Aluminum Welding Questions

[whydontu]

My welding skills would be 0.3 out of ten, but my business partner has asked me if I can help him with a small project. After upgrading his 36ft speedboat to twin 300HP Yamaha outboards, the attachment post for water skiers no longer clears the top of the outboards. (I know, the horror of first-world problems.)

The request is to increase the distance between the two cross arms and the plate. The plate attaches to the top surface of the transom. The cross arms need to be 12” farther away to clear the outboards. The open end away from the cross arms is drilled and tapped in two places to bolt to a couple of angle brackets below the transom. The top is capped off with a 1/2” thick plate.

The problem is the post is bizarre. It’s fabricated from two pieces of aluminum pipe - 2” Sch40 sleeved inside 2-1/2” Sch40. The two pieces of pipe are welded at each end, with the cross arm as a single piece of 1” aluminum bar welded to the outside of the 2-1/2” pipe. So I can’t just cut and weld in a section, because it’s impossible to weld the inner pipe.

I‘m about 90% sure the manufacturer made up this kluge so they would have enough wall thickness to drill and tap, my math says adding the inner 2” pipe doesn‘t provide much extra strength.

So - try to cut it apart and do a multi-step staggered weld, or cut off the plate and just buy two new pieces of pipe and make a whole new post?

 

[Aliva]

I suggest buy a new 2" schedule 80 pipe and make new post, No farting around with different size pipes.

 

[DPittman]

After upgrading his 36ft speedboat to twin 300HP Yamaha outboards, the attachment post for water skiers no longer clears the top of the outboards.

I'm sorry I can't get past the thought of skiing behind 600hp.

 

[phaxtris]

@Aliva has a good suggestion

My question is what are you going to be welding this with ? 1" plate, 1/2 plate, sched 80 pipe....that all takes mega amps for aluminum, a 200a machine isnt going to cut it without some big time preheat

 

[Former Member]

I'm sorry I can't get past the thought of skiing behind 600hp.

Never enough power and speed .

 

[Tom O]

600 HP! Reminds me of Superdave!

 

[LenVW]

I suggest buy a new 2" schedule 80 pipe and make new post, No farting around with different size pipes.

Start with a hefty 2” Schedule 80 pipe.
I would agree that preheating would be required for the fusion process.

I would like to hear from current TIG welders.
It has been years since I had any aluminum welding done.
There must have been vast improvements in processes and welders.

 

[phaxtris]

i missed that the original od pipe was 2.5.....you should keep it at a 2.5" pipe at least, esp considering you would loose wall thickness by going with one pipe over the original two

you are absolutely going to be right to the floor with a 200a machine, 2.5 sched 80 is .276" thick, you will almost certainly require preheat...youll see

@LenVW the only real changes in the last 20 years is that they no longer recommend pure tungsten for aluminum, and inverters are more common (frequency control). Pulse, balance control, that has all be around for 20+ years, dynasty's are still the top machine (big buck inverter). Syncrowaves are still produced and i would say still more popular because of the huge price gap between a 400a transformer and a 400a ac inverter....if you knew how to tig aluminum 20 years ago you havent missed anything

 

[Former Member]

Start with a hefty 2” Schedule 80 pipe.
I would agree that preheating would be required for the fusion process.

I would like to hear from current TIG welders.
It has been years since I had any aluminum welding done.
There must have been vast improvements in processes and welders.

Good prep and Argon.

 

[phaxtris]

Argon.

or if you want to get real crazy argon/helium mix for all the BTU's

 

[LenVW]

i missed that the original od pipe was 2.5.....you should keep it at a 2.5" pipe at least, esp considering you would loose wall thickness by going with one pipe over the original two

you are absolutely going to be right to the floor with a 200a machine, 2.5 sched 80 is .276" thick, you will almost certainly require preheat...youll see

@LenVW the only real changes in the last 20 years is that they no longer recommend pure tungsten for aluminum, and inverters are more common (frequency control). Pulse, balance control, that has all be around for 20+ years, dynasty's are still the top machine (big buck inverter). Syncrowaves are still produced and i would say still more popular because of the huge price gap between a 400a transformer and a 400a ac inverter....if you knew how to tig aluminum 20 years ago you havent missed anything

Ryan,
20 years ago, I was designing moulds for vacuum formed HDPE pipe. We had to sand cast huge blocks with excess aluminum in places where we machined reference points that we needed to mount the blocks to the apparatus.

I had experimented with ‘fabricated’ moulds made from 6061 plate and extruded profiles.
The idea was never developed due to a changes in priorities and the sale of the company.

Do you have experience TIG welding large (3/4” thick) plates into sealed 6 sided boxes ?
Would welding the boxes (48”H x 20”D x 18” W) take a long time to TIG weld with 1/2” fillet welds at the corners with common welders these days ?

 

[phaxtris]

Do you have experience TIG welding large (3/4” thick) plates into sealed 6 sided boxes ?
Would welding the boxes (48”H x 20”D x 18” W) take a long time to TIG weld with 1/2” fillet welds at the corners with common welders these days ?

Yes, I have welded thick sections, 5/8 wall pipe with Tig the thickest that comes to mind. I can't say how long for sure without having an idea of how many inches of weld that is, but I would wager *if* you could find someone to do it with a tig your going to pay for a full day for sure if not two. Most guys are going to steer you towards MIG for that thickness of plate and that size of weld, faster and less warpage. Should be no concern of leakage, it's going take 3 passes anyways, MIG is really what a guy should use for that thickness and weld size

 

[Former Member]

I meet a fellow that welds Aluminum with Stick and he does it from thin sheet to thick plate.

No argon required.

 

[LenVW]

Yeah I was figuring on 3 passes per joint and MIG would best for the amount of wire used.
The advantage I was trying to ‘push’ through the design team was the fact that all the fabrication materials would be virtually void of porosity that can be produced when pouring is sand castings.
Thanks for your estimated welding time.

 

[Susquatch]

After upgrading his 36ft speedboat to twin 300HP Yamaha outboards,

I'm sorry, I can't get past wondering how you call anything 36ft long a speed boat.

 

[whydontu]

I'm sorry, I can't get past wondering how you call anything 36ft long a speed boat.

I know nothing about boats, just that it’s insanely fast. It’s 36ft long, maybe 7ft wide, and it’s fricking uncomfortable to be on it going 60 knots into pouring rain. First trip my favorite ball cap got whisked off my head about 20 seconds after partner cracked open the throttle, followed about 20 seconds later by the forward hatch whooshing out into the Salish Sea. Oops, forgot to tighten it down.

 

[DavidR8]

I'm sorry, I can't get past wondering how you call anything 36ft long a speed boat.

Put enough horsepower into anything and it'll be fast!