Construction Plan

Construction plan

The Westlawn scantling plan is a series of calculations based upon the constant C which is derived from the length overall (LOA) and the extreme beam (EB) using the equation (sqrtLOA +EB)/16. That constant is then applied in other equations to determine the scantlings. Suffice it to say that what you get is this,

PART                                                                      SIDED                                        MOLDED
PLANK KEEL                                                      0-1-2-0                                           0-2-4-0
UPRIGHT KEEL                                                  0-2-4-0                                           0-3-1-0
STEM                                                                    0-2-1-1                                           0-3-6-0
HOG                                                                      0-0-6-1                              KEEL PLUS 2 TO 2.5 IN.
TRANSOM                                                           0-0-7-1
BENT FRAMES                                                   0-0-7-1                                            0-1-2-0
BENT FRAME SPACING                                   0-7-4-0                                            0-0-0-0
FLOOR TIMBERS                                               0-1-2-0                                            0-3-6-0
SAWN FRAMES (SIDE) HEAD                         0-0-7-1                                            0-1-7-0
HEEL                                                                    0-0-7-1                                            0-4-3-0
SAWN FRAMES (BOTTOM)                             0-0-7-1                                            0-1-7-0
SAWN FRAME SPACING                                  1-8-0-0
DECK BEAMS (UNDER WALKING AREA)    0-0-6-1                                           0-1-2-0
SINGLE PLANKING                                          0-0-5-0
DOUBLE PLANKING INNER                           0-0-2-0
DOUBLE PLANKING OUTER                          0-0-3-0
CHINE                                                                  0-0-7-1                                            0-1-4-1
SEAM BATTENS                                                 0-0-3-1                                           0-0-7-1 OR MORE
CANVAS COVERED DECK                               0-0-5-0                                           0-0-0-0
CABIN ROOF BEAMS                                        0-0-5-0                                           0-0-7-1
CABIN ROOF (NOT WALKED ON)                  0-0-3-1                                           0-1-7-0
STRIP DECK                                                        0-0-6-0                                           0-0-7-1
CABIN SIDES                                                       0-0-6-1
CLAMPS AND BILGE STRINGERS                  0-0-6-1                                           0-1-7-0
ENGINE BEDS                                                     0-2-4-0

which reads in feet-inches-eigths-sixteenths. The reason there is no molded for the engine beds is that that measurement depends on the motor.

Hang on, I can hear you say, what does sided and molded mean? Sided is width and molded is depth. Except for the hog where the opposite is true.

We now have to apply that to our design.

You'll notice that the suggested spacing here is 20 inches whereas our station spacing is 15 inches plus a bit. I like to start the spacing from station 5 so we copy our lines drawing and erase the station lines except for station 5 and draw in the frame spacing remembering that the station line at 5 is the centre of the frame at 5.

The sawn frames, which is what we're using, are sided 7/8 plus 1/16 near as all get out to an inch so we'll heft up to an inch.

You will recall that I said from here on in I would be doing all the drawing in the CAD program and here's how you do it.

At the intersection of the waterline and station 5 draw two circles, one a half inch radius and the other a 20 inch radius. The first gives you your frame siding and the second the frame spacing. Draw two parallel lines through the intersections of the 1 inch circle and the waterline, then copy those two lines to the intersection of the 20 inch radius circle and the waterline and tell the program you want 4 copies, do that in either direction and you end up with this.

You'll want to tidy the drawing up and move the frame at the bow back about 4 inches and the frame at the stern forward about the same amount to get this.

There you have your frames all laid out.

I do the stem next and then the transom and then work aft from the bow as this is how I build an actual boat.

Our scantlings show the stem as sided 2 1/8 th and molded 3 6/8 ths. This is can be easily constructed out of three pieces of 1x4 glued together with a filler piece glued to the after edge. Using this form of construction allows for a constructed knee integral with the stem. For example,

However, having said that, you can draw what you want but the builder will build it their way unless they're an absolute novice. Be prepared for questions if they are.

The transom is 7/8 ths and a sixteenth, again close to an inch, up is better than down so 1” ply for the transom. And again the built up knee for the transom. 

 

Then the bottom frames go in, sided 1”, molded 2”. From frame 5 forward, forward of the side frame and from frame 5 aft, aft of the side frame, like this,

You'll notice that I show the bottom frame at the final aft frame let through the transom knee and the one forward above the stem knee, this is the way I build it, others might do it differently, that's up to them.

Next time we'll talk about chines, gunwales and stringers.