Brian asked some good questions in his thread 'Silk Sails?'. In this thread, I'll answer some of Brians' questions and add more information about fabric for your sails.
I learned how to sew when I was eight. Once upon a time, I sewed almost of my own clothes, everything from haute couture, designer dresses, lined tailored jackets, tailored skirts and more. Also Christening gowns, art quilts and sewing for my home. The one fabric that caused me the most grief was silk. To successfully sew silk, every setting needed to be perfect and flawless technique.
Brian, save yourself the grief and consider a high quality cotton fabric.
Muslin fabric is woven from the lowest quality, short and uneven fibers, essentially, what ever is left over. That piece of muslin fabric that came with your kit cost the manufacturer less than 50¢. Sewing your sails from muslin fabric, is the equivalent to building your model of the Constitution or Victory with balsa wood.
Brian asked: So how can we get a look that simulates the way a real sail would hang in a real situation?
Good question. The answer is using a fabric that has the needed characteristics. By that, I mean a fabric that has the fiber content, tpi and weave pattern. A high quality pima / upland cotton fabric has the characteristics needed, it will iron crisp, fold easily, strong, opaque, light weight. For furled sails, the fabric can be 'finger pressed' and will hold the fold crisply.
Skip the low end Egyptian cotton commonly found in bed linen. This Egyptian cotton is referred to as 'Fake Egyptian cotton'. The fibers in fake Egyptian cotton have low strength and breaks easily.
Real Egyptian Cotton is know as 'Giza Egyptian Cotton'. 'Giza' comes in ~10 different grades with 'Giza 45' being the highest quality. A Giza 45 sheet retails for ~$1,000 for the top sheet only! If the packaging doesn't say 'Giza Egyptian Cotton', it's fake Egyptian cotton.
Sea Island cotton is better than Fake Egyptian, but not close to Giza and difficult to find.
Brian Stated: Seems to me we have to use a fabric that's so light that it would hang like the real thing in a dead calm, and could flap like the real thing in a breeze. So it has to be as close to the scaled-down weight as possible.
Think about the characteristics of wood, each species of wood bends and twists uniquely, based on the woods fibers. Fabric behaves the same way, different fibers and weaves behave differently
Brian Stated: Cotton does come in weights lighter than 3 ounces, but this is more often achieved by having less threads per square inch than by using thinner threads.
Fewer tpi is one way of obtaining a lighter weight fabric. The better way to make a lighter weight fabric is use a finer cotton fiber. The tpi of Giza 45 is never disclosed, but it is generally believed to be about 350 tpi. Giza fabric is close in weight to silk and it's ultra strong.
FABRICS FOR YOUR SAILS
If you want to use the highest grade of cotton fabric, look for 'Giza 45' and be prepared to pay in excess of $100 per yard. The problem is Giza 45 is produced in such low quantities, I have yet to find Giza 45 available for retail sale.
For a more reasonable price fabric, I suggest a high quality pima cotton, found in high end quilt shops. I've visited a few quilt shops and found a couple of fabrics that have the qualities needed for sails. The 'Art Gallery Pure Elements' is lighter than the 'Kona Cotton' fabric and recommended for furled sails.
-Art Gallery - Pure Elements
100% pima cotton, available in 66 different colors, $12.00 / yard
-Robert Kaufman - Kona Cotton
100% pima cotton, available in 305 colors, $9.00 / yard
WHERE TO BUY
I've been in a JoAnns store twice in my life and both times I was totally under whelmed. I unrolled numerous bolts of fabric and every bolt of fabric contained flaws. Second quality fabric needs to be sold some where and is sold at a discounted price.
The best place to purchase these fabrics in first quality, is from a high quality quilt shop, specifically a quilt shop that also sells Bernina, Pfaff, Viking sewing machines (NOT! Singer.)
If you don't have a quilt store near you, I can ask the local quilt shop if they will mail order to the states.
What ever you select, don't use bed linen. Bed linen is woven in a sateen weave, over one under two, three or four, resulting in a fabric that is designed to sag. Sateen weave fabric also has a visible diagonal weave pattern (similar to denim jeans) and that's why the thread sits on top of the fabric. Regardless of what the packaging states, there's no such fabric that contains more than 400 threads per inch. This is a 'marketing game' where the actual number of tpi is multiplied by the number of plys in each yarn.
I was given a set of Giza 45 pillow cases and this fabric would be perfect for sails. Unfortunately it's a sateen weave. I've been looking for a retail source of Giza 45 for a couple of years, but it's produced in such small quantities.
Here's more information on Giza 45