Fabric vs Sals

[rwrogers]

I am looking at a Drifter and it has fabric and dope covered wing and most that I see are Sails. What if anything is the Pros & Cons of either?

[zaitcev]

I thought people just call the wing or wing covers "sails" in ultralight area. As in, "single sail" means just the top cover, "double sail" means conventionally wrapped wing. Therefore, an ultralight's sails can be made from any material. In recent decades, PolyFiber system seems to be the favourite, provided you have the money. Am I wrong about this? Does anyone actually use sailcloth for their "sails"?

[martymayes]

I thought a "sail" is cut and sewn to finish dimension before installation. Usually made from a material like rip-stop nylon. It has no "dope" or other finishing materials. A sail can be removed and reinstalled like a pair of pants because it has zippers and such. It's held taunt by the structure.

Conventional aircraft covering is something like polyester fabric, installed via either the envelope or blanket method, the fabric is attached, shrunk, sealed then finished painted. It's held taunt by the process. Can't be removed with destroying the covering.

[Jim Heffelfinger]

I'm really surprised no one jumped in here from the ultralight group to answer this basic question. The covering on many of the tube and fabric type ultralights and many of what are now LSA do indeed actually use sailcloth as the covering. sailcloth is polyester fabric that has been shrunk already and infused with a very high density resin. In many cases the sailcloth already had dyes added to provide a variety of color combinations before the fabric was resin coated. Like sails on sailboats this fabric will last a very long time but is indeed subject to UV damage just like everything else. The first thing that goes bad is usually the stitching that was used to sew the envelope and the fingernail test works great for this-drag fingernail across the stitching if it doesn't disintegrate under your fingernail pressure it's probably still good.

[Greg Wilson]

I don't know about current usage but here is what it was in the'80's. Sails were indeed "sail cloth" and did not need to be "doped', it was an airtight flexible fabric that aided in disassemble/storage of the aircraft, think "hang glider". When ultralights started to turn into airplanes, Weedhopper, CGS Hawk and were no longer taken apart to be stored the flexible "fold-able fabric was not as important. This led to polyurethane coatings to help protect the sailcloth from ultraviolet light and also began the weight gain that ultralights are faced with. On average a bare sailcloth cover will be the lightest followed by coated sailcloth and last is the airplane type polyester (stitts/ceconite) and dope/paint systems. The painted finish is "thought" to look better actual replacement "sails" are likely to weigh less. Back when I delt with them Jim's adice is correct, the stitching often will fail first with sailcloth as it is subject to abrasion as well as the UV light. Hope this helps some Greg