Basic Drafting Question(s)

Discussion in 'Boat Design' started by Clinton B Chase, Jan 19, 2008.

  1. Clinton B Chase
    Joined: Mar 2005
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    Location: Saco, ME

    Clinton B Chase Senior Member

    I've been drawing boats for a couple years yet still struggle with setting up a very accurate grid. I have struggled getting it right by using my plastic triangles and using two together to erect perpendiculars off my LWL. I just can't seem to get them truly perpendicular. I use 12" triangles, one long the baseline or LWL and then the other set up flush against it to make a perpendicular. I am quite accurate with my lines. Yet when I double check the perp that I had just drawn it is not exactly perp to the LWL. I have checked the triangles with a steel engineer square and did find one was off. I sighted my drafting table and did notice it is not flat; it sags in the middle. It is very frustrating. Advise would be great!

    Cheers,
    Clint Chase
     
  2. timgoz
    Joined: Jul 2006
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    timgoz Senior Member

    Clint,

    Have you tried parallel rulers, such as used for chart work? Obviously, your non-flat table is going to present challenges with obtaining accuracey. Same goes for the triangle that is 'off'.

    The best instruments and equipment will allow your full potential to show through. Defective ones cannot help but hinder your work.

    Take care up there. I've visited Portland on several occassions & really liked it.

    Tim
     
  3. Landlubber
    Joined: Jun 2007
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    Landlubber Senior Member

    First thing first. With your square set on the base line, draw a vertical, then reverse the square and draw another vertical from the reversed square exactly from the same base point, if there is any off square in the set, then it will be obvious to you where the lines show a gap at the top.

    Beyond that, it may simply be practice, because we have been doing parallel lines for a long time before the computers took over.

    Keep trying, like using a sextant to get a fix, it will not happen overnight, but it will happen.

    I am a shooter, always thought that I was fairly good, untill I learnt to benchrest, that was about 8 years ago, and I am still learning. Good luck.
     
  4. alan white
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    alan white Senior Member

    You have to have a flat table. Go to a used restaurant supply and buy a table. Try Bluecold for example (they're in the Portland book... Scarborough?). You can buy a good drafting machine on Ebay for short money.
    Best of luck.

    Alan
     
  5. masalai
    Joined: Oct 2007
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    Location: cruising, Australia

    masalai masalai

    Clinton, I uae A3 graph paper & work in metric (easier for maths) the sheets are about 24" (600mm) x 17" (43mm) and mine have a 2mm grid in pale blue.

    I also got a 1000mm (1 metre = 39.37") stainless rule. I can join several pieces to give a larger picture. Because of stretch/shrinkage use a count the squares method for getting take-off distances.

    Recently I started using DelftShip (free) and find it easy to share data files.

    For a flat table - get a second hand glass window, (with the frame for strength & safety), which can be stored along a wall when not needed. It also makes an excellent "light-table" for copying when redrawing or transferring values etc....

    Good luck.:D
     
  6. Trevlyns
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    Trevlyns Senior Citizen/Member

    I use just a T square (about a meter long) and provided the board edges are straight and true, the set square sits snugly on the T square edge. As already mentioned flatness is important (like the glass idea Mas) and always check by reversing the square.

    Best!
     
  7. Clinton B Chase
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    Clinton B Chase Senior Member

    TX all...I'll check the table more closely...with a steel straightedge (it may not be THAT bad) and I'll look for the grid paper. Recommendations for where (on the Internet presumably) to buy good stuff (my local art supply is limited)

    Cheers,
    Clint
     
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  8. Eric Sponberg
    Joined: Dec 2001
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    Location: On board Corroboree

    Eric Sponberg Senior Member

    Clinton,

    T-squares, in my opinion, are too cumbersome and not accurate from position to position. I use a Mayline straight edge, and have for over 40 years. You can buy them at www.dataprint.com. I just checked their catalog, and they don't seem to have the Mayline brand anymore, but they have two others: Mobile and Spiroliner. These are sliding straight edges that ride on wires strung around the perimeter of the table and through the straight edge itself. It always stays parallel as it slides up and down the table top to bottom. You position your triangles along one of the two parallel edges as you draw lines. Buy a straight edge that is nearly as wide as your drafting table, and they come from 36" to 60" wide. You can even by a drawing kit which includes a table with a straight edge attached, sizes 18" x 24", 24" x 36", and 31" x 42", at prices $64.60, $91.20, and $113.24 respectively. They have larger drafting tables with straight edges that go up to $315. By the way, I have found Dataprint to be the least expensive and most dependable supply of drafting and art equipment, and they carry all the brand name supplies.

    I attach a photo of me at one of my drafting tables. The long black shape at the bottom of the drafting table, beneath my arms, is the straight edge. One of the triangles is positioned against it. Straight edges are far better than T-squares.

    Another thing that you should have on your drafting table is a vinyl drafting board cover. Unfortunately, Dataprint does not have good sizes or prices on this, but you can get them at a reasonable price at www.draftingsteals.com:

    http://www.draftingsteals.com/catalog-drafting---drawing-equipment-vinyl-board-covers.html

    These are thick vinyl pads with a different color each side to suit your own eyes, that simply lay on top of the drafting table surface, and you work on this. You can see my cream-colored cover in the photo. They are easy to clean with soap and water. They provide the best surface for making accurate, well-detailed lines on paper or Mylar. They are "self-healing", meaning that if you stick a compass point into them, the point hole closes up on its own. Same for planimeter points.

    If you want to spend more money, you can buy a drafting machine, also available at Dataprint, with prices in the $700 to $900 range.

    I hope that helps.

    Eric
     

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  9. Jratte
    Joined: Jul 2007
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    Jratte Junior Member

    As for finding a good table close by try ebay or craigslist. I grabbed a 3' x 6' Hamilton drafting table with light and a brand new chair off of craigslist for $200. I added a vinyl cover and 60" Mayline straight edge attached to it. I've only done a few small drawings on it but it has been great and I would definitely recommend a similar setup. I've also used Modern School Supplies to purchase a few extra parts I needed for my straightedge, they seemed reasonable priced and the service was good. best of luck.

    Josh Ratty
     
  10. Clinton B Chase
    Joined: Mar 2005
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    Location: Saco, ME

    Clinton B Chase Senior Member

    Eric, I just may upgrade to a new table with the straightedge. Thanks for the info.

    I just made some perps (station lines) by squaring up from the waterline and measured the diagonals of the box I created this way. I am very close...within 1/8" with the scale I am working on. So should I call it good or try tweaking the "box" such that it is perfect and then drop vertical lines from top to bottom to make my stations?

    Cheers,
    Clint
     
  11. timgoz
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    timgoz Senior Member

    Clinton & Eric,

    It is refreshing that people still draft in the traditional manner. The capabilities of CAD are noteworthy & useful, but the asthectics and personal 'feel' of a hand drawing are indisputable. Keep it up.

    When I took several technical drawing courses in college I used the mats Eric speaks of. I agree 100% with his recommendation.

    Take care everyone. And for those in the NE US. keep warm. Here it is not to go much above 0'F all day. :(

    Tim
     
  12. Olav
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    Olav naval architect

    An alternative to T-squares and the like may be the use of a pair of compasses to erect perpendiculars to the baseline (or whatever): Draw a straight baseline using a long high-quality ruler. Then adjust the compass to your desired section interval and mark the stations on the BL. Next, mark two points equidistant from each station position (left and right). By taking these as the centre points draw circles (better: circular arcs) with such a radius that they will intersect. Connecting the intersection with the station position on the BL will give accurate perpendiculars.

    Another hint (if you don't do so already): Use transparent polyester drafting film. It's much more robust than ordinary paper and it will not shrink with changing humidity. It also allows the grid to be drawn on the one side and the ship's lines on the other, so you can erase easily without doing any harm to the grid.
     
  13. alan white
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    alan white Senior Member

    I'd mentioned restaurant tables (heavy 1 1/4" particle board with formica laminate overlay) as making a good drafting board. I have done this. i also used to sell used restaurant tables myself, and usually for under thirty dollars.
    shimming the base/top attachment gets you a good 10 degree angle, which is pretty good for drafting with ducks.
    You have to be dead on with your squareness because you get your tables directly off the drawing. Accuracy means less fiddling with the lofting.
    I bought a K&E new drafting machine from ebay for $150.00. The restaurant table I bought for $25.00. Chinese lights look great and are pieces of s$%t.
    I found a 50 yr old flourescent lamp with a base that must be full of lead.
    Whatever you do, buy the best lamp you can afford. Unfortunately, that means Staples and Office Depot are out. Charettes in Woburn Mass (or thereabouts) has the real McCoy I think.

    Alan
     
  14. Eric Sponberg
    Joined: Dec 2001
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    Eric Sponberg Senior Member

    Drafting advice

    I wish I could say that I draft by hand all the time, but the reality is I don't. I use hand drafting for the first concept drawings of a boat, or for sketches in a design study or report. Frequently, I will do some drafting by AutoCad, then add other notes by hand on a letter-size printout.

    Drafting by machine can look almost as good as drafting by hand. The keys to a good drawing either way are:

    Good Organization: The drawing has to tell a story. Ideally, it should read left to right, top to bottom. It should be no larger than 24" x 36" maximum, and in many cases I find tabloid size, 11" x 17", to be ideal. If your drawing is larger, it is cumbersome. Too much paper (or Mylar), too unweildy, and you cannot grasp the entire drawing in one glance. You should be able to gaze at the drawing on the table in front of you and grasp its story without having to shift if one way or the other. Leave some blank space somewhere in the drawing; don't cram it with detail. If you can't leave a little bit of blank space, then do a second drawing as a continuation of the topic and spread the details around so that they are easier to see and read.

    Good lettering: The cardinal sin of lettering is using all capital letters in your printing. NO, NO, NO! All capitals is extremely hard on the eyes--ask any advertising artist or copy editor. Use capital letters as in the normal course of writing--First letter of a sentence or comment, proper names, etc. All the rest of the lettering should be lower case letters. This makes the drawing look ever so much better. Lettering should be uniform in style, size, and slant--practice, practice, practice. Actually, it should not take too long to learn proper technique. Study other artists' work, particularly the styles of of Bill Garden and Bob Perry. I was taught to letter properly by an architect boss I had once; it took him all of 5 minutes to show me the proper lettering technique, and within an hour or so of practice I had it down. Unfortunately, it is difficult to show here on this forum, but it is possible. For CAD drawings, select a font that looks like a hand-lettered font, there are plenty of them out there.

    Clean line work: When drafting by hand, it is possible to vary the boldness (width) of the line by using different hardnesses of pencil (more on that later) and by different bearing pressure to the paper or Mylar. Typically, by hand, I have about 3, maybe 4 different widths that I use on any given drawing from bold to fine. In AutoCad, I use 5 different widths. I still use the color codes to establish my line widths, called plot styles, although I understand some people use line width definitions in the properties table to establish line widths. If you are using color codes, then you will see that working on a black background illuminates the colors the best. A white or gray background washes out the colors so that you cannot see them well. There are instances where I will use only one line width on a drawing, in which case I have a separate plot style that sets all the colors except the border color to a constant mid-to-fine width.

    Pencil hardness: USE SOFT PENCILS! This is another trick I learned from the architect. Naval architects typically use pencils that are way too hard--3H, 4H, 6H etc. I use B, HB, H, 2H, and 3H, and concentrate at the lower end of the scale. I use regular lead on Mylar as I can't stand that plastic lead stuff, and Mylar wears the pencil point really fast. Be sure to rotate your pencil as you draw a line so as to even out the wear on the tip. This should be second nature to your drafting. I use a lot of 2H and 3H on Mylar, but all my lettering is done with a broad tip, 0.5mm, HB pencil. On paper, I drop to the B hardness for lettering. The soft leads make the lines very black and they will reproduce in printing much better than the harder pencils.

    Those are some of the basics. I hope that helps.

    Eric
     
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  15. SamSam
    Joined: Feb 2005
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    SamSam Senior Member

    Check with printing companies, architects, etc for drafting tables. Computers have rendered manual drafting obsolete for a lot of people and excess equipment takes up space. I have a commercial/industrial metal desk with a tilting 3x4' table and parallel straightedge that cost me $10. I have a 4x5' old oak tilting artist table, used with a t-square for layout work in a printshop, that cost nothing.
     
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