Dangers of Old Mylar
On the last day of the 2012 US Sports Class Nationals in Parowan Utah, as I descended under the start height with the spoilers the right top surface mylar lifted. It made a horrible buzz as it was lifting off of the wing. When I closed the spoilers it settled down. I opted to head back for a relight.
Once on the ground the mylar looked fine with no signs of being lifted. I rubbed it down very aggressively with a towel and my Leatherman and fortunately had no problems for the rest of the flight. We did the entire glider once home. Now I change them before the contest.
Ron Tabery a multi US National Champion talks about a frightful experience in Omarama NZ in the wave with his elevator seals. In the cold at altitude it would lift and loose elevator authority... Safety tape and mylar really need to be in good shape.
You generally see the safety tape begin to fail first. This should be changed before it is brittle. The adhesive tape will eventually begin to fail, some replace it and reapplied the old mylar or patch stick it back on (generally on the ends). Mylar will eventually loose its curvature and no longer stay attached to the control surface. This is most common when left in the trailer with a control surface deflected bending the mylar.
Replacing safety tape every 1-2 years and mylar every 3-5 years is a good way to stay safe and avoid the above mentioned exciting flights.
Banner Photo by Mika Ganszauge
PVC tape often referred to safety tape is really something that should be replaced at least every two years. This is the first line of defense to hold your mylar on. Many shops replace this yearly. Since you hard wax your glider yearly it is easy to do at this time.
Mylar instillation simplified
- Remove glue residue (may take 5x longer then you think it should)
- Trim mylar to fit, scuff and clean
- Scuff and clean wing
- Apply adhesive tape
- Clean mylar again
- Apply mylar to transfer tape
- Apply A LOT of pressure to make sure mylar is adhered
- Apply safety tape
Repeat step 7
Garret Willat holds a flight instructor rating with over 8000 hours in sailplanes. His parents have owned Sky Sailing Inc. since 1979. He started instructing the day after his 18th birthday. Since then, Garret has represented the US Junior team in 2003 and 2005. He graduated from Embry-Riddle with a bachelor's degree in Professional Aeronautics. Garret represented the US Open Class team in 2008 and 2010 and the Club Class team in 2014. Garret has won 3 US National Championships.