Minimum plastic static tube radius...

[Michael Burbidge]

The picture below shows my static line feeding into my air speed indicator. What is the minimum practical radius for plastic tubing. I'm worried that the bend int the tubing is putting too much lateral pressure on the quick connect fitting and that it will not make an air tight seal.

What is your experience with the quick connect fittings and bent tubing?



Michael-

[Zuluzephyr]

Hi Michael,

You can heat the plastic tubing with a hot air gun to decrease the bend radius.

Need to sneak up on the temperature over a larger area and hold the tubing into the shape you want while it cools. Practice with some sample pieces. If you get too hot the tubing will collapse. Be patient with the heat gun and try to get a uniform heat on the tubing on all the way around. The tubing will stay in the new shape with no tension on the fittings.

Rocky Morrison

[Snowflake]

To be honest, that bend radius looks fine... But if your gut feel is that the hose is "stressed" into that shape, you could buy a 90 degree fitting for the hose instead. Either a 90 degree fitting with quick disconnects on both ends, and put it 3 inches away from the instrument, or even a 90 degree fitting that would replace the one on the instrument.

My static system has about 6 Tee and 90 degree fittings in it to get the pitot and static lines to the Dynon D10A and the steam gauges without sharp corners. They work fine.

[Michael Burbidge]

Snowflake, are all the 90 degree fittings secured? Or do you have some that just float?

Michael

[FalloutMan]

What about using two adel clamps to secure the two hoses together to act as a strain relief? Is it possible to use steel braided lines instead? We use them on our MH-60S backup ASI.

[BillL]

Originally Posted by Zuluzephyr

Hi Michael,

You can heat the plastic tubing with a hot air gun to decrease the bend radius.

Need to sneak up on the temperature over a larger area and hold the tubing into the shape you want while it cools. Practice with some sample pieces. If you get too hot the tubing will collapse. Be patient with the heat gun and try to get a uniform heat on the tubing on all the way around. The tubing will stay in the new shape with no tension on the fittings.

Rocky Morrison

+1 A 1" radius is not too hard to get with heating, I experimented with some pieces and it is easy to heat and bend. It will take longer than you think to cool, so a damp/wet towel will help freeze it back. If it gives off an odor, it is heated just a little more then needed. The odor will begin before uncontrollable deformation occurs. (damage)

BTW - always have the static line come UP to the instrument in the last few inches. That way a water drop can not get in the sensor. A single drop can/will damage the sensor when it freezes.