Help support the WCHA Forums by making a tax-deductible donation!

Standing Lug Draft

Discussion in 'Canoe Sailing' started by Louis Michaud, Jan 10, 2007.

  1. Louis Michaud

    Louis Michaud LOVES Wooden Canoes

    This winter's project is making a sailing rig for a 16' Ogilvy type canoe. I'll be using a 46 sq.ft. standing lug sail, as seen in Todd's book. I've been told that in normal conditions the sail would be used relatively flat. I am thinking of having it loose-footed on the boom (instead of laced) so I could fine tune the draft to the conditions. I would appreciate comments from more experienced canoe sailors than me (zero experience)...

    Best,

    Louis Michaud
    Rimouski, Quebec
     
  2. Todd Bradshaw

    Todd Bradshaw Sailmaker

    Yes, you want a fairly flat sail, though not dead flat. In general, deep sail draft creates power, but at the expense of speed and quick acceleration. A sail used to push a fat, wide, heavy sailboat through a chop can benefit from a fair amount of power-creating draft. A light, skinny boat, like a canoe doesn't need that much power to move well, in fact, a drafty sail may tend to overpower it. If you're having to constantly ease the sail out for survival it's seldom very efficient or fast. A sail with less draft (flatter) will be easier to control, quicker to accelerate and have a higher top-end, speed-wise - so it makes a better choice.

    With modern sailcloth, we're somewhat limited as far as shape adjustability goes on small sails because even the lightest weights of cloth are so stable these days. Unlike the old cotton sails (which were about like a high-quality bed sheet) Dacron, in such a little sail, for all practical purposes doesn't stretch. The shape you sew in is pretty much the shape you'll be sailing with. A loose-footed sail and an adjustable outhaul will have a limited effect in the sail's draft, but trying to get a 46 sq. ft. sail to really change from one good shape to another, different good shape, rather than just distort, may not be terribly realistic. Easing the outhaul very much, in hopes of creating more draft at times, may simply result in a sail that looks like it needs it's outhaul tightened up.

    If it helps, this is how I build that sail. The shaping is done with a combination of edge-rounding and broadseaming (selectively increasing panel-to-panel overlap at the seams). I've built enough sails that I do it be eye and don't measure anything any more except the basic perimeter dimensions to get the corners in the right places, but the estimates given for shaping should be pretty accurate.

    Luff - The luff edge is cut dead straight - no round, no hollow. It's so short and the fabric is so stiff that trying to create draft with luff-round won't work - it just makes a bulge, so cut it straight. We'll get our draft elsewhere. You do want to use two layers of luff tape to bind the luff edge as there is a lot of up-and-down strain on the luff of a standing lug.

    Leech - Hollow the leech edge about 1.5" with the deepest part about half-way up. This keeps the leech from flapping as the cloth ages and softens a bit. I usually add about .75" to this edge, fold it over and make a simple hemmed edge.

    Head - I add maybe 1.25"-1.5" of round, making the head a convex curve with the deepest part about 45% of the way aft of the throat corner.

    Foot (loose) - I'll add round here as well, also about 45% of the foot's length aft of the luff and tack corner. This time, I'll generally make the round about 2.5"-3" deep at it's deepest point.

    I have on occasion built sails by measuring straight from the computer drawings and pre-cutting the panels before assembly, but it's a lot easier to loft the sail out, full-sized on the floor with strings and masking tape and work with the roll of fabric right over the lofting. Cut all panels a few inches long (past the edge marks on the floor) and only cut the final shape after all the seams are done and the sail has shape.

    The edge rounds at head and foot have done little at this point other than make humps in the edges. To turn them into draft and real, 3-D shape, we use broadseams as the panels are basted together with double-sided seaming tape and later sewn together. Most panel seams are simple overlaps about 1/2" wide. A broadseam is just a gradual increase in overlap as you approach the edge of the sail. We're usually looking for a smooth, gradual increase in overlap, starting at a specific point and heading toward the edge. At it's end, the last few inches before you hit the edge, there is a little bit more added, which creates a slightly cupped edge. The combination of the added edge round and broadseams along the head edge will create draft up high and those along the foot will create the draft in the lower part of the sail and give the entire foot a little bit of a cupped shape. The fact that we're messing with the seam overlaps (and in turn, the lengths of the edges we're building from all those pieces) is why we don't cut the sail to size yet.

    This leaves two important questions. #1 is where do the broadseams start?.... and #2 is how much do I increase the overlaps?

    (ask a simple question...get a realy long, complex answer huh? I'm going to split this post, just so that I don't accidentally hit the wrong button and erase it and I need to hunt up a drawing. More to follow.)
     
  3. Todd Bradshaw

    Todd Bradshaw Sailmaker

    OK, drawing attached below. For a vertical-cut lugsail, the broadseams fall inside the areas between the dotted lines near the head and foot and their respective edges. You tape the sail's perimeter lofting out on the floor and run a couple more lines of tape to mark off the broadseam areas. When you start taping fabric panels together over the lofting you can see the broadseam lines right through the cloth. As you're basting a panel seam together (panel seams are the vertical orange lines on the drawing) and come to a line, you start broadening the seam at that point and continue it out to the edge. As you can see, in the middle of the edges the broadseamed sections will be pretty long and near the corners they'll be pretty short sections of the panel seams. The exact location of the dotted lines is pretty much a matter of experience with a particular fabric and practice (unless you want to invest a couple hundred grand in a computer design and plotting system, which I don't). For a sail this size, I'll locate the "peak" of the foot section's dotted lines slightly below the spot where I want maximum sail draft. It would end up 40%-45% of the way aft of the luff and maybe 3' or so above the bottom of the sail. For the head edge, I seldom come down farther than 12"-15" below the edge for the point where the dotted lines meet and again 40%-45% of the sail's width aft of the throat corner. You're not trying to create a lot of draft up there. You just want to give the top a little shape.

    Question #2 was how much to increase the overlaps when making the broadseams? This will depend upon just how many seams there are. If we use wide fabric and can make the entire sail with only three or four panels, the overlaps will need to be increased quite a bit. For full width, 36"-wide fabric panels, it's fairly typical to increase the overlap 1/2" for every 30"-36" of broadseam length, so some of our seams that are the regular 1/2" width in the middle of the sail may wind-up being up to 1" wide at the edges along the foot in the broadseamed areas.

    I usually split my fabric into 12" wide panels. The narrow-paneled sails have a nice classic/antique look for traditional boats that you just can't get with full-width panels. This also means that I have more panel seams running through the broadseam areas and can do my shaping with smaller overlap increases, because there are more of them. Seldom do I need to increase the overlap more than 1/4" per seam and very short broadseams near the corners may just get a tiny bit of broadseaming.

    For a sail of this type and size, the overall amount of draft you build in is a function of how much edge round you start with, how big the broadseamed areas are and how much you increase the width of the seams. More round, bigger areas and wider broadseams generate deeper draft. More modest rounds, smaller broadseamed areas and smaller overlap increases makes for less draft. These measurements are fairly typical for the shallow-draft sails commonly used on canoes and small dinghies. You'll notice that during the broadseaming process, you may be removing a couple inches or more in the length of a head or foot edge, due to the increase in seam overlaps. If we had pre-cut everything to size before seaming, these edges would now be a little short, compared to our original plan. So we wait until all of the panel-to-panel seams are finished and then place the sail back over the lofting to find and mark the corners and determine the final cutting lines for the edges. Add a couple more days of reinforcing corners, binding edges and installing hardware and you've got yourself a lugsail.

    Standing lugs generally need a lot of luff tension just about all the time. Out on the water, you can then experiment with the outhaul/foot tension to see what kind of shape/draft variations it will generate. For the most part though, the shape and draft of a small sail made from relatively stiff fabric is more a matter of what shape you designed into it than how much tension you're putting on it's foot.

    You can see a photo of that particular finished sail near the bottom of the list in this folder (it's "standing lug #1 copy.jpg)

    http://webpages.charter.net/tbradshaw/Sails/
     

    Attached Files:

  4. Denis M. Kallery

    Denis M. Kallery Passed Away July 3, 2012 In Memoriam

    Ya know Todd , As I read your answer I can't help thinking that you deserve a special thank-you for your willingness to take the time to help. Even though I may never sail a canoe the throughness of your answers is interesting and your helpfulness a great asset to this forum- so THANK_YOU! Denis
     
  5. Todd Bradshaw

    Todd Bradshaw Sailmaker

    My pleasure Denis. Some day I hope to actually post an answer that's about 25 words long, but it may be a while. A lot of good people took the time to answer my questions when I was getting into the sport, so passing some of that information down to the next generation seems like the logical thing to do. If we all do our parts, someday there may be regular folks out there paddling around in beautiful, 200 year-old wooden canoes! How cool would that be?
     
  6. OP
    OP
    Louis Michaud

    Louis Michaud LOVES Wooden Canoes

    Thanks a lot Todd!

    Very generous of you to share and take time to post all this information. With these detailed instructions, your book and the "Sailmaker's Apprentice" by Marino I should be able to make a decent sail and understand the hows and whys. If I could find the time I would really like to make the sail from scratch. With a canoe restoration in the works, the sailing rig, a few paddles... maybe I'll have to go for a "sew-yourself" kit.

    Best,

    Louis
     
  7. Todd Bradshaw

    Todd Bradshaw Sailmaker

    The Sailrite kits are a good option and excellent sails. Essentially, they will do all the shaping for you before you even open the box with their computer design and plotting equipment. One nice difference is that computer-cut sails don't require broadseams. All panel-to-panel seams will be a standard width for their entire length. This is done by the software and plotter slightly curving the cut edges of the panels where needed. You simply seam these curved edges together to generate a 3-D shape, instead of using the traditional, straight-sided panels and adjusting their overlaps along the various parts of the seams to do it. It takes most of the mystery out of the process so that you can concentrate on just the assembly phase. You'll still have plenty of work to do, but you're almost guaranteed a good sailshape just by following the directions.
     

Share This Page