Re-rivetting SS fixtures to aluminium mast

[ganter]

Hi,

I've removed various stainless-steel fittings; tangs, plates, shroud caps, etc, from the aluminium mast for inspection - all were riveted from new.

For the re-attachment of them I intend to use Duralac to create the seal between the two metals (of course) but what spec is required for the rivets to attach them to the mast?

They must obviously be of the utmost high-performance in terms of Load and Anti-corrosion.

Please only post if you have direct knowledge of this topic.
If you find yourself starting your reply with; "I haven't done this personally but..." then don't bother posting.

Thank you in advance.

ganter.

 

[vyv_cox]

You will find two grades of aluminium pop rivets on the market. They are either described as 'aluminium', 99.9% pure, 1xxx grade, or 'alloy', an aluminium/magnesium alloy of 5xxx grade. There is a world of difference in the strength and corrosion resistance of the two. RS components do both and no doubt plenty of other quality suppliers do also.

 

[Champagne Murphy]

You will find two grades of aluminium pop rivets on the market. They are either described as 'aluminium', 99.9% pure, 1xxx grade, or 'alloy', an aluminium/magnesium alloy of 5xxx grade. There is a world of difference in the strength and corrosion resistance of the two. RS components do both and no doubt plenty of other quality suppliers do also.

So where do ‘monel’ rivets come in that classification?

 

[PetiteFleur]

I always thought you always used Monel pop rivets for this application - this is what I've used in the past, much stronger than Aluminium and no corrosion as long as you use Duralac or similar. They are MUCH harder to fit and you may need to use a Lazy Tong or long handled riveter. You can buy them in small quantities and length.

 

[matthewriches]

Selden instructed us, and therefore we have used, Monel with Duralac.

 

[ganter]

I always thought you always used Monel pop rivets for this application - this is what I've used in the past, much stronger than Aluminium and no corrosion as long as you use Duralac or similar. They are MUCH harder to fit and you may need to use a Lazy Tong or long handled riveter. You can buy them in small quantities and length.

I was hoping for "Monel" to come up - I have an Air-Riveter - but what exactly are the properties of Monel Rivets - and why are they the choice?

What does "Monel" mean - in terms of metallurgy?
I apologise for my ignorance on the subject.

 

[lw395]

Monel.
Expensive and you'll want a good tool.
I use these for anything high load.

For light load, ordinary ali is fine. You don't need monel for the courtesy flag halliard, but just about everything else?

 

[NormanS]

I used monel rivets for the mast steps on both my masts. No way was I going to use any second choice material for such a safety critical installation.

 

[doug748]

Here you go:

https://shop4fasteners.co.uk/monel-dome-head-rivets.html

Alloy rivets are pretty good but they tend to struggle in a salty environment. Good you have an air gun OP, although the newer lazy tong riveters will react a 1/4 in rivet, you do tend to suck your shirt lap up your backside as you do it.

 

[ganter]

Here you go:

https://shop4fasteners.co.uk/monel-dome-head-rivets.html

Alloy rivets are pretty good but they tend to struggle in a salty environment. Good you have an air gun OP, although the newer lazy tong riveters will react a 1/4 in monel rivet, you do tend to suck your shirt lap up your backside as you do it.

Could you expand on what you mean by that please re; Lazy Tong riveters and shirts getting sucked up, etc...

Thanks in advance.

 

[doug748]

Here is a good quality one, note it will only cope with up to 5mm rivets:

https://www.ebay.co.uk/itm/Eclipse-...052972?hash=item5669abc7ec:g:SHMAAOSwPe1UEGDS

Even those go off with a crack and are difficult if not impossible, unless you are in a good position and well braced. So no good if you are up the mast on a step ladder.

 

[NormanS]

I used a "Faithful Long Handled" riveting tool, which at £20 from Amazon, seems like a much better buy, and is much more controllable than the lazy tongs type. My mast step rivets were 6.4mm (1/4").

 

[matthewriches]

Just had to lol at that comment

, you do tend to suck your shirt lap up your backside as you do it.

 

[thinwater]

Sealing (the mandel falls out on most, leaving a leak--important on dinghy masts)? High strength? Head style? Lots of options.

 

[john_morris_uk]

I fitted all my mast steps with the mast up and working from a bosuns chair. Monel rivers fitted with a Lazy tongs riveter but at each station I had a length of line round my torso and round the mast to brace myself against.

I marked the height and then put the step up against the position and marked and drilled the first hole (usually top right). I then riveted the step in place using the first single hole but didn’t cinch the river up completely. I then used the stainless step as a guide/template to drill the remaining holes. I used a Makita cordless drill and a Cobalt drill bit. My steps were supplied with four polythene washers to fit between the step and the mast and the reason I didn’t cinch the first rivet up tight and to breaking off the mandrel was to allow enough slack to slide the nylon/polythene washers in place. I was always worried that I was going to drop one of these polythene washers but in the end only dropped one which I replaced by cutting one (rather crudely) out of a polythene bag.

Monel rivets all the way up the twenty or so steps I fitted. (Obviously you fit two steps either side at the top to stand on when you’re working at the masthead.) I didn’t have any great difficulty popping the rivets with the Lazy Tongs riveter with a line round my shoulders/torso, but I’m a big guy (over 6’2” and used to work out a lot).

The steps have been up a few years now. They’re the fold in sort and one draw back is they’re a bit stiff to deploy or stow as you’re climbing up or down the mast. A squirt of PTFE spray lubricant helps. The very thin nylon/polythene washers isolating the stainless mast step from the aluminium mast have worked well with no signs of any corrosion at all so far.

 

[vyv_cox]

So where do ‘monel’ rivets come in that classification?

Monel 400 used for pop rivets is a copper-nickel with about twice the tensile strength of aluminium alloys in the 5xxx series. It is expensive and for that reason is rarely used by professional spar makers. The vast majority of rivets used in mast construction are made from 5056 alloy. Very few applications on most masts require the additional strength of monel, and the corrosion resistance of 5056 is perfectly adequate, particularly when bedded in Duralac.

My Selden mast is well over 30 years old and riveted throughout with aluminium rivets that I assume are 5xxx types. I have never seen any rivet that might be monel or stainless steel. There is no corrosion and it has never been necessary to replace any rivets.

 

[BabaYaga]

Monel 400 used for pop rivets is a copper-nickel with about twice the tensile strength of aluminium alloys in the 5xxx series. It is expensive and for that reason is rarely used by professional spar makers. The vast majority of rivets used in mast construction are made from 5056 alloy.

My Selden mast is well over 30 years old and riveted throughout with aluminium rivets

Are you sure about this?
In their booklet 'Hints and advice', Seldén recommends monel rivets:

'Bearing in mind the risk of corrosion, monel pop rivets are the best choice for fastenings, particularly when attaching something to a thin-walled (< 3 mm) section.'

It would surprise me if they didn't follow their own advice.
I have a 40 years old Seldén mast and have always believed the rivets were monel.

 

[vyv_cox]

Are you sure about this?
In their booklet 'Hints and advice', Seldén recommends monel rivets:

'Bearing in mind the risk of corrosion, monel pop rivets are the best choice for fastenings, particularly when attaching something to a thin-walled (< 3 mm) section.'

It would surprise me if they didn't follow their own advice.
I have a 40 years old Seldén mast and have always believed the rivets were monel.

How old is the booklet? 5056 rivets have excellent resistance to corrosion. In these over-cautious days they may have different views from those of years ago.

 

[BabaYaga]

How old is the booklet? 5056 rivets have excellent resistance to corrosion. In these over-cautious days they may have different views from those of years ago.

It's from the current edition, taken from their website:
http://www.seldenmast.com/files/1571039872/595-540-E.pdf

 

[vyv_cox]

It's from the current edition, taken from their website:
http://www.seldenmast.com/files/1571039872/595-540-E.pdf

40 years ago monel was fairly exotic stuff. The booklet looks quite recent. I have little doubt that all my rivets are aluminium alloy.