Preview: How to Build a Caledonia Yawl, Part 21 – The Centerboard Trunk

21 Responses So Far to “How to Build a Caledonia Yawl, Part 21 – The Centerboard Trunk”

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  Mark Morgen says:

  I’m building a Caledonia Yawl right now and at the point of glueing the floors in. I see from the centerboard video that it looks like you don’t glue the #4 floor to the keelson. Just screw it to the mold in the correct location so you can attach the garboard and broadstrake to it during planking? Thanks, these videos are a real inspiration and guide.

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  Joshua Parker says:

  Geoff,

  So the keelson has a 1-3/8” slot for the centerboard, but the trunk has a inside width of an 1-1/2”. Am I missing something or does that create a small lip between the CB trunk and the keelson? I have watched the videos multiple times and the plans also confirm those measurements. Is there a reason they are not the same and doesn’t that make it hard to line them up when installing the trunk? Thanks for all the help!

  Josh

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    Geoff Kerr says:

    You are right in imagining that the two widths should match. In my boats and my plans that measurement is 1 1/8″. I do not have a set of plans for the seven strake model on hand.
    1 1/2″ seems absurdly large for a CB that is barely an inch thick…I suggest you check again, both with a scale ruler and looking for Iain to have spec’d the measurement in a note…

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  Genaro HERNANDEZ says:

  Great video. However, I’d like to ask, what kind of support do you use for the empty hull once it’s on the floor that would allow for one to be moving about inside doing the installation of the center board?
  Thanks!

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    Geoff Kerr says:

    It can be very simple. I suggest you collect a pile of of 2×6 scraps, perhaps 12-18 inches long. These could be salvaged from your now idle building jig. A stack of 3 or 4 under each end of the boat, a shorter stack under the cb slot, and stacks amidships at the outer edge of the garboard, shimmed and maybe padded as desired, and you will be able to clamber around. Alternatives are old tires or a purpose built cradles scribed and fit to the shape of the hull. The hull will be fine, but I caution you to make your support system stable…if it shifts while you are moving about both you and the boat may take a fall, and nothing good will come of that.

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  Richard Schneider says:

  I was taught a long time ago when building a centerboard case to make the posts long to extend through the keel to be cutoff after installation. This supposedly anchors and aligns the cast to the boat. Then again this was when we used resorcinol glue not epoxy.
  Is there a reason not to do that here?
  Terrific series that has convinced me to buy from Hewes and save myself a lot of time and frustration. For that I Thank You.

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    Geoff Kerr says:

    Traditional construction techniques usually depict extending the posts through the slot, and as you suggest it does allow for positive alignment and some intuitively solid structural support. However, legend suggests that every CB trunk in history has leaked, and if you look carefully at that arrangement that interface between the post and the bottom of the boat is a pretty slim surface for bedding compound or epoxy as the case may be It is also an impossible challenge to get compound into that seam. I like the comfort of being able to slather a good slug of thickened epoxy on the base of the posts and having that bigger surface area where they rest on the keelson well glued up.

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      Richard Schneider says:

      Great point, you are right they always at sometime leaked. Supposedly that was why they were bedded with compound not glued so they could be removed when they leaked. Thank you.

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  Paul Gill says:

  Geoff:

  I have set up my building frame and installed the molds. Everything was going swimmingly until I started double-checking the molds for accuracy. In checking the heights of the DWL from the top of the building frame, I discovered that they are all short 3/16″-1/4″. (The distance from top of the frame to DWL is supposed to be 27″.) I went back to the plans to see if I could find the error, and discovered that the error is in the drawings (sheets 6,7 and the stem patterns). I talked with the gentleman from Hewes who makes the CY kits, and he said there was no such error in his set of CY plans. I am concerned that there may be other inaccuracies in the plans. Have you ever encountered this problem in building CYs? I have built 4 previous boats from plans, and have never encountered such a problem before. Perhaps the error was introduced in the copying process. Thoughts?

  Paul

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    Geoff Kerr says:

    Paul, I don’t have any specific intelligence to offer you. In general terms let me suggest that it should be pretty easy to check your set of plans to see if the copy scale is right. Iain generally calls out needed measurements so you can put the ruler to them and see how they compare. Be aware that humidity can change measurements rather dramatically on paper plans. I wouldn’t spend a lot of time and anguish over the DWL measurement. As long as your building frame is reasonably true and you have mounted the molds accurately you have done what you can. If anything is wrong it will show up when you check the molds for fairness with a batten.Trial fitting the keelson will be the test. If it clamps in fair you are in business. In the finest tradition of the trade there is some point in every project where you have to build the boat in front of you…not the theoretical boat in the drawings…that is sort of the badge of being a boatbuilder .Carry on and enjoy the puzzle.

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      Paul Gill says:

      Geoff:

      You, Iain and Gardner Pickering are all of one mind about this, so I will proceed with a lot more confidence that the process will result in a fair and beautiful hull!

      Iain is sending me dyeline prints of the mold patterns, which will help as well.

      Thanks for sharing your Caledonian wisdom!

      Paul

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  Lee Fox says:

  Thanks OCH crew for this great video that demystify centerboard trunk construction and installation with great tips from Geoff Kerr! I’ve really enjoyed this series.

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  Tom Bolko says:

  Geoff, I am loving these segments of boat finishing. I spent a week with John Brooks, at The Wooden Boat School last summer. During week 2 which I did not attend the class began finishing Ellen. I won Ellen in the draw and picked her up last August. Ellen is 75% complete. I am using your expertise on finishing the Yawl as my guide to finishing Ellen. I am really looking forward to the next video. Thanks. Tom Bolko

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  John Trussell says:

  For moving around under a boat, I’ve found that a furniture dolly with a piece of plywood over it makes a workable crawler.

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  Bob McKay says:

  How many man hours start to finished product will it take to build this boat? Assume a some what experienced amateur.

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    Steve Stone says:

    Hi Bob. Here’s a page that should answer your questions regarding the building of a Caledonia Yawl, or the like.
    https://www.offcenterharbor.com/building-a-caledonia-yawl/

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      Bob McKay says:

      Thank you for the information.

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  Larry Cheek says:

  As with all the preceding episodes, I appreciate Geoff’s patient and immaculately detailed explanations here. I’ve also gained a fresh admiration for Iain Oughtred’s design work. At first I thought that ⅜” ply would be too light and flimsy for the trunk, but as Geoff put it together, I could see that the mahogany frame and exterior bracing would make the trunk exactly as strong as it needed to be without excess weight.

  One thing, though: I’m dubious about sealing the inside faces of the trunk with a single coat of epoxy. If there’s ANY piece of a sailboat that needs sealing like the very gaskets of Hell, it’s the CB trunk. At the least, I would seal it with three coats. Better would be to sheathe the interior faces with fiberglass or Dynel and epoxy for superior abrasion resistance. Another sealing scheme is to surface the trunk interior with waterproof kitchen countertop laminate. In these cases, the builder should widen the trunk dimension slightly to allow for the width of the extra lamination. Finally, any exposed plywood end grain, such as the pivot hole, should be sealed with even more extravagant care than the veneer surfaces.

  It would be possible to remove and replace a CB trunk that had rotted from inside because of moisture intrusion, but it would be an expensive, painful, nasty, incalculably miserable job. Spend another day and a couple of bucks’ worth of extra epoxy during the original build. It’s cheap and painless insurance.

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    Geoff Kerr says:

    You are correct in pointing out that there are various alternative strategies for armoring the inside of the trunk. The extreme I’ve witnessed is a friend’s traditional catboat with a bronze centerboard case. Some designers specify glassing the case sides, and indeed I have done that when a customer asked. My own experience is that it is unecessary. A good coat of epoxy, flowed on and carefully sanded smooth seems to suffice. Whatever philosophy you adhere to, just keep in mind that the spacer posts control the width of the trunk, so do your surface prep, then assemble.

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  Gustavo Krause says:

  Very nice! I like this sequence of videos!

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  Michael Seibert says:

  Perfect timing for this excellent video! I am just days away from gluing my Lightning centerboard trunk together and am feeling much better about that job after watching this one.