Source of green donuts for instrument tubing installation?

On Friday, April 6, 2018 at 4:55:52 PM UTC-7, wrote:
I dont use the docking rings anynore, after a few years they deteriorate to mush. I now use a short length
of silicon tube that fits over the instrument tube, a much better lasting material, and cheap.
Dave

Silicone is a good choice. If you prefer O-rings, though you cannot always go by color, green ones are used in auto air conditioning system seals and indicate HNBR. This would be a particularly good rubber for glider tubing "clamps" as well. See the link for HNBR characteristics:

http://www.mantaline.com/capabilitie...e/hnbr-rubber/

bumper

Is there a particular reason to use donuts or anything similar at all for instrument installation? Just push the tube to pneumatic port and go flying.

Using them prevents leaks later on, clamping the tubes.

On Monday, 9 April 2018 10:05:36 UTC+3, wrote:
Using them prevents leaks later on, clamping the tubes.

I have fixed two leaks in pitot static systems over the years. Both were caused by clamped fitting. That's when I started to take seriously the instruction to never clamp pneumatic tubes with anything. Silicon tubes are idiot-proof, PVC tubes age and may become loose if fitting is connected frequently, the fix is to shorten the tube few centimeters and then plug it back.

krasw wrote on 4/9/2018 12:39 AM:
On Monday, 9 April 2018 10:05:36 UTC+3, wrote:
Using them prevents leaks later on, clamping the tubes.

I have fixed two leaks in pitot static systems over the years. Both were caused by clamped fitting. That's when I started to take seriously the instruction to never clamp pneumatic tubes with anything. Silicon tubes are idiot-proof, PVC tubes age and may become loose if fitting is connected frequently, the fix is to shorten the tube few centimeters and then plug it back.

Yep, use silicone tubing. It doesn't age like the clear plastic stuff, and remains
easy to push on and pull off. My glider came with the plastic lines for the pitot,
static and TE, so I shortened them, then added back the length needed with a
barbed plastic fitting and silicone tubing. No more tubing problems, and easy to use.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1
- "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm

http://soaringsafety.org/prevention/...anes-2014A.pdf

On Monday, April 9, 2018 at 3:05:36 AM UTC-4, wrote:
Using them prevents leaks later on, clamping the tubes.

Has anyone ever tried a short piece of shrink-sleeve - no longer than the barbed fitting on the instrument - over the tubing? Slip it into place and hit it with a hot-air gun. Should shrink uniformly before doing damage to the tubing.
Uli
'AS'