28-Foot Cabin Cruiser "Mollyhawk". Part III.
Briefly stated, the process of planking may be compared to the construction of a barrel. As the barrel staves are made wide in the middle and narrow at the ends, so is the yacht planking wider amidships. Just how wide each plank shall be you have to determine by bending a thin batten around one of the midship frames and dividing it up into such widths as your stock of planking will permit. For instance, if most of your cedar planking which the lumber yard has delivered to you will only allow you to get out a plank five inches wide in the middle without leaving bark on the edge, do not lay your boat for six inch planking. This distance, measured on the batten in inches, divided by five, will show you how many planks your boat will require. How wide these planks will be forward or aft at any other frame can be determined the same way, by dividing the length along the frame to be planked into the number of planks that are being put on amidships, which would probably give you something like 2 3/4 or 3 inches.
The top strake, or "sheer strake" as it is called, and two or three more below it and then the garboard or plank which goes next to the keel are generally fitted in first arid then the space between is divided up as previously described. To find the shape of the garboard requires what is called "spilling." In other words, it requires the spoiling of one plank which is generally a thin pine or cedar board about 3/8 of an inch thick. This thin board is used as a pattern cut roughly by eye so as to fit along the keel, and then, with a pair of compasses, set so as to span the greatest interval between the edge of the rabbet and the edge of this pattern, proceed to prick off a line of spots along the pattern, keeping one point of the compasses at the edge of the rabbet. By laying this pattern out flat on the one inch cedar board from which you are going to cut your garboard, and pricking these distances back you can readily see that you get a line of spots the same shape as the rabbet against which the edge of this plank must fit. This "spilling" process is repeated for almost every plank. The only ones that will not require it are the few on the flat of the side of the boat just under the "sheer strake."
You will hardly be able to get these planks all out of one length. Not many boats nowadays are built that way, but where you do have to use two, make the seam where the two ends meet come midway between two frames and then rivet their ends to an oak block fitted snugly between the frames about half an inch wider on each side than the planking, so that the plank above and below will lap half an inch over this butt block. Common sense alone will tell any man not to make all these butts in his planking come in a line in one spot between the same two frames, but to shift the butts as far apart as possible, using the long length of a plank forward in one case and aft in the next, so that at least two planks come between butts made in the same frame space.
There are few places in this boat where the round of the side is so pronounced as to require hollowing and rounding the inside and outside of a plank so as to make it fit against the frame. Aft, on the quick round on the counter and in the few planks that end in the hollow of the after frames this may be necessary. Never rivet a plank fast to the frame until its inner edge makes a perfect joint on the face of the frame. I know what you will be tempted to do. I have seen it done time and again, but those who did it always regretted doing so. That is to chisel off the face of the frame into a series of flats so that a flat plank will fit where it should be rounded. The result is the boat shows a series of ridges or if enough is planed off to make the plank show a smooth rounded surface the plank will be reduced to only about 5/8 or 1/2 inch in thickness, and as this is just where the fastening goes it is where the plank should have its full strength.
To fasten the planking to the frames use 2 1/2-inch copper nails rivetted over copper burrs, and to make a good job first bore a hole so the heads of the nails will sink in or be counter sunk about half an inch. These holes, after the nails are rivetted up, are to be filled with cedar or white, pine plugs dipped in white lead and tapped in over the nail heads, so that when the. planking is finally smoothed off all will show a clean wooden surface and she will not look like a spotted pig, as she will if the nail heads are left flush. This is only done in very light rowboats or racing boats where the thickness of planking will not permit of countersinking; there the nail heads are smoothed off with a file, but Mollyhawk is not a racing shell.
Along the garboard seams, in the ends of the planks and such places as under a clamp where it is impossible to rivet up a copper nail use 2 1/4-inch galvanized iron boat nails, but bore for them just the same. Do not try to clout them in with a hammer for if you do you may spoil a plank that has taken you considerable time to shape, due to the nail buckling over in the hard oak and splitting the plank.
When all the planking is on, calk each seam carefully with boat cotton spun out and rolled to suit the size of the seam and paint each seam with thin white lead paint. This will stick the cotton in and hold it while you proceed with the rest of the work and make the putty stick when you come to putty and paint the outside.
Molds of 28-Foot Cabin Cruiser "Mollyhawk"
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