Thus it becomes necessary to manually draw the shape of each frame. How to
do this is described below, using the information in the Lines Drawings and the
Body Plan.
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| Single & Double Frames
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| "molded" and "sided" sizes
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I suppose the greatest difficulty likely to be experienced by the average model
builder on his first attempt at a plank-on-frame job, will be the fact that the
Lines Drawing will have to be adapted to suit this type of construction, since
he will have to make his own templates for the frames, but this is not the
formidable task it may at first appear, in fact it is really quite simple. The
most common frame spacing for a model of a merchant ship will be what is termed
"room and space", whish means that the space between any two frames is equal to
the thickness of the frame, this applies whether tile frames are single or
double. (Sketch No. 1) The two dimensions of the material forming a frame are
known as the "molded" and "sided" sizes, (Sketch No. 2).
It will be obvious that with frames so closely spaced it would be impossible
for any Lines Drawing to show the shape of them all, since the variation
between one frame and the next, particularly in the centre of the ship,
together and become a. solid mass. For this reason the cross-stations on a
Lines Drawing are usually placed at intervals convenient for the displacement
calculations and may have no relation to the position of the frames, and even
if they do fall on any Of the frame stations, there will still be quite a,
number of frames to be filled in between them. All the same, whether they fall
on any of the frame stations or not, all the information necessary for finding
the shape of every frame in tile ship is already in the Lines Drawing and can
he found by a little of the most elementary draughtsmanship, and with no other
instruments than a pair of compasses and a straightedge.
At this stage we will forget the thickness of the frames and the method of
deciding the frame spacing, and confine our efforts to "lifting" the frame
shapes from an ordinary Lines Drawing in which the frames do not correspond
with the station lines. On your Lines Drawing, the Sheer Plan (showing the side
view of the ship) and Half-breadth Plan (showing the shapes of the various
waterlines) will be placed one above the other, with the station lines
"fairing" through. We will assume that your frames are to be at 1/2 in.
centres, so along the uppermost -waterline in the Sheer Plan mark off 1/2 in,
intervals on either side or the midship station, do the same along the
centerline of tile Half-breadth Plan, and then rule lines through these dots
right across both Sheer Plan and Half-breadth Plan, just as the station lines
of the original Lines Drawing do. These lines you have just drawn represent
one face or each of your frames. At the extreme end of the ship where the
waterlines taper into the stem, frames fitted at right angles to the
centerline, like those just drawn, would have too much bevel on their outer
surfaces to be of much use, so at this point the frames will be arranged at
varying angles to the centerline and are known as cant-frames, but these can be
ignored for our present purpose which is merely to show how the shape of a
frame, either cant or square, can be lifted off the Lines Drawing.
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| Underhill's Sketch No. 3
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The next step is to make a tracing of the "grid" of the Body Plan, that is to
say, the vertical centerline, the vertical buttock lines (A.B.C.D. in Sketch
No. 3) and the horizontal waterlines, drawn full width of the Body Plan. Place
the needle of your compasses at the intersection of the centerline and the
frame you wish to "lift", on the Half-breadth Plan, and measure to where this
frame crosses the uppermost waterline. Place the needle of your compasses at
the intersection of this waterline and the centerline on your tracing of the
grid, and mark the distance on either side. Do this for each waterline in turn.
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| The rabbet of the keel, or rabbet-line
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Now move to the Sheer Plan, and from the base line, which will usually be the
rabbet of the keel, or rabbet-line (Sketch No. 4), measure up to where your
frame crosses the first buttock line ("A", Sketch No. 3) and transfer this to
your tracing on both sides of the centerline. Do the same for the remaining
buttock lines. Next measure from the rabbet line up to the rail and mark this
on either side of your tracing, also from the rabbet line up to the deck line
or the level of the wale according to the type of ship to be built, and
transfer this to your tracing in the same way and rule lines right across. On
these respective rail and deck lines mark off the width of the vessel at these
levels as shown on the Half-breadth Plan, and your tracing will have a series
of dots as shown in "A" Sketch No. 3. Join up the dots, as "B", and when this
has been done on both sides, you have the proper outline of the frame you have
selected. On this tracing you will now add the internal shape of the frame and
also the bevel, but these points I will cover later, in the meantime I only
wish to show how the various shapes are transferred from the Lines Drawing, on
which they do not originally appear. Marking off the rail and deck or wale
lines from the Sheer Plan is very important, for on the accuracy of these
levels will depend the sweet run of the sheer of the ship.
Having outlined the general principle of lifting off the frame outline, we will
now take this a stage further and show how the complete frame, including
bevels, can be taken off, and for this purpose we will assume that we are
building a model of the brigantine Leon, plans of which are published here.
We will assume that the Lines Drawing in possession of the model builder is
drawn to the inside of the planking--in many cases it will not, but I deal with
that later--in which case the rabbet line of the keel (Sketches No. 3 and 4)
will form the base line as already described. In Leon, a small merchant ship,
the timbering is not quite "room and space", and on the size of model shown in
the plans the sided size of the frames is 1/8 in. while the space between them
is 3/16 in., making a total of 5/16 in., for a frame and the space to the next
one, so the first task will be to rule lines across both Sheer Plan and
Half-breath Plan.
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| Spacing of frames
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1/16 in. on either side of the midship frame (Sketch No. 5),
which will represent the thickness, or sided size of the midship frame. Now on
either side of the midship station on both Sheer Plan and Half-breadth Plan,
set off points 5/16 in. apart, goings right aft to the stern, but forward only
to where the bow starts to taper in sharply, beyond which cant-frames will be
required. In Leon this is station No. 3, as shown on the Lines Drawing Plate
No. 1. One word of warning here, although it will not be needed by anyone used
to setting out equal spaces such as this. When marking out these 5/16 in,
spaces, do not measure the first .5/16 in., then move the rule along and
measure the next, in this way you are almost certain to develop a slight
"creep" in your measurements. Hold the end of your rule on the midship line and
then mark off 5/16 in.; 5/8 in.; 15/16 in.; 1 1/4 in.; 1 9/16 in.; and so on,
keeping the end of the rule fixed on the starting point all the time, in this
way, should you make a fractional error on any of the measurements, it will he
corrected by the next, and not carried forward as would he the case if the rule
were moved along from point to point. In the same way, do not use a pair of
dividers or compasses to "step" off the distances, for ii is surprising how one
can get out of truth by such a method. It only needs tile point of the needle
to find a pin hole in the drawing board, or grain in the bench, to throw the
spacing out, and this error will be carried forward.
Having ruled the lines representing the faces of the frames across both Sheer
Plan and Half-breadth Plan, measure forward 1/8 in. of all lines in the fore
part of the ship, and aft of all lines aft of the midship section, and rule
these lines right across both plans. You now have the sided size of all frames,
except the cants, drawn in on your plan, and it will be seen that all your
frames in the forward part of the hull are forward of the station lines, and
all those in the after body of the ship, aft of the station lines, the reason
being that tile ship tapers toward the ends, and you want to be able to trim
the taper or bevel off the edges of your frames, not add it on.
Now that all the thwart-ship frames are drawn in, the cant-frames can be added.
Your Lines Plan will show the thickness of the keel, but if this does not run
back from the stem, then extend it as far as your last square frame. Now from
the outer end of your last square frame as shown on the Half-breadth Plan,
divide the outer line of the deck into spaces approximately equal to the
spacing of the frames in the rest of the hull, i.e. 5/16 in, in the case of the
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| Cant Frame location
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1/8 in. scale model of Leon. (Sketch No. 6) and from these points draw in the
cant frames so that their outer faces are about true to the run of the
planking. The sketch referred to and Plates No. 1 and 2 will make this clear.
These frames will of course not run sight across the s2lip, but be fixed to the
dead-wood---the solid timber joining the stem to the keel.
All the frames are now lined off on the plans, and the "drawing office" work is
complete, so we are now ready to start on the actual construction of the model.
Seen in print this "drawing office" stage may appear rather complicated, but,
as the reader will find when he comes to put it into practice, it really is
extremely simple, and when once the basic principle is understood it will not
offer any difficulty.
However before going on to the practical work, it may be as well to add a few
words on the subject of building a model for which plans of the right scale are
not available, and which have to be either enlarged or reduced. This, since the
frames have to be lifted off the Lines Drawing in any case, offers no
additional work, and it is as easy to enlarge or reduce the size during the
construction of the model as to build to the same size as the drawings, for
unlike the laminated or solid block model, it is extremely unlikely that there
will be any moulds or templates which can be traced direct from the plans,
except perhaps the curve of the stem.
If you do intend to work to a different scale to that of the plans, then It is
well worth investing in a pair of
draughtman's proportional dividers,
such as
can be obtained from any shop dealing in drawing instruments. These dividers,
Sketch No. 7, are double-ended and pivot on a central screw which slides along
a graduated scale on the body of the instrument. Moving this screw up or down
the scale varies the relative opening of the points at opposite ends. Different
graduations are available, but the most common is that which indicates the
number times the wider end is greater than the smaller. Thus if the screw is
set to "3" on the scale the ratio between the two ends will be 3 to r, so that
if the small end is opened to 1 in., the points of the other end will be 3 in.
apart. The marking of the scale is however not really important, for any ratio,
no matter how unusual, can always be obtained by trial and error. For example,
if you should want a ratio of say 1 5/8 in. to 1 in., which is extremely
unlikely, it is only a matter of setting the points of the small end to 1 in.,
and moving the screw along until those at the other end are at 1 5/8 in., and
clamping it at that, after which any measurement taken by the small end will be
reproduced 1 5/8 times larger at the other
The use of this instrument in say enlarging your model is obvious, simply set
the screw at the enlargement you require, measure from your plan With the small
end, and set out the work with the other. If you are reducing the scale, then
the dividers are used the other way round, measuring with the large end and
setting off the work with the small. These dividers can also be of the greatest
assistance in setting out the: run of the planking, but of that more later.
I mentioned the stem as being something for which you would not have a full
size template in the case of a model to a different scale to the plans, but if
you can enlarge the frames, you can, obviously, enlarge the stem in the same
way, the only difference being that it is not covered by a grid as in the case
of the frames. However all you have to do is to rule a grid over the stem on
the Sheer Plan, any kind of grid will do, you need not even measure it, for you
will enlarge it by means of the proportional dividers, then take off all the
vertical dimensions where the curve of the stem crosses the vertical lines and
transfer them to the enlarged size on your new grid. Do the same with the
horizontals, join up the dots and you have the enlarged outline of the stem.
This same principle can of course be used for enlarging any curved surface
throughout the whole plan, also in making deck fittings, etc., it is only a
case of measuring them on the drawing with one end of the instrument, and
setting them out directly on the material to be used with the other.
So, let's actually lay out a frame.
Using the dividers, we'll transfer the point, where waterline 1 crosses
the aft side of the frame (red line), from the Half
Breadth lines to the Grid drawing, and mark that point on the corresponding
waterline, both port and starboard. Repeat for all the other waterlines.
Connect the lines. We now have the shape of the aft side of the frame
(Blue line).
As one approaches the bow and stern, the bevel on the frames gets increasingly
steep. Since the trunnels used to attach the planking are driven perpendicular
to the planking surface, they will be traversing square frames at an angle.
Also,
We'll need another Grid to plot the Cant Frame. The first thing we measure is
the distance from the centerline of the keel to each edge of the tenon (along the side
of the Cant Frame), and plot that onto the Grid.
We now measure the distance from the centerline of the keel to each of the
waterlines, and plot those onto the individual waterlines. Repeat with the deck
and rail. Now connect the dots, and we have the shape of this Cant Frame.
Note that there is very little bevel on the outside edges; we've instead
imposed that bevel onto the tenon.
{John O. Kopf}
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