building aluminum masts

[boathemian]

Hello I want to build new aluminum masts and need to know if my sections of 6061 t6 pipe should be sleeved and bolted with flathead screws or plug welded and the seam welded? will the heat from the welding affect the joint and need to be re-treated? Where's Brent Swain when you need him???

[Geoduck]

I would sleeve the sections together, plug weld, leave enough gap at the butt inorder to weld into the sleeve making a 100 percent penetration.
If you really want to get fancy, cut a deep V into the ends of both pipes so they lock together. That way the weld joint will staggered around the pipe.

[Panope]

Originally Posted by Geoduck

If you really want to get fancy, cut a deep V into the ends of both pipes so they lock together. That way the weld joint will staggered around the pipe.

That is what I did for the tapered octagonal top of my mast.

I am not sure how far the "heat affected zone" propagates from the weld. Using the small "V" scarf technique might not leave enough heat treated metal for adequate strength.

If I were joining two sections of the same material I might just use a simple scarf joint of maybe 8 to 1 (assuming I had enough material length to sacrifice for the joint).

Steve

[Geoduck]

That's a pretty wild looking joint!
Maybe a little over kill?
What I had in mind was a birds mouth scarf joint..
From what I've seen over the years, and it seems to work, is a simple butt weld backed up with a sleeve to weld to, with the sleeve generally plug welded above & below the butt joint.
This is the way I've done it in the past and haven't had one fail yet, knock on wood!

[Panope]

Ya, it is a little weird. Part of the rationale was to elegantly blend a tapered octagon into a round tube. Also, this technique does not require that the welds be very strong. A good thing given my welding ability.

Steve

[Cheechako]

Most production masts seem to be sleeved at the joint and either welded or riveted. Evidently extrusions cant be gotten that are long enough.

[model 10]

They added 4' to our mast and they welded the simple butt joint and riveted the inner sleeve.

[barnakiel]

I have seen welds where the original extrusion has been used (sections cut out). Rivets where extrusion got extended.

b.

[Geoduck]

Years ago, when I was working at Summerfields boat yard in Ft Lauderdale, we had replaced a guys rigging and used stay locks. The cap shroud failed and put a hell of a bend in the mast at the spreader. Fred Sparry, the yard manager was having a fit! He thought he'd have to eat a new mast.
I told him that I might be able to straighten it out, given enough time, by heat shrinking it.
So we laid it out and I went to work with a weed burner and a garden hose, heating it up and cooling it off with the bent side up, allowing gravity to help.
I had it straight as an arrow in a couple of days.
I became Fred's hero.
The boat sailed away and we never heard another word so I guess it must have held up or maybe the rig fell down and the boat sunk, I don't know. The mast was about 70' long, it would have been an expensive item to replace. I should have gotten a raise but I didn't!

[boathemian]

Thanks guys, I'm concerned my welding skills aren't up to the job and think maybe I should bolt or rivet the section s together.... ANy ideas how to calculate what size and how many screws I should use for this???

[Jim Cate]

Originally Posted by boathemian

Thanks guys, I'm concerned my welding skills aren't up to the job and think maybe I should bolt or rivet the section s together.... ANy ideas how to calculate what size and how many screws I should use for this???

Well, another approach would be to do all the prep work and fitting yourself and then have a pro do the welding. The actual welding wouldn't take very long and thus shouldn't cost much.

Cheers,

Jim