X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Fri, 30 Apr 2010 08:00:52 -0400 Message-ID: X-Original-Return-Path: Received: from qmta15.emeryville.ca.mail.comcast.net ([76.96.27.228] verified) by logan.com (CommuniGate Pro SMTP 5.3.6) with ESMTP id 4241999 for lml@lancaironline.net; Thu, 29 Apr 2010 17:51:56 -0400 Received-SPF: pass receiver=logan.com; client-ip=76.96.27.228; envelope-from=draerogel@comcast.net Received: from omta10.emeryville.ca.mail.comcast.net ([76.96.30.28]) by qmta15.emeryville.ca.mail.comcast.net with comcast id BTE01e0CA0cQ2SLAFZrM06; Thu, 29 Apr 2010 21:51:21 +0000 Received: from [10.0.1.3] ([98.225.112.12]) by omta10.emeryville.ca.mail.comcast.net with comcast id BZrL1e00A0G6Jyi8WZrMWF; Thu, 29 Apr 2010 21:51:21 +0000 From: Poco John Mime-Version: 1.0 (Apple Message framework v1078) Content-Type: multipart/alternative; boundary=Apple-Mail-1-65441453 Subject: Re: [LML] Cabin Door Window-IV-P X-Original-Date: Thu, 29 Apr 2010 14:51:41 -0700 In-Reply-To: X-Original-To: "Lancair Mailing List" References: X-Original-Message-Id: X-Mailer: Apple Mail (2.1078) --Apple-Mail-1-65441453 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=windows-1252 Bob, the pictures are not totally clear (no pun intended) as to the = cause of the problem but here is my two cents worth. The = "crystallization" I believe is the plexiglass separating internally due = to stress. Think of it as de-laminating although the material is not = made by laminating. Plexiglass is made by polymerization in a variety = of ways and then usually molded to different shapes -sheets, rods. etc. = The polymerization of the plexiglass forms an amorphous structure with = no crystals formed unlike glass. The bonding of the window to the door = appears to be very good and the "crystallization" area shows the = initiation stress riser. Had the window bonding been less well done = the possibility is that the window would just have separated from the = frame. The likely hood is that there was a small flaw in the plexiglass = and an initial stressor (perhaps the mechanics) that started the = internal crack. Once the crack starts it will "runaway" till its = stopped (stop drilling) or it fails. I didn't stay at a Holiday Inn but I did spend many years in polymer = chemistry research...=20 It would be interesting to see the outside edge of the window to see = where the initial propagation point was. John Poco =20 On Apr 29, 2010, at 11:10 AM, Robert Pastusek wrote: > Lancair builders, > =20 > Two weeks ago, I discovered what appeared to be about a 1=94 = =93crystallization=94 just visible by looking through the Plexiglas at = an angle within the carbon fiber =93sandwich=94 holding the door window = in my Lancair IV-P. This is just visible in the attached photos of the = upper back corner of my cabin door. It=92s in the lower center of the = =93outside=94 photo; upper center of the =93inside=94 photo, and is = directly across the door frame from the upper rear door latch. > =20 > I asked Bill Harrelson to have a look at it on Saturday, and by that = time, the small defect I originally saw had clearly spread to a crack = of about 4=94 running from below the original crystallization area to = the upper back curve of the window. The pictures show the resulting = crack generated in the interior and exterior paint. > =20 > Brent Reagan sent detailed pictures and instructions on how to repair = this (MANY THANKS BRENT), and I am ready to pull the door and start = cutting out the window for replacement. Fortunately I have an extra = window available from buying the =93fast build door=94 in 2004 after = buying the complete kit, with window, some years earlier; but before I = cut into it, I was trying to figure out what=92s caused this, and seek = your advice on how to prevent a reoccurrence. > =20 > The background: The complete fast build door was installed in 2004 and = the aircraft painted in 2006. It first flew in June, 2008 and has just = over 500 flying hours to date. I normally fly in the high teens/low = flight levels, but tested the airplane to FL250 and have been there a = few times since to avoid weather. I normally leave the cabin altitude = controller set at 1000=92, generating the rated 5.5 PSI pressure = differential any time the aircraft is above 14,000=92 or so. I would = estimate the airplane has 200-250 hours at 5+ PSI. I first noticed the = crystallization while cleaning the windows. There was no crack visible = at that time, and the defect was directly across from the upper rear = door latch. Note also that the door lift strut attaches to the door = frame just above this point. This new strut attach location was = incorporated in the factory fast build door that I received. > =20 > I have been very careful with the door and have not had any problems = with it at all. It closes and latches easily without binding, and with = very light pressure on the closing handles. The only possibly-related = thing that I can think of is that I left the airplane for a minor = servicing last month, and the maintenance crew worked it on the ramp on = a windy day. It=92s possible that the door was opened by someone not = familiar with it, and allowed to extend upward hard against the lift = strut by the wind. I don=92t know this to be a fact, but it=92s the only = possibility I can think of=97and even so, the flaw did not start at the = lift strut attachment point. I flew the airplane at 17,000=92 (full 5.5 = PSI differential pressure) for three hours after the maintenance work, = and flew it four more times in the local area with the cabin partially = pressurized. Lucky?? Another explanation?? > =20 > Any thoughts/comments appreciated. Also, is there anything I should = look for as I cut out the old window? > =20 > Many thanks in advance, >=20 > Bob Pastusek > -- > For archives and unsub = http://mail.lancaironline.net:81/lists/lml/List.html --Apple-Mail-1-65441453 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=windows-1252 Bob, the pictures are not totally clear (no pun = intended) as to the cause of the problem but here is my two cents worth. =  The "crystallization" I believe is the plexiglass separating = internally due to stress.  Think of it as de-laminating although = the material is not made by laminating.  Plexiglass is made by = polymerization in a variety of ways and then usually molded to different = shapes -sheets, rods. etc.  The polymerization of the plexiglass = forms an amorphous structure with no crystals formed unlike glass. =  The bonding of the window to the door appears to be very good and = the "crystallization" area shows the initiation stress riser.   Had = the window bonding been less well done the possibility is that the = window would just have separated from the frame. The likely hood is that = there was a small flaw in the plexiglass and an initial stressor = (perhaps the mechanics) that started the internal crack.  Once the = crack starts it will "runaway" till its stopped (stop drilling) or it = fails.
I didn't stay at a Holiday Inn but I did spend many years in = polymer chemistry research... 
It would be interesting to = see the outside edge of the window to see where the initial propagation = point was.

John Poco  
On Apr = 29, 2010, at 11:10 AM, Robert Pastusek wrote:

Lancair = builders,
Two = weeks ago, I discovered what appeared to be about a 1=94 = =93crystallization=94 just visible by looking through the Plexiglas at = an angle within the carbon fiber =93sandwich=94 holding the door window = in my Lancair IV-P. This is just visible in the attached photos of the = upper back corner of my cabin door. It=92s in the lower center of the = =93outside=94 photo; upper center of the =93inside=94 photo, and is = directly across the door frame from the upper rear door = latch.
I = asked Bill Harrelson to have a look at it on Saturday, and by that time, = the  small defect I originally saw had clearly spread to a crack of = about 4=94 running from below the original crystallization area to the = upper back curve of the window. The pictures show the resulting crack = generated in the interior and exterior = paint.
Brent = Reagan sent detailed pictures and instructions on how to repair this = (MANY THANKS BRENT), and I am ready to pull the door and start cutting = out the window for replacement. Fortunately I have an extra window = available from buying the =93fast build door=94 in 2004 after buying the = complete kit, with window, some years earlier; but before I cut into it, = I was trying to figure out what=92s caused this, and seek your advice on = how to prevent a reoccurrence.
The = background: The complete fast build door was installed in 2004 and the = aircraft painted in 2006. It first flew in June, 2008 and has just over = 500 flying hours to date. I normally fly in the high teens/low flight = levels, but tested the airplane to FL250 and have been there a few times = since to avoid weather. I normally leave the cabin altitude controller = set at 1000=92, generating the rated 5.5 PSI pressure differential any = time the aircraft is above 14,000=92 or so. I would estimate the = airplane has 200-250 hours at 5+ PSI.  I first noticed the = crystallization while cleaning the windows. There was no crack visible = at that time, and the defect was directly across from the upper rear = door latch. Note also that the door lift strut attaches to the door = frame just above this point. This new strut attach location was = incorporated in the factory fast build door that I = received.
I = have been very careful with the door and have not had any problems with = it at all. It closes and latches easily without binding, and with very = light pressure on the closing handles. The only possibly-related thing = that I can think of is that I left the airplane for a minor servicing = last month, and the maintenance crew worked it on the ramp on a windy = day. It=92s possible that the door was opened by someone not familiar = with it, and allowed to  extend upward hard against the lift strut = by the wind. I don=92t know this to be a fact, but it=92s the only = possibility I can think of=97and even so, the flaw did not start at the = lift strut attachment point.  I flew the airplane at 17,000=92 = (full 5.5 PSI differential pressure) for three hours after the = maintenance work, and flew it four more times in the local area with the = cabin partially pressurized. Lucky?? Another = explanation??
Any = thoughts/comments appreciated. Also, is there anything I should look for = as I cut out the old window?
Many = thanks in advance,

Bob = Pastusek
<Outside.JPG><Inside.JPG>--
For archives and unsub