Patching a hole in aluminum

[Spud]

Here's what the threads here and my research have led me to. 1. Patch the hole with West Marine's Fix Fast and a layer of fiberglass cloth. 2. Remove boat seats by drilling out rivets, applying gentle heat to loosen adhesive and driving glued parts apart with a narrow wedge per SamSam and West Marine tech support. 3. Abrade aluminum by sanding or wire brush and apply West Marine's Aluminum Etching Kit #860 to delay oxidation and enhance adhesion. 4. Apply any good epoxy and fiberglass cloth tabbing to install wood parts and epoxy and rivets to install metal parts.

Thanks to all who helped me work this out including DanishBagger and Frosty whose advice I'm ignoring not out of disdain, but for lack of both trust in my welding source and money in my pocket plus a life-long tendency to do it my way even if I end up going down with the ship.

Still - if anybody has negative experience with this approach, I'll sure give your response careful attention.

[DanishBagger]

Haha, fair enough, Spud.

About epoxying aluminium and the oxydation that takes place:

If you haven't tried epoxying aluminium before (it's a bit tricky, imo), make sure that you have someone that has some mixed epoxy ready at hand, so you can apply it instantly after you have rinsed the aluminium with the etching kit. Aluminium oxydises (spl?) very fast, and you want it to adhere well.

If possible, see if you can find som scrap-aluminium to try it on first - it's much easier to toss the scrap metal away rather than removing hardened epoxy from the boat.

(I have covered some aluminium parts with epoxy filled with graphite powder before)

[mydauphin]

Epoxy is a good fix above waterline in non-critical areas. Never use graphite in aluminum boat, it is lower on galvanic scale than zinc or AL and will corrode AL. Sanding or sandblasting works good, for cleaning but also read up on alodine, or other zinc chromate processes. If the part is critical or under stress have parts welded Aluminum instead of epoxy. For small parts, JB Weld works pretty good.

[DanishBagger]

Perhaps I wasn't clear - the parts I'm talking about weren't integral to the hull, and the first two layers weren't with graphite, so ...

[bgeddes]

When I worked on aircraft the panels were glued to the airframe with some stuff we called "ProSeal". It was an epoxyish stuff that used MEK for a thinner/hardener. It would stick to clean aluminum with incredible strength, it's UV safe, and non-corrosive. I think it's pricey.

[Jimbo1490]

An option I have not seen mentioned is to rivet a patch over the hole with structural rivets and using a sealant applied to the overlap. Such a patch can be made to take the full structural load passing through the aluminum, if sized and riveted properly. Solid or 'bucked' rivets are the best, made of high alloy aircraft grade aluminum. This type of repair has the advantage of not using any heat. The aluminum ally your boat is constructed may not be weldable; if it was originally riveted together this is a clue.

Proseal is a polysulfide sealant. I mixed up a batch for some cockpit glazing just this afternoon. Very good stuff, though dreadfully toxic, especially the catalyst (as usual). It is very pricey, but has the advantage of containing a chromate in the mix specifically to help prevent corrosion on aluminum.

Getting a permanent structural bond on aluminum is not rocket science, but it does have its pitfalls. And if you get it wrong, the bond WILL fail. Even if you do it right, with time corrosion will inevitably creep under the bonded areas from adjacent areas . Salt water just sucks that way

I would go with a riveted patch with sealant. It's even quick to do, IF you have the tools and perhaps a helper if the hole is more than arm's length from the gunwale.

Jimbo