Static Port Tubing??

[Phil]

Howdy everyone,

I am getting ready to start routing the tubing from the static ports...

I will be using aftermarket static ports on the L and R sides. They'll run up to a "T" in the top center of the tail cone. Then I plan on bringing the static line forward.

1st - I'm opposed to using Van's static line, so that's not an option.

I was told that Tygon (Tygothane) was the type of line that I want to use. But it cost $25 + shipping for 20'. I can buy 20 feet of 1/4" vinyl tubing at Lowes for $2.

What's up? Is there some specific reason why I should stay away from vinyl?

Thanks,
Phil

[roee]

I was told by a pitot-static systems professional that that the materials of choice are "Poly-Flo" polyethylene tubing with "Nylo-Seal" nylon compression fittings. This is relatively inexpensive ($0.34/ft, so $6.80 for 20ft), and available from Spruce and others.

See summary: http://www.kalinskyconsulting.com/rv...itotstatic.htm

[David Clifford]

Do yourself a favor and buy the SafeAir kit from Stein. Under $100 with everything to plumb an RV.

[rzbill]

Originally Posted by Phil

They'll run up to a "T" in the top center of the tail cone. Then I plan on bringing the static line forward.

Phil,
Have you considered that the arrangement described above can create a condensate trap between the "T" and your instrument panel? If the "T" is placed as low as possible, near the left static vent, the water trapping geometry is minimized if not eliminated.

[Phil]

I wish I had known of Steins offering, but it's too late now.

I've already:

1) Purchased the machined static ports from iflyrv10.com.
2) Drilled a 1/2" hole in both tailcone skins to fit the static port.
3) Riveted them into the tailcone.

With that 1/2" hole in the skin, I'm now married to using them.

They don't have NPT fittings though. They have a male fitting machined into them with barbs to hold the tubing on. I was planning on using sealant and a clamp to seal the tubing onto the back of the static port.

Anyone have any thoughts on that? I wish I could use a NPT fitting, that would be better. But at this point, I'm committed to using what fits in the holes I drilled.

I'll be using compression fittings rest of the way through the static system though.

Phil

[Phil]

Originally Posted by rzbill

Phil,
Have you considered that the arrangement described above can create a condensate trap between the "T" and your instrument panel? If the "T" is placed as low as possible, near the left static vent, the water trapping geometry is minimized if not eliminated.

That makes some sense too..... I was going to keep it up top for a couple of reasons.

1) It forces both static ports to run uphill and eliminates any chance of water getting into the system.

2) It makes each run from the "T" connector to the static port equal length meaning that if you're slipping the airplane and one side is catching more air than the other, they should average out.

But the condensation is another consideration. I'll have to put some thought into that. What are the chances of condensation forming in those lines and have there been any accidents, etc. as a result of a blockage caused by condensation?

Phil

[roee]

Originally Posted by rzbill

Have you considered that the arrangement described above can create a condensate trap between the "T" and your instrument panel? If the "T" is placed as low as possible, near the left static vent, the water trapping geometry is minimized if not eliminated.

Originally Posted by Phil

But the condensation is another consideration. I'll have to put some thought into that. What are the chances of condensation forming in those lines and have there been any accidents, etc. as a result of a blockage caused by condensation?

I've also given a bit of thought to the water trapping issue. Here are some points to consider:

Firstly, a good question to ask is "in what way(s) would water enter the tubing in the first place?" I could see two possible ways: 1. liquid water entering the static port under positive pressure (weather, airplane wash, etc.), or 2. condensation forming in the tubes, as Bill describes. While both are theoretically possible, I don't know (I would like to know) if either really occurs in practice. On every preflight I diligently drain the pitot & static drains in the Cherokee I fly, and to this day I've never seen a drop of water (although I live in Southern California, where we don't have a lot of moisture). So, has anybody ever known this to be a real issue?

As far as solutions to this alleged problem: If the concern is liquid water entering through the static port under pressure, then having the "T" as high as possible on the bulkhead as Phil describes would give the best measure of protection against the water entering in the first place. If the concern is condensation however, then that can happen anywhere along the length of the tube, so the only real solution would be to provide adequate drainage. Having the "T" below the forward tubing run as Bill suggests would provide drainage for the very aft part of the tube, which is good. However, there are still likely to be other low spots in the tube further forward that could trap water. Specifically to the -7A, the forward canopy deck slopes down toward the panel, so there will be a low spot in the forward cockpit. Likewise, the pitot line and any AoA pressure lines coming from the wing will inevitably have a low spot at the wing root due to the dihedral angle. There would also likely be low spots in the tubing between the instruments. So if condensation is a real concern, then every one of these low spots in the tubes would need a drain. That seems a tad impractical.

I've asked the question before about whether people have installed pitot and static drains in their RV's, and the overwhelming answer was "no, and it's never been an issue". So before I'd go to the trouble of installing drains, I'd like to ask that question again. Has anybody ever had condensation or any other kind of water intrusion or trapping problem in the pitot/static tubing in an RV? Has anyone found that low spot drains really are necessary?

[Phil]

I seem to agree with all of those points.

One of the things I've been wrestling with in thinking this through is.....

...... If the air in the volume of air in the static lines were fully saturated and then cooled to the dew point, would there be enough water to block the line?

I don't think there would be or could be for that matter. If you repeated the process several times and left the residual water in the bottom of the line, then it might be possible. But that seems like a really big set of what-ifs...

Still undecided and willing to listen to a few more opinions.

[Bugsy]

I ran 1/4 inch aluminum tubing from the dual machined static ports with T AN fitting up to a junction port and then plan tygon tubing to the instruments.