HOW TO ROOF A CIRCULAR BAY. The trouble that one carpenter had with such a job work ing "by rule o' thmnb" is well illustrated in the following letter.
"I executed a piece of work last week which acci dentally proved satisfactory to the contractor I am work ing for, but not to myself. Not knowing the proper way to go about it, I had a deuce of a time and worried myself half-sick.
"The job in question was framing a roof over a circu lar bay window, as they are termed here. The window had a radius of 15 feet, with a projection of 2 feet 6 inches and a rise at the center of 1 foot 6 inches. The roof was sheathed and covered with tin.
"The way I went about it at first was to strike my 15 feet radius, and then lay off the rise at center, allowing for projection. Next I struck the radius of my roof, which was 19 feet, something—do not call to mind just what it was. By doing so I expected to get the true rise and run of my rafters. The rafters were spaced on 32-inch centers—that is, I spiked my lookouts on every other joist, and set my rafters on top of them. I spaced off my drawing 32 inches, commencing at the center and working each way. Then took the run and rise of each rafter separately and cut them, but when I commenced to put them up something was wrong. The first. or center rafter, was all right and the others were wrong. I felt awfully cheap, but of course the work had to be done, and not knowing any better way than by the old, old fashioned one, or the rule of 'thumb,' I finished my roof that way. It looks all right, I suppose, to most people outside of a good practical man, but I am not satisfied. The chances are I will have more of the same work to do, as they are getting to be quite the style.
"If it is not asking too much, I certainly would esteem it a great favor if you would, or eould, afford the time to enlighten me as to the simplest method of executing the above described work." The above letter is printed in full, because it is clear-cut and shows that the writer is after information pure and simple. He admits his error, and is anxious to avoid a like occurrence in the future. His frankness in the matter shows that he is on the right track to better fit himself for his work and give value received to his employer, with a good share of interest thrown in.
We are all given to mistakes; and from one another's experience we gain our knowledge for paving the way for still others to follow.
To the experienced, such questions may seem simple and a waste of words in the way of explanation, but all such should remember that they too were once groping in the dark for information just as thousands of others are to-day; and so it will ever be.
The great trouble experienced by the would be learner is that he does not stop to think that is, of the rules of application or relation of one part to another.
Take, for instance, the above example. If the bay window had been a full half-circle, this man would without hesitation have framed his rafters the same as for a circular roof—all of same length and radiating from a common center; but when only a fraction of the roof is wanted, he forgets that the rafters must lie in the same position as for the half-circle bay. In one case, the wall line of the house, as it were, cuts through the center of a circular conical roof; while in the other, it cuts off only the edge of the roof. Therefore, being a part of the same roof, the seat and plumb cuts must be the same in either case; but not being whole rafters, they must be considered as jacks, and therefore need a side cut, with the exception of the center, which is No. 1 in Fig. 63. The others of like numbers, will be rights and lefts, and may be obtained with a bevel square provided it is paralleled with seat cut line or at right angles—square out from the plumb cut.
For work of this kind, it is better to lay out a full-size diagram of such parts as are required, on a level space, to get the measurements as shown in Fig. 63. The plan shows the indi vidual run of the rafters as A-1, B-2, 0-3, etc. The elevation shows the rise of same, as 1-1', 2-2', 3-3', etc.; and the stretch-out of their lengths, as a-1', b-2', c-3', etc. This part shows the shape of the boards for the covering. The elevation also shows the curve the roof has at the intersection of the wall; however, this part will not be a true circle as our friend tried to have it. This should cause no worry because it will take care of itself, provided the rafters are cut to the right length and placed radiating to a common center. Further explanation, we trust, is not necessary.