welding an aluminum spar

[a64pilot]

Aluminum could be ultrasounded, X-ray and I think even eddy current.
However dye pen is so easy and inexpensive why go further. Only issue with dye pen is defect has to be exposed to the surface, for a subsurface crack you would need X-ray etc.
Dye pen is very easy no reason why not to buy it and try it yourself.
The regular visual stuff is OK, but to do it right you need a very bright UV light to highlight the penetrant.

[Cherod]

Let's not get carried away here , it is not NASA nor nuclear , it's not even a main stay , its just a spiniker boom !!!

[groundtackle]

Originally Posted by a64pilot

Aluminum could be ultrasounded, X-ray and I think even eddy current.
However dye pen is so easy and inexpensive why go further. Only issue with dye pen is defect has to be exposed to the surface, for a subsurface crack you would need X-ray etc.
Dye pen is very easy no reason why not to buy it and try it yourself.
The regular visual stuff is OK, but to do it right you need a very bright UV light to highlight the penetrant.

I agree, very simple skill, even my sharpie works great in a pinch.
AL is difficult to dye as there is a slight undercut that show false negatives. Even when you grind it back. Its annoying.
As you say it also needs to be surface which is hopefully obvious. Usually looking for Pourosity, lack of fusion etc.
It also appears the op pic person did a non filler beauty wash pass, that is ok if you planned to do it.

Originally Posted by Cherod

Let's not get carried away here , it is not NASA nor nuclear , it's not even a main stay , its just a spiniker boom !!!

I guarantee NASA dudes google cracked aluminum welds when it goes bad.
Its all the same medium..
spoonikor bom?

[AKA-None]

Not sure if this was mentioned but the corners should be rounded not square and you should never start stop in a corner if at all possible.

And yes that original weld is drek

[groundtackle]

Captain Bill, so how did it all go?
Chris

[Captsteve53]

Just to confirm that stress relieving would be and is quite an easy procedure (yes even in the field or a mast) portable thermo coupling devices (220-110 v)are available for use with Aluminium, Stress relieving should be done for many hours (2-6) @ around 300-400 Celsius dropping after that by around 30-50 C an hour depending on type of Aluminum,

There's not to much data around on Stress reliving Aluminium or it's alloys but it does work, some years back I was involved in a 90 ft fishing vessel (Aluminium) that kept cracking the whole transom welds to the point of near sinking, we stress relieved with custom made thermo couplings @375 C for 6 hours, happy owner's never cracked again!

Modern portable digital equipment can be used for crack detection with good results but even the dye penetrate (used correctly gives acceptable results)

Cheers Steve

[BarryBlitzzz]

Originally Posted by Lepke

Certified in aluminum many years ago... Welds shrink when cooling. If you take two strips of mast thickness material and butted them together, and start welding from one end, by the time you get to the middle, the far end of the butt would be overlapped.
Just rewelding may not last as long as originally, new stresses along with the old ones. Usually production welding is done with wire, and after the original setup, done with less skilled welders, and rarely does post welding heat treatment get applied. Heat treating usually is heating the entire part uniformly and slowly cooling. Done in an oven. Finding one for a mast would be tough.
In repairing, I would drill the crack at both ends to relieve stress, grind the crack to clean metal, and Tig weld. Tig uses much less heat, so less shrinkage as the metal cools. Also skip weld. Short welds in opposite directions counter some of the shrinkage. Also slow cooling of the weld. In my day we wrapped the part in an asbestos blanket or dropped it into a tank of loose asbestos. All without any knowledge of the hazards. It's hard with a torch on aluminum because it transfers heat so well.
If it was my mast, I'd look into fitting some sort of reinforcement, gussets or a plate fitted to the mast shape to spread the stress over a larger area. Short welds. Full welding would just lead to more stress.

I'm gonna have to stoke this fire again here guys, about to do something similar.
i do not have a weld to fix, but am adding doublers over mast section where spreader bases attach. I am not thrilled about doing any welding.

my current idea and plan is replace the cast aluminum spreader bases with a stainless spreader base set up to take a thru-bar set up, all with a doubler sleeve wrapped around mast... my bond for sleeve to mast would be- aluminum rivets, along with "alumibond" epoxy in the sandwich.
Do we like this alumibond idea? or is it going to crack and flake off with first big flex?

[OceanSeaSpray]

Originally Posted by BarryBlitzzz

I'm gonna have to stoke this fire again here guys, about to do something similar.
i do not have a weld to fix, but am adding doublers over mast section where spreader bases attach. I am not thrilled about doing any welding.

my current idea and plan is replace the cast aluminum spreader bases with a stainless spreader base set up to take a thru-bar set up, all with a doubler sleeve wrapped around mast... my bond for sleeve to mast would be- aluminum rivets, along with "alumibond" epoxy in the sandwich.
Do we like this alumibond idea? or is it going to crack and flake off with first big flex?

Side note, I think Lepke meant MIG, not TIG, to control the heat. TIG is slow and puts a lot of heat in the parent material as a result.

Don't even think about aluminium rivets, they are weak and will briefly act as a little protective anodes for the stainless steel before disintegrating... Monel rivets are used for riveting in alloy spars, even when you rivet aluminium to aluminium. Most aluminium rivets are not even marine grade (there is copper in the alloy) and they disintegrate with salt water.

Wrap some cellophane film around the mast, fiberglass an insulator pad for the spreader sockets, then mark the edge of the stainless socket on it and trim it. It will give you a proper insulator with very high compressive strength. Before you assemble, put some lanolin between all the parts to protect the metals and keep the water out. Sometimes you can instead use a thick (~1mm) sheet of Nylon to the same effect if the pressure is well spread out. If you are going to use stainless steel, you need an excellent insulator. Corrosion between stainless and aluminium in rigs progresses very slowly, but it invariably ends up burning holes underneath the fittings.

Assuming that the old cast alloy sockets are not reusable, a better idea could fabricating new spreader sockets out of aluminium and anodising them.

If you use a through-bar design, then you don't normally need sockets, only a plate on each side to spread the pressure. On bigger boats, it becomes less and less acceptable to compress the mast wall and bolted spacers are used through the mast.