gluing to aluminum?

[thadJ]

Have an Aluminum hull (Pacific Boat) bought used. Want to ad rod holders/storage built of wood along sides. Will 3M 5200 be the right glue for the job?

[Bergalia]

Thadj - this is purely a personal opinion (because I'm not too familiar with aluminium boats - timber being the good lord's natural choice) but I've yet to meet a glue which can give a 'permanent' grip to this manmade material.
As the alloy ages it deteriotates giving off a 'powdery' surface - which destroys the glue 'key'.
Why not attach your 'extras' by 'through' bolts or screws backed by timber brace plates (with suitable waterproof sealant between)
However - stand by for the 'alloy' crews with much, much more expertise.

[D'ARTOIS]

It won't hold - for a time yes, but tell me how long you want the connection to hold and I give you the appropriate answer.

[Deering]

Sand the surface first with 80 grit, then use 5200 and you should be fine. The adhesive prevents air from oxidizing the aluminum, so it'll last a long time. Through bolting with stainless hardware is even better. Or both! Belt and suspenders!

[PAR]

Aircraft have had their aluminum skins glued down for quite some time now. They use a Super Glue type of product and it works very well.

Deering is correct, in that the absence of oxygen in the joint will prevent oxidation (the powdery stuff). 3M 5200 is a sealant that has very high stick properties, but it still is a sealant, not a true adhesive. I'd be inclined to mechanically fasten the pieces you want (rod holders, etc.) and bed the mating surfaces with a good sealant like BoatLife Caulk or similar. If you're intent on "bonding" to the hull sides, rather then making some supports that hang down from the side deck (or something) then epoxy would be my choice.

Aluminum requires some special prep for most adhesives to bond properly, epoxy is no exception. Log onto www.WestSystem.com to learn about epoxy bonding techniques on aluminum, in their "how to" section.

[Bergalia]

Par is correct in saying that aircraft have had their skins gued on for some time. (Originally Aero-lite - developed at Duxford in Cambridge, UK). However, aircraft skins do not have weights hanging from them as would be suggested by Thadj's original query. To the contrary, aircraft skins have pressure, rather than 'lift' applied.

[PAR]

Actually there would be glued surfaces in tension as well as compression on an aircraft, plus the other forces. Aluminum isn't a difficult material to glue, as long as it's prepped properly.

[Thunderhead19]

Glues don't like uneven forces that would tend to peel the part away from the base. If the part was in straight tension or shear it would be best. Aluminum will slowly oxidize under the 3M5200 because it has a porosity to it. It is actually a moisture-cure urethane and has to absorb moisture from the air in order to ...well, cure. It is true that the oxide layer will eventually de-bond from the substrate. Simple solution-primer it first. The meanest stuff I ever saw for gluing aluminum was made by Locktite. I think it was called H8000 and it was a two-part acrylic ahdesive. In thirty minutes it bonded so hard that I couldn't get the parts appart with a hammer. After a whole day, those parts were stuck there for good. I was told that with primer, it would be even better and last longer.

[thadJ]

Thanks all very much for all your advise. You are all very knowledgable and helpful. I'll give all suggestions careful thouhgt!