Connections to mast, screws or rivets?

[LouK]

In the process this weekend of replacing steaming light & VHF antenna, question is which makes more sense, using screws or aluminum rivets to secure to mast?

[Reefmagnet]

I'd be inclined to use screws for any application where the attachment may need to be removed or replaced in between major refits, rivets otherwise. Use TefGel or Duralac as a galvanic isolator with both.

[LouK]

I had pondered this, rivets are pretty strong & no problem w/galvanic action. They also are less apt to chafe internal lines. As noted,screws definitely easier to remove

[Jim Cate]

Both those items require occasional replacement, so I'd use screws myself with whatever flavor of anti-seize you prefer. I've had equally good results from Duralac, various brands of anti-seize and lanolin. Slather it on, and if the antenna base or light fixture are stainless, put a barrier between the fixture and the mast as well.

If you rivet them, next week something will require you to remove one or the other!

Jim

[RaymondR]

I'm a rivet favourer myself.

When an SS screw "grows" into aluminium they are buggers of things to drill out. Aluminium blind rivets self pilot the hole, are easy to drill and tend to drill clean without enlarging the hole. Unfortunately, if what you are riveting to the mast or boom is made of SS the heads will tend to sacrificially corrode off the alloy rivets so in that case monel rivets are better.

Also the advantage of not sticking through so far or being as mean to ropes and wires.

[er9]

Is it acceptable to use aluminum screws on aluminum mast if they are decent diameter and reasonably strong maybe 10-24 or larger?

[vpbarkley]

Regarding aluminum screws, they are not often used or found.
The heads tend to round easily.
McMaster-Carr does have some: www.mcmaster.com

[PaulvR]

Raymond has it, monel rivets are the best option by far in my experience. Very easily removed and replaced. Stainless eats aluminium, continuously!

some gratuitous waffle.....I had an Ibold ketch, an Endurance 40 for a decade in the 90's, and she was 10 yrs old when I bought her....the owner/builder told me he'd put the SS steps, all the way to the masthead, with a (dental?) barium paste barrier and rivets. I never replaced a single one, and they were all firm when the new owner climbed to the mastead. I suspect they remain so, as she still sails ever westward....

[bobgarrett]

Another option is aluminium rivnuts. No foreign metals and aluminium machine screws that can removed easily.
Look them up.

[Clivevon]

+1 for monel rivets. much stronger than aluminium.

[Stewie12]

I dont like the idea of being at the top of a mast and drilling a rivet out. When working with aluminium I put a barrier of rubber or whatever behind whatever I am attaching to the aluminium so that it is insulated. Then I drill the holes and put in rawlplugs, then use SS screws to fasten whatever to the aluminium. With the insulation there will be no corrosion.

[Cheechako]

For those particular items I'd use screws. Coat the screw with Lanolin or Lan O Cote so they dont corrode into the mast.

[thinwater]

I assume we are talking about self-taping screws.


You can do that at the masthead in general, but NEVER us self taping screws down the mast. The point can snag and shred lines and cut wires. Machine screws in threaded holes are safer.


Honestly, if I had to rate them in order of the failures I've seen...

1. Seized or stripped, self-tapers. Ick.
2. Failed aluminum rivets. The heads don't last. Also weak.
3. Failed machine screws. Either corroded or poorly taped. But a good method.
4. Stainless Rivets. Can corrode after 30+ years, but not always. Pretty easy to drill out--can't say that about stuck screws or machine screws. Best method in thin masts, not so much thicker masts, where they are likely too small. Think how many 30-45 year-old beach cats are held together with these before you disparage them too heavily.
5. Monel rivets. Never seen a failure.

I will use all of these, each in it's place. Except aluminum rivets. And self-tapers in aluminum.

[OS2Dude]

I made covers for the gates in our mast so the sail can lay flatter to the boom. I used aluminum for the covers and aluminum screws. I drilled and tapped the mast. No problems in the few instances when I've had to remove the sail.

[Cheechako]

Yes, no self tapping screws, Drill and tap. Use coarse thread in aluminum. Rivets are fine but it's just that you have to drill them out up the mast if you ever need to remove the item.