Stretching out the beam?

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Steven r
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Re: Stretching out the beam?

Postby Steven r » Mon Dec 04, 2017 12:56 am

Bill,
A lurning curve! I have never been very interested in computers but reading on this forum how good they are, I have a lot to lurn. Only last week I went into a small wood working shop and saw a CNC rautor. The owner said if you want anything done £60 per hour my eyes lit up he said he draws it all out. No cad. No skan2cad. The con has started.one of our university's not to faraway has very large printers and do not charge to much, so understand you skan to memory stick the software is not very expensive or free if needed now it can talk to the CNC in DFX. A lurning curve!
Steve.

Kevin Morin
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Re: Stretching out the beam?

Postby Kevin Morin » Mon Dec 04, 2017 3:32 pm

Stevenr , I'll use your posts to reply about some of the implications in this thread. The purpose here is to help the Forum understand some basics of the various elements involved in CADrafting/CADrawing/CADesign (CADDD) and CAManufacturing or controlling an NC (numerical control- digital controller for XYZ cutting tables).

First, just a clarification that there are two types of drawing files involved at the design or drawing stage- one file is a 'bit map' where every single dot on the screen (yes; all screens display in tiny dots including those that make up the letters of this post) has an XY address. One mantissa of the screen is the left side vertical the other is the lower horizontal so every dot has some X,Y coordinate and this is a 'pixelated' or bit mapped file.

The other is a vector file where a line, curve or other shape is stored, displayed and drawn using a math formula to describe the line, curve or shape. This is a vector file and is very important to understand this is what is converted to a 'Tool Path' or guiding command set for NC cutting/routing/plasma/laser cutting of materials like boat building plywood or sheet metal.

The very first thing to understand- then- is: Which is the software you're using working in? A) bit mapped storage and manipulation or B) vector storage and manipulation? Scan2CAD works to convert one file type to the other- and provides tools to work in both bit mapping AND vector files. In fact Scan2CAD allows images (bit maps) of drawings to be converted to CAD or vector files- and there are even semi-automated routines in the software to make that process less time consuming and more accurate.

But that is where the entire 'conversion-is-easy' idea hits a vertical wall. If you scan a set of paper plans- that is- digitize hard copy to digital file- the image is not perfect. SO.... while the Scan2CAD software is a great time saver, it does require some significant editing of the file vector files to 'clean them up' - or the results are not reliably useful for CAM work.

CAM files need to have the objects (like parts' outlines to be cut) from a CAD file in a certain accuracy - CAD files don't always come out up to CAM required standards- many objects' line ends don't meet! That fact won't show up on a PC screen - you'd have to zoom 10x to find these line ends aren't EXacTLy the same point in the file! Yes, there are routines and setting to correct this potential fault- and there are steps using software tools in both the CAD originating file and the CAM final goal files to help the designer or builder simplify these editing necessities.

Autodesk, the company that publishes AutoCAD, probably the most widely used professional CAD (does all three D's) software package has published a DrawingExchangeFormat file- *.dxf along with several other file storage standards. This has allowed the CAD market to find a common file type so that other CAD packages can exchange by storing information in this widely used file exchange format.

And most CAM software packages can 'read' or 'open' these *.dxf files, so this provides a common language path from "design" software to "cutting" software - BUT.... this technical compatibility doesn't mean that one simply takes plans sheets, scans them and makes an auto conversion to Vector or CAM cut files from paper copies of plans.

There is very significant work (computer time and software expertise required) to make a successful set of "cut files" from paper plans. Steven r, I would say your somewhat brief description of some of those steps in your posts does begin to approximate the steps implied - however, I'd caution you that there was much more detailed information and software understanding required before scanned images could be converted reliably into cut file- tool paths- or G-code that will result in acceptable hull panels or framing elements for a boat.

Now to mention a contrast, art files; scanned images of photos, converted to black and white then outlined for cutting files- don't need to have smoothed curves- they don't need to have 12-30' long curves smooth to 1/32" - they can have a kink, hard spot, wrinkle, hogg and no one is the wiser. The reason art files can be fairly easily converted is the very nature of the bit mapped image is not geometrically 'clean' or as we'd say in boat building - the lines aren't "fair".

I've been involved, somewhat, in the processes being discussed and would suggest that my experience is somewhat generic- there will be quite a bit of effort involved to convert from paper to cut files that are truly- ready to build. It surely can be done- and with some experience can be done in a fairly short time- but the conversion is not without time and effort; the conversion of useful lines does not happen simply at the push of a computer key.

Good luck with your project Steven r, and please keep us posted on your progress? If you have any questions that you think I could help answer, or if others are engaged in learning to cut with NC systems, please don't hesitate to post. I'd be happy to share my list of hundreds of mistakes as I've figured out how to incorporate NC cutting in my work.

cheers,
Kevin Morin
Kenai, AK
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Steven r
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Re: Stretching out the beam?

Postby Steven r » Tue Dec 05, 2017 6:51 am

Hi Kevin,
Well what can I say? An amazing reply thank you. If it is PDFs format to start with would it make life easier? Would you need cad? To go to DXF? I am thinking up skaleing it 25% 1.25?
Thanks Steve.

Ps An old timer trying to get his head around this is hard!

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Re: Stretching out the beam?

Postby JoeM » Tue Dec 05, 2017 8:17 am

Steven r wrote:Hi Kevin,
Well what can I say? An amazing reply thank you. If it is PDFs format to start with would it make life easier? Would you need cad? To go to DXF? I am thinking up skaleing it 25% 1.25?
Thanks Steve.

Ps An old timer trying to get his head around this is hard!


I'm in my 30's and i'm lost. So you're fine Steve!
Check out my project and blog! http://fv-escape-hatch.com/project

Kevin Morin
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Re: Stretching out the beam?

Postby Kevin Morin » Tue Dec 05, 2017 12:30 pm

Steve r, JoeM,

pdf's are another type of file for both text and graphics originated by Adobe as a 'portable document format' and they do make documents more compact (portable in a sense) but they are not the 'answer' in converting paper to NC cut paths, or G-code tool paths. Without going into the discussion about *.pdf's any deeper- I'll say that file type is just another step in handling a conversion- not one needed especially for the central part of the discussion about converting boat plans from paper to NC.

The paper drawing, print out, image hardcopy all have lines that are inexact- if you take a very strong hand lens or 3x to 5x power microscope and put a printed line on the boat drawings under the magnification- you will see the lines are sort of smudged. What I mean by using that term is; the edge of the lines 'fade out' into the paper- there is no hard black and white edge to a line. Our eye sees the lines as pretty fine and sharp edged but when you take a drawing and put your scale ruler on that drawing; you'll find times when you have a question about reading the inches and fractions of an inch even in larger scale drawings. If you're working in 1/2" = 1'-0" then reading fractions from the scale is a 'guess' because the line's actual printed width is greater than 1/2" fraction IN SCALE!

Incidentally this is very well known by anyone who's done much boat building- and so you also get a "table of offsets" with boat designs so you can scale THOSE up, and then either redraw (if you're working from paper plans) or, loft full size (the intention of a Table of Offsets) and that process of lofting 'corrects' the fractions of an inch where the designer/naval architect had the same scale reading problem we all have- and that I've mentioned above.

However using a PC to eliminate the lofting steps, does require some provision for fairing lines - or remodeling the entire boat? Remodeling implies marine design software and familiarity using those applications so is not a real reply or solution to the topic of making modifications to plans at the shop level OR to paper to NC conversion.

Let's get back to lines on paper, they're not crisp and sharp edged to a photographic scanner- as they may appear to our eyes:

This means that when you use a scanner to lift printed lines into a PC image file (bit mapped first) you're getting the entire line width -smudged edge to smudged edge- not some very fine, clean edged lines that your eyes tell you the page contains. So when you 'convert' (using Scan2CAD for example) to vector lines you're asking the software application to 'decide' where the designer's lines "should" be?

Let's take an example and see if this bottleneck can be made easier to understand? If a roadway lane is paved 12' wide and your car is 8' wide and the lines on both sides of each lane have lines painted there to indicate where you need to "keep between the lines"- you can drive safely with a 2' boundary both sides- or a total 4' of tolerance?

Your actual track (filmed from a drone flying just above your car) can vary side to side -remaining inside the lines by 2' either side and a total of 4' variation! AND you'd still be 'in your lane'. But the roadway was layed down by surveyor's stakes and is accurate in path on the ground to 1" -not 4'! Further the road is 'printed' 12' wide and the track or path of your automobile is only 8' wide- so..... you can wander back and forth 4' side to side as you travel- but be in your lane. So to a wide, smudged line on paper will be photographed wider than our eyes see- and then can be interpreted by the scanner's conversions to vector- as wandering between the sides of the wider 'line' and the results can mean a wandering tool path.

An auto-conversion software that has a wide smudged/printed line may provide solutions as vector conversions of bit mapped photo images of curves taken from a scanner- where the curves wander and are not "fair" enough for boat building seams- especially in metal or welded seams. Therefore, once the image is scanned and 'auto-converted' there is still the requirement to have a human CAD operator/designer/builder/operator visually inspect the lines and 'fair' or 're-fair' the lines.

The NC router/plas/laser needs a railroad track- (vector line/curve) to follow- it cannot have any tolerance or the cut will be wandering, kinked, hogges or have angle points- and the gain of Numeric Control cutting of boat parts would be largely lost by the poor quality of curves; if the lines on paper are converted but not re-faired to fair curves.

in terms of our analogy between roads, rail tracks and printed versus digital lines- the roads have much more tolerance than railroads - on a highway you can wander side to side and be OK- no so on a railroad - the track doesn't allow any wandering off the track. In paper drawings the image in the scanner is much wider than our eyes to to convert to a useable 'non-wandering' Tool Path for the router/plas table, someone has to inspect the auto-conversion and correct any wandering in the lines converted from the scanner's photographic bit map.

This is not the end of the discussion, only a beginning to explain why the process being discussed is not a trivial exercise. There are software tools as well as various on-screen techniques to clean up these converted bit map files into useable vector files so the CAM or tool path software can convert to the G-code needed to drive the NC table's two axis' motors accurately enough to cut smooth curves.

I do realize the topic is complex and perhaps seems more so if you're not already familiar with computers in their application to graphics in general- as we're digging down into a pretty specialized part of computer graphics in this discussion.

If anyone has specific questions, or if reading my attempts to detail the ideas implied- please don't hesitate to ask and I'll try to write something semi-lucid in reply. If I might make a suggestion for readers who are not already familiar with scaling issues and recreating curves- as well as the lines of a hull on which most of these 3D graphic principles are based: There are a couple of threads here in the Metal Category exploring boat building methods that show some of the mechanical basics of scaling curves and what 'hull intersection planes' are and what information they provide.

If you are planning to scale a design, having a grasp of the "lines plan" seems required knowledge? If you'd like to begin to explore curves being stored in a 'table of offsets' so they can be recreated; then the building method thread can help introduce the concepts involved in that process.

Cheers,
Kevin Morin
Kenai, AK
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Steven r
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Re: Stretching out the beam?

Postby Steven r » Tue Dec 05, 2017 1:54 pm

Kevin,
Ok it looks like back to my world. If you cut and shape by hand It is hand made and lot of hours. I thought I could have frames made in few hours not to be! After all they built boats on the river bank in third world countries.
Thank you Steve.

Kevin Morin
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Re: Stretching out the beam?

Postby Kevin Morin » Tue Dec 05, 2017 2:14 pm

Steve, I don't want to discourage you! and maybe someone has already converted the design to CAD files or NC cut files? I just wanted you to be mentally prepared to the series of tasks involved in the conversion!

Yes hand lofting still works fine, and for a one-off boat is one main reason that unless the original designer goes through the steps of scaling, digital design or other steps to change the building methods- others don't often spend the energy to convert unless they've licensed a given design for production of that boat.

You can do it! (convert to digital cut files) if you want too? All you have to realize is there are steps a little more involved than just feeding paper into a scanner and cutting from the image files!

cheers,
Kevin Morin
Kenai, AK
Kevin Morin

Steven r
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Re: Stretching out the beam?

Postby Steven r » Tue Dec 05, 2017 2:31 pm

Kevin,
I would like to have a go, but I need to be in control and do not want to be in some one else's hands! The chance of the CNC for £60 per hour in the UK s cheap. Lots to think about! It's hard to find the right boat to build and engine is very high that I may use.
Thanks Steve.

Kevin Morin
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Re: Stretching out the beam?

Postby Kevin Morin » Tue Dec 05, 2017 6:18 pm

Steven r,
if you have a table of offsets- and you give them a 1.25 multiplier- you can get the size increase but... when you scan the frames and photographically zoom them 1.25 you'll need to check in with the table of offsets to confirm the new dimensions.

Next, ifffffff, a huge word in this instance, your hull design has lines between sheer and chine and then again chine to keel? (big question in this explanation) THEN, you can use CAD to draw lines between the new points of the frames' tips.

For example if you scan a frame and then zoom 1.25 and move to CAD or some inexpensive drawing application that has line tools (?) you could rely on the keel point, chine point and sheer points of the scans as the POINT to draw the topsides section and bottom section lines of the frames.

Note of Caution: Some software requires you to locate the center of a "scale" operation- you'll have to use the keel line center bottom most point along the base line - otherwise the table of offsets (referring to this point in the drawing in all three views) will not be useful as a scaled up reference! So if you have a scan of a frame and scale it up from the center of the frame there is a good possibility you'll end up with different information in the scaled bit map image that is not referenced to the base line of the lines plan! Make sure to check this by printing two copies of an example frame scale operation- then overlay them - if this is not done you may find the software you're using to perform the scaling operation uses the center of object or image - not the baseline! That would be inconvenient!


This depends on #1 the Body Section Plan showing lines not curves/arcs/cambers to the frames, if shown in elevation: And #2 the scanner can handle the paper size and you're able to work with the scanned image to obtain the three key points of the frames.

Then by using just the line tool to connect these points you'd have the outer/hull side frame surfaces in vector files to use with CAM software to get tool paths.

There is almost always and "offset" command to allow you to draw the two outer lines and then 'offset' inboard some amount to get frame scantlings that comply with the design. I will be important to increase the frame scantlings in both directions by some factor (not addressed here) in order to keep the structural integrity of the original lines and design.

So, if its the frames that are in your plans? you can get by finding new apexes for the key points and drawing lines between them.

I have been focused on the hull panel outlines- long slow curves that usually require a bit of editing to 'clean up' the scans. But, if you're only focused on frames, and they happen to be lines not curves? THEN you can use a PC/Scanner/Scan2CAD to help get the increase in size you're seeking AsWellAs relying on the frames to be faired After they're erected on the building jig.

Hope I'm making sense? we're definitely discussing a non-trivial topic!

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

Steven r
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Re: Stretching out the beam?

Postby Steven r » Wed Dec 06, 2017 2:12 am

Kevin,
What if the plan comes in PDF not paper? Do you get offsets must find out? Printing is not a problem as one of our university's 60 miles away has a printer that does 3 feet and has a larger one. Just costs! But lot cheaper than private company.
Regards Steve.

Kevin Morin
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Re: Stretching out the beam?

Postby Kevin Morin » Thu Dec 07, 2017 4:37 pm

Steven r,
if the plans sets are *.pdf files then you can print them any size- and learn with a simple trick how clean the lines are- helping predict how well they will digitize?

Print the *.pdf files of the lines and any parts on regular A size paper (8-1/2" x 11") in an ink jet or laser quality printer at the highest resolution the printer driver provides?

Now, with the page held in your hands or lying on a table -move the page so your eye is at the end of the paper sheet/page and just above the surface. You should see the entire page/sheet of paper as a very 'foreshortened' image of what you'd see by holding the page up in front of you.

The purpose of this exercise is to 'test' the curves for fairness, if there were angle points, hoggs or other flaws in the boat's curves of the lines - they show up exaggerated by the 'foreshortened' view of the lines. Also this view compacts the entire lines set into a short set of very bulged curves- again and aid to visual inspection of a lines drawing.

In fact, many marine design software packages have a tool to provide a shortened view of the various lines and outlines of developed surfaces. The reason is; this technique allows a change in your perception of the curves - that change allows you to spot flaws in a curve.

If the lines print well, they're clean and your CAD/CAM application will accept *.pdf files- you may have a good chance of a simpler conversion- all depends on the cutting services' file requirements- so if there is an NC vendor (I think you've mentioned someone?) then ask for their table control software file type to confirm if the *.pdf will 'read in' to their control software?

Would save lots of time - if they can open and interpret *.pdf directly?

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin

Steven r
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Re: Stretching out the beam?

Postby Steven r » Fri Dec 08, 2017 10:38 am

Kevin,
Thanks you for your reply, I have a lot to think about? I think the plans will be in PDF.
Regards Steve.

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NAMEngJS
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Re: Stretching out the beam?

Postby NAMEngJS » Mon Dec 11, 2017 9:04 am

In regard to what Kevin is saying about the viewing of the lines on paper is true, as even with a computer faired design there is something to be said about actually looking down the lines in person. In my own experience if you have the design in a CAD format (I realize you do not and it will most likely come in PDF) I recommend taking the time to still still print out the CAD drawing and look it over.

Also I like to purposely exaggerate one of the axis and then view the lines. For example if looking at the lines in profile (from the side of the vessel) if you expand the scale of the Y-axis to 2,3 times the original scale and then print the drawing as large as is possible on your available plotter. Again looking at the vessel on paper as Kevin suggested this will cause any hard points or flat spot in what should be a smooth fair line to be easier to spot.
All men dream, but not equally. Those who dream by night in the recesses of their minds, wake to find that it was vanity: but the dreamers by day are dangerous men, for they may act on their dreams with open eyes, to make them possible.

Steven r
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Re: Stretching out the beam?

Postby Steven r » Mon Dec 11, 2017 11:31 am

Nameng,
If I got cad I would need a lot help with it? People may get fed up with me! Iam sure its the right way to go. This is a big issue.
Regards Steve.

Kevin Morin
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Re: Stretching out the beam?

Postby Kevin Morin » Mon Dec 11, 2017 12:31 pm

Steven r,
there are forums for each CAD software package, like Glen-L's Forum more or less dedicated to the Glen-L catalog of designs and those building them.... but those CAD forums are dedicated to that particular software.

That seems to me there are several forums where your questions will be normal postings for as long as you have questions. First, the CAD forum for any given application will have those who spend time helping your CAD learning curve, fielding your CAD questions about those features you're learning and may not find complete answers in the training exercises? Next, there are online videos in most niche interests that are without count!! so that resource is always a fast way to look up an answer... finally,

As CAD applies to marine lines or boat planning and building, there are sites like this one where readers try to field questions of members as they can from whatever experience the replying poster has to offer. These subjects are slightly less on point at the CAD forum since they're most often concerned with the CAD use of a wider scope of graphic use; 2D(or flat) drawings like mechanical, structural and symbol based drawings. OR if a discussion is involved with 3D, then modeling is more often concerned with mechanical or structural drawings where marine design is a pretty small percentage of CAD use.

My answer to your question is that you will be able to learn CAD by yourself- with the help of online forums, including Glen-L's, you will be able to solve any serious question or slow down of your work flow.

Curves are not as quickly learned, either in CAD or in real (life-size) lofting of boats, but there are many here at Glen-L's Forum who have no formal training in drawing curves, with CAD or by hand, who have learned to work in curved lines as witnessed by the many beautiful craft shown.

You can do it, I'd be happy to try to answer some questions, and point to a source for an answer when I don't know that answer. I might not always be able to answer in a short time, but there are plenty of people here with lots more knowledge who can help you as well.

My last remark(s) is about getting help online from specialty forums; these are about what I see (personal opinion) as good manners of those who post questions.

#1 many times the answer to a question is already posted- the poster hasn't taken time to read the site's archives! That implies that others' time is being asked to spend on something that poster could well have found for themselves - in past threads. Not too considerate in my view? So I always recommend a thorough archive reading before posting, I've spent as much as a week of evenings reading entire archives to become informed enough to ask my questions and often found many of my questions have been addressed before!

#2 in CAD, often times a new-to-CAD, or new-to-boat building poster will not use specific terms in the question! Therefore an experienced reader who may be able to reply will find confusion in the question: "How do you draw that part that kind of crosses the middle of the boat?" - Lots of questions! pronouns aren't very conducive to high levels of communications, relative areas and relative terms are always difficult to reply! "What's the best way too.....?" Best to whom? Based on what criteria? Time?Costs?ease of work....? OR "What's the best way to form that board in the middle, or left side near the back of the boat?"

Hard to talk online if we're not using the same language!

#3 Another point is that CAD, marine design and almost any endeavor we undertake, requires practice. Many new CAD operators and first time designers haven't taken time to perform practice exercises - therefore they are not proficient in the CAD tools or design helix implied by a marine design. This leads to poor online manners when the learning poster doesn't take the time to work on the principles and practices that have been shown them.... where future questions would be answered by doing a series of practice exercises that haven't been done.

#4 The design helix allows for correction of designs, redesigning and rethinking with the corresponding edits of the process..... However, if you're getting design suggestions and you've provided some level of detail in reply to thread where you've asked for help? If you continue to change your design parameters instead of being able to make a firm decision and stick to it???? Well that can lead to a responding poster feeling you're not ready to make any useful gains from his or her replies and they may refrain from further replies.

Here again, if you're not able to make a decision about your project, and ask for advice from a Forum, then argue with replies or continue to rethink over and over your design point of the original question- I'd say it was likely you will find others are in fact tired of that behavior?

I think if you keep in mind these points as you begin to learn a CAD application that you'll find your questions always get reply posts and the Forum is not 'tired' of hearing from you?

Cheers,
Kevin Morin
Kenai, AK
Kevin Morin


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