finding canopy leaks

[Matt Herron Jr.]

After a recent canopy replacement (keep it latched on the ground if you don't have your hand on it!) I was dismayed to find that there were significant leaks while flying that caused both wind noise and a lot of unwanted cold air in the cockpit, due to the frame being a bit "sprung" after the repair..

I bought some 1/4" x 1/16 and 1/4 x 1/8 Poron weather stripping on Amazon to apply to the canopy frame, but how would I know where the leaks were, and if I had sealed them? I wanted to put on the minimum amount that was effective to avoid springing the frame more, and making the canopy difficult to close.

Enter the electric leaf blower. I taped it to the nose of the glider (Ventus C) over the air intake so that all of the air went into the cockpit through the vent. I then taped the exits at the wing box to insure an adequate pressure differential. With the canopy closed and locked, I could then feel along the crack for leaks from the outside and mark the bad spots with tape. Instruments were unaffected as the pitot and static ports were outside the cockpit.

After 2-3 iterations with application of the Poron foam tape in various thicknesses and places, I was satisfied I had sealed things well. A flight test that weekend including side slips and high speed flight, confirmed that there were now no leaks, noises or drafts from the canopy. A welcome improvement!

Of course, your milage may vary.

Matt

[[email protected]]

Matt-

Great idea, but others should be sure to clamp off or disconnect the pitot if it is in the nose with the air intake. Another leak detector that works with this method is one of those "punk" firework igniters. It produces smoke and can be waved over the canopy gap to show escaping air. A cigarette will also work, but I am not so politically incorrect to suggest THAT! (although it is what I use)

[JS]

On Monday, March 27, 2017 at 5:07:24 AM UTC-7, wrote:
> Matt-
>
> Great idea, but others should be sure to clamp off or disconnect the pitot if it is in the nose with the air intake. Another leak detector that works with this method is one of those "punk" firework igniters. It produces smoke and can be waved over the canopy gap to show escaping air. A cigarette will also work, but I am not so politically incorrect to suggest THAT! (although it is what I use)

A piece of instrument tubing used as a stethoscope in flight can help find leaks too.
Don't confuse it with the pee tube.
Jim

[Dan Marotta]

Years back I sealed my LS-6a canopy perfectly by first draping plastic
wrap over the entire canopy opening and securing around the edges with
masking tape. I then shot clear silicone around the groove in the
canopy, locked the canopy down and left it for a day. The next day I
opened the canopy, removed the plastic wrap, and using a razor blade,
trimmed off all of the silicone that squeezed out. Result: a perfectly
sealed and quiet canopy.

On 3/27/2017 8:37 AM, JS wrote:
> On Monday, March 27, 2017 at 5:07:24 AM UTC-7, wrote:
>> Matt-
>>
>> Great idea, but others should be sure to clamp off or disconnect the pitot if it is in the nose with the air intake. Another leak detector that works with this method is one of those "punk" firework igniters. It produces smoke and can be waved over the canopy gap to show escaping air. A cigarette will also work, but I am not so politically incorrect to suggest THAT! (although it is what I use)
> A piece of instrument tubing used as a stethoscope in flight can help find leaks too.
> Don't confuse it with the pee tube.
> Jim

--
Dan, 5J

[Andy Blackburn[_3_]]

On Monday, March 27, 2017 at 9:24:52 AM UTC-7, Dan Marotta wrote:
> Years back I sealed my LS-6a canopy perfectly by first draping plastic
> wrap over the entire canopy opening and securing around the edges with
> masking tape. I then shot clear silicone around the groove in the
> canopy, locked the canopy down and left it for a day. The next day I
> opened the canopy, removed the plastic wrap, and using a razor blade,
> trimmed off all of the silicone that squeezed out. Result: a perfectly
> sealed and quiet canopy.
>
> --
> Dan, 5J

I tried that with my LS-4 (many) years ago. I did it in a nice, cool garage where I could focus on doing a clean, precise job - an not glue my canopy shut. Problem was that on a hot runway the canopy expanded enough that I couldn't latch it. It took some time and effort to carve all that silicone out of the groove. Be careful out there - some decisions are hard to undo.

Andy, 9B

[bumper[_4_]]

What Andy says!

In that regard, silicone behaves like an incompressible fluid, before or after curing, when squeezed it must have somewhere to go (urethane springs are another example of this).

Stemme got it right when they designed the S10 canopy seal, using silicone tubing and, as when making an O-ring groove, they made the groove wider than the tube so it would have somewhere to compress to. Also, using a tube, rather than a solid extruded silicone rod, allows the seal to deflect with much less pressure for easy canopy latching and softer elasticity.

With my current ASH26E, made during the cold German winter, when it arrived at Minden the canopy could not be latched and stood proud by a good 3/16". The 26E depends on a tight fitting canopy and has no elastomeric seal, which is sub-optimal with broad and rapid temperature swings.

[Dan Marotta]

I must have done it on a warm day at the airport after flying. On
really hot days it would be a little tight, but never too difficult
close. Maybe I got lucky or you got unlucky or some combination of
both? 8-)

On 3/27/2017 11:22 AM, Andy Blackburn wrote:
> On Monday, March 27, 2017 at 9:24:52 AM UTC-7, Dan Marotta wrote:
>> Years back I sealed my LS-6a canopy perfectly by first draping plastic
>> wrap over the entire canopy opening and securing around the edges with
>> masking tape. I then shot clear silicone around the groove in the
>> canopy, locked the canopy down and left it for a day. The next day I
>> opened the canopy, removed the plastic wrap, and using a razor blade,
>> trimmed off all of the silicone that squeezed out. Result: a perfectly
>> sealed and quiet canopy.
>>
>> --
>> Dan, 5J
> I tried that with my LS-4 (many) years ago. I did it in a nice, cool garage where I could focus on doing a clean, precise job - an not glue my canopy shut. Problem was that on a hot runway the canopy expanded enough that I couldn't latch it. It took some time and effort to carve all that silicone out of the groove. Be careful out there - some decisions are hard to undo.
>
> Andy, 9B

--
Dan, 5J