Rivets - monel or aluminium?

[webcraft]

On the way here an enthusiastic attempt to flatten the main led to the kicking strap coming away from the boom.

It was reattached with 4mm monel rivets, which fitted the 4 existing holes.

Our crew thought these were too small, and advised replacing them. I have some 5mm monel rivets, but at 18mm long I think these are too long to rivet a thinnish plate to the boom.

I can get shorter 5mm aluminium rivets. Should I use these, use the long monel rivets or leave it with the current 4mm monel rivets?

- W

 

[vyv_cox]

There are two types of aluminium rivets. The cheap and ubiquitous ones are 1xxx series, pretty much pure aluminium with low strength. The others, usually described as 'aluminium alloy' are 5xxx series, stronger and with far better corrosion resistance. I would use the 5xxx ones for your fairly heavy duty fastening but not the 1xxx.

 

[cherod]

The monel ones are certainly stronger , fitting them is murder , a big gun is needed ,

 

[Malish]

Er, replace with Monel ones that are the correct size and length; not exactly expensive, e.g : Monel Dome Head Rivets - Shop4Fasteners

 

[webcraft]

There are two types of aluminium rivets. The cheap and ubiquitous ones are 1xxx series, pretty much pure aluminium with low strength. The others, usually described as 'aluminium alloy' are 5xxx series, stronger and with far better corrosion resistance. I would use the 5xxx ones for your fairly heavy duty fastening but not the 1xxx.

Thanks Viv, I will wander down to the (French) chandlery and see if it gives a clue on the packet. I suspect it may not.

Otherwise I think we will just have to be gentle with the kicker until we get to Spain.

- W

 

[webcraft]

Er, replace with Monel ones that are the correct size and length; not exactly expensive, e.g : Monel Dome Head Rivets - Shop4Fasteners

I am in Audierne in France with a very limited choice.

I am also not sure how one knows what the correct length is. Is there a formula?

- W

 

[webcraft]

The monel ones are certainly stronger , fitting them is murder , a big gun is needed ,

I've got a decent gun on board, it seems to cope with 5mm monel OK

- W

 

[billcole]

I don't know if the main is loose footed, but if it is, could you do something with a big jubilee clip (maybe from a car parts shop if not available in the chandlers) through the eye of the fitting and around the top of the boom to temporarily add strength until you can get the correct rivets and fix it properly ?

As far as rivet length goes, I found this..

The length of the rivet should be equal to the thickness of both objects you are fastening, plus 1.5 times the diameter of the rivet's stem. For example, a 1/2-inch diameter rivet being used to fasten two one-inch thick plates will have to be 2 3/4 inches long.

although I don'r expect your boom is made from 1" thick metal !

 

[webcraft]

So assuming the boom is 4mm thick and the plate is 3mm thick, rivet length should be (for 5mm rivets) 14 or 15mm

There are 5mm x 14mm ally rivets in the chandler's in a marine multipack. If these are 5xxxxx then maybe I will try them.

It's not a loose footed main, so the jubilee clip idea is a non starter I am afraid.

There IS a keyhole slot just forward of the existing plate which might take an M10 bolt, so perhaps that is a possible bodge in extremis.

- W

 

[cherod]

Just fit the buggest dia that will fit into the existing hole , monel if available , not rocket science ?,,,, good luck , i hope you are enjoying your trip ?

 

[rogerthebodger]

So assuming the boom is 4mm thick and the plate is 3mm thick, rivet length should be (for 5mm rivets) 14 or 15mm


- W

That is the minimum length you can use longer, you just reset the rivet gun for a second to third pull until the mandle breaks.

I would use you 5mm 18mm long monel

 

[Graham376]

There are two types of aluminium rivets. The cheap and ubiquitous ones are 1xxx series, pretty much pure aluminium with low strength. The others, usually described as 'aluminium alloy' are 5xxx series, stronger and with far better corrosion resistance. I would use the 5xxx ones for your fairly heavy duty fastening but not the 1xxx.

Matter of interest, what material is the pin in aluminium rivets?

 

[webcraft]

That is the minimum length you can use longer, you just reset the rivet gun for a second to third pull until the mandle breaks.

I would use you 5mm 18mm long monel

Is there not a limit to how much you can compress the rivet? I've had one of these break the mandrel when riveting something to the mast and the rivet was not totally tight.

Could I use suitable wee washers?

- W

 

[rogerthebodger]

Is there not a limit to how much you can compress the rivet? I've had one of these break the mandrel when riveting something to the mast and the rivet was not totally tight.

Not really, but sometimes you can get a weaker mandle that breaks prematurely. That has happened to me sometimes I just drill or shear off the rivet and replace with a new one.

Could I use suitable wee washers?

- W

Yes you can but I don't think it's really necessary.

 

[TernVI]

Matter of interest, what material is the pin in aluminium rivets?

Steel generally.
Fastidious people take care to remove the little broken off bit from inside the spar.

 

[BabaYaga]

Could I use suitable wee washers?

When I removed my gooseneck after almost 40 years, there was some corrosion under the rivet flanges, despite monel being used (see photo).
When refitting, I chose to use thick (1.5 or 2 mm) nylon washers between rivets and boom surface in order to slow the process.

 

[rogerthebodger]

Could I use suitable wee washers?

- W

What I have done in the past is to make up a plastic gasket between the fitting and the mast/boom. Normally it quite thin but I could be thicker to tale up the extra length.

Also if the fitting is stainless onto an aluminium boom it will help stop corrosion.

 

[vyv_cox]

Matter of interest, what material is the pin in aluminium rivets?

Most commonly steel on all rivet materials, but there are aluminium rivets with aluminium mandrels, and stainless steel rivets with stainless steel mandrels.

 

[AngusMcDoon]

When I removed my gooseneck after almost 40 years, there was some corrosion under the rivet flanges, despite monel being used (see photo).
When refitting, I chose to use thick (1.5 or 2 mm) nylon washers between rivets and boom surface in order to slow the process.

That's to be expected. Monel is quite noble, down with the brasses & bronzes. It is an alloy of nickel & copper. It's only the relative size of spars versus Monel rivets that stops the aluminium fizzing away rapidly.

 

[TernVI]

That's to be expected. Monel is quite noble, down with the brasses & bronzes. It is an alloy of nickel & copper. It's only the relative size of spars versus Monel rivets that stops the aluminium fizzing away rapidly.

And the mucky yellow paste...