.
My question revolves around development of the individual frames. The major lines were taken from a table of offsets and drawings from the Mystic Seaport.

Ed

Shouldn't be a problem. I'd go with Splines -- and in my experience, one should resist the temptation to specify a whole LOT of points when drawing a Spline.

Henry H

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* October 05, 2009, 12:05:29 PM
#5
I have a question Henry. Based on your experience as an engineer, do you think that the 3D boat hulls that can be designed in TurboCAD would really cut the mustard in the real world? As you know the user is really at the mercy of the loft tool and to get it to create a smooth hull one must really tweak those profiles - often quite a ways off from what seemed appropriate in the 2D design. Can you comment?

Your implied criticism of the loft tool's limitations is most pertinent, Don. It has a mind of its own and often successfully defies attempts to control its output. I don't think I'd use TCad for serious hull design work. Or automobile body design, or aircraft design.

Ed's problem is of course a little different, since he's working with a well defined existing design and -- as I understand it -- needs only to produce 2D drawings based upon that design. I daresay we can agree that TCad is well suited to that task.

Henry H

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* October 05, 2009, 12:16:20 PM
#6
Ed, whenever a new forum member asks a question about boat design in TCad, I cannot resist the temptation to post this picture (created in TCad v11).

Henry H

[attachment deleted by admin]

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* October 05, 2009, 12:42:14 PM
#7
Anything can be done in TCAD.  It might be easier in a CAD app made for boat designs.   However, they cost much more to get. 

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* October 05, 2009, 01:36:41 PM
#8
If that was done in TCad there seems to be a major design flaw as to leakage. ;)
Ed

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October 05, 2009, 02:13:53 PM
#9
I have a question Henry. Based on your experience as an engineer, do you think that the 3D boat hulls that can be designed in TurboCAD would really cut the mustard in the real world? As you know the user is really at the mercy of the loft tool and to get it to create a smooth hull one must really tweak those profiles - often quite a ways off from what seemed appropriate in the 2D design. Can you comment?

Your implied criticism of the loft tool's limitations is most pertinent, Don. It has a mind of its own and often successfully defies attempts to control its output. I don't think I'd use TCad for serious hull design work. Or automobile body design, or aircraft design.

Ed's problem is of course a little different, since he's working with a well defined existing design and -- as I understand it -- needs only to produce 2D drawings based upon that design. I daresay we can agree that TCad is well suited to that task.

Henry H

Thanks for the input Henry. I guess it was pretty rude of me to ask this question in Ed's thread.

BTW, I agree about managing the boat design it 2D - should be no trouble at all.


* October 05, 2009, 03:38:26 PM
#10
Don - Not Rude at all.

Your input and suggestions are always welcome. It also reminded me about the loft tool. I was originally going to do the preliminary work in 3D, but Lofting gave me fits ;D

Ed

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* October 06, 2009, 12:33:09 AM
#11
Some time ago i posted a message about a site that offers a free version of a program for hull design.

It might be useful to Ed

See www.delftship.net

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* October 07, 2009, 10:30:42 AM
#12
PeterDD

That is a good product, as well as it's predecessor, Freeship.

I've used them in the past.

I was just wondering what other TC users used for curves.

In other software I have been using Beziers, since they supposedly replicate what a traditional batten would do. In TC, however, Beziers seem to loose out to splines in overall smoothness. Probably just a case of the algorithm used.

It will be interesting to see how the 93 frames look when I am finished,

Ed

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October 07, 2009, 07:55:19 PM
#13
Sorry, but just gotta ask...
Quote
been using beziers for buttocks
What...why...how?

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Julian

TC18 / 38.5 Platinum, AL5. XP, Core2 Duo E6750 OC'd 3.0Ghz, Render test: 3mins 3sec.


* October 08, 2009, 05:34:08 AM
#14
Just tradition, I guess. Beziers are supposed to respond to curves like a wooden batten would.
Ed

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* October 08, 2009, 05:54:56 AM
#15
Have you sampled PolyCAD, Ed?  Its great for illustrating the relationships between polylines and curves, meshes and NURB surfaces, can switch one to the other simply, and has smoothness indicators to guide your curves.  As a general curve and surface editor, I recommend it highly, and it does hull surfaces parametrically, too.  Surfaces can be exchanged with TC through IGES.

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* October 08, 2009, 09:26:43 AM
#16
Just tradition, I guess. Beziers are supposed to respond to curves like a wooden batten would.
Ed

Some years ago, there was a considerable argument about this, between one or two users (I was one) and the developers. I argued the point that you just made, saying that the terms Spline and Bezier were applied bassackwards in TCad, but was unable to change the situation. One gets used to it :-(

Henry H

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* October 08, 2009, 11:13:02 AM
#17
Henry H

Ya gotta be kidding. So that's the reason splines give a better looking fit than Beziers?
Underbelievable :(

If nothing else they should own up to it and put a statement in the help file under Curves.

Ed

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* October 13, 2009, 04:28:55 PM
#18
So what are the "improved Beziers" that the release of V16 was touting?

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* October 14, 2009, 09:24:58 AM
#19
Darned if I know, I'm using 16 and have no other earlier one to compare.
Ed

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* February 19, 2012, 11:50:40 AM
#20
Ed, whenever a new forum member asks a question about boat design in TCad, I cannot resist the temptation to post this picture (created in TCad v11).

Henry H
Very nice looking picture well composed all the materials flow together.

w.d.

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