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From: John Barrett <2thman1@gmail.com>
Subject: Re: IVP pressurization

Sounds like a good plan I hadn't considered.  Thanks, Pete.

John

Sent from my iPad


On Sep 5, 2013, at 9:00 AM, "pete@leapfrogventures.com" <pete@leapfrogventur=
es.com> wrote:

> John,
>=20
> Cover your outflow valve (or remove it and cover the opening and the press=
ure sense line) and take a flight.  If you get pressurization then the probl=
em is the valve.  If not, somewhere else.
>=20
> 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 a=
void over pressurizing the cabin.
>=20
> I assume you installed a cabin altimeter to monitor the cabin differential=
 pressure?
>=20
> Pete
>=20
> -----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
>=20
> Having trouble getting my pressurization to work effectively.
> I did my best to seal the pressure vessel but never got above .25 PSID wit=
h 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 membran=
e removed.  Outflow valve is covered during these tests.
>=20
> After lots of frustration i hired a guy who has built and/or pressurized a=
bout 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 t=
hrough the aft pressure bulkhead and after doing this he declared the vessel=
 seal very good. =20
>=20
> So we deduced that maybe the shop vac is not as efficient at blowing air a=
s 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
>=20
> Wondering why there is inadequate pressurization with a good pressure vess=
el 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 diaphrag=
m could be failing, etc.  I removed the outflow valve yesterday and tried to=
 examine the parts.  i lubricated the mandrel that the poppet valve slides o=
n with a very small spritz of LPS1 lubricant in case there was stiction ther=
e.  I did notice that with the poppet valve manually moved to the furthest c=
losed position the diaphragm still had somewhere around a 1/32" gap at the s=
eating perimeters.  Should the air pressure in flight fill that diaphragm to=
 close the gap or does this indicate the valve needs servicing?
>=20
> 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 e=
levation airports, (KRDM) and lower - most at sea level.
>=20
> Thanks for any help.
>=20
> John Barrett
>=20
> Sent from my iPad
>=20