X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from imr-ma03.mx.aol.com ([64.12.206.41] verified) by logan.com (CommuniGate Pro SMTP 6.0.2) with ESMTP id 6111612 for lml@lancaironline.net; Fri, 08 Mar 2013 09:04:40 -0500 Received-SPF: pass receiver=logan.com; client-ip=64.12.206.41; envelope-from=Sky2high@aol.com Received: from mtaomg-mb01.r1000.mx.aol.com (mtaomg-mb01.r1000.mx.aol.com [172.29.41.72]) by imr-ma03.mx.aol.com (Outbound Mail Relay) with ESMTP id 518111C000153 for ; Fri, 8 Mar 2013 09:04:06 -0500 (EST) Received: from core-mte002a.r1000.mail.aol.com (core-mte002.r1000.mail.aol.com [172.29.236.69]) by mtaomg-mb01.r1000.mx.aol.com (OMAG/Core Interface) with ESMTP id 9979BE000091 for ; Fri, 8 Mar 2013 09:04:05 -0500 (EST) From: Sky2high@aol.com Full-name: Sky2high Message-ID: <2402c.317a9aa5.3e6b49d4@aol.com> Date: Fri, 8 Mar 2013 09:04:05 -0500 (EST) Subject: Re: [LML] Pressurization To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="part1_2402c.317a9aa5.3e6b49d4_boundary" X-Mailer: AOL 9.6 sub 168 X-Originating-IP: [67.175.156.123] x-aol-global-disposition: G DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mx.aol.com; s=20121107; t=1362751446; bh=NkyPSJdQ6qsF1uOElxVlLNuTLThxYkRUdZg2DWbb+84=; h=From:To:Subject:Message-ID:Date:MIME-Version:Content-Type; b=HmpGLfkpbsJCnxNtU3ifNd5vi9YL07+v/A3PMf9qnjjN4yPawKRurxzacK1NyKIj5 ot5WL3jvXRmE3GaqceEvzhXv/nMKTwopPaSlSRDEnHBNqDMIl8iSb1hS8yZnY/eAld RYNKM4YcAThkM7zA1YB4H5+alm1eKjOxwOYIMjjk= X-AOL-SCOLL-SCORE: 0:2:427710528:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d29485139efd52d4c --part1_2402c.317a9aa5.3e6b49d4_boundary Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Content-Language: en John, =20 Try using psia (absolute) for the different altitudes and subtract the =20 values instead of psid since altitude pressures do not decrease linearly. =20 Here is a chart that should help: =20 _http://www.nypts.com/Downloads/Altitude.pdf_=20 (http://www.nypts.com/Downloads/Altitude.pdf)=20 =20 The difference between 10,000 feet (10.11 psia) and 30,000 feet (4.37 psia)= =20 is 5.74 psi. =20 Grayhawk =20 =20 In a message dated 3/8/2013 7:11:49 A.M. Central Standard Time, =20 jbarrett@carbinge.com writes: =20 I didn=E2=80=99t think I=E2=80=99d need help with measurement issues, but = I=E2=80=99m hitting=20 some stone walls.=20 I have a pocket altimeter I thought I=E2=80=99d use but wonder if it will = have a=20 stop on negative altitude. Also I went online to see how to convert=20 altitude differential to PSID. Not much luck. The one site I found had= =20 conversion formulae that don=E2=80=99t seem correct. It lists a correlati= on 1=E2=80=9D of mercury=20 to 1,000 feet of altitude and that should be ok. It then goes on to list = a=20 .49 conversion factor to get from inches of mercury to psi. =20 My calculations show that at a service ceiling of FL290 the altitude=20 difference to 10,000 foot cabin alt is 19,000 feet. .49 times this differ= ence=20 is about 9.5 PSID. That=E2=80=99s WAY higher than the 5.0 PSI we=E2=80=99= re supposed to be=20 seeing in the LIVP at FL 290. I had hoped to test to about 6 PSI.=20 Short of an altimeter that allows negative readings all the way to=20 something over 19K and a formula that works, the only other instrument I c= an think=20 of is a gauge that reads psi. I found some online that sell for from a=20 couple hundred bucks to $450 or so. They all appeared to be set up for=20 plumbing into a pipe system and I don=E2=80=99t know if they would read co= rrectly if=20 placed inside the cockpit. =20 How have you IVP builders out there gone about getting measurements when= =20 sealing up the pressure vessel?=20 Thanks,=20 John Barrett, CEO=20 Leading Edge Composites=20 PO Box 428=20 Port Hadlock, WA 98339=20 www.carbinge.com=20 --part1_2402c.317a9aa5.3e6b49d4_boundary Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Content-Language: en
John,
 
Try using psia (absolute) for the different altitudes and subtrac= t the=20 values instead of psid since altitude pressures do not decrease linearly.
 
Here is a chart that should help:
 
http://www.nypts.com/D= ownloads/Altitude.pdf
 
The difference between 10,000 feet (10.11 psia) and 30,000 feet (4.37 = psia)=20 is 5.74 psi.
 
Grayhawk
 
In a message dated 3/8/2013 7:11:49 A.M. Central Standard Time,=20 jbarrett@carbinge.com writes:
=

I didn=E2=80=99t think I=E2=80=99d need help with me= asurement issues, but=20 I=E2=80=99m hitting some stone walls.

 

I have a pocket altimeter I thought I=E2=80=99d use = but wonder if=20 it will have a stop on negative altitude.  Also I went online to see= how=20 to convert altitude differential to PSID.  Not much luck.  The = one=20 site I found had conversion formulae that don=E2=80=99t seem correct.&nbs= p; It lists a=20 correlation 1=E2=80=9D of mercury to 1,000 feet of altitude and that shou= ld be=20 ok.  It then goes on to list a .49 conversion factor to get from inc= hes=20 of mercury to psi. 

 

My calculations show that at a service ceiling of FL= 290 the=20 altitude difference to 10,000 foot cabin alt is 19,000 feet.  .49 ti= mes=20 this difference is about 9.5 PSID.  That=E2=80=99s WAY higher than t= he 5.0 PSI=20 we=E2=80=99re supposed to be seeing in the LIVP at FL 290.  I had ho= ped to test=20 to about 6 PSI.

 

Short of an altimeter that allows negative readings = all the=20 way to something over 19K and a formula that works, the only other instru= ment=20 I can think of is a gauge that reads psi.  I found some online that = sell=20 for from a couple hundred bucks to $450 or so.  They all appeared to= be=20 set up for plumbing into a pipe system and I don=E2=80=99t know if they w= ould read=20 correctly if placed inside the cockpit.

 

How have you IVP builders out there gone about getti= ng=20 measurements when sealing up the pressure vessel?

 

Thanks,

 

John Barrett, CEO

Leading Edge Composites

PO Box 428

Port Hadlock, WA 98339

 

www.carbinge.com

 

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