X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 16 Dec 2013 12:17:02 -0500 Message-ID: X-Original-Return-Path: Received: from mail-vc0-f180.google.com ([209.85.220.180] verified) by logan.com (CommuniGate Pro SMTP 6.0.7) with ESMTPS id 6640728 for lml@lancaironline.net; Mon, 16 Dec 2013 11:02:15 -0500 Received-SPF: pass receiver=logan.com; client-ip=209.85.220.180; envelope-from=dragonnorth@gmail.com Received: by mail-vc0-f180.google.com with SMTP id if17so3280140vcb.39 for ; Mon, 16 Dec 2013 08:01:40 -0800 (PST) MIME-Version: 1.0 X-Received: by 10.52.249.105 with SMTP id yt9mr616835vdc.67.1387209700059; Mon, 16 Dec 2013 08:01:40 -0800 (PST) X-Original-Sender: dragonnorth@gmail.com Received: by 10.52.248.12 with HTTP; Mon, 16 Dec 2013 08:01:39 -0800 (PST) In-Reply-To: References: X-Original-Date: Mon, 16 Dec 2013 11:01:39 -0500 X-Google-Sender-Auth: xSvavkWlNZ9kLUfT9CbiXVKMG9U X-Original-Message-ID: Subject: Re: [LML] Re: Paint Cracks From: Michael Newman X-Original-To: Lancair Mailing List Content-Type: multipart/alternative; boundary=089e0153686466b09e04eda8ed7e --089e0153686466b09e04eda8ed7e Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable I had cracks extending from the corners of the door hinges. They sound similar to Bob's. They were thoroughly investigated as part of the structural repairs now nearing completion on N776CM. Because there was other working going on to replace the windows we were able to grind into them fairly deep and make sure nothing was going on. My opinion is that these are caused by pressure flexing and that there is nothing you can do about them. On Mon, Dec 16, 2013 at 9:33 AM, Robert R Pastusek wrot= e: > Justin Wrote: > > > > I recently had my ESP painted and there are already significant cracks > showing in the paint around the door frame corners and hinges. I was told > that the flexibility of modern urethane paints would prevent this. How > common is this for the pressurized aircraft? > > Justin, > > I went to great pains to prevent this while building my IV-P=85bedded eve= ry > through-bolt in flox/epoxy, and covered every through-bolt around the > door and over each =93chicken plate=94 where the pressure bulkheads attac= h to > the fuselage (except two that I missed=85but that=92s another story). Any= way, > N437RP looked perfect when we first flew it=85and for about a year. Then = I > started noticing very slight =93dimples=94 where the screw heads were loc= ated. > No cracks or breaks, but the surface was being pulled inward very > slightly=85I presume by flexing during pressurization. To be sure, these = are > very difficult to see; I=92d likely need to point them out with a light o= r > specific sun angle for you to see them at all, but they are noticeable to= a > discerning builder=85 > > At almost 6 years/1200 hours now, I am starting to develop slight cracks > in the paint around the door latches. Nothing longer than =BC,=94 but eve= ry > latch attachment as at least one. They are more noticeable than the > dimples. I am sure these are not structural defects, and I took one of th= e > latches off the fuselage to look at the flox pad it=92s mounted on=85just= to > be sure. It=92s absolutely solid; no cracks or visible defects. My opinio= n is > that the fuselage/door undergo a lot more flexing/expansion than you=92d > imagine during pressurization cycles; that some deformation/cracking at t= he > stress points is inevitable. =85one reason to be sure the cabin over-pres= sure > relief works as intended=85 J > > I=92d be interested in the comments of others, but I=92m not sure how/if = these > can be completely eliminated. > > Bob Pastusek > --089e0153686466b09e04eda8ed7e Content-Type: text/html; charset=windows-1252 Content-Transfer-Encoding: quoted-printable
I had cracks extending from the corners of the door hinges= . They sound similar to Bob's. They were thoroughly investigated as par= t of the structural repairs now nearing completion on N776CM. Because there= was other working going on to replace the windows we were able to grind in= to them fairly deep and make sure nothing was going on.=A0

My opinion is that these are caused by pressure flexing and = that there is nothing you can do about them.


On Mon, Dec 16, 2013 at 9:33 AM,= Robert R Pastusek <rpastusek@htii.com> wrote:

Justin Wrote: <= u>

=A0

I recently had my ESP painted and there are already = significant cracks showing in the paint around the door frame corners and h= inges. I was told that the flexibility of modern urethane paints would prev= ent this. How common is this for the pressurized aircraft?=A0

Justin,

I went to great pains to prevent this while b= uilding my IV-P=85bedded every through-bolt in flox/epoxy, and covered every through-bolt around the door and= over each =93chicken plate=94 where the pressure bulkheads attach to the f= uselage (except two that I missed=85but that=92s another story). Anyway, N4= 37RP looked perfect when we first flew it=85and for about a year. Then I started noticing very slig= ht =93dimples=94 where the screw heads were located. No cracks or breaks, b= ut the surface was being pulled inward very slightly=85I presume by flexing= during pressurization. To be sure, these are very difficult to see; I=92d likely need to point them out with a ligh= t or specific sun angle for you to see them at all, but they are noticeable= to a discerning builder=85

At almost 6 years/1200 hours now, I am starti= ng to develop slight cracks in the paint around the door latches. Nothing l= onger than =BC,=94 but every latch attachment as at least one. They are more noticeable than = the dimples. I am sure these are not structural defects, and I took one of = the latches off the fuselage to look at the flox pad it=92s mounted on=85just to be sure. It=92s absolutel= y solid; no cracks or visible defects. My opinion is that the fuselage/door= undergo a lot more flexing/expansion than you=92d imagine during pressuriz= ation cycles; that some deformation/cracking at the stress points is inevitable. =85one reason to be sure the cabin ove= r-pressure relief works as intended=85 J

I=92d be interested in the comments of others= , but I=92m not sure how/if these can be completely eliminated.

Bob Pastusek


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