Return-Path: Sender: "Marvin Kaye" To: lml@lancaironline.net Date: Fri, 01 Oct 2004 23:39:48 -0400 Message-ID: X-Original-Return-Path: Received: from imo-m20.mx.aol.com ([64.12.137.1] verified) by logan.com (CommuniGate Pro SMTP 4.2.3) with ESMTP id 440080 for lml@lancaironline.net; Fri, 01 Oct 2004 22:13:46 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.12.137.1; envelope-from=Newlan2dl@aol.com Received: from Newlan2dl@aol.com by imo-m20.mx.aol.com (mail_out_v37_r3.7.) id q.1e8.2b3d61fc (4362) for ; Fri, 1 Oct 2004 22:13:10 -0400 (EDT) From: Newlan2dl@aol.com X-Original-Message-ID: <1e8.2b3d61fc.2e8f68b6@aol.com> X-Original-Date: Fri, 1 Oct 2004 22:13:10 EDT Subject: Re: [LML] Re: Legacy missing wing panel, sanders and bond prepping X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1096683190" X-Mailer: 9.0 for Windows sub 5032 -------------------------------1096683190 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Hi Mike Are the angle brackets you talk about aluminum? There is definitely a problem bonding aluminum if it isn't prepped right. Aluminum oxidizes rapidly and while you might get a great bond to the oxide, the oxide doesn't have a good bond to the aluminum. Adhesive is also critical, and Hysol is one of the few appropriate adhesives. And as you said, the prepregs are difficult to bond to and easy to do incorrectly. I also use a technique for nonstructural bonds in aluminum that works pretty well by first sanding the aluminum prior to bonding, then mix the epoxy and wetsand the aluminum again with wet sandpaper so that only clean aluminum is exposed. Then I wipe it down to get rid of the excess and contaminated adhesive and bond it in with some more epoxy. It works well but the bonds are not reliable enough to use for critical structures. When it really counts, use bonding epoxy and CAA or PAA (chromic acid anodized or phosphoric acid anodized) treated aluminum, cleaning with de-ionized water and technical grade acetone. Speaking of which, it costs more but I like to use technical grade acetone for the critical bonds. A wipe with the Jasco from the hardware store is OK I think for getting the gross amounts off but I'd rather do the last wipe with a higher grade of purity than the constituted 'tone. If you keep it as your last wipe, a gallon would probably do the whole plane. You can get it from chemical supply stores. And as a former scientist, one thing you learn is that you never put the rag against the bottle and tip the bottle since it washes contaminates from the rag back into the bottle. I would disagree with the idea of exciting the molecules by sanding though. What you want is a good clean unreacted surface for your bonds, not one that has been left open and linked to other miscellaneous bits of whatever. Many people in the industry say that a surface that has just had the peel ply removed is perfect for bonding, then others have said that they prefer a light sanding even if it was just released. What I suspect is that it's fine after the peel ply is removed but it is my old training earlier that makes me want to sand it anyway. I'm sure someone has the data comparing it but I haven't come across it. The next posting I do is going to have the data I collected on Jeffco vs Hysol and WEST epoxy. Dan -------------------------------1096683190 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable

Hi Mike

Are the angle brackets you talk about aluminum? There is definitely a p= roblem bonding aluminum if it isn't prepped right. Aluminum oxidizes r= apidly and while you might get a great bond to the oxide, the oxide doesn't=20= have a good bond to the aluminum. Adhesive is also critical, and Hysol= is one of the few appropriate adhesives. And as you said, the prepregs are=20= difficult to bond to and easy to do incorrectly. I also use a techniqu= e for nonstructural bonds in aluminum that works pretty well by first sandin= g the aluminum prior to bonding, then mix the epoxy and wetsand the aluminum= again with wet sandpaper so that only clean aluminum is exposed. Then= I wipe it down to get rid of the excess and contaminated adhesive and bond=20= it in with some more epoxy. It works well but the bonds are not reliab= le enough to use for critical structures. When it really counts, use b= onding epoxy and CAA or PAA (chromic acid anodized or phosphoric acid anodiz= ed) treated aluminum, cleaning with de-ionized water and technical grade ace= tone.

Speaking of which, it costs more but I like to use technical grade acet= one for the critical bonds. A wipe with the Jasco from the hardware st= ore is OK I think for getting the gross amounts off but I'd rather do the la= st wipe with a higher grade of purity than the constituted 'tone. If y= ou keep it as your last wipe, a gallon would probably do the whole plane.&nb= sp; You can get it from chemical supply stores. And as a former scient= ist, one thing you learn is that you never put the rag against the bottle an= d tip the bottle since it washes contaminates from the rag back into the bot= tle. I would disagree with the idea of exciting the molecules by sandi= ng though. What you want is a good clean unreacted surface for your bo= nds, not one that has been left open and linked to other miscellaneous bits=20= of whatever. Many people in the industry say that a surface that has j= ust had the peel ply removed is perfect for bonding, then others have said t= hat they prefer a light sanding even if it was just released. What I s= uspect is that it's fine after the peel ply is removed but it is my old trai= ning earlier that makes me want to sand it anyway. I'm sure someone ha= s the data comparing it but I haven't come across it.

The next posting I do is going to have the data I collected on Jeffco v= s Hysol and WEST epoxy.

Dan

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