Fiberglas over Aluminum

Hi, Again. I have a repair where I need to have some solid support behind a fiberglas cloth surface added on. Because of the shape and need for an internal hollow,, I want to use an aluminum rectangular tube, and then lay fiberglas cloth over it. Question is whether there are any concerns (corrosion, chemical activity, or the like) in putting epoxy coated cloth over aluminum? It's early. Am I making sense? Many Than ks Charlie Annapolis

Charlie, The only real concern I would have with cloth over aluminum is the size of the area. Aluminum will grow and shrink with temperature changes more than the glass. If the area is large, this might cause the aluminum to shear itself from the epoxy. This may not be an issue in your application once the glass is cured as the tube will remain encased in the glass (if that it's what you have going on, of course). I have experienced temperature related shearing on the steel boat I work aboard... I won't use epoxy as a filler again as it is too brittle for my application. I'm chipping rust yet again. Mike "Husar, Charlie [USA] (ASE)" <hu… [at] bah.com> wrote: >Hi, Again. I have a repair where I need to have some solid support >behind a fiberglas cloth surface added on. Because of the shape and >need for an internal hollow,, I want to use an aluminum rectangular >tube, and then lay fiberglas cloth over it. > >Question is whether there are any concerns (corrosion, chemical >activity, or the like) in putting epoxy coated cloth over aluminum? > >It's early. Am I making sense? > >Many Than ks >Charlie >Annapolis --

The other concern is getting the fiberglass to stick to the aluminum. I put a notch in my whisker pole a few years ago and had to put a fiberglass patch on it. I was advised that the issue is the aluminum will oxidize immediately and the fiberglass will not stick to the aluminum oxide. They gave me two choices. 1) coat the aluminum with the West System and wet sand though the raw epoxy. 2) Alodine the aluminum first. This is a chemical process that involves brushing on one liquid, washing it off, then brushing on a second one. It is an alternative to anodizing, a complex process. I already had the chemicals required from another project so I went that way. The patch held right up to the day we bent the tube and had to replace it. Now if the aluminum tube you are using is already anodized, just use it. Allen On Sun, Dec 22, 2013 at 6:09 AM, Mike <mi… [at] wahini.org> wrote: > > > Charlie, > The only real concern I would have with cloth over aluminum is the size of > the area. Aluminum will grow and shrink with temperature changes more than > the glass. If the area is large, this might cause the aluminum to shear > itself from the epoxy. This may not be an issue in your application once > the glass is cured as the tube will remain encased in the glass (if that > it's what you have going on, of course). > I have experienced temperature related shearing on the steel boat I work > aboard... I won't use epoxy as a filler again as it is too brittle for my > application. I'm chipping rust yet again. > Mike > > > "Husar, Charlie [USA] (ASE)" <hu… [at] bah.com> wrote: >> >> >> >> Hi, Again. I have a repair where I need to have some solid support behind >> a fiberglas cloth surface added on. Because of the shape and need for an >> internal hollow,, I want to use an aluminum rectangular tube, and then lay >> fiberglas cloth over it. >> >> Question is whether there are any concerns (corrosion, chemical activity, >> or the like) in putting epoxy coated cloth over aluminum? >> >> It's early. Am I making sense? >> >> Many Than ks >> Charlie >> Annapolis >> > > -- > Sent from my Android phone with K-9 Mail. Please excuse my brevity. > > >

On 12/22/2013 6:30 AM, Husar, Charlie [USA] (ASE) wrote: > Hi, Again. I have a repair where I need to have some solid support behind a fiberglas cloth surface added on. Because of the shape and need for an internal hollow,, I want to use an aluminum rectangular tube, and then lay fiberglas cloth over it. I saw the comments about thermal movement and adhesion. Then your later description made it sound as though the aluminum does not need to be bonded securely to the epoxy and cloth--it's there for backing-plate service, essentially. As long as the resin/cloth matrix captures it adequately, you're all set. The Gougeon Bros.' written materials have a discussion of fastener bonding with epoxy. You might want to consult their analysis of tension & sheer forces on the fasteners and consider whether you could rebuild the structure without aluminum. Chris Campbell

Use wood. :-) On Mon, Dec 23, 2013 at 8:18 AM, Chris Campbell <cc… [at] lsnm.org> wrote: > > > On 12/22/2013 6:30 AM, Husar, Charlie [USA] (ASE) wrote: > > Hi, Again. I have a repair where I need to have some solid support > behind a fiberglas cloth surface added on. Because of the shape and need > for an internal hollow,, I want to use an aluminum rectangular tube, and > then lay fiberglas cloth over it. > > I saw the comments about thermal movement and adhesion. Then your later > description made it sound as though the aluminum does not need to be > bonded securely to the epoxy and cloth--it's there for backing-plate > service, essentially. As long as the resin/cloth matrix captures it > adequately, you're all set. > > The Gougeon Bros.' written materials have a discussion of fastener > bonding with epoxy. You might want to consult their analysis of tension > & sheer forces on the fasteners and consider whether you could rebuild > the structure without aluminum. > > Chris Campbell > > >