X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from elasmtp-mealy.atl.sa.earthlink.net ([209.86.89.69] verified) by logan.com (CommuniGate Pro SMTP 6.0.2) with ESMTP id 6114430 for lml@lancaironline.net; Sun, 10 Mar 2013 13:49:12 -0400 Received-SPF: none receiver=logan.com; client-ip=209.86.89.69; envelope-from=colyncase@earthlink.net DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=dk20050327; d=earthlink.net; b=oRCQcd8cvZ4vjvwN/g2ulL4yfXWZIKIOsMqLxAIpPbSwdYD2Fhbj9DIaWuZNDDzy; h=Received:From:Mime-Version:Content-Type:Subject:Date:In-Reply-To:To:References:Message-Id:X-Mailer:X-ELNK-Trace:X-Originating-IP; Received: from [71.161.209.221] (helo=[192.168.1.24]) by elasmtp-mealy.atl.sa.earthlink.net with esmtpa (Exim 4.67) (envelope-from ) id 1UEkMR-0005ve-3f for lml@lancaironline.net; Sun, 10 Mar 2013 13:48:39 -0400 From: Colyn Case Mime-Version: 1.0 (Apple Message framework v1085) Content-Type: multipart/alternative; boundary=Apple-Mail-52-230945912 Subject: Re: [LML] Re: Pressurization Date: Sun, 10 Mar 2013 13:48:38 -0400 In-Reply-To: To: "Lancair Mailing List" References: Message-Id: <394240AD-90D6-4337-A89D-B1B7E4F0172F@earthlink.net> X-Mailer: Apple Mail (2.1085) X-ELNK-Trace: 63d5d3452847f8b1d6dd28457998182d7e972de0d01da940a60e4f4252e950251ef8f5d87f4509c2350badd9bab72f9c350badd9bab72f9c350badd9bab72f9c X-Originating-IP: 71.161.209.221 --Apple-Mail-52-230945912 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=windows-1252 In addition to all the reasons Pete mentioned, I would add that there = will be lots of times where you will want to be able to monitor how your = pressurization system is doing. having delta psi + cabin altitude are = both really useful. After you reseal that main gear (seat bottom) = inspection plate; develop a pinhole leak in your door seal; adjust your = mixer valve etc. I don't know the chelton or VP systems but it's hard to believe they = don't have configurable aux ports into which you could plug a pressure = transducer if you absolutely don't have room for the analog instruments. On Mar 10, 2013, at 10:11 AM, John Barrett wrote: 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 data. Yes, I would appreciate borrowing the tools you have. I would be happy = to pay shipping and a rental fee to help defray your acquisition costs = for anything 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 reads out both the cabin differential in psi and the cabin altitude. = It is a must have IMHO to monitor and prevent cabin over-pressurization. = It is the only 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 opening. The overpressure valve was no match for the amount = of pressurized air coming in the cabin, and the pressure quickly went = over 6.5 psi before I was able to do a manual dump. If you look at the = teeny size of the overpressure 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 provides inadequate over pressurization = protection. > =20 > I think you are using a G900 like me. It has an annunciator input = called CABIN ALTITUDE. I connected that annunciator to a pressure = switch set to 6 psi that compares the pressure in the cabin to the = pressure under the floor in the baggage compartment (where the switch is = mounted). In case the Dukes valve fails and the cabin pressure rises = too high, at least I will get some notice (see note above about not = depending on the manual vent valve). > =20 > I do have a digital differential manometer that measures PSI you are = welcome to borrow. I used it to calibrate the overpressure valve that = mounts next to the Dukes (I set it to 6psi). I built a plenum from a = large plastic food container that you can pressurize with a compressor = (carefully) that you can 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=92t think I=92d need help with measurement issues, but I=92m = hitting some stone walls. > =20 > I have a pocket altimeter I thought I=92d use but wonder if it will = have a stop on negative altitude. Also I went online to see how to = convert altitude differential to PSID. Not much luck. The one site I = found had conversion formulae that don=92t seem correct. It lists a = correlation 1=94 of mercury to 1,000 feet of altitude and that should be = ok. It then goes 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 = difference to 10,000 foot cabin alt is 19,000 feet. .49 times this = difference is about 9.5 PSID. That=92s WAY higher than the 5.0 PSI = we=92re supposed to be 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 = something over 19K and a formula that 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 $450 or so. They all appeared to be = set up for plumbing into a pipe system and I don=92t know if they would = read correctly if placed inside the cockpit. > =20 > How have you IVP builders out there gone about getting measurements = when sealing 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-52-230945912 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=windows-1252 In = addition to all the reasons Pete mentioned, I would add that there will = be lots of times where you will want to be able to monitor how your = pressurization system is doing.   having delta psi + cabin altitude = are both really useful.   After you reseal that main gear (seat = bottom) inspection plate; develop a pinhole leak in your door seal; = adjust your mixer valve etc.

I don't know the chelton = or VP systems but it's hard to believe they don't have configurable aux = ports into which you could plug a pressure transducer if you absolutely = don't have room for the analog instruments.

On = Mar 10, 2013, at 10:11 AM, John Barrett wrote:

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 = data.

Yes, I would appreciate borrowing the = tools you have.  I would be happy to pay shipping and a rental fee = to help defray your acquisition costs for anything 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" = <pete@leapfrogventures.com>= ; wrote:

John,

 

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

 

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 = opening.  The overpressure valve was no match for the amount of = pressurized air coming in the cabin, and the pressure quickly went over = 6.5 psi before I was able to do a manual dump.  If you look at the = teeny size of the overpressure 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 provides inadequate over pressurization = protection.

 

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

 

I do have a digital = differential manometer that measures PSI you are welcome to = borrow.  I used it to calibrate the overpressure valve that mounts = next to the Dukes (I set it to 6psi).  I built a plenum from a = large plastic food container that you can pressurize with a compressor = (carefully) that you can borrow as well.

 

Pete

 

From: John Barrett [mailto:jbarrett@carbinge.com] =
Sent: Friday, March 08, 2013 5:11 AM
To: lml@lancaironline.net
Subj= ect: Pressurization

 

I didn=92t= think I=92d need help with measurement issues, but I=92m hitting some = stone walls.

 

I have a pocket altimeter I thought I=92d use but = wonder if it will have a stop on negative altitude.  Also I went = online to see how to convert altitude differential to PSID.  Not = much luck.  The one site I found had conversion formulae that don=92t= seem correct.  It lists a correlation 1=94 of mercury to 1,000 = feet of altitude and that should be ok.  It then goes on to list a = .49 conversion factor to get from inches of mercury 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=92s = WAY higher than the 5.0 PSI we=92re supposed to be seeing in the LIVP at = FL 290.  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 that 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 $450 or so.  They all appeared to be set = up for plumbing into a pipe system and I don=92t know if they would read = correctly if placed inside the cockpit.

 

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

 

Thanks,

 

John = Barrett, CEO

Leading Edge = Composites

PO Box = 428

Port Hadlock, WA = 98339

 

www.carbinge.com

 


= --Apple-Mail-52-230945912--