Preview: How to Build a Caledonia Yawl, Part 34 – Milling the Wood For a Birdsmouth Mast

33 Responses So Far to “How to Build a Caledonia Yawl, Part 34 – Milling the Wood For a Birdsmouth Mast”

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  Munroe Scott says:

  I am wondering if an alternative method of preparing the staves would be to cut the birdmouth first, and then tack a batton onto the stave in line with the taper. When that is prepared, set up a raised fence on the tablesaw that will be at the right height to hit the batton only. Setting the fence so that it is directly in line with the blade, cut the stave running the batton along the fence. This will provide a nice steady cut and feel safer than freehanding it. Just make sure there is a splitter behind the blade to ensure that offcuts don’t ride up the back side if the blade and get shot out under the raised fence. I’ve seen that happen and its not pretty. It goes like a bullet. The next staves can be cut using the first stave fastened to the top instead of a batton. This ensures exact duplicates.

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    Munroe Scott says:

    By the way…I am building Vivier’s “Ilur” sailing dinghy.

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    Geoff Kerr says:

    I’ve adopted a version of what you propose after a visit to a very accomplished builder across the border in Quebec. He had been a commercial cabinet maker for years, and was a far more accomplished table saw wizard than I will ever be. His suggestion was to make a pattern of the tapered stave and use that tacked to the stock rather than a batten. This eliminates having to repeatedly lay out the taper, and allows you to tack the straight side of the pattern to the straight side of the stave stock, making alignment pretty simple. His raised fence was much as you describe. This is a far more efficient and accurate system.

    I still cut the bird’s mouths after tapering, I guess to reduce the handling of those vulnerable cut edges, but I doubt that really matters.

    Finally I have built ILUR twice, (love that boat!) and used this systen for her masts,

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  Ang Roberts says:

  Geoff,
  In the video you mention the mast is tapered a good bit from the partner to the base. Could you tell me what the base diameter (where the tenon is installed) of the mast is on the Caledonia? Ang

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    Ang Roberts says:

    Geoff, In addition to my question above… What’s the reason for the taper at the bottom of the mast? Ang

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      Geoff Kerr says:

      I am going to default to the position I voiced in February: I’m not a designer, not an engineer, just a builder. I think the Caledonia main tapers from apprx. 3 1/4″ at the partner to approx 2 1/2 at the butt.( I’m not near my shop and the drawings at the moment). My artisan brain understands the max diameter being at the partner on an unstayed mast, and also it makes sense that it would taper to the top. Perhaps tapering to the butt is purely aesthetic, and I imagine an ounce or two of weight are saved.

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        Ang Roberts says:

        Geoff,
        Thanks again for indulging me with your artisan brain and answering my questions! Again, I can’t thank you enough for your help, and most of all the videos you’ve made that inspired me to go outside my comfort zone. Ang

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  Jaren Peterson says:

  Any thoughts on where to put the halyard sheaves? On the spars plan for the Gunter Sloop mast it shows them internal to the mast. Is this advisable with a hollow birdsmouth mast? Or would you want to use some kind of mast band/ring assembly with external blocks? Thanks again for the great videos! I’m 4 years in and finally getting to the spars!

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    Geoff Kerr says:

    I have lately been putting internal sheaves into the masthead of lug rigged Caledonias, mortising into the plugged section at the top and cutting an over width mortise, then lining it with pieces of 1/4″ plywood for reinforcement. It is a bit involved but works like a charm. I have built the jib headed gaff rig one time, and on that rig i hung the halyard sheaves and shrouds and such from through-bolted s.s. tangs. It all worked well and looked shipshape. I really liked that rig in the boat…hope you do too.

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  Ang Roberts says:

  Geoff,
  My brother, on the west coast has built a 14′ Pygmy Wine Glass Wherry and wants to convert it to a sailboat. Pygmy only offers a diagram of a Sprit rig with 55 sq. ft. or a Marconi rig with 42 sq. ft.. with no mast dimensions or placement. I’m taking on the project here on the east coast building the mast, center board, and tiller/rudder. We would like to use the Marconi rig with a birds mouth mast, with a solid boom, and we’re scratching our heads trying to figure out how tall a mast should be with approximately 42-50 square feet of sail. This boat only weighs 90lbs. and we’re not sure if a birds mouth design is overkill, even though we love the design and time is not an issue. Are there any formulas to go by in guiding us to a safe and practical plan?

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    Geoff Kerr says:

    I fear I am not the person to help you here. I am definitely not a designer, just a guy who builds from plans. I took a peek at Pygmy’s website and wonder if you have missed a detail or two ( or maybe even a page?) in their instructions and plans? Their description of the kit certainly implies that the needed details are included. If not they should certainly respond to a request for help.

    I generally build birdsmouth spars if above 2 1/2″ diameter, and solid if smaller. I’d certainly guess your mast will be smaller.

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    Gil Rhoads says:

    Just finished building a Phil Bolger cartopper sailboat, approximately 90 lbs and I bought a leg-o-muton, 60 sq ft. sail from polysail.com. Great guy to deal with! Building a 16ft hollow mast sheathed with 6 oz. fibreglass. I built it with four tapered 3/4 ” boards and overlapped the one side. Look at the Chase Bank logo. Mast is 2-3/4 at bottom and tapers to 1-1/2 at the top.

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  Damien Brockmann says:

  These are the best videos on birdsmouth spar construction that I have found on the web! I really appreciate your website (and wish that I had found it earlier..)

  A friend and I are completing construction of our first wooden boat – a 17′ ketch – using stitch and glue. We’re not the most skillful of woodworkers, but we have the epoxy thing down. We’re on to working on the two masts and have come to loggerheads over which method to use.

  I would like to use the birdsmouth method like you’ve laid out here; my friend thinks that it would take too much time, and would rather just glue some 2×4’s together to cut and sand down to size – what we call the “block” method.

  Our main mast is 21′ long and has a base diameter of 3″, tapering to 1 3/8″; the mizzen mast is 20′ long with a base diameter of 2 3/4″, tapering to 1 1/8″. In your video, you say that the efficiencies gained from using the birdsmouth method begin at around 3″ in diameter. Well, my friend and I have interpreted that to mean whatever we want it to mean to support our respective arguments.

  So what say you? Are there downsides to using the “block” method to creating a mast? Would it actually be easier to cut it birdsmouth-style, even for a couple of newbies?

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    Geoff Kerr says:

    Ain’t life grand? Sounds like you might be building a Core Sound 17… if so it will be a fun boat.
    You are right at the crux here, and I routinely stick to the guidelines I spouted in the video. If this is a one off for you, I suggest you build the mizzen first, solid or glued up block as you described it. Then do the main with the same technique. If you build a birdsmouth you’ll spin your wheels getting set up, practicing, dry fitting, etc., and take longer to finish the project. Your solid main will only be a couple of pounds heavier, and in this size spar you’ll never notice it. Birdsmouth is an intriguing technique, and with practice just as fast as the alternative. With your self assessment of your woodworking skills maybe save it for the next boat, or a replacement spar someday…

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  John Brame says:

  Did not think to use the table saw to cut out the taper. I used the electric planer and small block plane to finish off.

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  John Brame says:

  I have just finished making a birdsmouth mast and yard for a Phoenix 111. Ripped up some old Douglas fir and did lots of scarfing (1:6). Turned out okay. Will make the boom solid. Enjoyed the birdsmouth process. Seemed daunting at first but soon got the hang of it. Would have been good to see this video before I got going. Alls well that ends well.

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  anthony hulse says:

  Why not convert the measurements to millimeters? Much easier to divide by 20% or 40%

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    anthony hulse says:

    And then I read your comment below, that after building a Vivier boat you were converted!

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  Robie Gardner says:

  Geoff,

  As I begin the process of cutting the staves for the birdsmouth constructed main mast, I see on your “cheat sheet” of dimensions, you have the distance between the station marks set at 30″, shortening the overall length to 17′. Clearly on the plans I have, the mast length is 18’6″. How does that 1.5′ effect the sail plan? Do you think Ian’s plans have to mast to tall? I’d like to know what your thoughts are on a shorter mast. Thank you.

  Robie Gardner
  Portsmouth, VA

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    Geoff Kerr says:

    It sounds to me like we are building two different sail plans. I recommend you build whatever your plans say. I have been known to add three inches to the original Caledonia lug rig main mast, but the 1.5 feet shorter you have discovered makes no sense to me. Make sure you have the right spar plan for the sail plan you think you want.

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  THOMAS ANDERSON says:

  In other type’s of glueup’s, it is recomended to alter or oppose the grain direction so they will “pull” straight. There is no mention of this in this video and series. Does that matter with this layup?

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    Geoff Kerr says:

    I do alternate by flipping four of the staves end for end before cutting the tapers. Seems like a good idea.

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  Rob Roy says:

  Another great video. Must say though… With all those laborious diameter calculations, I have never been so glad to live in a Metric country!

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    Geoff Kerr says:

    I now build them as a metric project! It only took one Francois Vivier designed project to convert me.

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      Tony Vink says:

      Hey Geoff, which Vivier boat did you build?
      Regards

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  Paul Hitchman says:

  Just noticed how thin your table saw blade was. I have the same Dewalt table saw with the original rip saw blade in. I was wondering how many teeth and the thickness and diameter of the blade? I’m guessing its some kind 90+ tooth square tooth blade. Please tell.

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    Geoff Kerr says:

    I fear that was a borrowed saw and blade. I recall it was a Diablo brand blade and fresh and sharp, but no details beyond that. At home I use a 10″ Delta contractor grade table saw with a Delta Industrial duty 24 tooth carbide tipped blade. When pondering blades and long cuts in large stock I’ve found thin blades challenging. Thicker blades seem more stable and a wider kerf keeps things clear and moving. Whatever the blade choice, sharpness is important. Find the local wizard and get good blades sharpened regularly, or replace a dull blade with a new one if the cost of sharpening vs. a new blade so indicates.

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      Paul Hitchman says:

      Cheers Geoff thanks for the reply. I’ve heard good things about the Diablo blades if you get the industrial carbide version and not the HomeCheapo versions BUT I’m finding it hard to find a European supplier and US purchases include a hefty 24% customs tax on the blade plus it’s delivery.

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  Larry Hall says:

  Where do I find part 35 of birds mouth construction?

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    Steve Stone says:

    Hi Larry. It’s coming soon, next week in fact. We’re releasing a new video in the Caledonia Yawl series every other week.

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  Marcus Taylor says:

  Thank you for an excellent tutorial and demonstration. Spars for an Atkins Willy Winship under construction are on my winter projects list. I’ll be trying the router bit and table saw to see which I like best. I’m using clear vertical grain Doug Fir. I’m looking forward to your glue up methods and tips.

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  Richard Schneider says:

  This is by far the very best and most understandable as well as applicable explanation of building birds mouth spars I have ever seen. Just watch this video and you can basically build a great mast. My compliments and thank you to Geoff and the staff at OCH for this video.

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  Mark Steffens says:

  I have built ten glued lapstrake boats including John Leather’s 17 foot “Oyster”. I wish I could have had these videos when I started as it sure would have saved me days of turmoil and frustration and kept me out of my ‘moaning chair’ as I struggled with the builds. It is nice to see that you also have used your fence on the table saw at some time as a sacrificial fence. ;’tis nice to know that I’m not the only one to have done that. Your videos are a wonderful legacy to leave to the boatbuilding community. I salute you, sir!
  Thanks.