flion
Well Known Member
Last winter I was descending into Lake Havasu from the East. Normally I would do a circle to the North to get around to the West side and enter the pattern. In the process, I would reduce throttle and descend leisurely to pattern altitude. This time I was a bit behind the breakfast gang and wanted to give my passenger a bit of excitement, so I pushed the nose down as we crossed the ridge and did a cruise-power descent to the airport.
We got more excitement than we expected. At about 150 KIAS (closing on VNE at that altitude), there was a loud BANG! Did we hit a bird? Engine is still running, controls are working, breath resumed after a few seconds but it may be a while before my butt stops clenching the seat. Nothing really to do but land the plane, so I do and tie down but don't notice anything out of place. It's after breakfast when I am doing my pre-flight that I notice that the 'targa strip' is gone from the canopy.
I've got a tip-up, Sika bonded, and the canopy joint is(was) covered with a fiberglass layup bonded to the front canopy. When I had done the layup, I thought I had roughened the surface well enough and, to be fair, it has stayed on since the first flight in 2008. But then, I normally don't cruise faster than 135 KIAS, even for descents. But it had departed cleanly, fortunately without damaging the aircraft (I looked carefully for where it must have hit the plane, causing that BANG! but found no marks or dents).
Well, the canopy was secure so I could fly it home though there were gaps in the left and right lower rear corners where the plexi and side strips don't quite meet the rear canopy, so it was a bit cold and loud. That turned me into a fair-weather pilot and there hasn't been much fair weather here since then (nice days but colder than I wanted to deal with). It finally got warm enough to do some glass work, so I masked off the layup area.
This time I used a carbide tip in a drill to rough up the bonding area (last time it was 80 grit in a detail sander). For good measure, I used a 3/32" drill to put some holes in the bonding area (and to stop-drill the one crack caused by the departing strip) which I made sure got plenty of attention when I wetted the bonding area. I used three layers of 2" glass tape staggered at 1/2" intervals aft to front to lay up the new strip and it came out beautifully. I'm going to add another strip to the back (butted to the front/top strip and trimmed to match the current back) to give the aft lip some extra stiffness, plus a little reinforcement at the left/right bottom of the strip.
I don't expect to have a problem again but I am making this cautionary tale to emphasize two points. First, you can be more aggressive than you think in preparing a surface for glass. I knew this but at that point in the project I think I was hurrying (it was the last thing to do before the inspection) and when it held through the first 100 hours, I quit worrying about it. That is the second thing - I should have paid more attention to it and looked for separations. It was probably only a little bit near one end of the strip but it would have been enough for the airstream to get under and peel the entire strip off. And so, first sentence of this paragraph notwithstanding, I will be checking this regularly in my pre-flight from now on.
We got more excitement than we expected. At about 150 KIAS (closing on VNE at that altitude), there was a loud BANG! Did we hit a bird? Engine is still running, controls are working, breath resumed after a few seconds but it may be a while before my butt stops clenching the seat. Nothing really to do but land the plane, so I do and tie down but don't notice anything out of place. It's after breakfast when I am doing my pre-flight that I notice that the 'targa strip' is gone from the canopy.
I've got a tip-up, Sika bonded, and the canopy joint is(was) covered with a fiberglass layup bonded to the front canopy. When I had done the layup, I thought I had roughened the surface well enough and, to be fair, it has stayed on since the first flight in 2008. But then, I normally don't cruise faster than 135 KIAS, even for descents. But it had departed cleanly, fortunately without damaging the aircraft (I looked carefully for where it must have hit the plane, causing that BANG! but found no marks or dents).
Well, the canopy was secure so I could fly it home though there were gaps in the left and right lower rear corners where the plexi and side strips don't quite meet the rear canopy, so it was a bit cold and loud. That turned me into a fair-weather pilot and there hasn't been much fair weather here since then (nice days but colder than I wanted to deal with). It finally got warm enough to do some glass work, so I masked off the layup area.
This time I used a carbide tip in a drill to rough up the bonding area (last time it was 80 grit in a detail sander). For good measure, I used a 3/32" drill to put some holes in the bonding area (and to stop-drill the one crack caused by the departing strip) which I made sure got plenty of attention when I wetted the bonding area. I used three layers of 2" glass tape staggered at 1/2" intervals aft to front to lay up the new strip and it came out beautifully. I'm going to add another strip to the back (butted to the front/top strip and trimmed to match the current back) to give the aft lip some extra stiffness, plus a little reinforcement at the left/right bottom of the strip.
I don't expect to have a problem again but I am making this cautionary tale to emphasize two points. First, you can be more aggressive than you think in preparing a surface for glass. I knew this but at that point in the project I think I was hurrying (it was the last thing to do before the inspection) and when it held through the first 100 hours, I quit worrying about it. That is the second thing - I should have paid more attention to it and looked for separations. It was probably only a little bit near one end of the strip but it would have been enough for the airstream to get under and peel the entire strip off. And so, first sentence of this paragraph notwithstanding, I will be checking this regularly in my pre-flight from now on.
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