Fishing Craft Technology

Practical 5 - Lines of plan of boat

The sheer plan, half breadth plan and body plan are collectively called as “LINES PLAN” or “SHEER DRAWING’. This is the most important drawing of all, because it imparts the three planes of reference to show the exact form of a hull.

Fig.1 shows the profile view of the hull also called as sheer plan. It gives the general outline of the ship, such as position of sheer, deck and also load water line.
Fig.2 shows the “plan” in which only half of the boat plan is shown because the other half will be exactly the same as the former. Hence it is called as the “half breadth plan.”
Fig.3 shows the “section view” or “body plan.” This view shows the number of sections of the boat.

Buttock Lines:
Buttock lines are the straight lines drawn parallel to the centre line and perpendicular to the reference line. These lines appear as straight lines in the plan as well as in the section view and as curved lines in the profile view.

Diagonal Lines:
Diagonal lines are the lines drawn diagonally to the centre line in the section view.

Mould Lofting:
This is the process of transferring the plans or blue prints into full-size interpretation on a floor or series of boards.

Off set table:
Off set table is drawn by the designer and it should be attached to the plans. The off set table is particularly relative to the body plan. The measurements on the table normally expressed in feet, inches.

Drawing of sheer plan

Aim: To draw the Sheer plan using off set table.
OFF-SET TABLE
Sheer plan
Height above the baseline

Station	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0	-1
Keel	0	0	0	0	1	3	4	6	7	8	10 ½	11 ½	13	15	16	17	18 ½	21 ½	30	63	158
Rabbet	-	-	-	-	7	8	10 ½	12 ½	13 ½	15	16 ½	18	19 ½	21 ½	22 ½	23 ½	25	28	38	86	-
Deck	-	92	90	88	87	86	86	86	87	88	88 ½	90½	93	96	99½	103	107	112	117	121 ½	-
Sheer	113	112	110	109	108	107	106	106	107	108	111	113	115	119	122	127	131	136	140	147	-

Half breadth plan

Height from the centre line

Sheer	61	64	66 ½	68	70	71	72 ½	73 ½	74	74	74	74	73 ½	72 ½	72	68	64	55 ½	42	24	-
DECK	57	61	64	66 ½	69	71	72 ½	73 ½	74	74	74	73 ½	73	72	70	65	59	50	35	16
LWL	-	8 ½	43	55	60 ½	65 ½	69	70 ½	71 ½	72 ½	72	70 ½	66 ½	62 ½	57 ½	48 ½	38 ½	25 ½	12 ½	-	-
WL –III	-	-	-	22 ½	40 ½	50 ½	57	61 ½	64 ½	66 ½	65	62	59	53	46	36 ½	26	18 ½	8 ½	-	-
WL-II	-	-	-	-	13	22 ½	22 ½	32 ½	41	47 ½	51 ½	52 ½	49 ½	44 ½	36 ½	30	23 ½	16 ½	11	6 ½
WL – I	-	-	-	-	5 ½	9 ½	13 ½	17 ½	22	24 ½	24 ½	23 ½	21 ½	18	13 ½	10	6 ½	5	-	-	-
KEEL	-	2 ½	3	3 ½	3 ½	3 ½	3 ½	3 ½	3 ½	3 ½	3 ½	3 ½	3 ½	3 ½	3 ½	3 ½	3 ½	3 ½	3 ½	3 ½	3 ½

All Measurements are given in inches
Vessel parameters
Length over all --- 43' 6" Depth moulded --- 6' 0"
Load Water line --- 38' 8" Draught --- 3' 10"
Breadth --- 12' 4" Distance between water plane= 2'
Distance between each station is 25¾"

Procedure:

• With help of a T-square draw a reference line.
• Draw a centre line at right angle to the reference line.
• With reference to the given data mark the stations to a given distance on the reference line.
• From the centre line mark nine stations towards aft side and nine stations towards forward side (i.e. distance between each station is 25 ¾ ").
• Locate the stations “19” and station – “1” towards aft and forward side respectively for a distance of 29".
• Draw the vertical lines from each station.
• With reference to the offset table readings mark the points on the above vertical lines for the respective stations (say keel line).
• Draw a smooth curve joining all these points to obtain the keel line.
• Similarly draw rabbet, sheer and deck lines.
• Locate the point on the centre line for a given draught height (i.e. 3' 10") from the top of the keel line.
• Draw a horizontal line from that point to obtain the load water line (LWL).
• Locate the points on the centre line for the given water lines
• (say WL-I, WL-II etc.) and draw the horizontal lines from the respective points.