X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Mon, 16 Dec 2013 16:34:54 -0500 Message-ID: X-Original-Return-Path: Received: from mail-qe0-f48.google.com ([209.85.128.48] verified) by logan.com (CommuniGate Pro SMTP 6.0.7) with ESMTPS id 6641118 for lml@lancaironline.net; Mon, 16 Dec 2013 14:47:44 -0500 Received-SPF: pass receiver=logan.com; client-ip=209.85.128.48; envelope-from=dave.saylor.aircrafters@gmail.com Received: by mail-qe0-f48.google.com with SMTP id gc15so4269892qeb.7 for ; Mon, 16 Dec 2013 11:47:08 -0800 (PST) X-Received: by 10.49.2.170 with SMTP id 10mr35855166qev.24.1387223228171; Mon, 16 Dec 2013 11:47:08 -0800 (PST) MIME-Version: 1.0 Received: by 10.97.2.233 with HTTP; Mon, 16 Dec 2013 11:46:28 -0800 (PST) In-Reply-To: References: From: Dave Saylor X-Original-Date: Mon, 16 Dec 2013 11:46:28 -0800 X-Original-Message-ID: Subject: Re: [LML] Re: Paint Cracks X-Original-To: Lancair Mailing List Content-Type: multipart/alternative; boundary=047d7b6da3d4bd4b0404edac13a8 --047d7b6da3d4bd4b0404edac13a8 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable I think one of the conditions that puts cracks in paint is when you have several base materials in close proximity. I often see cracks around windows, especially windows installed to an exterior joggle. No surprise, since in that area the window material, adhesive, cloth/resin, filler, primer, and paint, all reside within a few thousandths of an inch from each other. As the mix heats and cools, each material expands and contracts at a different rate, vibrates at a different frequency, flexes differently, etc. Tough duty for the paint. One investment that seems to protect the paint from cracks is a single layer of very fine cloth (ACS P/N 1080-50) on any seams, potted areas, bodywork, joints, gaps, whatever. Then the paint only has to flex against a single, unitary base. Regarding being able to see the weave--I eventually just started thinking of it as proof that you were dedicated to keeping it light! Dave Saylor 831-750-0284 CL On Mon, Dec 16, 2013 at 9:17 AM, Michael Newman wr= ote: > 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 wr= ote: > >> 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 tol= d >> 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=E2=80=A6bed= ded every >> through-bolt in flox/epoxy, and covered every through-bolt around the >> door and over each =E2=80=9Cchicken plate=E2=80=9D where the pressure bu= lkheads attach to >> the fuselage (except two that I missed=E2=80=A6but that=E2=80=99s anothe= r story). Anyway, >> N437RP looked perfect when we first flew it=E2=80=A6and for about a year= . Then I >> started noticing very slight =E2=80=9Cdimples=E2=80=9D where the screw h= eads were located. >> No cracks or breaks, but the surface was being pulled inward very >> slightly=E2=80=A6I presume by flexing during pressurization. To be sure,= these are >> very difficult to see; I=E2=80=99d likely need to point them out with a = light or >> specific sun angle for you to see them at all, but they are noticeable t= o a >> discerning builder=E2=80=A6 >> >> At almost 6 years/1200 hours now, I am starting to develop slight cracks >> in the paint around the door latches. Nothing longer than =C2=BC,=E2=80= =9D 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 t= he >> latches off the fuselage to look at the flox pad it=E2=80=99s mounted on= =E2=80=A6just to >> be sure. It=E2=80=99s absolutely solid; no cracks or visible defects. My= opinion is >> that the fuselage/door undergo a lot more flexing/expansion than you=E2= =80=99d >> imagine during pressurization cycles; that some deformation/cracking at = the >> stress points is inevitable. =E2=80=A6one reason to be sure the cabin ov= er-pressure >> relief works as intended=E2=80=A6 J >> >> I=E2=80=99d be interested in the comments of others, but I=E2=80=99m not= sure how/if >> these can be completely eliminated. >> >> Bob Pastusek >> > > --047d7b6da3d4bd4b0404edac13a8 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
I t= hink one of the conditions that puts cracks in paint is when you have sever= al base materials in close proximity.

I often se= e cracks around windows, especially windows installed to an exterior joggle= . =C2=A0No surprise, since in that area the window material, adhesive, clot= h/resin, filler, primer, and paint, all reside within a few thousandths of = an inch from each other. =C2=A0As the mix heats and cools, each material ex= pands and contracts at a different rate, vibrates at a different frequency,= flexes differently, etc. =C2=A0Tough duty for the paint.

One investment that seems to p= rotect the paint from cracks is a single layer of very fine cloth (ACS P/N= =C2=A01080-50)=C2=A0on=C2=A0any seams, potted areas, bodywork, joints,= gaps, whatever. =C2=A0Then the paint only has to flex against a single, un= itary base.

Regarding being able to see th= e weave--I eventually just started thinking of it as proof that you were de= dicated to keeping it light!



Dave Saylor
831-750-0284 CL


On Mon, Dec 16, 2013 at 9:17 AM, Michael= Newman <mnewman@dragonnorth.com> wrote:
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.=C2=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>

=C2=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?=C2=A0

Justin,

I went to great pains to prevent this while b= uilding my IV-P=E2=80=A6bedded every through-bolt in flox/epoxy, and covered every through-bolt around the door and= over each =E2=80=9Cchicken plate=E2=80=9D where the pressure bulkheads att= ach to the fuselage (except two that I missed=E2=80=A6but that=E2=80=99s an= other story). Anyway, N437RP looked perfect when we first flew it=E2=80=A6and for about a year. Then I started noticing ver= y slight =E2=80=9Cdimples=E2=80=9D where the screw heads were located. No c= racks or breaks, but the surface was being pulled inward very slightly=E2= =80=A6I presume by flexing during pressurization. To be sure, these are very difficult to see; I=E2=80=99d likely need to point them out with = a light or specific sun angle for you to see them at all, but they are noti= ceable to a discerning builder=E2=80=A6

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 =C2=BC,=E2=80=9D 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=E2=80=99s mounted on=E2=80=A6just to be sure. It= =E2=80=99s absolutely solid; no cracks or visible defects. My opinion is th= at the fuselage/door undergo a lot more flexing/expansion than you=E2=80=99= d imagine during pressurization cycles; that some deformation/cracking at the stress points is inevitable. =E2=80=A6one reason to be sure the cab= in over-pressure relief works as intended=E2=80=A6 J

I=E2=80=99d be interested in the comments of = others, but I=E2=80=99m not sure how/if these can be completely eliminated.

Bob Pastusek



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