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Square Knot
A 20'8" trailerable cruising sailboat.
Design by David Telles Alerion5@earthlink.net


LOA   28' 8" Ballast   647 lbs. Water/
320 lbs. Lead
LWL   18' HR   4' 4"
Beam   8'7'5" Trailer wt   2307 lbs
Draft   1' - 2' Sail area   223
Disp   3,354 lbs. Mast ht   29' 6"
SA/WS   .2.51 # per In. Imm    440


This proposal is an elaboration of a small (14') daysailer I built last year. The fourteen footer is relatively narrower and shallower but the general hull shape is the same; a flat bottom with two chines and a non-radiused transom. As I was designing the daysailer, I kept wondering how she'd work out scaled up to 28', but had to conclude that her model was unsuitable. This boat, a more burdensome and stable model, is the next boat Ill be building if I don't come up with something else in the next year of sailing.  Originally, for the purposes of this competition, I had envisioned a large v-bottomed scow of 22' or so.  A transom at both ends is easier and less intimidating to the amateur builder, and the added deck space is always welcome.  I must also confess that designing a transom at both ends is a hell of a lot easier - Square Knot's bow required conical development and several erasers.  But I wanted a boat that was a little more conventional and I thought that most people would agree, so I abandoned the scow idea.  I settled on the daysailer model and gave her a length of twenty feet, eight inches, Her beam is seven feet, five inches and she draws fourteen inches with her board up and about three feet with the board down.  With the cabin as designed, she'll have about four feet, four inches headroom between the laminated cabin top and the plywood floor.  In a cabin this small, tandem centerboards would allow for an un-obstructed floor roughly four feet wide and seven feet long, so at some point I might work out their placement.  That's a good deal of leg room even with the two transoms and the galley flat. However, I completely sympathize with the builder who rolls his or her eyes at the thought of building two boards and trunks and so went with the single board alternative, though it is a less comfortable one.

This little boat's cruise-ready weight is about 3,400 pounds. That's pretty heavy for a trailer boat but six hundred or so of that is in water ballast and another five hundred in crew and supplies.  On the trailer I would guess her weight to be about twenty-three hundred pounds.  If the tow vehicle were to be a powerful one and the added weight isn't crucial, the floor boards in the cabin could be made from Pau Lope or Ipe. Both these wood types ( I think Pau Lope is a trade name, not a species) are heavy, strong, straight-grained and very resistant to rot.

The sloop rig seemed a sensible compromise between handiness and performance.  A simple single shroud and forestay arrangement for the mainmast is about as simple as you get, short of the spar standing free.  Sail area is kept low and the small jib shouldn't be too much hassle, though I wouldn't hesitate to make it self-tending.

Originally I thought to make this boat a schooner.   A large (relatively) Marconi main and a gaff foresail pushed up towards the bow with a correspondingly small jib looked good on paper and spread a lot of canvas down low. To tend the foresail without going on the cabin top, I drew the double slide companionway hatch so that one could stand in the cabin with head and shoulders sticking out of the front of the hatch to set or lower sail or to reef. I liked the idea enough to keep it in the sloop.

Ballast posed a problem.  To keep trailing weight low and still afford the stability and carrying ability I wanted, I knew water ballast was called for.  The boat's weight is still pretty darned high but if she performs as well as her little sister, I'll consider the extra hassle worth it.

One thing that's always bugged me about water ballasting is the filling ports below the waterline.  I hate spending all that bloody time building, water-proofing and fairing a hull and then cutting holes right where the waters going to be! Still, I wanted a passive system to avoid having to pump ten or so cubic feet of water at each end of a cruise.  I devised the flooding ports just at the waterline in the transom as a solution. They connect to hoses which lead to the ballast tanks in the berths, which are below the waterline. When launching, the mast will still be lowered in its tabernacle and the weight over the transom should dip it just enough to flood the tanks when the transom plugs are removed. If not, one person could sit on the transom till the tanks filled. That's the way its supposed to work, anyway.

Below, I wanted a simple, easy to clean interior that was roomier, more comfortable and drier than my tent.  There's not much leg room when sitting on the berths, but then I remembered that I spent ninety percent of my time below on my catboat stretched out and propped up, reading or just spacing out.  Eating will usually be done outside in the cockpit so I can put up with the occasional crowded meal.   The Porta-Potti is pretty much where I'll put it.

The cook (on cold or rainy days) is supposed to sit on a seat on the centerboard trunk, facing forward to use the camp stove on the removable cooking flat.   I've always wanted to try this arrangement because it keeps all the cooking gear off the floor and the berths and generally out of the way.  A small opening port in the forward end of the cabin would make it that much better.

Out in the cockpit, I wanted to have some room.  I really hate cruisers this small that have elaborately constructed water-proof seat lockers that hold a few life preservers, the boom tent and lots of junk. I would much rather have the entire cockpit open, store the life preservers and boom tent below and do without the junk. The seats can be simple planked benches and if you really need it, netting can be rigged to hold stuff under the benches. Under the cockpit sole is foam flotation.  The longitudinal supports for the sole run forward to form the berth fronts.  The cockpit drains through the transom.  A really small outboard is all I would want for this boat.   Five horsepower would be plenty.  The motor will sit on the transom on a bracket. I know this detracts from the appearance of a boat but it beats having the thing in the cockpit with you.

Construction will be 3/8" plywood covered with glass and epoxy.   Framing is minimal since the 3/4" ply bulkheads should suffice.  The bottom is double and I am seriously considering making the second layer of bottom sheathing Kevlar.  That's pricey stuff but I'm only building this boat once and I really like the freedom of running up on shore without worry.  I drew the lines plan to the inside of the planking as I usually do, to make the lofting process that much simpler.  Construction is conventional tack-and-tape.  Spars are of the birds mouth type and made of Doug Fir.  I've built five spars from fifteen to twenty-five feet this way and I'm convinced that this is the easiest way to go.  I can't fathom why someone would waste their time with spar gauges and the like.  If you have a good table saw (you'll need one) and rudimentary planing skills you'll be just fine.  For details on this method check Woodenboat and Good Old Boat magazines.

Keeping this whole project under ten thousand dollars is going to be tough

Note: I did all of the preliminary sketches on architects ruled velum and felt sure it was somewhat less than accurate.  I therefore went ahead and re-drew the lines to a 1:1 scale to make sure everything was as it should be.   It was damn close.  Since its easier to mail off something I've already drawn than to ink in and reduce a twenty three inch drawing, that's what I'm doing. Rest assured that I've gotten as close as I ever get to complete accuracy when I design a boat.

Brief Bio

I'm forty years old and have designed seven boats before Square Knot.  Three of them I've actually built and one of them my brother is building.  I work in the corporate world now but spent most of my life on the road as a musician.  I live in South Dartmouth, Massachusetts and own a mooring half a mile from the old Concordia yard and half a block from the Marshall Catboat yard.  Extreme low tide there is about two and a half feet, hence my attraction to shallow boats.



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Cross Section

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Sloop sailplan

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Schooner sailplan

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