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Date: Thu, 05 Sep 2013 15:10:53 -0400
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From: "pete@leapfrogventures.com" <pete@leapfrogventures.com>
Subject: RE: IVP pressurization
Thread-Topic: IVP pressurization
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John,

Cover your outflow valve (or remove it and cover the opening and the pressu=
re sense line) and take a flight.  If you get pressurization then the probl=
em is the valve.  If not, somewhere else.

You should easily get 5 psi during the climb.  Once it reaches 5 psi, pull =
the pressure dump handle (you do have one? - connects to the mixer box) to =
avoid over pressurizing the cabin.

I assume you installed a cabin altimeter to monitor the cabin differential =
pressure?

Pete

-----Original Message-----
From: John Barrett [mailto:2thman1@gmail.com]=20
Sent: Wednesday, September 04, 2013 4:42 AM
To: lml@lancaironline.net
Subject: IVP pressurization

Having trouble getting my pressurization to work effectively.
I did my best to seal the pressure vessel but never got above .25 PSID with=
 my 6 horse shop vac.  Used both pressure and vacuum to check for leaks.  N=
o smoke but used a down feather and then a stethoscope with tympanic membra=
ne removed.  Outflow valve is covered during these tests.

After lots of frustration i hired a guy who has built and/or pressurized ab=
out a dozen IVPs to come take a look.  He determined using smoke that there=
 were a couple of slight improvements to be made mostly in the wire bundles=
 through the aft pressure bulkhead and after doing this he declared the ves=
sel seal very good. =20

So we deduced that maybe the shop vac is not as efficient at blowing air as=
 I thought, but my flying experience with the aircraft is that it doesn't d=
o much better than the .25 PSID in flight up to 14.5K ft. =20

Wondering why there is inadequate pressurization with a good pressure vesse=
l leads to thoughts of outflow valve problems.  I bought the device with th=
e kit in 1996 so it occurs to me the valve could be dirty or rubber diaphra=
gm could be failing, etc.  I removed the outflow valve yesterday and tried =
to examine the parts.  i lubricated the mandrel that the poppet valve slide=
s on with a very small spritz of LPS1 lubricant in case there was stiction =
there.  I did notice that with the poppet valve manually moved to the furth=
est closed position the diaphragm still had somewhere around a 1/32" gap at=
 the seating perimeters.  Should the air pressure in flight fill that diaph=
ragm to close the gap or does this indicate the valve needs servicing?

Finally is there a way short of the manual dump switch to keep the system f=
rom pressurizing better than what I see by mismanaging the controller?  Am =
I just setting the pressurization up  wrong?  Have only been up to 3,000 ft=
 elevation airports, (KRDM) and lower - most at sea level.

Thanks for any help.

John Barrett

Sent from my iPad
=20