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  #16  
Old 03-08-2017, 12:52 AM
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PAR PAR is offline
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Sweet God, with all the experts on aluminum bonds, I'm surprised modern vessels and aircraft can live more than a few months at all.

If paying attention in say, the last several decades about composites in general and sandwich structures in particular? Ever seen the construction drawings for a modern airliner? How about a modern race boat? It's amazing they manage to complete a single race or Pacific crossing flight, given your concerns about "thermal expansion".

I live a few miles from this place;


. . . guess what it's made out of? The Epcot Center was opened in 1982 and the thermal expansion issues you're might be worried about, have been addressed.

Emendel, PC-11 has been around for decades (many) and it's a thickened, rather crude BPA epoxy formulation. It works, but is extremely costly per ounce, compaired to even the major brand premixes now available.

Lastly, bonding aluminum with epoxy isn't hard, unless you you want the very last ounce of modulus, out of the resulting composite. The aluminum wings and structural elements of some seriously large aircraft are bonded with epoxy, not to mention some humble boats too.
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  #17  
Old 03-08-2017, 04:45 PM
Dukke57 Dukke57 is offline
 
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Aluminum tank install

Thnks Barry for your feedback , yes it is gas .
1) if I drill a couple of weep holes into bilge from old tank then water from bilge will be able to get in from bilge to tank , but I understand what ur saying it's 1979 and most likely impossible from keeping water from leeching in from deck
2) any idea where I can purchase plastic strips , for bottom of tank to mount, I need 1 inch thick and side 3/4 . The only plastic I can find are cutting boards , I don't think composite decking would due the trick if soaking in water . All feed back greatly appreciated . Fishing days ahead . Thnks
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  #18  
Old 03-08-2017, 05:01 PM
Barry Barry is offline
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Quote:
Originally Posted by Dukke57 View Post
Thnks Barry for your feedback , yes it is gas .
1) if I drill a couple of weep holes into bilge from old tank then water from bilge will be able to get in from bilge to tank , but I understand what ur saying it's 1979 and most likely impossible from keeping water from leeching in from deck
2) any idea where I can purchase plastic strips , for bottom of tank to mount, I need 1 inch thick and side 3/4 . The only plastic I can find are cutting boards , I don't think composite decking would due the trick if soaking in water . All feed back greatly appreciated . Fishing days ahead . Thnks
I would not know where to get it in NY but there will be a lot of plastic retailers where you should be able to find some
Probably a good choice would be lexan, but you have to abrade the surface for the adhesive to stick to it

Stay away from acrylic, as it can shatter easily
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  #19  
Old 03-10-2017, 12:23 AM
valery gaulin valery gaulin is offline
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I think the best most verstile adhesive for aluminum is Metacrylate. There is many different type of metacrylate adhesive but from what I understand you dont even need to buff the oxide layer on aluminum. Otherwise I would use 3m 5200 polyurethane adhesive. Avoid epoxy for this, I think that the prep needed is not for the DIY for aluminum.
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  #20  
Old 03-10-2017, 01:04 AM
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Wow, more 3M-5200 fans, likely that haven't any idea of the tensional modulus of this sealant, that happens to have fairly aggressive adhesive qualities. It shouldn't be confused with a real adhesive, because once you compare the properties, it becomes very apparent which is better. Of the polyurethanes it ranks high (about 700 psi in tensile), but again shouldn't be considered a true adhesive, but an adhesive/sealant.

MMA's are an option, though availability and pricing (generally the MMA's are about $10 per ounce) might be interesting and would be typical of the methacrylate products around on the retail level. I previously mentioned Plexus, which is a methacrylate adhesive.

Again, those that are down playing epoxy, need to justify these claims, as it's not hard to get good results, is easily DIY friendly and products are commonly available, relatively inexpensive with tested and proven results.
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  #21  
Old 03-10-2017, 05:18 AM
valery gaulin valery gaulin is offline
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@PAR: You are right that polyurethane like 3M 5200 are more of an ahesive/sealant type of product. But setimes when it is close to impossible to get perfectly close mating surface inbetween the two part that needs to ne glued the polyurethane makes it very easy to achieve good result.

Epoxy is the stronguest of all if everything is perfect when using it with Aluminum. If there is just a little gap in the joint nothing will adhere. Just try it yourself and try to glue aluminum together with epoxy! You will see that it is very hard to get consistent result.

Again from my limited experience it seams that the best result are with Metacrylate adhesive when aluminum is involved. Verh forgiving but not as good as polyurethane for gap filling netween the mating surface. But methacrylate is a real adhesive.
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  #22  
Old 03-10-2017, 07:48 AM
Barry Barry is offline
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http://www.compositesworld.com/artic...poxy-adhesives


An interesting read about the three types of adhesives that have been discussed
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  #23  
Old 03-10-2017, 08:07 AM
Manfred.pech Manfred.pech is offline
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New

New development: Nano metal sculpturing by electrochemically etching - http://www.uni-kiel.de/pressemeldung...anosculpturing .

www.uni-kiel.de/download/pm/2016/2016-285-6.jpg
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  #24  
Old 03-10-2017, 10:37 AM
valery gaulin valery gaulin is offline
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@Barry: Awsome article! Now when are going to build an aluminum glued sailboat!!!
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  #25  
Old 03-14-2017, 07:23 PM
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Ike Ike is offline
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Quote:
You could private message Ike who was involved with writing the ABYC specs. Once you get him started on foam, you will probably not consider it.
Thanks Barry: You're right. I could probably go on ad infinitum about this. But you have pretty well covered it. The basic problem is adhesion of the foam to the tank. No matter how well you think it has adhered to the tank eventually it will begin to separate. Once the separation occurs moisture gets trapped against the tank, and that is a sure prescription for a leaky tank. The Federal Regulations and ABYC have specific requirements for adhesive strength of foam to the tank. The adhesive strength has to be greater than the shear strength of the foam. Very hard to achieve.

As for 3M 5200 I can attest to it's "agressive adhesive strength" about twelve years ago a fitting on the side of my motorhome fell off. The screws had worked loose and damaged the holes where attached. This device acts as a stop for the slide, stopping it from damaging the side of the MH and damaging the mechanism that moves it in and out. After thoroughly cleaning the surface I reattached it with 5200. It's still there. No screws. Rain, snow, sleet, hail, hot sun. Nothing has affected it. Hopefully I will never need to replace it.

I have used it on my boats and it is definitely a wonderful adhesive. But if you want to remove the item at some future date, don't use 5200.
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