Lofting - 2.Lines / Lines Plan

Lines Plan

Lines Plan is a drawing with three views of a subject(in this case, the dinghy) with many lines in it, including profile, half breadth and body plan.

Until now, all I did was a just preparation for lofting and now it's time to hit the board! REAL lofting.

One thing to note is that there is a priority or sequence in drawing lines which means if you don't have a certain line before you draw a specific line, then you can't. But if you have it already, then you can.


1. Grid Line(for Profile & Half Breadth)

Once we got a table of offset, we need to draw Grid Line first, which is a guide line and basis for each measures in the table.

- Station is common grid line for both Profile and Half Breadth.
- LWL, WL100, WL200, WL-60 are grid lines for Profile.
- Buttock 50, 200, 400 are grid lines for Half Breadth.

Note. LWL, CL and FP are called as a Datum Line which means reference lines from which all the measurements are made.

Grid Line in lofting on cardboard


- Size of cardboard for lofing is about 4000*1250.
- The highest point in Profile is 406, so added 14 as a buffer, LWL is 420 away from top edge of the paper.
- The widest point in Half Breadth is 530, so add some more, fix the Center Line from bottom edge.
- Make sure that those two lines(LWL and CL) are parallell.
- Then, mark AP and FP using measure of length. Distance between AP and FP is called LOA(Length Over All).
- Then, each station can be easily marked using CI(Common Interval, distance between each station) value.
- To avoid possible measuring error with a rule, mark each station point first using long tape measure as seen below and then, use common interval to mark station.

Precesion Method
- Make sure that each station line is perpendicular to those LWL and CL. Below is to prove and secure perpendicular station line.


* How to draw Station line which is vertical to the other.

Darw perpendicular station line.

ⅰMark station point using CI value on LWL.
ⅱMark two bisect point before and after the station on LWL.
ⅲDraw an arc from each bisect point upawrd and downward usin trammel arm with CI length.
ⅳTwo intersects of those arcs and station point on LWL are all right on the line, then it is perpendicular station line.

- When all the station line is done, then finish all the rest of longitudinal lines.



2. Sheer Line(Profile) and Deck Line(Half Breadth)

Sheer Line and Deck Line are an identical line but it only appears differently in each view.

Table below is part of Table of Offset which shows height in Profile and beam in Half Breadth. All you have to do is makr all the height at eahc section in Profile and beam at each section in Half Breadth, then draw a line using a batten

Note. To make fair(not kinked, smooth curve) line runs through all the marked points, we use a wood strip called batten and nails to fix the batten. It is quite important to get the right batten for each curve. Since there are many battens with varied thickness(flexibility and hardness - trade off), length and types woods, batten selection for each line is important.

- Thickness --> Flexiblity and hardness

- Surface --> Whether it's dressed or damaged, this could cause wobbled line or wood split stuck in your finger.

Battens is usually made of sitka spruce which is quite expensive wood.
Before all I know about the batten is, the one in batten pocket of sail which makes camber. Same name, different use but similar function.



3. Chine in Profile

Draw chine with value below.

4. Canoe Body and Stem Face in Half Breadth

Use Table of Offset and Stem Face deatils altogether to draw Canoe Body and Stem Face. Each angle of fair canoe body and stem face is quite different and if you use draw it at once wiht one batten, it's almost impossilbe to draw and batten will break. So you have to draw fair line of Canoe Body first and then draw Stem Face using stem face detail.

As you see here, since we drew the Canoe Body in Profile, now we can draw Chine, WL-60, LWL, WL100 and WL200 in Half Breadth. That is, intersects between Canoe Body and the lines I mentioned before are the start point of each line in Half Breadth.

From now, you could draw whatever line you want to draw, since we have all the start point of all those lines.

- All water lines in Half Breadth: Start points are intersects between Canoe Body and all the water lines in Profile.
- Chine in Half Breadth: Start point is intersect between Chine and Canoe Body in Profile.
- Buttocks in Profile: Start points are intersects between Deck Line and all the Buttock Line in Half Breadth.


5. Chine in Half Breadth

As you concluded start point of Chine in Half Breadth from intersect in Profile, now you could draw Chine in H.B.

6. Buttock 50 / 200 / 400 in Profile.

For buttocks, some of buttock might have kinked points in it, so you have to check buttock details just like the way you checked the Stem Face details.


7. 4 Water Lines in Half Breadth ( LWL, WL200, WL100, WL-60)

8. Body Plan
Now we are finished with Profile and Half Breadth of plan and Body Plan is the only one left for the plan.


1. Grid Line
We also need grid line for body plan with 4 horizontal lines (LWL, WL200, WL100 and WL-60) and 7 vertical lines (Center Line, B50, B200, B400 and its symmetrical lines to Center Line)

For horizontal lines, you simply extend all those waterlines from profile. Then for vertical lines, you just set up the Center Line first then, draw B50, B200, B400 and its symmetrical lines to CL.

2. Marking with Tick Stick(Pick-Up Stick)
Tick Stick is a long piece of paper on which you could mark specific point by ticking it. The reason why we are using Tick Stick is that it is more convenient and simple than measuring all the values with a rule.

On one side of tick stick, you mark all the height of the intersecting lines at the station and on the other side of tick stick, you mark all the beam of the intersecting lines at the station.
Then you mark those points on the stick to body plan and do it all over for all the station.

And just like you do it in Half Breadth, you draw half of each station in body plan because it's symetrical.

* Marking Height

Ⅰ.Canoe Body

Ⅱ.B50

Ⅲ.Chine

For Chine, we don't have its width(distance from CL) at the moment, just remember its height. We will get its width later.

Ⅳ.B200

Ⅴ.Sheer

For Sheer too, we don't have its width(distance from CL) at the moment, just remember its height. We will get its width later.


* Marking Beam(Width, Distance from Center Line)

Ⅰ.WL-60

Ⅱ.LWL

Ⅲ.Chine

Now, we have beam of Chine and the intersect is the exact Chine.

Ⅳ.WL100

Ⅴ.WL200

Ⅵ.Sheer/Deck Line

* Drawing Line by connectig point

Now we have all the points to draw a line. But one thing you should know is that this one has a Chine, which means it has Top Side and Bottom. And for each Top Side and Bottom, you should use different batten. One for stiff and another for fair curve.

And this is the final output and it is the Station Line 0.5. And by doing all the process above for other station lines, you will get total body plan for this dinghy.