Mast steps: aluminum mast with stainless steel screws?

[Brassmonkeys]

In the process of planning a design for mast steps. I have seen many people connect the steps with rivets however I don’t trust that method. I have also seen people use stainless steel screws but now I worry about corrosion. Would love to hear your input

[Joh.Ghurt]

Rivets are better than screws in many instances. If your steps are made of plastic or aluminium, you'll have least troubles by using aluminium rivets.

[tkeithlu]

Two different metals in contact with each other does not per se result in corrosion. There has to be an electrolyte in there as well. If you can seal up the screws against water, it's OK. But then, rivets work and you don't have to concern yourself with the issue. Note here that there is very little load involved. The mast sits on the step in compression, and bears on the sides of the step for any lateral load.

[wsmurdoch]

I have an aluminum mast with cast aluminum folding steps installed with flat head aluminum machine screws set into drilled and tapped holes in the mast. The screws and the holes were both covered with Tefgel before the screws were installed. The screws came from McMaster-Carr. The holes were drilled and tapped with a combination 1/4-20 drill and tap bit.

[Manateeman]

It’s difficult to answer your question with no information about your boat or your mast or where you plan to sail.
We could open a Pandora’s box by suggesting the following.
TIG weld first, then drill and tap flat head titanium screws then cover the heads with glass set in epoxy.
This should be load tested by supporting the weight of two frolicking manatees.
We tried to find data on aircraft crashes due only to rivet failure but an FAA data base search did not confirm any cases.
Happy trails to you.
Mark and his manatee crew still perplexed by why they call them “pop” rivets and what does that have to do with the “snap, crackle and pop” cereal.
Should you dip the rivets in milk not Tef-Gel ?

[Brassmonkeys]

Thanks, it’s a 40’ fiberglass catamaran with an aluminum mast that will be sailing in salt water, I found affordable stainless steel steps that I am considering which adds complexity. Would 5200 be an option to buffer the stainless steel step from the aluminum mast? Then I was thinking stainless steel screws with tefgel. Tell me everything I am thinking is wrong ha

[thinwater]

Originally Posted by Brassmonkeys

In the process of planning a design for mast steps. I have seen many people connect the steps with rivets however I don’t trust that method. I have also seen people use stainless steel screws but now I worry about corrosion. Would love to hear your input

Practically all of the negatives you can think of for rivets apply to machine screws. Rivets can be installed poorly, but so can screws. Screws can chafe cables and ropes. Screws can be removed. Isolation and corrosion issues are the same. Depending on dimensions, strength is comparable. Trust is the one thing that should not be in the equation.


A better question is "why steps?" But that's on you.

[tkeithlu]

I apologize for misunderstanding the question. I was thinking "mast step" not "mast steps." If you are going to use rivets, go up a step or two to aircraft quality, rather than the cheapo "Pop Rivet." CherryMax is a usual standard:

https://www.aircraftspruce.com/catal...AaAi6oEALw_wcB

[MicHughV]

I put mast steps up by drilling and tapping for machine screws.

Prior to inserting each screw, I put a dab of 5200 on it, and also on the underneath side of the step where it touched the mast...ie, the top and bottom. in other words, the actual "connection" to the mast was completely sealed from the elements. A little bit of the 5200 oozes out, once the machine screws are tightened down, you can clean that off with acetone right after you finish each step or just leave as is.

Never had a lick of problems with it.

[JohnHolland]

Ditto , also installed aluminum steps with machine screws and small dab of 4200 over tapped holes before screws just in case removal is necessary.
Spray painted mast and steps with white Awlgrip after installation.
NP so far

[Martkimwat]

Originally Posted by tkeithlu

Two different metals in contact with each other does not per se result in corrosion. There has to be an electrolyte in there as well. If you can seal up the screws against water, it's OK. But then, rivets work and you don't have to concern yourself with the issue. Note here that there is very little load involved. The mast sits on the step in compression, and bears on the sides of the step for any lateral load.

I believe he is asking about fitting steps to the mast not a mast step.

[vpbarkley]

The best way to install aluminum steps on an aluminum mast is as follows.
Drill the mast and install aluminum Riv Nuts.
Fasten with aluminum machine screws.
McMaster.com is the source for these items.
You will have no worries about galvanic corrosion.
The steps will be easily removable and very strong.

[Clivevon]

If using rivets in an aluminium mast, monel metal rivets would be much stronger than aluminium rivets, but still use a barrier compound such as Duralac, 5200 or 4200 .

[sailingchiro]

I second the rivnuts although they require a larger hole than tapping or pop rivets. Rivnuts are pretty inexpensive and easy to install. They make a special tool for them but I have just used the bolt with nuts that compress the inside. They will stick out about 1/16"-1/8" due to round mast and the outside edge of the rivnut.

I can't imagine how many beers it would take to tap all the holes for screws. Hats off to you guys that have done it. I don't have the patience or desire.

I think, drilling a pop rivet is easier than trying to get a corroded stainless screw out of a mast if they need to be removed. If you make a bigger hole while removing the pop rivet, use a rivnut in its place.

I would use stainless pop rivets dipped in gel with the rivet gun with the 2' long handles. Second choice is the rivnuts dipped in gel.

I keep several sizes of rivnuts on hand just in case I overdrill a pop rivet. I also keep bigger pop rivets as well.

Several years ago, we almost took delivery of a Bonanza airplane with wings from Mexico. Someone decided to drill out a several rivets and kept putting bigger and bigger rivets in place. Some with washers. We didn't take the plane.

[Redline452]

FWIW, I drilled and tapped to 1/4-20 and used stainless machine screws dipped in Tefgel on aluminum steps on an aluminum mast. I can’t imagine having to ever remove them, so if they do seize not a problem. With three 1/4” screws per folding steps, they are, and I’m sure will remain, solid. Fresh water boat, for now.
It did take a while but I took the opportunity while the mast was down for other reasons. Measuring and calculating the spacing so as to use spreaders as steps took almost as long as the installation.