Lug sail design

[Ron Carter]

I'm building a 13'6" sailing sharpie without a specific set of plans. Was planning to use a leg-o-mutton sprit sail I have on hand but really want the shorter spars of the lug sail for stowing in the boat. There are obviously many versions of the lug sail. Looking for something in the 80 sq ft range reefable to about 60 sq ft. Also need to be able to calculate center of effort. Must be a reference work that I haven't run across that would be of assistance. Google has been interesting but not very enlightening.

[almeyer]

Jim Michalak uses a balanced lug on a number of his designs, and his on-line newsletters provide some good reading. If I'm doing this right, here's the link to his article on calculating CE:
web page (http://homepages.apci.net/~michalak/15jul05.htm#Sail%20Area%20Math)

IIRC, there's also a couple of articles on rigging the lug.

Al

[Ron Carter]

Al, Precisely what I was looking for. I had visited a number of Jim's pages but had missed this one. Thanks.

[Lewisboats]

Duckworks sells sails for Jim's boats, you might get one there in the range that you are looking for. Each sail is made to order out of a choice of materials.
Not affiliated with the mag, just was considering getting one for my little 11 footer.

Steve

[Ron Carter]

Was aware of the Duckworks connection. I'm thinking of a PolyTarp sail to start in order to get a satisfying shape and size before committing to a relatively high dollar sail. Dabbler is also apparently very good at the odd small boat sail. Also find it fun to re invent the wheel again as opposed to being uesful and productive!! Part of what makes self unemployment so enjoyable.

[Lewisboats]

http://www.simplicityboats.com/simplicitysailrig.html

modify until the correct size is obtained!

Steve

[Todd Bradshaw]

That one is a prime example of my biggest gripe with polytarp sailmaking - lack of sound sailmaking/sail-cutting/shaping knowledge. The material itself is what it is - not the best, not the worst, but with so little basic knowledge and those poor instructions nobody is ever going to build a good sail that way. I can certainly understand people who either don't want to invest big bucks in sails or who just can't afford to, but will never understand why so many of them aren't willing to spend some time learning the basics of sail design and construction before they're out there on some website publishing instructions on how to make bad sails? Knowledge is cheap, it just takes some effort.

[Ron Carter]

White poly tarp properly shaped is one thing for determining size etc. I have to agree the blue tarp hung like a bed sheet is way beyond my embarasment threshold.

[Tonyr]

Todd Bradshaw is too nice to mention his own book - "Canoe Rig". It has great illustrations and ideas on all sorts of rigs for small boats, with Lug Sails well represented.

Tony.

[Todd Bradshaw]

Yes and no. It will address many of the overall design and rigging questions, but it isn't really a sailmaking text. The transition from a tarp that looks like a sail to a sail that happens to be made from a tarp requires most of the same basic sailmaking principles that would be explained in any good text on the three-dimensional design and construction of sails. They're fairly simple concepts and most of it will boil down to doing a little work with a ruler, a calculator and a decent lofting batten. Without these concepts you're still pretty much trying to power your boat with a tarp instead of a sail.

You can think of polytarp as if it was a less stable, less durable grade of modern Mylar laminated sailcloth. It's construction is actually quite similar, the difference being the quality and characteristics of the materials used to make it and the fact that polytarp generally is not available in a wide variety of weights and reinforcing weaves (meaning that once you get up to a certain sail size, it's just not sturdy enough to be a decent choice). Working with the two materials is also similar in most aspects, and the design phase and much of the construction should be nearly identical. This is where I have a big problem with most of the polytarp builders. The design, layout and building techniques they use often show quite clearly that they have never really studied basic sail design and construction. Rather than sitting down with a good book and learning the simple steps that it takes to shape a sail, they're re-inventing the wheel in the back room with a roll of carpet tape and that wheel is coming out square.

[bibbio]

which sailmaking text would you recommend Todd?

[Todd Bradshaw]

Marino's book "The Sailmaker's Apprentice" is without a doubt the most comprehensive sailmaking book ever written and worth every cent. It's also full of excellent drawings that really show the reader clear examples of what's being written about.

Another very good "book" is actually a series of small booklets by Jim Grant (founder of Sailrite, the sail kit company). It's called "The Sailmaker's Library" when sold as a set, and they're also available individually as "The Mainsail Manual", "Jibsail Design and Construction", "Spinnaker Design and Construction", "The Stormsail Manual", "The Staysail Manual" and "The Sail Repair Manual" (about $12 each). They're not lavish books. They get straight to the point, show you the calculations that you'll need to make and take you through the steps of designing the sail and then building it. If you have a decent chunk of flat floor and a roll of fabric and want to wind-up with a new sail, these booklets are probably the fastest way possible to get it done. Jim has taught more people how to build sails than anybody on the planet. Add his "Complete Canvasworker's Guide" and it will show you how to build a dodger, sailcover, boat cover or Bimini top to go along with your new sails.

If I can't remember the best way to lay out a fancy trim detail, I usually look in Marino as it's likely to have a drawing that shows how. If I can't remember a formula for something or how much to allow for this or that, I'll usually look in one of Jim's books because I can find it faster. The average polytarp sail would benefit substantially from a $12 investment in a booklet that would show how it's really supposed to be cut and shaped.

I have several others that fill in gaps and get deeper into design theory and aerodynamics, but the Grant and Marino books are the ones that I really wouldn't want to be without.

[Ron Carter]

Appreciate the ongoing discussion. I had ordered Marino's book last week and am anxiously awaiting its arrival. Stumbled on Atkin's "Alone" last night, which is the sail dressed version of the skiff I'm building. 54 sq ft lugsail on a 11' mast will be ideal and probably more realistic for the 4'1" beam. COE falls exactly in line with the dagger board I designed, using the mast partner already installed.

[brian.cunningham]

Originally posted by Todd Bradshaw:
Rather than sitting down with a good book and learning the simple steps that it takes to shape a sail, they're re-inventing the wheel in the back room with a roll of carpet tape and that wheel is coming out square.You made me spit coffee on that one. :D LOL

[Ron Carter]

Sailmaker's Apprentice has arrived. I thank those who recommended it. Not only is it full of good, apparently solid information, in a clearly understandable form, but his writing is worth the book all by itself. While he claims not to be a writer he sure is a good story teller. I'm usually somewhat let down when I buy a book highly touted by others and find it less than meeting my expectaions. That is not the case here as it is way beyond what I was expecting.

[Roger Long]

Forget about the center of effort. If it looks anything like a boat, it will work just fine.

[Lewisboats]

Originally posted by Roger Long:
Forget about the center of effort. If it looks anything like a boat, it will work just fine.Right! :eek:

[Ron Carter]

Had one of those "looks like a boat" things years ago. Ray Greene Rebel which was over canvased to begin with and had been set up wrong by a previous owner. Huge weather helm and poor windward performance. Had I understood COE & CLR back then I could have tuned it and made a boat out of it. As it was I sold it to someone even more poorly grounded in the basics of sailing and went to crewing for others where I actually started to learn how to sail.