Lee Boards

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  • David Geiss
    Sailing canoes, SOF kayak
    • Sep 2005
    • 554

    #16
    Re: Lee Boards

    Small world....... I know Zingaro and some of its owners (maybe different composition now). She's moored here in Barnegat Bay, actually Manahawkin Bay, off North Beach section of Long Beach Island, NJ. I have come up on her in my lateen rigged leeboard equipped canoe. IIRC, Zingaro is based upon Munroe's Egret. She's a lovely sight to see under press of sail on that lovely bay. As much as I like a single leeboard on a canoe, think it's safe to say that on a vessel of that size, twin leeboards is probably a requirement.http://web.me.com/geisser/Site/Photos.html#grid
    Last edited by David Geiss; 11-04-2011, 06:01 PM.
    Live and let live

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    • Nicholas Scheuer
      Senior Member
      • Aug 2006
      • 13579

      #17
      Re: Lee Boards

      One thing I like about the Leeboard on the Egret which KAIROS posted is the sweep of the leading edge. That sweep will maximize the area of submerged leeboard when swept way aft in shallow water.

      Moby Nick

      Comment

      • earling2
        Senior Member
        • Feb 2006
        • 1181

        #18
        Re: Lee Boards

        The leeboards on the Black Skimmer I built sold me on them, more or less. A (snooty voice) "proper leeboard" is canted outward so that it's close to vertical when the boat heels. That's a big advantage over daggers/centerboards/keels. Another nice thing about a big boat with leeboards is that the windward board, which (according to me anyway), ought to be tended every tack is about a 100 pound hunk of ballast as far out as it could go, while the leeward one is almost completely immersed and weighs quite a lot less. Win win. As for surface-piercing turbulence... who cares. It's a square edged sharpie with external chine logs that got most of it's speed from it's large, low rig. The bigger the boat, the less that kind of stuff matters as it becomes a progressively smaller factor in the overall scheme of things.

        Also use a leeboard on the Defender that I sail and that boat reaches hull speed pretty much all the time, on every point of sail, and it's close winded, so over all I have no complaints. (other than it's tender as hell because it wasn't ever meant to sail) That rig consists of one clamped-on leeboard for both tacks (though a lot of that boat's lateral plane is in the skeg in the first place).

        They're pretty OK in my book, but if I had the perfect boat, it would have a well-integrated off-centerboard hidden in the interior cabinetwork somewhere. Bolger's the first guy I'm aware of who did that, there are definitely others.

        Comment

        • brucehallman
          Bolgerphile
          • Jan 2011
          • 722

          #19
          Re: Lee Boards

          Originally posted by P-man
          ..lee boards. ... I like the look, very traditional. Does anyone have actual experience with them they would be willing to share?
          Absolutely, leeboards are ancient and very traditional in shallow waters. Ask any Dutch sailor, or anyone sailing the Thames estuary. Also, leeboards are very common in sailing canoes.

          Comment

          • St.J
            Member
            • Aug 2009
            • 367

            #20
            Re: Lee Boards

            Originally posted by brucehallman
            Absolutely, leeboards are ancient and very traditional in shallow waters. Ask any Dutch sailor, or anyone sailing the Thames estuary.
            An astonishing number of people sailing the Thames estuary have the wrong boat!
            Many look like they're designed for the med.

            I am interested in how long and thin you can make them. Or is that deep and narrow?

            Zingaro could probably accommodate significantly longer/deeper boards. How much would high aspect ratio leeboards, almost vertical in the water, help windward performance?

            St.J
            thequietworkshop.wordpress.com

            Comment

            • brucehallman
              Bolgerphile
              • Jan 2011
              • 722

              #21
              Re: Lee Boards

              Originally posted by St.J
              An astonishing number of people sailing the Thames estuary have the wrong boat!
              Similar for the San Francisco Bay (estuary). Probably 90% of the surface area of the water of San Francisco Bay is shallow mudflat, inappropriate for almost all of the deep keel sailboats common around here. I think the average depth of the SF bay is 12 feet, and the southern half, it has an average depth of 6 feet. The deep fin keel sailboats are confined to the dredged channels, and most don't even dare to try. Leeboards make a lot of sense, yet the modern locals don't use them.

              Comment

              • Dan St Gean
                Senior Member
                • Nov 2004
                • 1138

                #22
                Re: Lee Boards

                Originally posted by brucehallman
                Similar for the San Francisco Bay (estuary). Probably 90% of the surface area of the water of San Francisco Bay is shallow mudflat, inappropriate for almost all of the deep keel sailboats common around here. I think the average depth of the SF bay is 12 feet, and the southern half, it has an average depth of 6 feet. The deep fin keel sailboats are confined to the dredged channels, and most don't even dare to try. Leeboards make a lot of sense, yet the modern locals don't use them.
                Maybe that's 'cause there aren't any commercially made. One of the reasons I like multis btw...fast and shallow draft.

                Comment

                • Nicholas Scheuer
                  Senior Member
                  • Aug 2006
                  • 13579

                  #23
                  Re: Lee Boards

                  While it would be easy to say high-aspect is better than low-aspect for minimizing leeway, when a high-aspect leeboard, or centerboard is pivoted aft, the center of lateral plane moves aft, also.

                  For maximun efficiency, you really ought to try assymetric foil leeboards which can maximize lift to windward on alternate tacks. You won't find much written about this, as there is such a huge prejudice against leeboards among the "experts", and BVolger himself was fond of short, flat, broad leeboards.

                  Moby Nick

                  Comment

                  • goodbasil
                    Basil
                    • Feb 2005
                    • 5537

                    #24
                    Re: Lee Boards

                    Anyone contemplating leeboards should read this: http://www.duckworksmagazine.com/01/...ards/index.htm
                    basil

                    Comment

                    • Nicholas Scheuer
                      Senior Member
                      • Aug 2006
                      • 13579

                      #25
                      Re: Lee Boards

                      I would take exception to several points in the Duckworks articlel for which goodbasil posted a link to.

                      First, canting the leeboard inward toward is not as bad as the writer says. Proof? Edey & Duffmounted their leeboards directly against the flared sides of their Dovekie, and it works fine. I cruised in Dovekie #56 for 12 years, and I'll bet dollars to doughnuts that is WAY more experience than the Duckworks writer has with similar leeboards.

                      Peter Duff even wriote about the benefit of such cant. When the lee board is immersed more deeply due to heel, it is still effective on the light displacement Dovekie. When the leeboard is used on the "wrong" side (windward) the leeboard is immersed significantly less, however kthe board is then about vertical, giving the boat a good gripe on the water.

                      While the idea of a curve on one side of a leeboard, with a flat on the opposite side, may go way back in history, that actually involved only a simple arc on the curved side, and sometimes just a long bevel, not even a blended curve. Thw "wing-like" chord shown in the drawing of a Dutch boat would not have been done untill after the invention of the airplane. Scow "Square Toed" Schooners in Maine had leeboards, too, and they were mounted so as to give the lee board a bit of positive angle-of-attack for added lift to windward. Chapelle points out this feature in American Small Sailing Craft. Those SAcow Schooner leeboards also had bevels, or a curve, on the windward side of the lee board, and a flat on the opposite side, in addition to the angle.

                      Plenty of the Dutch boats today have flat leeboards with the forward edge rounded and the trailing edge beveled. That aircraft-like wing is not nearly universal.

                      I may have a few things yet to learn about leeboards, however, I have been studying them rather intensley for decades. My Shearwatrer Yawl had a pair of laminar flow leeboards (laminar flow airfoils became common after they were used on the P-51) which were a huge success in minimizing leeway.

                      Use of any foil other than a NACA-0012 for sailboats is almost unheard of. One need look at what the hydrofoil folks are doing for state of the art stuff, and that is where someone suggested I try a laminar flow foil for my Shearwater.

                      Moby Nick

                      Comment

                      • David Geiss
                        Sailing canoes, SOF kayak
                        • Sep 2005
                        • 554

                        #26
                        Re: Lee Boards

                        I have a lot fun experimenting with various leeboards on the identical canoe. By keeping the hull constant, you can learn some interesting things about how particular boards behave. It's only a few minutes to beach and switch a board allowing comparison between boards in identical conditions.

                        I prefer modestly a high aspect leeboard which, in profile has its aft edge plumb and the fore edge nicely tapering from wider at top (near leeboard thwart) to narrower at the bottom. Wider seems better for light winds and really high aspect seems better when it's really blowing. Naval architects please hijack thread here........

                        I generally mill a flat on the inner surface, about 8" in height, where the board mates to the bearing surface of the leeboard thwart I also drill a series of holes, all parallel, each sized for the leeboard thwart (protruding hanger bolt). Reason being is I like to deploy less board for a smaller rig and more board for a larger rig. Yes, you can reduce immersed surface of the board by titling it aft but you also affect the helm whereas with the series of drilled holes you can modulate how much of the board is immersed when it's in its vertical position.

                        Vertical or close to vertical lee board seems to me to perform better to windward. At 45 degrees seems good on my canoe for most reaching, except for broad reaching, and of course before the wind (or nearly so) when all I want immersed is only the leading edge of the board nearly parallel to the canoe gunwale.

                        Best,
                        David
                        Last edited by David Geiss; 11-10-2011, 03:46 PM.
                        Live and let live

                        Comment

                        • tdem
                          human
                          • Sep 2008
                          • 156

                          #27
                          Re: Lee Boards

                          Originally posted by Nicholas Scheuer
                          While the idea of a curve on one side of a leeboard, with a flat on the opposite side, may go way back in history, that actually involved only a simple arc on the curved side, and sometimes just a long bevel, not even a blended curve. Thw "wing-like" chord shown in the drawing of a Dutch boat would not have been done untill after the invention of the airplane. Scow "Square Toed" Schooners in Maine had leeboards, too, and they were mounted so as to give the lee board a bit of positive angle-of-attack for added lift to windward. Chapelle points out this feature in American Small Sailing Craft. Those SAcow Schooner leeboards also had bevels, or a curve, on the windward side of the lee board, and a flat on the opposite side, in addition to the angle.

                          Plenty of the Dutch boats today have flat leeboards with the forward edge rounded and the trailing edge beveled. That aircraft-like wing is not nearly universal.

                          Moby Nick
                          About the wing shape not evolving until after the airplane, what is your source for this? I don't know either way but I don't see why it couldn't evolve by itself. I have a book from the 70's or so which is unfortunately a bit vague, but it states that most boats (this is fishing vessels, not recreational) have the inside front rounded, and the back inside feathered out, like a wing shape. It also says that some boat builders even made a hollow in the outside of the board. The rule for how deep it should be was that you should just be able to empty a single bucket of water in the hollow to fill it completely. So that is quite sophisticated, and I doubt that some of the boatbbuilders around the time the book is talking about (also vague, I think basically between the two world wars) were up on high tech aerodynamics.

                          I have another very detailed book on dutch boats (around 300 pages), but haven't really read it yet, so can't confirm what this says on the subject.

                          Comment

                          • gilberj
                            Senior Member
                            • Aug 2010
                            • 4157

                            #28
                            Re: Lee Boards

                            I have quite a bit of experience with leeboards. Many years ago I had a small skiff with leeboards which I sailed a lot and cruised a little in smaller lakes in northern Ontario. At that time I had no reason to doubt the efficiency, and it allowed me to roll out a sleeping bag in the bottom of the boat comfortably.

                            I now sail a Herreshoff Meadowlark "Whimbrel" I can offer more insight on the overall plus's and minuses.

                            Herreshoffs design shows leeboards less than 6 feet long. These were clearly not up to the job....too small. Mr. Herreshoff later recommended boards about 1 foot longer. Mine are almost 10 feet long but they are mounted on a welded hinged bracket on deck instead of the big eye bolt through the sheer strake. My boards are cambered on the inside and flat on the outside, and toed in about 2 degrees. These boards do swing out 'broken wing' when on the weather side for short tacking. I read somewhere the area of the board('s) should be 4% of the sail area. Mine are shy of 3% and less than ideal in light conditions. If I find time I will modify them, increasing the area 20% or so. Once I reach 3 to 3.5 knots I am getting enough lift to be useful. Slower than that the foil is stalling. This is also exacerbated by the interference of the main sail on the mizzen. In light conditions plenty, maybe most boats can pass us at least when close to the wind. Off the wind the issue is less apparent. When the wind gets up a little we are fast and efficient. I have made passages pretty much straight 20 odd miles to windward in 20 odd knots of wind, say distance over the bottom 30-ish miles in 4.6 hours. I have tacked to windward in 30 odd knots of wind under full sail, tacking through ~95 degrees, averaging over 7 knots and spurts over 8 knots. The point here is we get to windward quite reasonably, even in light wind conditions, we are just slower in light conditions. Once the wind pipes up we do not give up much to anyone. My boards are high aspect ratio. When fully down I draw about 6 feet. This is both good and bad. the length is useful for adjusting the balance, giving me quite a range when playing with sail combinations
                            On any point of sail, close up or running free we can sail hands off after a few minutes of fiddling with sheets and leeboards etc.
                            When short tacking, say out the harbour, I leave both boards down. Once I am clear the windward board will be hauled up after each tack. They are similar to handle to an overlapping jib but less time critical when tacking. You drop the windward board before putting the helm down, and haul up the other board after you have filled away on the new tack and the sheets are all tended.
                            I'd really not want a centre-board or dagger board trunk in the cabin .
                            I'll have to go now but if you have questions please ask....

                            Comment

                            • Nicholas Scheuer
                              Senior Member
                              • Aug 2006
                              • 13579

                              #29
                              Re: Lee Boards

                              I don't have a link. However, I've been reading aviation and sailboat books for over 60 years. Early aircraft all had comparatively thin-chord wings having a concave underside (high pressure side). The illustration of the Dutch boat appearing at http://www.duckworksmagazine.com/01/...ards/index.htm showing what appears to be a NACA foil (not yet invented at the time of Lillenthal and the Wrights) shows a chord thickness quite a lot thicker than leeboards on ordinary Dutch sailboats.

                              My Laminar Flow leeboards incorporated a very slight, narrow hollow (concave) along the trailing edge of the high pressure surface. BTW, the most conspicuous feature of Laminar Flow foils is the maximum chord thickness being located almost halfway back from the leading edge instead of approximately 30% aft of the leading edge with a NACA foil. The radius on the leading edge is also somewhat smaller.

                              I was very interested to read gilberj's experience with his Meadowlark Ketch. When we cruised across Vineyard Sound in my Dovekie we were dramatically outsailed by a Meadowlark we encountered on our way to Tarpaulin Cove form Katama Bay. that ML appeared to have leeboards reflected in the original design. Tenfeet seems awfully long for a ML leeboard, especially when swept aft in shallow water, but I'm sure would perform very satisfactorily when vertical. I wonder whether more ballast is required at the lower end of such boards to keep them down whn underway at speed? I like the idea of stouter pivot anchors.

                              The chord centerline of my Laminar flow foil leeboards are parallel to the keel because the foil's designer said the foil itself incorporated a 3-degree positive angle attack. My Shearwater's progress is virtually straight ahead when sailing close hauled in winds over 10-knots.

                              Moby Nick

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                              • P-man
                                Senior Member
                                • May 2011
                                • 692

                                #30
                                Re: Lee Boards

                                thanks everyone for the excellent information. apparently there are more leeboard fans out there than i realized. this gives me a lot of information to digest.

                                these are some comments from WB #27 about Atkin's Gretchen:
                                [IMG][/IMG]


                                perry

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