[sschefer]

This may sound like a dumb question but I gotta ask anyway.. I've got a bunch of frames for a boat that I have to build out. The frames are cut from 1/4" 5052 H-32 and the perimeter has a 1/4x1.5" 6061-T6 flat bar attached all around. The flat bar is attached to the face edge of the frame so it creates either a tight butt joint to weld or a fillet weld if done from the opposite side.

So I'm sitting here overthinking again and seeing that if I grind a bevel on both pieces and then weld from the top down I have a good chance of full penetration and a weld I can clean up and virtually make dissappear. The problem is I'll be welding right on the edge and I'll need to practice a lot before I go live. If I choose to go with a fillet weld, I could MIG or TIG it and be done with it but TIG would mean a lot of cup walking unless I just skip welded it. MIG would mean spray welding and my MIG doesn't have pulse so I'd probably skip weld that way also.

So if you can see it in your minds eye from my description, what do you think you would opt for. The frames are 50-50 as far as structural is concerned. It all depends on what I do after the plating is on the frames. The flat bar is strictly for stiffening. I'm always concerned about 6061 and HAZ but I think I'll be O.K. there. I'm having a problem finding 5052 flat bar locally. I may be able to remedy that so let's not consider it as part of the problem for now.

Thanks to all

[jpence38]

Is this the type of joint you are describing? A corner joint. And is the 1/4" 5052 a piece of flat stock too?

[sschefer]

Exactly, those are my options. As of right now that 1/4" flat bar is 6061 T6. The frame piece is 5052. I can special order 5052 for the flat bar which is what I will likely do. The level of difficulty is about the same for all three joints I guess. I'm favoring TIG over MIG since there could be some moderate strike forces on what will end up being a flange.

[jakeru]

It seems like there are enough factors to consider (which side points "up", which is out, which is visible and important aesthetically, from what direction torch access and good torch control would be easiest) that making this call without seeing more pictures would be difficult.

However I wanted to throw out that in addition to the pictures of various corner joints above, you could do an open corner joint. That is where you set the pieces up just touching each other at the corners. It leaves a big gap to fill, which is a good bet for achieving a high strength/full penetration weld, when welding from just one side, without doing any grinding.

Here is a picture I found on der interweb that illustrates the concept well:

[sschefer]

Thank you guys, the corner joint is one I had considered but the flat bar sits flush with edge of the frame and the height and square is critical. I could probably get by with 1/16" but not a 1/4". I think I'll just run the flat bar through the router table and put a bevel on it then TIG it with a copper backer bar to deal with the HAZ and the 6061 flat bar if I end up having to use it.

Thanks again..

[sschefer]

Burnt up a bunch of filler rod today and the winner is,,,, 60 deg bevel. Best strength and smallest HAZ.. Thanks again for the ideas.

[dustelf]

how can you tell the haz on AL?

[sschefer]

You use heat crayons.

[Joe]

Somebody please tell a noob what HAZ stands for?
Thanks,
Joe

[Rugar]

Somebody please tell a noob what HAZ stands for?
Thanks,
Joe

Heat Affected Zone