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@leapfrogventures.com> wrote:

> John,
>
> Cover your outflow valve (or remove it and cover the opening and the pressure sense line) and take a flight.  If you get pressurization then the problem 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]
> 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.  No smoke but used a down feather and then a stethoscope with tympanic membrane removed.  Outflow valve is covered during these tests.
>
> After lots of frustration i hired a guy who has built and/or pressurized about 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 vessel seal very good.  
>
> 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 do much better than the .25 PSID in flight up to 14.5K ft.  
>
> Wondering why there is inadequate pressurization with a good pressure vessel leads to thoughts of outflow valve problems.  I bought the device with the kit in 1996 so it occurs to me the valve could be dirty or rubber diaphragm 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 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 furthest closed position the diaphragm still had somewhere around a 1/32" gap at the seating perimeters.  Should the air pressure in flight fill that diaphragm 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 from 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
>