As you might recall, the last thing I did on my new guideboat was to “get out the ribs” from the “roots” or flitches. I selected each flitch so that its grain followed the contour of the rib pattern as best I could. I then shaped the hull side of each one so that it matched the rib pattern as closely as possible. Now I must shape the inside of each of the fifty ribs that make up this boat.
I lay out the height of each rib, 3/4 of an inch, using a compass. I cut away the excess using my band saw. I then make final adjustments to the overall shape with a spoke shave.
The top surface of each rib is rounded off and the toe cut to the proper length. I like to shape the toe to form a “bull nose”. You can see the bull nose below.
I shape the bull nose running from left to right. It is easier for a right-hander to do it that way. You do want to be consistent each time you shape the bull nose. Once you start either left-to-right or right-to-left don’t change amid stream. Otherwise you will be unpleasantly surprised when you go to attach the ribs to the bottom board.
I use the following tools to round off the top of the ribs.
I use a Veratas spoke shave, a contour plane and my long board for sanding. I don’t mark off where the rounding begins on each side but do it by eye. You can mark it off with a compass it you like.
Here I am rounding off a rib.
Making the bull nose at the rib toe.
Finally the ribs are all finished and on a rack for holding them.
I was careful to leave the ribs longer than their final dimension. This is to accommodate any adjustments in the sheer line as the boat comes together.
I have always wondered how much weight each component of a guideboat contributed to its overall weight. I decided that this time around I would find out. I bought a small food scale for about $30 so I could weigh the ribs, stems and other such things. Here is a set of four ribs on the scale.
I found the average weight of all fifty ribs in this boat weighed 2.5 oz! I thought that was pretty extraordinary. The total weight of all 50 ribs was 7.9 lbs. This weight is on the high side since some of each rib will be cut off after the gunwale is installed.
I also checked the moisture content of the ribs.
Here I am using a moisture meter to measure the moisture content of a rib. All ribs that I measured came in around 7%. I had expected the moisture level to be higher since the flitches were all air dried. They must have been dried for quite awhile.
I also wanted to see how well I did matching the contour of the ribs to the grain in the roots. I took masking tape and marked off the grain direction a several points along each rib with a marker. Below are the results. The ribs are, right to left, number 0, number 8, and number 11.
As you can see the grain direction follows the rib contour quite well. Only down near the rib heel does it not conform very well. But this certainly shows how clever the early boat builders were in choosing spruce roots for the ribs of their boats. Because the grain follows the rib contour, the ribs are exceptionally strong. Not only that, but they are very light weight as well.
Next time I work on the stems.
Have you considered doing a stress test on scrap rib materials to compare a laminated rib to a rub cut from a knee? And have you heard of guide boat builders using any other species of tree knees, like tamarack?
Shane:
I would love to do a stress test of laminated ribs and compare the results obtained from spruce roots. I am sure they would be vastly different. I have found the spruce roots to be springy and supple whereas the the laminates are much stronger and very stiff.
I am wondering how rowing a boat made with laminated ribs compares in its “feel” to one made in the traditional manner with ribs made with spruce roots. I have been told that there is a difference. I guess that I will find out when I finish the boat I am building now.
Tamarack has been used for building guideboats. Josh Swan started a guideboat at the Adirondack Museum that used tamarack for stems and ribs. Allyson went on to finish it. As I remember tamarack was heavier than spruce and tended to split more easily.
Just a quick hello to Gordon and an apology for not staying involved in this blog and forum. But I still enjoy catching up when I can. I got sidetracked and I am now using my red spruce root flitches for something other than guideboats. Perhaps a sacrilege, but I am preparing to make a couple of cello tops from two of the flitches and I just completed what may be the first book-matched red spruce root picture frame. The cello tops are an experiment to see how the root wood compares to straight grained spruce that is typically used for violin making. I suspect the lightness and strength may offer a very interesting and probably very different sound. Regardless of the outcome, it will be a fun experiment. Even if the sound is no improvement over the norm, at least I will have a couple of unique and beautiful cellos. I hope all is well with you and your projects. Great work on your posts as well as your boatbuilding. Tom
Tom:
Thanks for logging in. Sounds fascinating! let us know how it turns out. Making a cello is something that would be way beyond me.
Gordon