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Beemer
Joined: 26 Aug 2006
Posts: 87
Location: Middle Georgia
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 Posted: Thu Feb 08, 2007 8:39 am Post subject: Vixen Information |
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Well, I disagree. That’s why I used a long tube to sit in the seat while doing it, so I can see the ASI. It’s really easy to only blow only hard enough to get to 70mph or so. If you start off blowing like the Big Bad Wolf, then yeah, you can toast it.
The Lancair and RV guys attached tubing to the pitot tube, and roll the tubing up to slowly increase the pressure. You can then clamp it there and hold whatever you need. A poor man’s tester.
Besides, your method, while there’s nothing wrong with doing it that way, will not tell you if your connections are leaking. That was the point of doing it my way. Get a little pressure in there, then seal the end with your tongue (couldn’t get a good seal with my finger), and it should stay there for a long while. After all, the point of the whole system is to get the instrument to read the pressure at the pitot opening. And since it’s not practical to hang the instrument on the wing, nor the pitot on the panel, a sealed tubing system is the only way, and any leaks will cause erroneous readings. That’s why there is a calibrated airspeed, vs. indicated.
If your worried about moisture that much, you can dry your mouth out before doing it, and/or install a moisture bottle in the line (ACS sells one).
I agree about the sealed pitot covers. I now have new ones that have a small vent in them to keep this from happening. It was just neat to see the instrument hold the pressure that long.
Bradley
From: owner-kitfox-list-server(at)matronics.com [mailto:owner-kitfox-list-server(at)matronics.com] On Behalf Of john perry
Sent: Thursday, February 08, 2007 8:14 AM
To: kitfox-list(at)matronics.com
Subject: Re: Re: Vixen Information
Brad
You never ever want to blow into the pito with your mouth , You can over pressure the airspeed very quickly , use a fan and stand back away from pito and just blow towards the pito tube from several feet away from the opening . You never want to seal up the opening attached to the airspeed and leave it over night you can over pressure it also . it needs to breathe.
Again this is my opinion and only mine and no one paid me or forced me under duress to say any of this .
Fly safe fly low fly slow
John Perry
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01234
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Beemer
KF2 (and now an M3!)
Suzuki G10 three-banger
Middle Georgia |
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rjdaugh
Joined: 30 Aug 2006
Posts: 195
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| Posted: Thu Feb 08, 2007 8:41 am Post subject: Vixen Information |
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Paul,
Just think how fast you will be when you get the gas cap covers on. 
I did fair my gas caps for the reason you mention.
I really like that first picture that you sent showing a pretty little plane on floats sitting on the asphalt inside the yard and in front of the garage in front of the Ford. It just strikes me as incongruous and thus amusing. Cool!
Randy
Randy,
Those are custom fibreglass covers that cover my electronic fuel senders since the sender sits higher than the top surface of the wing. They are also hinged at the front so I can get at the potentiometers that calibrate the senders if needed. Fwiw it works pretty well for fuel levels, but I also use the sight tube as a secondary system for checking fuel level. I've attached two pics that show where they are located on the wing in relationship to the fuel caps.
Ironically, these covers do look like the fuel cap fairings others have used. I haven't installed fuel cap fairings yet, but it's in the works. I had a conversation once with an aerodynamic engineer about those gas cap fairings, and he indicated the reason you should have them is not so much because of the drag of the cap, but the disturbed airflow over that part of the wing is critical and is probably causing a loss of lift. That all made sense to me so it is on my list of projects to do yet.
Maybe my gas cap covers are what make my little float plane so much faster than most other LSA type float planes?? (chuckle)
Paul
[quote]
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Randy
Kitfox 5/7 912S
Black Hills, South Dakota |
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Float Flyr
Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland
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| Posted: Thu Feb 08, 2007 8:44 am Post subject: Vixen Information |
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Paul:
I expect the reason your ASI is non linear is the position of your static
port has a slight vacuum across it at higher speeds. This would cause a
greater differential pressure at speed.
What I would do is install a second static port on the other side of the
plane in a slightly different location. "T" the second static port in with
the original one. This will remove some of the errors some planes
experience while slipping on one side.
As for operating without the static port I have tried this and found the
cabin of my plane has a slight pressure in it at speed this of course gives
me a smaller pressure differential and in turn a lower air speed indication.
If you can find one you could use a static line similar to the one used by
several Aeroncas. It looks like a second pitot tube except the end is
plugged and there are little holes drilled around the sides of the tube.
The advantage of that system is it can be installed at the far end of the
wing strut well away from the prop wash. Tubing could be routed down
inside the strut fairing.
Noel
[quote] --
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Noel Loveys
Kitfox III-A
Aerocet 1100 Floats |
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FLIER(at)sbcglobal.net
Guest
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| Posted: Thu Feb 08, 2007 8:50 am Post subject: Vixen Information |
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A much safer way to test is to use a piece of
surgical tubing. Slip one end on the pitot then
start rolling it up from the other and clamp it off
once you get an airspeed reading as a benchmark.
Then see how long it takes to bleed off.
I built a simple ASI tester that uses water in a
column made of clear tubing in a U shape with
surgical tubing to apply pressure as above. The
water column is graduated with airspeed markings.
Regards,
Ted
--- Original Message ---
From: "Bradley M Webb" <bmwebb(at)cox.net>
To: <kitfox-list(at)matronics.com>
Subject: RE: Re: Vixen Information
| Quote: | The balloon test I got from the RV builders. Seems
to be a good way to =
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| Quote: | see
if the lines are sealed up. Visual inspection of the
tube isn=92t good =
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| Quote: | Sent: Thursday, February 08, 2007 10:44 AM
To: kitfox-list(at)matronics.com
Subject: RE: Re: Vixen Information
I'd try the balloon test but don't ask me to try to
regulate a low =
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| Quote: | enough
pitot pressure with my warm damp breath on my
expensive ASI.
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| Quote: |
Better still find a friend who has access to a
Barfield tester.
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[quote]
Noel
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