Jim Michalak's Boat Designs

118 E Randall, Lebanon, IL 62254

A page of boat designs and essays.

(1NOV98) This issue will describe the sewing of a lugsail from ordinary polytarp using the pattern we created in the last issue. Next issue (about 15Nov) will finish the topic with details I use to rig the lug sail.

HOUSE CLEANING NOTICE....I think I have the hard drive replaced. But in December I will have to start deleting the links to the past issues so that only the last 25 issues or so are listed. I will try to keep on file the few that I know have been linked to by other sites. The problem is that I have about used up the free storage that Apci gives me. I should be able to keep a year's issues stored for your use. That's enough.







Contact info:


Jim Michalak
118 E Randall, Lebanon, IL 62254
Send $1 for info on 20 boats.





Craig O'Donnell, whose web site you will find down in my links, read the last polytarp essay and wrote me:

"I've attached a tarp-sailed boat photo. This was taken by my friend Nick Burningham in Australia, who's an expert on Indonesian working craft. He says tarp sails are the standard on Indonesian sailboats now. He explains they are sewn in double thickness "like bricks" so the seams overlap. No shape. Just sewn up and hoisted."

Well, you can see there are lots of ways to make a sail and some folks have figured out how to use the cheap material on a large boat.


You recall the pattern we developed for a small lugsail to be made from a single sheet of polytarp. The pattern was predetermined to give a certain draft. The pattern below is for a Piccup Pram sail, about 70 square feet of area and 10% draft. We're going to cut and sew this sail.

As we discussed last episode, we have this pattern drawn in felt tip pen on polytarp such that no edge comes within about 2" of the edge of the tarp. We will not use any of the preformed edging on the tarp. Don't be tempted to do so. As for tarp material, I prefer the "Coleman" brand sold at Wal-mart stores although I doubt if the other ordinary tarps are much different. I haven't tried any of the "heavy duty" tarps although they might be worth a try. A few issues ago I suggested looking at the polysail page for gourmet tarps. Since I wrote that I saw some examples of those tarps at the messabout at Bloomington, Indiana in September. They are indeed superior to the common tarps, not only slightly heavier, but they can be bought in pure white, something I've never seen in a polytarp.


The tarp will be hemmed along the foot, head, and leech. So those lengths should be cut about 2" outside the line. The luff can be cut right to the line. DON'T CUT THE LONG V'S FROM A-C-A2 AND FROM D-E-D2! Instead cut straight across from A to A2 and from D to D2.


The darts at the two major shaping seams will be sewn as shown in Figure 3. In Figure 2 the two shaping seams appear as the deep V's of A-C-A2 and D-E-D2.

Break out the sewing machine. Any sewing machine will sew polytarp although you should use one that will sew a zigzag stitch. Use a rot proof thread like the V69 polyester SailRite sells. Practice a bit if you aren't used to sewing. Read the manual if you've got one.

I'd suggest you try the widest seam first, the wide ones seem the easiest. Practice sewing one or two with some scrap. First fold the cloth on the centerline of the seam. You might secure the fold temporarily with clothespins or paperclips. Then sew, using a straight stitch, from the inner part of the seam to the outer edge along the smoothly curved line shown in the figure. If you were to sew a straight line from point C to A you would end up with the double wedge shape of the original pattern (or something like it - the flexible cloth probably wouldn't take the exact shape.) But if you sew the ever-broadening curved line shown you will get a sail with smooth curves and the original double wedge will be converted to a smooth airfoil with the desired draft.

Next open the fold and pull the cloth tight across the seam. It won't be flat anymore but that's the whole point of the special seams. There will be a little flap of material sticking out. Fold it flat and sew down the loose edge with a zigzag stitch. Then sew over the other edge of the flap, that is the edge with the straight stitch, with the zigzag stitch to further secure it.

Repeat with the other seam.

Let's take stock of what we've done. The sail has already been cut to its final dimensions and seamed to its final shape. All that remains to complete the sail is to sew in the corner reinforcements, sew the perimeter hems and reinforcements, and set the grommets. It took me an hour to get to this point on the Piccup sail. It took me two more hours to complete the finish details.


The corners and reefing areas need to be reinforced with four layers of polytarp. Two layers of regular Dacron sailcloth would also do the job.) That provides strength against tear out of the grommets and stiffens the material to prevent folding under stress. I usually make the reinforcements about 8" long on a side. There are lots of ways to shape these patches. Sew the patches down well with a zigzag stitch.


On a smaller sail like this 70 square footer I usually make all the hems, except the luff hem, with a simple folded over hem about 2" wide. I've had no trouble. Some might prefer to reinforce all the edges, especially the head edge, with something like 4 ounce sailmaker's tape, 3" wide, folded in half and sewn over the edge. Sew it all down with a zigzag stitch. Reed Smith, who sometimes sails his Piccup in the open ocean (Gulp!) said he had a problem with the leech stretching so perhaps that edge might get a treatment similar to that of the luff.

The luff hem needs a stiffer and stronger treatment. I've been using 3" wide fiberglass tape, the same stuff used to make taped seam plywood hulls. It's fairly inexpensive and very easy to sew. It's edges are treated to prevent unraveling. Dacron sailmaker's tape would also be ideal. Here is how I do the job with fiberglass. I just sew a 3" wide tape down each side of the luff. The ends, which will unravel badly if left raw, are doubled under the last 6" or so before being sewn down. That prevents unraveling and also provides a second layer of material in the region of the end grommets, the most highly loaded grommets in the system. It might be advised to sew a final protective layer of tarp over the top of the glass tapes as the tapes seem to abrade easily with handling. All the luff sewing is with zigzag.

At this point all the sewing is done.


A smaller sail like this one can use ordinary brass #3 grommets all around. A good hardware store might have them plus the simple tools needed to install them. A bit of warning - I've heard that some of the grommets are brass plated steel. That type looks exactly like real brass when new in the box but they will rust shortly. Try to get real brass.

Practice setting a few grommets in scrap. They need to clamp tightly on the cloth but not so tight as to cut the cloth.

Place grommets at each corner with about 1" edge distance. Then along the hems in the head and foot spaced about every 15".

Large sails and heavy boats need better grommets in the corners. I've had very good luck with SailRite's riveted "Jiffy " grommets. (SailRite also has all the types and sizes of brass grommets.)

The sail is done! It took me three hours of work to get to this point. No doubt it could be done quicker. If you're not used to sewing you should expect to take longer.


I'll show the details of how I rig a lug sail.




Someday I may get to put my full catalog on the net. For now I'll put one design in each issue.


Moby Dink was one of my first projects. I built and used the prototype for a few years before selling it to a man who uses it to tend his farm pond. If I were to do this one again I wouldn't change the hull at all but would try the small lateen that I put on Tween. Indeed, Tween is pretty much a redesign of Moby with the idea of giving it a V entry on the bow for better action in chop, and the lateen sail for simpler set up. But the gaff sail was instructive. The photo shown above is of Dean Raffaelli's Moby up in Chicago. One thing I noticed was that the gaff takes a while to set up because it has so many lines. Perhaps it is not a good choice for a trailer or cartopper because of that reason. But the payoff is that all those lines give you great control of the sail shape. You can tweak the thing in any direction to adjust for any wind condition. Also I think I became convinced that the mast stiffness of a gaffer is critical for sail control in a stiff wind. If the mast bends aft, as it will in strong winds, the gaff sags off, the sails leach bellys out and she is no longer close winded. But if the mast is stout and the skipper can play all the lines properly, the gaff sail can be quite effective.

Here are the Moby words from the catalog:

Moby Dink was designed to be a very easy, inexpensive beginner's project and, at the same time, to be a dinghy for a rich man's yacht. Fitted with a trolling motor, she would make an excellent pond fishing boat.

She is 7'6" long, 3'10" wide, and weighs 63 pounds empty. She'll easily float 370 pounds.

Moby Dink's construction is of the old fashioned nailed-together type, and anyone who has built a shoe box in high school shop can handle it. All panel shapes and bevels are defined in the drawings. The sides are cut to shape, bent around the center frame, and the end transoms are nailed in place. The wales and chines are installed and the bottom is fitted and trimmed like a pie crust and nailed in place. There is no lofting required and no construction jig need be built. Two sheets of 1/4" plywood will make all her plywood parts, including the sail rig parts. A pattern for sewing your own sail is also given on the plans. The prototype required 60 hours labor and $160 to build including building the sail rig. The sail rig absorbs about half the cost and labor of almost any sailing project, large or small.

Moby Dink's sail rig is a geniune gaff, stepped up front out of the way. Her sail area is modest and she is handy in a good breeze. (Keep her in protected water, please.) She will tack in one second. Moby has a pivoting leeboard and rudder which will allow sailing her right up to a beach. Serious yachters might also use her as a tender. The 6-1/2 foot oars are detailed on the plans.

Moby Dink plans are $15.


Prototype News

Some of you may know that in addition to the one buck catalog which now contains 20 "done" boats, I offer another catalog of 20 unbuilt prototypes. The buck catalog has on its last page a list and brief description of the boats currently in the Catalog of Prototypes. That catalog also contains some articles that I wrote for Messing About In Boats and Boatbuilder magazines. The Catalog of Prototypes costs $3. The both together amount to 50 pages for $4, an offer you may have seen in Woodenboat ads. (If you order a catalog from an internet page you might state that in your letter so I can get an idea of how effective this medium is.) Payment must be in US funds. The banks here won't accept anything else. (I've got a little stash of foreign currancy that I can admire but not spend.) I'm way too small for credit cards.

Usually when a design from the Catalog of Prototypes starts getting built I pull it and replace it with another prototype. So that boat goes into limbo until the builder finishes and sends a test report and a photo.

Here are the prototypes abuilding that I know of:

IMB: Click here to visit Tim Webber's page and see some photos of the Texas IMB under construction. Then poke around Tim's web page a bit. I heard this week from the Texas IMB builder who said,"I want to let you know that IMB is alive and looking good. She is now right side up and sitting on her cradle. Soon this boat and carrier will be mounted on the small trailer I have ready......"

Fatcat2: There is an old timer (80 years +) in Minnesota who has completed the hull of a Fatcat2. Fatcat2 is a simple 15' x 6' catboat, gaff rigged and multichined. I think the sail rig will be done this coming winter. Not only has he finished the Fatcat2 hull but he has started a....

Twister. Go back to the 30dec97 issue in the index to see this one. The Twister hull is pretty well cut and fitted, ready to tape. Walt lives north of Green Bay, working in an unheated shed. He tells me there will be no more building until things warm up again next year in late Spring. If you live up there and would like to contact Walt, let me know.

QT Skiff: Paul Krayniak of Odessa, NY, sent this photo of his prototype QT. I'll have a full report in an issue or two.

Jonsboat: A buider in Florida has started a stretched version of Jonsboat (16' stretched to 19'). This boat was featured in the 15 April issue.




Mother of All Boat Links

Cheap Pages

Messing About In Boats

Shantyboats (archived copy)

Backyard Boats

The Boatbuilding Community

Kilburn's Sturdee Dory

Bruce Builds Roar

Dave Carnell

Herb builds AF3 (archived copy)

Hullforms Download (archived copy)

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