Preview: How to Build a Caledonia Yawl, Part 4 – Building Frame & Molds

10 Responses So Far to “How to Build a Caledonia Yawl, Part 4 – Building Frame & Molds”

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  Charles Neuman says:

  Hey, what’s the name of that tool at 3:53? It allows you to line up with a mark on one side of a piece of wood and then continue it to a perpendicular face of the same piece of wood. Basically it’s just a right angle. Not necessary, of course, but it sure seems convenient. I hate it when I use a square on one side and try to line it up with a line on the other side and it comes out a little off. It wouldn’t do that with this tool.

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    Geoff Kerr says:

    I know it as a “saddle square” Pretty common in the house framing world. I probably picked mine up from Veritas…

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  Marinus Veenman says:

  I’d be really interested in learning how to make my own molds. Can you point me in the right direction?
  Thanks!

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    Geoff Kerr says:

    Mold making fall into the mystical secrets continuum starting with plans and offsets and then lofting to produce faired, full-sized sections for each mold. One then must transfer those shapes to mold stock. In the world of texts and manuals I like Stewards “Boatbuilding Manual” for its clarity and brevity. I will say that lofting falls right in there with spiling as among the skills most difficult to learn from a text. I suggest finding a course or workshop to see it done hands on. Even a day long workshop will save hours of puzzling. I highly recommend the courses at The WoodenBoat School in Brooklin, ME. Note that in this day and age many small boat designs/plans include full sized patterns for the molds.

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      Charles Neuman says:

      I was just going to ask about making molds. I notice two versions of the CY sold at the WB store (one version has four planks per side and the easier version has seven planks per side). Both say “no lofting required”. I don’t know if that means “full sized patterns”. It could mean that enough dimensions are given to be able to create the full sized patterns just by measuring and marking. In any event, it seems it’s possible to avoid lofting or buying pre-cut molds.

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        Charles Neuman says:

        R.e. numbers of planks: I just did some checking. The CY built in these videos appears to have seven planks per side. Looking at Video #1, it looks like Ned Ludd and the other one shown in that video have four planks per side, if I’m counting correctly. Any comments on the differences?

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          Geoff Kerr says:

          The original version of the Caledonia was four planks per side. After several years a builder commissioned Iain to redraw it as a seven plank per side boat, on the longstanding principle that more, narrower planks makes a lapstrake boat look “finer”. The seven plank version is the one that has been digitized and is therefore the version for which Hewes is able to CNC cut molds and planks.

          I continue to build the four plank version in my shop. I am not alone in thinking that the seven plank hull is no better looking, and indeed, I think the seven plank stern is far less distinctive and powerful looking. The overall hull shape is barely different between the two, and any other details that were changed are of little consequence. Probably the most important detail to attend to is to keep track of which sail plan you order from the sailmaker…they differ slightly. With a deftly drawn sheer stripe the four planker is indistinguishable from a bisquit toss distance. Should a client ask for the seven planker I’d be happy to do it, but 22 boats under my belt no one has ever demanded it.

          “No lofting required” means in this case that Iain supplies full sized paper drawings of the molds and stems. The molds are half breadths, so it takes a bit of careful manipulation and transfer to produce symmetric molds, but those challenges are half the fun. There is a little addendum sheet that must be taped to one end of the fwd stem drawing to make the paper bigger, but again it is perfectly logical. Old school boatbuilding would suggest if you don’t loft a boat you are asking for trouble down the road. In this specific case I can vouch for the accuracy and fairness of Iain’s impeccable drawings… you will still have to understand moldmaking, work accurately, and set them up correctly.

          Or you could order a boat…..

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            Charles Neuman says:

            Thanks for your insights. It did notice that the paint job makes the sheer strake look like two. So there isn’t that much difference from afar.

            “Order a boat…” Ha! That actually makes too much sense. I have no response other than, “But then I couldn’t build one.” It shows how irrational this whole thing is.

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  John Hughes says:

  When they re-set that frame to make it vertical, it’d be nice to mention that it’s a good idea to shoot the screw through a NEW hole from the bottom of the brace into the strongback: if you use the old one, the screw may choose to find its way back into the old hole and pull things out of line, esp. if you’re trying to adjust only a sixteenth or so. It’s also not a bad idea, if you’ve got two people, to have EACH of them have a tape measure, so that you don’t end up warping the frame by adjusting one side more than the other. In fact, it’s also not a bad idea to cut a stick that’s a bit more than the length you need (for, say, 29″, you cut a 32′” stick). Then tack a piece of plywood that sticks out a bit at 29″, so that you’ve overall got an “L” shape where the foot of the L is very short. Now you never ever screw up and measure 28 instead of 29, etc. — this stick becomes your absolute standard. For a job like this boat, it might not be worth it, but for any repeated measurement, sticks like this are really useful.

  Last but not least: when you make a strongback like that, there’s no use in truing it up unless the lumber you use is pretty decent…which is hard to get at the local big box store, and expensive at the fancy lumberyard. I prefer to build the strongback out of 3/4″ ply (which often IS cheap at the big-box store), sawn 8″ wide, say, and then laid up to double thickness with the seams offset, glued and screwed. That gets me a very clean and straight edge that’s not very likely to move with changes in temperature and humidity.

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  Lee Fox says:

  Great job on showing how to build the frame and set the molds in place on their stations. Thanks!