New sailcloth options and recommended configurations
There are several distinct attributes associated with every fabric style and I think it’s important to consider them independently in order to make the choice that best suits your needs.
Appearance and fashion
Structural performance (strength, stiffness and weight)
UV stability and longevity
Appearance and fashion often drive the marketplace. Pilots seem to let those factors dominate the conversation simply because it’s easier to choose ‘what looks good” when they don’t have easy access to technical details.
As an example of why choosing by ‘what looks good’ is a bad idea, consider that white and black polyester fibers look just like the much stronger Technora and PEN fibers. Similarly, UV-modified film is indistinguishable from clear polyester film but lasts more than twice as long in strong UV environments. So, not only can’t you tell from inspection how well a fabric will perform, but it often takes 100 or more hours of airtime for a superior fabric to show its advantage.
We introduced fabrics based on high-strength PEN and Technora fiber over a year ago. High strength and stiffness are essential to control twist and prevent trailing edge flutter especially as gliders age. PEN and Technora fabrics offer significant advantages over the popular ‘PX’ polyester-based styles. Our PEN-based fabrics weigh 180 gms/m^2, match the structural performance of PX15T (270 gms/m^2) and exceed the common PX10T style (230 gm/m^2) typically used on trailing edge panels. ODL Technora-based fabrics are even stronger with a 20% weight savings compared to PEN.
The lighter weight of these PEN and Technora based fabrics allow us to make the entire sail body from high strength fabric which is important because some of the highest sail loads are in the interior panels at VG tight. In years past we were constrained to using the stronger but heavier PX10T/PX15T fabrics in relatively narrow trailing edge panels because of the weight and handling penalties.
For most of this year we offered two PEN styles (PE10 and UVMPE10 white) and ODL04 Technora. PE10 has a grey polyester film, and UVMPE10 is structurally identical except for UV film and bright-white pigment replacing the grey film. The performance of these fabrics has been extraordinary and we now unconditionally recommend them over PX10T for every application. The only disadvantage of these fabrics is higher price but that is easily justified by their other attributes.
The performance of sailcloth depends on the direction that you apply the load. Most fabrics used on hang gliders are stronger on the warp (long axis) than across the fill (width) or the bias (diagonal). I try to orient the sail panels to take advantage properties of the fabric by aligning the warp with the highest expected sail loads whenever possible. The orientation is not critical in lightly loaded panels or when a fabric type is relatively balanced in strength on the warp, fill and bias. High-performance sails are subject to high loads from several directions and it’s especially important to have high strength in the bias and “off-axis” direction. Off-axis strength is provided by the polyester film and the X-ply yarns if the X-angle is wide enough.
Earlier this year, I reconfigured our custom-UV-PEN styles by substituting Technora fiber on the diagonal X-ply and increasing the X-angle to improve off-axis performance. These new PEN-Technora hybrids are now in-stock and available with UV film in both grey and white. These new styles replace UVPE10 White. We consider these fabrics to be the all-round best choice for T2s and T2Cs.
We will continue to offer PE10 (with grey standard film) as a lower cost option on T2s and U2s configured with Mylar sails. Although PE10 is more expensive than PX styles, the fabric performance is so much better that we are the discontinuing PX05T/PX10T option for these models.
We also offer ODL06 (50% stronger than ODL04) as an extra-price option for T2Cs. ODL06 has Technora on the warp, fill and bias for unequaled structural performance. We don’t offer ODL06 with UV film and we still consider the new UV-PEN-Technora styles the best option for most pilots because they are somewhat more durable.
The UVPT fabrics are highly recommended if you live in an area with high-UV intensity. In northern latitudes, the standard film will last for years and is less expensive. The new UVPT fabrics are included in the price of T2Cs.
Altogether, we can rank the fabric attributes in the following order:
1. Appearance and fashion – up to you
2. Ranked in order of structural performance (strength, stiffness and weight)
UVPT10 (New PEN-Technora hybrids)
Woven sails (V170/205MT/Hydranet)
3. Ranked in order of higher UV stability and longevity
UVPT10, Woven sails.
4. Ranked in order of nicer flight characteristics
UVPT10, PE10, ODL06 are equivalent
5. Ranked in order of low price