Frames from the Loft Floor

Frame (v.)

Old English framian "to profit, be helpful, avail, benefit," from fram (adj., adv.) "active, vigorous, bold," originally "going forward," from fram (prep.) "forward; from" (see from). Influenced by related Old English fremman "help forward, promote; do, perform, make, accomplish," and Old Norse fremja "to further, execute." Compare German frommen "avail, profit, benefit, be of use."

Sense focused in Middle English from "make ready" (mid-13c.) to "prepare timber for building" (late 14c.).

This week marks the beginning of a lengthy and substantial process in the construction of the Maryland Dove: The beginning of framing the ship. Even a lay person in ship construction should be familiar with the series of core structural members to which we fasten planks to, called frames. The frames of the vessel attach to the longitudinal foundational backbone piece- the keel and are constructed of a series of smaller components called futtocks. In smaller ship construction we have frames that may be steam bent into a shell or over a mold sometimes called ribs, most commonly in smaller lapstrake or clinkerbuilt construction. On some vessels frames are cut out of grown timbers and are known as sawn frames. In larger vessels these large sawn frames are coupled in their sided dimension with another sawn frame and are thusly referred to as double sawn frames, precisely the method of frame building we will be using with the Maryland Dove.

It seems that historically, the term rib was used interchangeably with futtock. In ‘A Treatise on Shipbuilding’, c. 1620, a definition is given: “The futtocks or ribs of the ship are certain round pieces of compass timber swept out according to the mould of every bend”. During the early 17th century it seems that the practice of single sawn frames to have been more common, however large grown timber scarcity, as well as familiarity of construction in the double sawn style; has lead us to selecting this type of construction for our project.

The shape of the frame is patterned out from the loft floor using the body plan station lines which represent either the aft or forward face of the outside of the framing depending on if you are looking at the aft or forward projection of the ship in this particular view. Check out the previous post on lofting to get caught up on some of the terminology here. We use Scottish nails, trimmed finish nails, or registration sticks to transfer information from the lofting to the pattern stock. Scottish nails are simply nails to be used laid on edge with the heads trimmed into a triangular shape. The nails rest along the line to be picked up and the ply wood pattern stock is pressed into them to record the information. The taper from the keel upwards to the top of the frame is given by the architect and narrows substantially from 10” to near 4”; this information is battened off onto the pattern and the shape of our frame comes into view. After the pattern is made we have to record the rolling bevel along the frame. It should be understood that a ships frame has a bevel on the outside face to accommodate the planking as it bends across the shape of the vessel. This bevel is different closer to the keel or garboard strake than it is near the load waterline or sheer. Because this bevel changes inch by inch as you make your way along a frame we refer to it as a rolling bevel. The bevel degrees can be found in a few ways, two of which we have been using depending on the placement of the frame in the ship.

A square, bevel gauge, and bevel finder:

Our frames are 22” apart. If a square is projected upward normal to the station line in the body plan view and a straight edge is placed at the 22” vertical mark resting at the next station line. The angle created between the straightedge and the loft floor is the bevel to be recorded on the frame pattern. The image above is a simplification, when using this method repetitively a simple device is made which holds the square in an upright position to ensure accuracy and ease of use.

Another method is called “Magic Stick” and was the preferred method used by my mentor Bob Darr as well as his lofting mentor Jim Linderman:

A radius is drawn which represents the spacing between two frames (one can also be used, but two should give a more accurate bevel), in our case this radius is 44” as the frame spacing is 22”. An arc is drawn using our known radius and is boxed off to provide us with 1/4 the circumference of our circle. The circumference is found (π x d, 3.14 x 88) and equals 276.32”. This circumference is then divided by 360 which equals .767” or 25/32”. This gives us our incremental spacing to draw our degrees along the arc of 1/4 of our circle. When finished marking the degrees make sure that you have exactly 90. It might be helpful to begin by measuring out from each end, meeting in the middle. Then using a long straight edge you project the even degrees along the arc outward from the center of the circle to the y axis which is nearest the wooden “magic stick” in the image above. These degrees are transferred along the y axis and then onto your magic stick. In our case we only measured out every 2 degrees.

The magic stick is then brought to the frame in question on the loft floor where the 0 point rests and is laid normal to the line outward to the frame two spacings away. Whichever number is closest to that frame is the bevel in degrees recorded in that particular area on your pattern. There’s some obviously some front end work here, but it turns our to be a substantial labor saving device.

Whichever method is used, the found degree is then observed on a bevel board cut to the width of our futtocks, in our case 3 1/2”. The space between the top and bottom of the bevel is recorded on the side of the bevel board and represents how much material will be lost when cutting out our beveled profile on the ship saw. If an inch of material is to be lost on an underbevel than on the other side of the futtock you must add an inch to recover the loss so that each side of the frame remains the same dimension.

Our southern live oak futtocks are flattened on a router flattening jig and the bevels are cut using the ship saw with one person feeding and the other adjusting the bevel of the saw to the recorded degrees. The frames are treenail fastened on a large floor called the horning floor. Horning is the process by which frames are aligned to assure that they are level. We will have more on frame construction in the coming weeks. Below you will find an example of the kind of material that we cut our futtocks from as well as the flattening jig that we have rigged to our bandmill.

Till next time!

SH