X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from outbound-mail.dca.untd.com ([64.136.47.15] verified) by logan.com (CommuniGate Pro SMTP 5.4.1) with SMTP id 5113549 for flyrotary@lancaironline.net; Sun, 04 Sep 2011 12:35:53 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.136.47.15; envelope-from=alwick@juno.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=juno.com; s=alpha; t=1315154118; bh=47DEQpj8HBSa+/TImW+5JCeuQeRkm5NMpJWZG3hSuFU=; l=0; h=Message-ID:From:To:Subject:Date:Content-Type; b=OZC2E9OkM1b0Xi8vnzm4XHbLXKKV65HRnMm2CAVQSxzlch2e+EhnGnNaDyZYv5qav Wl3lnsLqJESCRcxJh9gW/kyfsmXiyUJmoPp2V6huMMQYfpEeNdjyILhYQp1cMKTc7z UKNsfLVOWimrlm5OSPg/cFsEx3YyTMfeFtDsMQnI= Received: from Penny (50-39-177-176.bvtn.or.frontiernet.net [50.39.177.176]) by smtpout05.dca.untd.com with SMTP id AABHGHLE3ACWXNGJ for (sender ); Sun, 4 Sep 2011 09:34:33 -0700 (PDT) Message-ID: <26835627FAE7434A8638086B87D2162A@Penny> From: "Al Wick" To: "Rotary motors in aircraft" References: In-Reply-To: Subject: Re: [FlyRotary] Re: vapor lock Date: Sun, 4 Sep 2011 09:34:32 -0700 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_018A_01CC6AE5.D9FD1A40" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Windows Mail 6.0.6002.18197 X-MIMEOLE: Produced By Microsoft MimeOLE V6.0.6002.18463 X-UNTD-BodySize: 14065 X-ContentStamp: 36:18:2615075443 X-MAIL-INFO:1c9838b5384859c848b5f171b591e868a5a8d1a969edbcdca9a8d831d8c88cbcd9d86878e979e9796de579656d7d656d01d9f161916901e8b55d9159c56c0d0daca1ec0939e98c7985d5e965212175d5084129004ce54ce1995de8196d0001a50ca501394cc54c499958b9edbcbc859105855cdc006599b9adf8dd95380538b521d82898a85cdc71c9c98848c1f80868c81c6cbcb961a17109f1256975e9e519ec2c09097d X-UNTD-OriginStamp: L941HVjjYzDhN3itp//mkD4PuPCMuGO9Ze3bT8N5zvg2OO8D/9jVNw== X-UNTD-Peer-Info: 10.171.42.35|smtpout05.dca.untd.com|smtpout05.dca.untd.com|alwick@juno.com This is a multi-part message in MIME format. ------=_NextPart_000_018A_01CC6AE5.D9FD1A40 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Charlie wrote: ) Steve Boese RV6A, 1986 13B NA, RD1A, EC2 -------------------------------------------------------------------------= - -- Homepage: http://www.flyrotary.com/ Archive and UnSub: = http://mail.lancaironline.net:81/lists/flyrotary/List.html ------=_NextPart_000_018A_01CC6AE5.D9FD1A40 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Charlie wrote:
<If you must pump to the sump, then the vent can't 'go anywhere' = unless=20 you're willing to risk pumping fuel overboard
 
Yeah. It seems so. It's a bit strange to think someone MUST = pump to=20 the pump. I'd be quick to question that assumption.
 
< removing several dozen screws, the vent line and fuel = line, and=20 then removing the tank before I could remove the 6 or 8 screws that = <hold on=20 the access plate to the tank
 
So, once every twenty years you might = have to=20 access the pump. And the number of screws is your reason to have = higher=20 risk fuel design? I try my best not to let anything get in the way = of=20 improving safety. That's why I changed my fuel design even though I'd = never had=20 a problem. I want that extra safety margin from sump tank with two wet = pumps,=20 self cleaning filter. It's real. It's significant.
 
<we would choose maintenance = ease vs life=20 risk: you have to be honest; *every* decision makes that choice
 
Of course not. I'd never agree with a = sweeping=20 assumption like that. Life risk SHOULD always carry more weight in = a=20 decision.
 
-al wick
 
 
----- Original Message -----
From:=20 Charlie=20 England
Sent: Friday, September 02, = 2011 12:21=20 PM
Subject: [FlyRotary] Re: vapor = lock

I'd have to differ on a couple of points.

If you = must=20 pump to the sump, then the vent can't 'go anywhere' unless you're = willing to=20 risk pumping fuel overboard.

On a typical RV, it would require = removing=20 several dozen screws, the vent line and fuel line, and then removing = the tank=20 before I could remove the 6 or 8 screws that hold on the access plate = to the=20 tank. So, there is a bit of a maintenance issue for us. If not for = that, I'd=20 use in-tank pumps. For my application, the external sump would add = more=20 weight/complexity.

To the implication that we would choose = maintenance=20 ease vs life risk: you have to be honest; *every* decision makes that = choice.=20 The safest G/a factory plane in the world uses bolt-on wings instead = of a=20 one-piece wing; a one-piece would be both lighter and=20 safer.

Charlie



On 09/02/2011 01:04 PM, Al Wick = wrote:=20
What fine work Steve. I love it = when someone=20 converts theory to facts. You measured that all at sea level. Now = just=20 subtract 5.35 from all your pressure numbers if you fly at 12k ft. = You've=20 now measured all of the variables that affect vapor lock. Only = remaining=20 item is measuring pressure at your pump inlet. You then can predict = exactly=20 how safe your plane is without ever flying! How cool is = that?
 
I use a submerged fuel pump for = added safety.=20 Two actually. Easy to maintain, just remove the 6 screws that hold = the pumps=20 in place. So there is zero significance to the argument of = maintenance.=20 Can't imagine how anyone could claim maintenance is more important = than life=20 risk anyway. I return all fuel to my 3 gallon sump. Vent can go = anywhere,=20 you don't have to tie vent into main fuel vents.
 
Once again, nice work Steve. =
 
-al wick
 
 
----- Original Message ----- =
From:=20 Steven W. Boese
To: Rotary=20 motors in aircraft
Sent: Friday, September 02, = 2011=20 12:04 AM
Subject: [FlyRotary] vapor = lock

For those concerned about the formation of vapor = in a=20 pressurized fuel rail, I've attached a plot of data collected from = local=20 samples of 100 LL avgas, 87 octane auto fuel with no ethanol, 91 = octane=20 auto fuel with 10% ethanol, and tap water.  The water was = measured=20 just as a check on the method.

 

The data would be considered more of a true = vapor pressure=20 rather than a Reid vapor pressure due to the method = used.

 

The data indicates to me that if the fuel = pressure in the=20 fuel rail is 35 psi as measured with a regular gauge referenced to = the=20 atmosphere at sea level, the temperature of 100 LL or 91 = octane 10%=20 ethanol in the rail would have to be in the neighborhood of = 240 deg F=20 for it to form bubbles of vapor (boil).  The sample of = 87 octane=20 would require a temperature of about 215 deg F to form a = vapor=20 phase.

 

My take on this is it may be more productive to = be=20 concerned about the fuel supply to the high pressure pumps rather = than=20 worrying about "vapor lock" downstream of those = pumps. =20 This seems to be the conclusion reached by the recent thread on = this=20 subject, possibly now supported by actual data.  Of course = the data=20 only applies to the samples I obtained.

 

The higher temperature tolerance of the auto = fuel with=20 ethanol compared to the auto fuel without ethanol was surprising = to=20 me.

 

But I only collect data --- it is up to an = engineer to=20 make sense of it ;>)

 

Steve Boese
RV6A, 1986 13B NA, RD1A,=20 EC2

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