Steps when drawing lines plan

@jehardiman I do not want to contradict you in any way, but for many years I have been involved in the fairing of large boats and I have always considered that the diagonals were one more element of verification, which was necessary to use. The "fairing" gives rise to the constructive drawings of the structure and no element that allows it to be improved should be forgotten. I have never thought, to draw it, in the water flow lines around the hull, it does not depend on the "V" or "U" shapes or on the propulsion, it depends on wanting to do a "fairing" as best as possible. Just my opinion .

 

In fairing a set of lines, either on a lines drawing or a loft floor, if there is a discrepancy you have to choose to move one or more lines. (Note to CAD people lurking: this includes CAD lines...which I have found most programs really suck at "fairing" based on their own programed in proclivities. Not to say that they don't fair, but I have generally drawn to +/- 1/32" (0.79mm) which is good shipfitting.) So TANSL, when a diagonal is a "verification" do you move the waterlines and sections to the diagonal when "fairing"? I think this is what I and Ike meant by "fairing to" a particular line...i.e. which line becomes the control. This is important considering that early in the preliminary design you might only have a profile, a sheer, one (1) waterline, three (3) stations, and three (3) diagonals or buttocks. As I have said before, the waterlines are the last to go in most of my drawings, diagonals or buttocks form the stations and waterlines are what is left. Different learning experiences..<shrug>

 

Note that I am talking about the "fairing" that serves as the basis for the constructive drawings of the structure. I am not talking about the body lines plan of the conceptual project, which is always much less exact, it does not need as much precision.
The normal thing, indeed, is to start defining the body lines plan through a series of cross sections and through the longitudinal profile (if, in addition, you have the points of the sheer line, better than better). With that base, buttocks, water lines or diagonals are traced, until the shapes are smoothed. For me, none of these lines is more important than the others, but it is very true that in the initial drawing, it is very normal to forget about the diagonals. I would not say that the last thing I draw are the water lines, on the contrary, the last thing I take for granted are the cross sections, which are the ones that will allow me to build the real frames of the ship.
Regarding your question, when a point on a line is moved, what is actually moving is a point on the surface of the hull, thus a change in a "secondary" line (as perhaps you would consider it) of course which will make me change the frame or any other "main" line. As I say, for me, all the lines are equally important and none influence more or less than the others on the smoothed shapes.
And I insist, imo, in this work, hydrodynamics, or the lines of water flow, do not intervene at any time.

 

Ditto...

 

Interesting discussion. Fairing is usually done in the loft, and I have to admit that I have very little experience with lofting. Most of it involved big ships. I mean BIG ships. when I was working at Lockheed ship yard in the late 60's and early 70's the people doing the lofting were working on LPD's which are around 680 feet. A +-1/32" means nothing at that size. (you should have seen that loft!) When you talk about small craft though it could make a huge difference especially if the vessel is for racing. Anyway I think we are all talking about the same thing just looking at it from different angles (pun intended).

 

Yeah, on an auxillary skimmer you could get away with that, on a submarine...not so much. Things often get moved on the loft floor. I think the furthest I was ever off was ~ 3/16" in a repair to a 40' fairing but it was a quick AutoCAD drawing so I knew that the curve was not fair going in (which is why I had them loft it after lifting the existing shape). Hardest thing I ever had to do was to convince the lofters on one fairing that I wanted a flat spot right there.

Even today it's typical shipfitting... Loft with a scratch awl, mark with chalk, cut with gas axe, heat and beat to fit, paint to match.

 

Still learning - and know more now than I did when I first posted in the thread a few months ago -anyways- I have a decent understanding of each of the types of lines used in the plans...Since I am not much of an engineer or designer by trade....I have taken measurements of a model, using a baseline(waterline) at each "station", also from the half breadth, body plan dimensions,

Using paper, how can I better understand how to scale these measurements? Can you give me some advice how to put this on graph paper whiling scaling the measurements? I beleive I am referring to the offsets, points...I am trying to simply for my understanding, as ideally Id want the tabletop model on say a large sheet of paper to scale up to a fullsize boat over 6 meters

 

Maybe the issue is I am using a graph paper with 1/4" blocks=1" real size, and with the pencil lines it's had to make out deviations of actual size of 1/16"...does that make sense?

 

First of all, graph paper is not uniform, you need a draftsman scale. Really, draw from blank paper or on mylar; think about the shape instead of the grid.

OK... basic draftsman kit. Not that I recommend these items, but I know they will work.
Drafting board 24x36 inch.... https://www.amazon.com/Helix-Drawing-Board-Plain-37415/dp/B004BNAAJ8/ref=sr_1_38?crid=F7K0VQRFARFW&keywords=drafting+board&qid=1689105920&s=office-products&sprefix=,office-products,293&sr=1-38&ufe=app_do:amzn1.fos.304cacc1-b508-45fb-a37f-a2c47c48c32f
T square 36 inch ..... https://www.amazon.com/Alvin-Transparent-Edge-T-Square-C24/dp/B000HESRR2/ref=sr_1_20?crid=FGSF1IRMOGC&keywords=t+square&qid=1689105515&s=office-products&sprefix=t+squ,office-products,151&sr=1-20&th=1
Triangles 45 & 30-60-90 12 inch...... https://www.amazon.com/ALVIN-Professional-Multipurpose-Architecture-Woodworking/dp/B004O7GM5C/ref=sr_1_7?crid=D9SLX4Y6WUCD&keywords=alvin+triangles&qid=1689106049&s=office-products&sprefix=alvin+triangles,office-products,138&sr=1-7
Triangular scale 12" (note: the old bamboo ones are better, do not get a metal one because of thermal expansion) .... https://www.amazon.com/Pacific-Arc-Architect-Triangular-Economy/dp/B08DDCX4ZZ/ref=sr_1_15_sspa?crid=3QXZSGV01AFJ9&keywords=triangular+architects+scale&qid=1689106403&s=office-products&sprefix=triangiular+anchitects+scale,office-products,142&sr=1-15-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9tdGY&psc=1
Basic compass set ... https://www.amazon.com/Geometry-Professional-Drafting-Extension-Engineer/dp/B08C4RQXJZ/ref=sr_1_22?crid=1NF3YECKO2C0Q&keywords=spline+for+drafting&qid=1689106471&s=office-products&sprefix=spline+for+drafting,office-products,166&sr=1-22
Basic Curve and template set ... https://www.amazon.com/SIQUK-Templates-Geometric-Measuring-Engineering/dp/B07L4H2K1B/ref=sr_1_25?crid=1NF3YECKO2C0Q&keywords=spline+for+drafting&qid=1689106773&s=office-products&sprefix=spline+for+drafting,office-products,166&sr=1-25
Basic erasing set (you WILL need this) ... https://www.amazon.com/Mr-Drafting-Dusting-Supplies-Drawing/dp/B07DP1CHT3/ref=sr_1_19?crid=1NF3YECKO2C0Q&keywords=spline+for+drafting&qid=1689106773&s=office-products&sprefix=spline+for+drafting,office-products,166&sr=1-19
Scum Bag ... https://www.amazon.com/Alvin-1248-Professional-Drafting-Cleaning/dp/B004O4I3EI/ref=sr_1_1?crid=14NQCN1H6LJ2C&keywords=drafting+scum+bag&qid=1689107412&s=office-products&sprefix=drafting+scum+bag,office-products,153&sr=1-1

Pencils or pens it is up to you, but have a selection of wide/soft to thin/hard...and you will always need 7H/8H/9H pencils for guide lines. When using pencils, keep them sharp and use a light hand to prevent cutting the paper. Know which side of the line is the moulded surface.

Splines and ship curve sets today are the hard part. You can get spline weights (i.e. ducks) but not splines; and ships curve and railroad curve sets seem to have gone the way of the dodo.

 

I have made 3 sets of Copenhagen Ship Curves a 1:3, 1:2, and 1:1 and I use them all the time.
Working on some oversize French curves. Also 3 sets of Dixon Kemp ovals. I have reduced the y axises by 1/3 each time.

Here are Copenhagen ship curves,


Scandinavian Ship Builder's Curves



Dixon Kemp ovals

 

Hi everyone! I'm currently a student and I just want to ask if you guy can help me with my lines plan cause I don't really understand how

 

Welcome to the forum.
I don't know exactly what you need because the pictures you have shown don't indicate anything, in my opinion. You have some main dimensions, okay, do you need to create a body lines plan for that boat? Please give us more information about what you already have and where you want to go so we can help you.

 

Thank you for the warm welcome! I appreciate your response. To clarify, I am trying to determine the waterline's distance for the boat based on its main dimensions. I don’t currently have a body lines plan, but I can provide more details about the dimensions and any other relevant information if needed. Please let me know what specific details would help you assist me better. Thanks again for your time!

 

As far as I know, there is no formula that allows the length at the waterline (Lwl) to be deduced from the length of the boat. It may rather depend, although this is not entirely true, on the general appearance of the boat, on its longitudinal profile. The body lines plan must be created and it must be checked whether the Lwl obtained is similar to what is desired (if there is something predetermined that limits the Lwl). To create the body lines plan it is necessary to know more about what you want to do with the boat (passenger, fishing, container ship,...), under what conditions it will sail, payload, cruising speed, autonomy,... in short, to make a description of the boat as detailed as possible. A provisional General Arrangement plan would also be very helpful.