Cracked weld in Aluminum help

OK this is the hive mind after all. Anyone have some good ideas on how to fix this issue?

Aluminum boat, cracked along what appears to be a weld joint between a extra plate over the bow section and the hull.

I had an acquaintance weld over it (tig) once last year, just cleaned it up a bit and went over the top, no dice. The crack should probably be chased to open it a bit before welding? Seems like it could use a much larger bead?

Its not really accessible from the top, and has a aluminum plate 5200'ed over it on the inside..... So realistically its nearly impossible to get the back side of the weld area clean. (although It seems to be a plate over the hull section, may not actually get to this section pf metal)

Thoughts as to making a long lasting repair?

Cracked along weld running R-L here

You can just see the spot above "oad" on the trailer here. it starts at the keel and runs up.

Get a better welder? "Cheap" is not always "cheap." I would think that a professional would be able to fix that. Might have to flip it on its side, grind most of the way through, etc., but they should be able to fix that.

Dr. Hess wrote: Get a better welder? "Cheap" is not always "cheap." I would think that a professional would be able to fix that. Might have to flip it on its side, grind most of the way through, etc., but they should be able to fix that.

Yeah I think that it may be fixable with a bit more prep. Hes a decent welder, doesnt do structural work, but does do sanitary piping. But im no aluminum expert although i have looked at spool guns. It sees a fair bit of stress in that location.

Chase crack, larger gap tig doesn't like to fill, ( I think??? ), pay pro with mig gun. Really dont want to flip if I can help it....

I've seen the TIG pros do some amazing work in aluminum. Like my cracked Europa head, decades ago. 3 cracks between the spark plug holes and the exhaust valve seats, if I recall. They ground them down and TIG'ed them up. Good as new. The prep work is probably a lot of the job, and welding down is a lot easier than up on sideways. I would think (in my amateur opinion) that TIG would be better than a spool gun.

If you can't clean it perfectly then welding just won't work.

In two situations where the issue was watertight integrity at my old job we employed thin two part epoxy to seal the surface.

Another option is brazing on a sealing coat of appropriately compatible metal.

If structural integrity is needed then bite the bullet and disassemble the boat to allow excellent cleaning before welding.

Also think about heat treatment of the area post welding to soften the joint.

In reply to Advan046:

I cant get it clean without cutting the floor supports out, Id like to avoid that If possible. However it may end up getting there. If I pound on the bow side I can feel the crack move, not much but enough to feel, I dont know that a epoxy will be flexible enough.

I thought about brazing it, but again I dont think it will hold with the movement there.

Welding a patch panel spanning over the crack may be the best route.... It just sucks that its on the bottom.

If I can get through the summer (drill crack stop holes, and use 2 part epoxy marinetex or similar or 5200 to seal it?), I may be willing to cut it all apart this winter...... Id Like it fixed right eventually.

You could always use what holds the U.S. Merchant Marine together: Red Hand.

Dr. Hess wrote: You could always use what holds the U.S. Merchant Marine together: Red Hand.

Help me out.... My google fu is failing. No idea what Red Hand is....

Red Hand marine epoxy. You'll probably have to look at a marine supply company. It was literally holding most of the US Merchant Marine hulls together, at least in the 80's. Sailors would even use it to replace fillings in their teeth.

In reply to Dr. Hess:

Thanks! Sounds very similar to marine tex, just heat cured.

I'm disappointed. This far into the thread and not one mention of this.

What is going on with the hull above the problem area? Is that a bend/crease running vertically? If so you need to fix the cause of that as it will be flexing on the crease causing it to crack where you are having problems.

In short I suspect a bigger problem.

In reply to dean1484:

That's vertical crease is from someone hitting something hard on that side if the boat.yiur seeing the framing structure of the casting deck on the inside.

That crease doesn't line up with the Crack. This boat hasn't had an easy life....

If you can't clean the back side at least tape some plastic bag material around the area and back fill it with Argon for a few minutes before and while your welding. A tent so to speak. you don't need a lot of gas flow but needs to be there ahead of time to flush out the O2 1st. A pro welder can fix this easily and re-plate over it if warranted.

Stop drill the crack. Pre heat the aluminum before welding. Then weld. You may have to stop and re heat the area part way through. I suspect that the previous weld was made with out preheating an this means that the welder had to use more heat in a concentrated area to make the weld. This application of high heat caused the aluminum at the area that was being welded to become brittle and crack again.

It must be the photo because the crack looks to line up with the vertical line above. It does not have to be perfectly aligned. It looks close enough to me that it is has caused a point in the boat that can flex more. A concentrated flex point if you will. Instead of the liafs being distributed across the skin of the boat evenly that creas is focusing the normal flexing of the boat in that location. It I like bending a new piece of paper. It will form a nice radious. But put a crease in it and then bend the paper and it always bends at the crease. The bending forces are concentrated at the crease. The side of the boat is acting like a creased piece of paper causing the crack at the bottom. It us being flexed everytime the boat hits a small wave or dome one moves around in the boat. I have seen this same thing in many aluminum rowboats. It I why many are patched with a plate that is riveted and bonded over a damaged area. It I trying to re distribute the loading away from the crease in the hull to prevent a concentrated flex point.

44Dwarf wrote: If you can't clean the back side at least tape some plastic bag material around the area and back fill it with Argon for a few minutes before and while your welding. A tent so to speak. you don't need a lot of gas flow but needs to be there ahead of time to flush out the O2 1st. A pro welder can fix this easily and re-plate over it if warranted.

The crack does not go through the hull, no way to flood the backside really. There are a couple of small pin holes drilled in the hull way up towards the bow that I assume were for allowing things to escape from between the plates. but I literally cant reach them.

In reply to dean1484:

Good point on the crease, I had not thought about that action. The crease and end of the reinforcement plate are out of line by 8" ish inches.

Went to town with the grinder and drill last night. There was a lot of weld bead on there, either someone was messy with the spool gun or it has been repaired before. stop drilled the keel side, it appears my previous drill hole at the other end has worked so far (it was welded over, but you could see where the tig weld stopped.) It cleaned up pretty good, but the plates are very different thicknesses also, could this be causing it? Hull is ~1/8" (maybe 9 or 10 gauge alum?) reinforcement plate is 3/16 or maybe even 1/4", I assume those move at very different rates.

There is still some water between them that I figure will cause issues as well... I stop drilled to bottom (keel side) and it seeped out for a while.

Thoughts on adding some rosette welds an inch or so back from the crack? That should help keep the hull and plate together.

Ok I went the quick and dirty route. Wanted to use it this weekend... I found some west systems epoxy designed for aluminum boats, supposed to be flexible.

I drilled a small hole on the high side, about 1" back form the crack, Started injecting epoxy in there, I could see it coming through the crack and the first two holes. Couldn't get it to flow down to the bottom so I went from below there. The lowest (keel side) hole took A LOT, but i was able to get it to force its way out of the crack there as well. I put about 6 oz into it, A fair bit is just on the surface, but there is definitely some between the plates.

Beat it pretty good this weekend, Lake was super wind chopped. No cracks so far, knock on wood!

Red Hand saves another U.S. hull.

Dr. Hess wrote: Red Hand saves another U.S. hull.

Pretty much. All my aluminum welding buddies were busy... Hopefully this lasts as it will be an absolute bitch to clean enough to weld...

packing tape is awesome.

after a quick sanding.

bottom paint.

But it got us here and back

alumaloy