Printing full sized patterns?

If you print full size, you should also print a scale to verify the accuracy. You can have a grid of maybe 6" square overlayed. That will let you check with a ruler how close you are and how much distortion there is from area to area. I think that if you print on paper at a regular printing place, the accuracy will dissapoint you.

 

Problem solved! It was a print memory issue. I had 600 dpi set and had to back it down to 144 dpi.

Paper problems are all understood. Mylar is the way to go....

For the nature of the project, it maybe worth while to experience the paper issues first hand. The paper print out is $11, while the mylar is $62. How does this pricing compare with what other have experienced. I'm curious if I should be looking for a different shop.

 

On small craft, lofting up full size is a much more economical option. It places you in an intimate relationship with the various shapes on the boat, plus you'll catch errors or can make alterations on the loft floor, without having to spend 5 to 10 bucks per square foot.

Printing a scale will just verify how badly a non-Mylar print comes out. It'll hit fairly close in one direction, but will be way off in the other direction. The paper stretches as it goes through the machine from the feed rollers and the drying drum, plus environmental changes.

Most copy houses use PDF, because it's easy, but you're locked down with line weights and other stuff. A 1 point line looks great on a 24"x36" line drawing, but when this is scaled up to full size, it becomes a crayon size line, making measurements a bit of guess work. DWG files can have the line weights altered or "not scaled with image" as do JPG's (if you know what you're doing). I use JPG's on the occasions I need full size prints. There are several reasons for this, first is the accuracy of the drawing, which is highest with a JPG, second is security, you can't edit them without using some very clunky software, so having your design highjacked and appearing in a German brochure as someone else's design with a new bow profile is much more difficult and lastly I can print a .001" line on a 24"x36" print, which scales up to a nice thin line in full size.

Again, don't discount the joy and familiarity you receive from lofting. Personally, I love to loft stuff. It's easy, once you get a hang of things and you can pull all your templates, bevels and angles from the lofting directly. You can do this with a full size print too, but most only print out station molds and stem profiles, which doesn't provide the "big picture".

I'm not sure if this is much help Greg, but there it is.

 

It's all useful information, Paul. I'm not actually printing a lines drawing, but the flat patterns for an S&G build. I've created them in Freeship. Imported them into my CAD package to modify them for printing. I can't think of an easier way to get the patterns full-size for cutting. I don't believe lofting will help with the flat pattern developement.

My question to you is more about getting a "something" from my computer onto paper or mylar. I believe your preferred was the JPG. I'm not concerned with secuity as these are only the flat patterns. I was curious if there was a typical industry standard for file output that print shops like to work with or that are more actuate as you mentioned regarding the different output files.

 

Full-sized and detailed.

 

Have you considered contacting somebody with a CNC router to cut the material directly?It seems that the intended purpose of the large prints will just be an intermediate stage in the process and you might have the boat a lot sooner and with a guarantee of good accuracy.

 

It's all about choices. My choice is to work the wood. It's not always about how soon I get the project done, but the whole process of creation, build and implementation. I like the journey and the destination.

The CNC aspect is an interesting projection of the project that I may investigate in the future. That is a whole other thread that has been discussed in the past and will be discussed in the future. I'm not sure of the cost of a CNC cut job, but the $62 mylar might go a big chunk in that direction.

 

CNC is quite costly, PDF is the standard at most copy stores, but DWG or DWX are the usual choices at architectural firms. Most that have a large format printer or plotter will be able to convert, so the choice is yours.

You should still be able to hand loft the developed panels from nesting file dimensions, which I'll assume FreeShip has available. If it was me, I'd just do the station molds and cut the panels directly from a tracing on the building jig. This eliminates and compensates for "pencil line thickness" and other errors that can creep into a project. In other words a direct tracing from the jig, is bound to be more accurate then the best cut pattern transfer, even from Mylar. This is because you pick up all sorts of errors as you transfer the full size pattern to the stock, then when you cut the stock and try to fit this piece to the station molds, which also can have very minor cutting and transfer error in them. None of this is the case, when you bend a piece of stock over it the jig and trace.

 

I'm with Par on this. The more steps between the drawing or table of offsets and the boat, the more errors will happen.

 

Hey Paul, Gonz,

As always, there is a lot of common sense in what you say. One of my goals is to maximize the product and minimize the materials. For me, if I can tweak a curve slightly to produce a more efficient nest, I'm game to put it to practice. I suppose I could create the flat pattern nesting with stategic excesses and cut a slightly larger panel than needed to allow for fine tuning and trimming in the fitting process. It might get be little tough holding a 4' X16' piece of plywood against a set of molds.

I'm still entrigued with the aspect of computer model developement with the direct output of the flat panels. My first projects have had predictable results with the panel developement and assembling. I've sorted out all of the details of getting the PDF output that the printers wanted and shipped the file out. The results were actually quite pleasing. I chose to have the file printed on 25 lb bond paper. There was possibly an error of 1/8" in the 16' foot of printing. This an acceptable error for me on this project. I was anticipating line widths the size of a "Marks-A-Lot", but they were actually usably thin. Once inspected, I rolled the plans back on their roll and there they will stay until the panels scarfed and ready to be cut. I'll be keeping them climate controlled until cut day.

For a "one-off", I think this will work out nicely.

 

Large plywood pieces are actually easier to bend over a mold then standard sizes. The weight and length helps pull them down to the molds. Check you prints for accuracy occasionally, you'll note they change a fair bit depending on temperature and humidity.

 

Demned amateurs

As an experiment I took a 8.5 x 11" print to a printshop and asked them what they could do. It took several operations and I did not have much expectation regarding accuracy, but it only cost around $20 and when I got it home it was accurate to the thickness of the line.

The thickness of the lines was the problem, of course; after a more than x12 blowup they were around 0.1 and getting fuzzy, but I probably could have used them with a fairing stick. I am finding out if the same people can print a .DFX file, but if not I can mess around to find a way to reduce line thickness.

As PAR notes, on plain paper it is not going to be stable and the print is now useless after a month or so, but if I have everything set up, did all the printing and copying on a cool, dry day, spray-glued it to the ply immediately and cut right away, it should not have appreciable time to distort IMHO. Hardly the sort of thing that a designer like PAR would care to send out to a customer of course but for us amateurs . . .

 

Very true.

The problem these days..well, when I say problem..is that most amateurs, and I mean that in the non-professional naval architect sense, whom have not grown up with their apprentiships in shipyards fail to fully appreciate the difference between a lines plan and a set of offsets and/or printing full size for templates.

The traditional design lines plan, has 10 stations and few extra around the bow and stern in way of changes of shape. This was then sent to the mould loft. The lines was drawn out full size and refaired when frame lines were extracted for making wooden templates for cutting plate. The mould loft did all the hard work. In my first yard the chap there, Reg, had been doing it for over 40 years. He could spot a wonky or bad line from a thousand yards in the dark!!

Today, with the easy access of computers and drawing a “lines plan”, this skill and a very real skill has been lost. Computer programs can never do what the mould loft did. You can get close to it, but, this assumes you have 1) a good lines fairing program and 2) understand how to truly fair a hull and at many many frames to minimise the errors.

There is now sadly a major disconnect between design lines and production lines. It appears most assume the design lines, from a fancy all singing all dancing program with its amazing number of decimal places and endless zooming in, is enough.

So, when you print out your hull unless you have created many frame sections you will spot errors, but it is not just in the stretching (as noted above), because the more sections you create the more errors you’ll spot….assuming that the design lines was or is, sufficient, is not enough. The mould loft caught all this, but your program and your “experience” or lack of it cannot.

On small boats, the errors are generally minor..but as you increase in size of boat these errors creep in and are very noticeable.

When Reg sadly retired, was when the yard went fully electronic, we would print out full size on the plasma cutter onto 25mm thick steel. This was the screive board and template for all farmes. Then each plasma cut frame would be offered up against the scrieve board to check the accuracy before and after welding.

But this is larger commercial yard practice of course.

 

A.H.

There is definitely a romantic and traditional side of boat building that is being lost. I'm working on larger projects that I plan to loft as they will be more permanent and longer lived.

Terry,

Rather than blowing up an 8.5 x 11, you should try outputing the actual size print in PDF format. I ended up spending $14 at a print shop here in Buffalo for my 24" X 16' print. I output a custom sized drawing from my CAd platform to an actual 24' x 16' formated file. The line size output is pencil width and highly useable. I plan to keep it rolled and protected from humidity and temperature changes as much as possible until I lay it out for cutting.

It was nice in that I created the PDF file, emailed it and went down and picked up the finished product.