X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sun, 10 Mar 2013 10:11:51 -0400 Message-ID: X-Original-Return-Path: <2thman1@gmail.com> Received: from mail-pb0-f48.google.com ([209.85.160.48] verified) by logan.com (CommuniGate Pro SMTP 6.0.2) with ESMTPS id 6113895 for lml@lancaironline.net; Sun, 10 Mar 2013 03:18:45 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.160.48; envelope-from=2thman1@gmail.com Received: by mail-pb0-f48.google.com with SMTP id wy12so2645480pbc.35 for ; Sat, 09 Mar 2013 23:18:10 -0800 (PST) X-Received: by 10.68.211.225 with SMTP id nf1mr17419472pbc.104.1362899890063; Sat, 09 Mar 2013 23:18:10 -0800 (PST) X-Original-Return-Path: <2thman1@gmail.com> Received: from [192.168.1.131] (c-66-235-58-245.sea.wa.customer.broadstripe.net. [66.235.58.245]) by mx.google.com with ESMTPS id kt5sm14089765pbc.30.2013.03.09.23.18.08 (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Sat, 09 Mar 2013 23:18:09 -0800 (PST) References: <2A14E6258A8534418F5498D73CCA51EF2243E99368@P3PW5EX1MB14.EX1.SECURESERVER.NET> In-Reply-To: <2A14E6258A8534418F5498D73CCA51EF2243E99368@P3PW5EX1MB14.EX1.SECURESERVER.NET> Mime-Version: 1.0 (1.0) Content-Type: multipart/alternative; boundary=Apple-Mail-F9567BF0-0C27-4A24-8865-5B62FC8DF060 X-Original-Message-Id: Content-Transfer-Encoding: 7bit X-Mailer: iPad Mail (10B146) From: John Barrett <2thman1@gmail.com> Subject: Re: Pressurization X-Original-Date: Sat, 9 Mar 2013 23:18:07 -0800 X-Original-To: "pete@leapfrogventures.com" , Lancair Mailing List --Apple-Mail-F9567BF0-0C27-4A24-8865-5B62FC8DF060 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Pete, Thanks for the info. I do not have a cabin altimeter inst on my panel and I= 'm pretty sure neither Cheltons nor the VP 200 can be configured for this da= ta. Yes, I would appreciate borrowing the tools you have. I would be happy to p= ay shipping and a rental fee to help defray your acquisition costs for anyth= ing that helps. John Barrett 243 Old Oak Bay Rd Port Hadlock, WA 98339 3603011066 Sent from my iPad On Mar 9, 2013, at 9:18 AM, "pete@leapfrogventures.com" wrote: > John, > =20 > I assume you are adding a cabin altimeter to your instrument panel? It re= ads out both the cabin differential in psi and the cabin altitude. It is a m= ust have IMHO to monitor and prevent cabin over-pressurization. It is the o= nly test instrument needed for calibrating the Dukes and sealing the cabin. > =20 > I know that there is an overpressure valve that mounts next to the Dukes. = However, my Dukes head was not working properly during testing and was not o= pening. The overpressure valve was no match for the amount of pressurized a= ir coming in the cabin, and the pressure quickly went over 6.5 psi before I w= as able to do a manual dump. If you look at the teeny size of the overpress= ure valve and compare that to the volume of pressurized air coming into the c= abin on climb-out, you will quickly come to the conclusion that it provides i= nadequate over pressurization protection. > =20 > I think you are using a G900 like me. It has an annunciator input called C= ABIN ALTITUDE. I connected that annunciator to a pressure switch set to 6 p= si that compares the pressure in the cabin to the pressure under the floor i= n the baggage compartment (where the switch is mounted). In case the Dukes v= alve fails and the cabin pressure rises too high, at least I will get some n= otice (see note above about not depending on the manual vent valve). > =20 > I do have a digital differential manometer that measures PSI you are welco= me to borrow. I used it to calibrate the overpressure valve that mounts nex= t to the Dukes (I set it to 6psi). I built a plenum from a large plastic fo= od container that you can pressurize with a compressor (carefully) that you c= an borrow as well. > =20 > Pete > =20 > From: John Barrett [mailto:jbarrett@carbinge.com]=20 > Sent: Friday, March 08, 2013 5:11 AM > To: lml@lancaironline.net > Subject: Pressurization > =20 > I didn=E2=80=99t think I=E2=80=99d need help with measurement issues, but I= =E2=80=99m hitting some stone walls. > =20 > I have a pocket altimeter I thought I=E2=80=99d use but wonder if it will h= ave a stop on negative altitude. Also I went online to see how to convert a= ltitude differential to PSID. Not much luck. The one site I found had conv= ersion formulae that don=E2=80=99t seem correct. It lists a correlation 1=E2= =80=9D of mercury to 1,000 feet of altitude and that should be ok. It then g= oes on to list a .49 conversion factor to get from inches of mercury to psi.= =20 > =20 > My calculations show that at a service ceiling of FL290 the altitude diffe= rence to 10,000 foot cabin alt is 19,000 feet. .49 times this difference is= about 9.5 PSID. That=E2=80=99s WAY higher than the 5.0 PSI we=E2=80=99re s= upposed to be seeing in the LIVP at FL 290. I had hoped to test to about 6 P= SI. > =20 > Short of an altimeter that allows negative readings all the way to somethi= ng over 19K and a formula that works, the only other instrument I can think o= f is a gauge that reads psi. I found some online that sell for from a coupl= e hundred bucks to $450 or so. They all appeared to be set up for plumbing i= nto a pipe system and I don=E2=80=99t know if they would read correctly if p= laced inside the cockpit. > =20 > How have you IVP builders out there gone about getting measurements when s= ealing up the pressure vessel? > =20 > Thanks, > =20 > John Barrett, CEO > Leading Edge Composites > PO Box 428 > Port Hadlock, WA 98339 > =20 > www.carbinge.com > =20 --Apple-Mail-F9567BF0-0C27-4A24-8865-5B62FC8DF060 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable
Pete,
<= div>
Thanks for the info.  I do not have a cabin altimete= r inst on my panel and I'm pretty sure neither Cheltons nor the VP 200 can b= e configured for this data.

Yes, I would appreciate= borrowing the tools you have.  I would be happy to pay shipping and a r= ental fee to help defray your acquisition costs for anything that helps.

John Barrett
243 Old Oak Bay Rd
Po= rt Hadlock, WA 98339
3603011066

Sent from my iPad

<= /div>

On Mar 9, 2013, at 9:18 AM, "pete@leapfrogventures.com" <pete@leapfrogventures.com> wrote:

=

John,

 

I assume you are adding a cab= in altimeter to your instrument panel?  It reads out both the cabin dif= ferential in psi and the cabin altitude.  It is a must have IMHO to mon= itor and prevent cabin over-pressurization.  It is the only test instru= ment needed for calibrating the Dukes and sealing the cabin.

 =

I know that t= here is an overpressure valve that mounts next to the Dukes.  However, m= y Dukes head was not working properly during testing and was not opening.&nb= sp; The overpressure valve was no match for the amount of pressurized air co= ming in the cabin, and the pressure quickly went over 6.5 psi before I was a= ble to do a manual dump.  If you look at the teeny size of the overpres= sure valve and compare that to the volume of pressurized air coming into the= cabin on climb-out, you will quickly come to the conclusion that it provide= s inadequate over pressurization protection.

 

I think you are using a G900 l= ike me.  It has an annunciator input called CABIN ALTITUDE.  I con= nected that annunciator to a pressure switch set to 6 psi that compares the p= ressure in the cabin to the pressure under the floor in the baggage compartm= ent (where the switch is mounted).  In case the Dukes valve fails and t= he cabin pressure rises too high, at least I will get some notice (see note a= bove about not depending on the manual vent valve).

 

I do have a digital di= fferential manometer that measures PSI you are welcome to borrow.  I us= ed it to calibrate the overpressure valve that mounts next to the Dukes (I s= et it to 6psi).  I built a plenum from a large plastic food container t= hat you can pressurize with a compressor (carefully) that you can borrow as w= ell.

 

Pete

 

From: John Barrett [mailto:jbarrett@carbinge.com]
Sent= : Friday, March 08, 2013 5:11 AM
To: lml@lancaironline.net
Subject: Pressurization<= o:p>

 

I didn=E2=80=99t think I=E2=80=99d need help with me= asurement issues, but I=E2=80=99m hitting some stone walls.

 

I have a po= cket altimeter I thought I=E2=80=99d use but wonder if it will have a stop o= n negative altitude.  Also I went online to see how to convert altitude= differential to PSID.  Not much luck.  The one site I found had c= onversion formulae that don=E2=80=99t seem correct.  It lists a correla= tion 1=E2=80=9D of mercury to 1,000 feet of altitude and that should be ok.&= nbsp; It then goes on to list a .49 conversion factor to get from inches of m= ercury to psi. 

 =

My calculations show that at a service ceiling of= FL290 the altitude difference to 10,000 foot cabin alt is 19,000 feet. = ; .49 times this difference is about 9.5 PSID.  That=E2=80=99s WAY high= er than the 5.0 PSI we=E2=80=99re supposed to be seeing in the LIVP at FL 29= 0.  I had hoped to test to about 6 PSI.

 

Short of an altimeter that= allows negative readings all the way to something over 19K and a formula th= at works, the only other instrument I can think of is a gauge that reads psi= .  I found some online that sell for from a couple hundred bucks to $45= 0 or so.  They all appeared to be set up for plumbing into a pipe syste= m and I don=E2=80=99t know if they would read correctly if placed inside the= cockpit.

 

How have you IVP builders out there gone about getting measu= rements when sealing up the pressure vessel?

 

Thanks,

 

John Barrett,= CEO

Leading Edge Composites=

PO Box 428

P= ort Hadlock, WA 98339

 =

www.carbinge.= com

 

= --Apple-Mail-F9567BF0-0C27-4A24-8865-5B62FC8DF060--