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Thread: CAD lofting

  1. #1
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    I use CAD (comuter aided design) (auto cad 2002 LT) daily, and have tryed to use it to create plans.

    I have discovered that it is not very welcome to this use (or I don't know how to manupulate it correctly).

    Does Anybody know of any programs that are made for this use (preferibly free)?

  2. #2
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    Cool

    Free? Well look here it may help.

    http://home.clara.net/gmatkin/design.htm

    Gary

  3. #3
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    AutoCAD Lite should work just fine unless you want to do fairly advanced 3d stuff - assuming you're not trying to develop lines plans. It's fine for construction drawings, sailplans, layouts etc..

    Try explaining exactly what it is you're trying to do. There are a number of free NA programs that you could use to do lines if that's what you need. If you're just having trouble using AutoCAD then using a freebie clone isn't going to help.

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    Forget free.
    I've used MultiSurf and it is an extremely powerful and useful design program. It is parametric with a very steep learning curve.
    $3,000.
    AeroHydro, Inc.
    The one I use on a regular basis now is Rhinoceros v3.0, Rhino for short. Not parametric, rather a NURBS modeler for Windows, and a more managable learning curve. This product has a different starting point and has been adopted to boat design.
    $875
    Robert McNeel & Associates

    You will not find one product that meets all your design needs. Usually you design in one, such as Rhino, then export to another package, such as AutoCAD for completing your design.

    The thing about Rhino or MultiSurf is the suite of tools needed to generate and analyze the quality or fairness of your curves and surfaces.

    Get on the web and start searching. Almost all these software providers have fully functional 30-day releases (save or print functions may be crippled) so you can try them out.

    Here is another fun place to look:

    3d Cafe

    No matter what package you choose, you have to dedicate a fair amount of time to learning in order to become adept at using them and fully exploiting all their capabilities. Built-in hydrostatics is another plus. Also plug-ins and formats they can save to. Often each has a newgroup. Stop in and see what they are talking about, what they are having problems with.

    Forgot to add: once you lofted in the computer, then what? You have fair lines but they are only 1s and 0s on a hard drive. You need output. Do you have a large plotter? Going to output as 8.5 x 11 on your inkjet? If you are lofting to build you loft by hand.

    Doug Wilde

    [ 04-28-2004, 08:33 PM: Message edited by: DougWilde ]

  5. #5
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    First, my trouble with auto CAD has been getting the curves right. I may not be using the right function, so far I've tried using the arc tool, this does not want to let me have two smoothly connected arcs of different radius.

    Second, I would like to use this to draw up some of my own plans from scratch. side, and station views being the most important.

    And I have access to a plotter so printing full size is not a problem for smaller boats.

  6. #6
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    The command to use is spline. Create the spline with the dimensions you think are correct then edit to smooth it. The best way to smooth it is to delete the point that appears to be bad this will let the computer smooth the curve, then make a new point on the smoother spline.

  7. #7
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    TurboCAD offers splines and bezier curves -- both of which do a decent job. AutoCAD must have 'em too.

  8. #8
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    As usual, the folks who really know answered while I was typing.

    Does Acad LT have polylines or splines? If it doesn't, you won't get good curves. What you can get are full size plots of points (use the POINT command, PDMODE 34 is good, PDSIZE to suit) which you can then fair with a batten and pencil.

    That's the direction I'm heading in but I cheated and I'm using off the shelf plans. Using Mechanical Desktop 6 and maybe Inventor if I open the box someday soon, the 3-D lines are easy. The hard part is turning the lines into solids. The other tricky part is going to be mating the deck and hull since the plotter is limited to 34".

    [ 04-28-2004, 09:32 PM: Message edited by: Venchka ]

  9. #9
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    Yep, splines is what you want. The icon is just a wiggly curve with dots on it. Use the minimum necessary number of control points to avoid lumpy bits. Just double click on the control points to move them around.

    AutoCAD and it's ilk isn't much good for developing a hullform. The various freebie surface modelling programs mostly suck, with only a few special purpose programs coming to mind that are pretty good. There's one called 'Hulls' (I think) that's good for lapstrake or multi chine ply. There are a couple of others that offer the user hostility of 'proper' surface modelling programs but without the benefits.

    Check out Boatdesign.net Forums for the drum on the various software options. There's a fair bit there on Rhino (which is a general purpose surface modeller) and I have to say I'm unimpressed. Some of the cheapies like Prolines or Prosurf are probably adequate for most purposes, but I find they lack several features that I use. AutoYacht and MaxSurf would be my picks. The link in the first reply in this thread will direct you to Gavin Atkin's site where you can find most of the freebies.

    A proper NA specific surface modelling program can be had for around $1000 if you're a student (or at least know one), and $2000 if you're not. WIth it you can do stuff like this (AutoYacht8 ):


    [ 04-28-2004, 10:07 PM: Message edited by: Aramas ]

  10. #10
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    I do CAD daily. But what's it got to do with BOZTS? Pleaze HELP!
    Todd

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    Aramas ;interesting picture, but I think you got the radius of the Earth's surface wrong .

  12. #12
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    There's one called 'Hulls' (I think) that's good for lapstrake or multi chine ply
    That'd be Carlson's Hull Designer -- a dandy program for playing around with small multichine boats. It's not a full-featured design program,but it does have some useful tools to help w/ basic hydrostatics calculations.

    http://www.carlsondesign.com/#Fun_Shareware

    http://home.clara.net/gmatkin/hullstut.htm

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    BOZTS? Baltic Organisation fur Ze Trailer Sailers?

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    Originally posted by Bill Perkins:
    Aramas ;interesting picture, but I think you got the radius of the Earth's surface wrong .
    [img]smile.gif[/img] The joys of being a 'hobby' designer. AutoYacht won't allow anything bigger than 20 metres long. Think of it as a frisbee with a boat stuck in it.

    If I could come up with around $15k I could have all the bells and whistles too [img]smile.gif[/img]

  15. #15
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    I've used AutoCAD Light a fair amount, including for one small boat design, and while it is very useful for adding details, I have to add my voice to the chorus that is saying that it is not so useful for lines plans. The key issue is that you cannot really tell how fair a line is -- on a drafing board you would step back and get a nice low angle view along the line to check it's fairness. You just can't do that on a computer so to draw lines plans on the computer you need software that will provide some other way of getting at this problem. The fancy apps that are dedicated to boat design or similar work have the ability to do things like exagerate fairness or the lack thereof.

    What I did, which worked fairly well, was to do the lines plan the traditional way and then transfer that information to the computer. Then I could do all the grunt work of adding construction details and so on using AutoCAD...

  16. #16
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    I've been using AutoCad LT to draw boats for the last ten years. I still do the lines first on paper with weights and splines. I then take the offsets and plot points in AutoCad. I create a polyline connecting the points, spline it and then edit the spline until it passes through the offset points. It's pretty labor intensive at first but you get faster.

  17. #17
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    I just have to ask. Why would you want to use Cad to loft? Believe it or not it takes only a few days to loft a 30' boat and you can pick up the molds right off the floor.

    As a professional Boat Builder, I lofted more than 20 boats. As a Yacht designer, I have used pencil as well as 2d CAD and 3d CAD to create more than 100 lines plans. In my opinion CAD is far over rated. For the case of lofting, it just isn't needed and is only worth the trouble if you already have a digital model to work from.

  18. #18
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    The reason I use CAD for 90% of the hobby things I do is I can squeeze it in between jobs--during the workday etc...if I have to get something done and I don't need it its not used.
    PTC ProDesktop Express might work...and its free. I've been using Solidworks since thats what I have on my desktop.

  19. #19
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    I use Rhino,
    its powerful and works really well with complex surfaces like boat hulls.
    Its not free, althought you can find older versions available for download on the "underground net", and a trial version is available from the site, it will save only 25 times but will still be functional after that. I use it for work from a long time so i can not be objective when i say that beside Form-Z (3d modeler) its one of the best cad around, it wont do calculations other than the normal volumetrics and projections though (but using it for just static models i dont really need any of the "nautical" kind, but i believe there are plugins for that from rhino, or you can import the file created in Rhino on a free software with less "drawing possibilities").
    In my opinion its worth a look in any case.

  20. #20
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    Originally posted by bainbridgeisland:
    I just have to ask. Why would you want to use Cad to loft? Believe it or not it takes only a few days to loft a 30' boat and you can pick up the molds right off the floor.

    For the moment, I don't have a floor for lofting. The space I plan to loft and build in is 500 miles away. What I do have is a 36" plotter which will run out long plots. Using the computer also allows me to "fill in the blanks" on the plans. "Lofting" full size gives me an idea of the size of various parts for material purposes. I can lay out rudder, centerboard, transom, floors, deck beams, etc. to best advantage on the rough stock. I can do it at home after work when it's raining cats and dogs.

    If/when I actually start lofting I plan to roll out my plots with all the points from the table of offsets printed and use proper battens to fair the full size curves. THEN I can pick up molds right from the floor.

    The computer isn't replacing lofting.

  21. #21
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    Thumbs up

    I just have to ask. Why would you want to use Cad to loft? Believe it or not it takes only a few days to loft a 30' boat and you can pick up the molds right off the floor.

    As a professional Boat Builder, I lofted more than 20 boats. As a Yacht designer, I have used pencil as well as 2d CAD and 3d CAD to create more than 100 lines plans. In my opinion CAD is far over rated. For the case of lofting, it just isn't needed and is only worth the trouble if you already have a digital model to work from.
    Yipee! Someone else see lofting as I do.
    The 'things' you find in full size lofting are many times missed other wise.

    There is a pertinent article in the companion magazine from our host, Professional Boatbuilder, and as soon as I receive permission to post a scan of a particular photo along with the side bar explanation, I will do so. It is very revealing and enlightening with regard to the importance of full size lofting.

  22. #22
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    I have been using DesignCad, and I have never used other cad programs, so I don't know if they work the same. I draw the initial hull lines in 3-D, and you can rotate the drawing and zoom in to check if a curve is fair. It is essentially like putting your eye close to the papar and looking down a line to see if it is fair.

  23. #23
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    I just did a search, and Design Cad is still available. I am still using DesignCad97, so I don't know how many new fetures thay added, but the price has come down.

    http://www.imsisoft.com/faminfo.asp?fam=2

    [ 05-01-2004, 03:17 PM: Message edited by: Mark Van ]

  24. #24
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    Originally posted by Dave Fleming:


    Yipee! Someone else see lofting as I do.
    The 'things' you find in full size lofting are many times missed other wise.

    No argument, Dave. I'm just not there. Yet. In the meantime, I (just my own feeling) find it useful to commit the plans in all three dimensions to the computer. I would never ever dream of building any boat without lofting it first.

  25. #25
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    Seems like a lot of trouble to use CAD in the design phase. I have been using various Vacanti software packages the last 5 years. Prolines 6 Basic and now Prolines 98 Basic have been relatively simple to learn and use. The prolines 98 is much better and I would recogmend you check it out. I set up a simple conversion table in Xcell to convert feet-inches-eigths to decimal equivilents, then enter as control points in prolines. Fair the hull, export as a DXF file in two dimensions to CAD,add any details and building references required and print full size sections, body plan and profile as required for building. A good architectural print shop should be able to print up to five feet wide by any length and at a surprisingly reasonable cost. While in CAD any transom projections or stem rabbets can be drawn with amazing accuracy. Hope some of this might help.

  26. #26
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    The magic number is 3.

    Three points determine a plane.

    In a plane, three points determine a UNIQUE line.

    If you divide a hull into two parts, forebody and afterbody, each can be controlled by 3 points.

    Sheer lines are easy. Keel lines need some straight segments in the middle - in many cases - but each end can then be done with three points.
    (Plumb stems can be helpful at the bow.)

    Waterlines really need the divided length treatment. Many of the old draughts have a large "O" with an "X" superimposed, to mark the fore point of maximum beam. This was the point where the slope of the water line was parallel to the fore'n'aft centerline. Aft of that there may be some parallel mid-body, between the curves of the forebody and those of the afterbody.

    You can always find an equation for each of the segments of the lines.

    I've even done this for frame sections, but it is a lot of work.

    Probably more work than the lofting full size.

    Ed R

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    LOL!!!!

  28. #28
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    Cool

    Itís two different things, why donít you guys chill.

    Gary

    [ 05-02-2004, 10:54 PM: Message edited by: G. Schollmeier ]

  29. #29
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    Originally posted by Venchka:
    For the moment, I don't have a floor for lofting. The space I plan to loft and build in is 500 miles away. What I do have is a 36" plotter which will run out long plots. Using the computer also allows me to "fill in the blanks" on the plans. "Lofting" full size gives me an idea of the size of various parts for material purposes. I can lay out rudder, centerboard, transom, floors, deck beams, etc. to best advantage on the rough stock. I can do it at home after work when it's raining cats and dogs.

    If/when I actually start lofting I plan to roll out my plots with all the points from the table of offsets printed and use proper battens to fair the full size curves. THEN I can pick up molds right from the floor.

    The computer isn't replacing lofting.[/QB]
    You might try fitting plans to building materials/stock by using styrene strips/sheets from Evergreen, available from most hobby stores and model railroading suppliers, at 1/4 scale and thus eliminate the need for full scale plans of the boat for the purposes of planning material layout...much cheaper too.

    Many things can be solved by building a scale model of not only the boat, but also scaling the building materials as well.

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    index recovery

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