Monel or stainless steel - the same?

[Strathglass]

Thanks for the replies. I have some Durulac paste so will be putting it under the mast steps as I rivet them to the mast.

When I was building my mast from a sailspar kit, they supplied self adhesive foam pads which was attached between all the larger stainless steeel items and the mast. This is less messy to use than durulax paste.

I still used the paste on all the rivets.

Monal rivets are much easier to use than stainless ones. I have quite a few 5mm stainless ones and they take more force to insert tham 6.4mm monal ones.

I have both a long handed gun and a set of lazytongs. The lazytongs can be used single handed which can be a bit of an advantage when up a mast. They also take less physical effort to set a rivet. However when the mandrel does shear there can be quite a jolt.

Iain

 

[Z SPARS UK]

Monel Rivets

Only use Monel Rivets! We sell 3/16 at £0.35p each and 1/4 at £0.89 each.
They need to be 3mm going into the section which will pull up nicely. Cheap rivets guns will not pull up 1/4 rivets!
Paste is not required if the step is alloy and you use Monel rivets.
Any stainless fitting needs paste to prevent corrosian.
Hope this helps.

 

[john_morris_uk]

Only use Monel Rivets! We sell 3/16 at £0.35p each and 1/4 at £0.89 each.
They need to be 3mm going into the section which will pull up nicely. Cheap rivets guns will not pull up 1/4 rivets!
Paste is not required if the step is alloy and you use Monel rivets.
Any stainless fitting needs paste to prevent corrosian.
Hope this helps.

Thanks for your advice. 3/16 is 4.75 mm which 'might' be ok in the 5 mm holes. 1/4 (or 6 mm) rivets at 89 pence each is not cheap when I need 80 rivets. The steps are stainless and have nylon washers to isolate them from the alloy of the mast. I will also use Durulac as previously mentioned.

 

[VicS]

Paste is not required if the step is alloy and you use Monel rivets.

That's interesting, at least that Duralac paste is not needed if Monel rivets are used. I assumed that because Monel alloys are in a similar position in the galvanic series to the stainless steels they would case similar corrosion of the aluminium if measures were not taken to prevent it.

You are saying this is not so! Any idea why not?

 

[Blueboatman]

Having gone through 2 lazytongs devices- each managed 3 rivets before returning to the shop, I now have this one.

http://www.karattool.com/product/77861.html

I also hated the 'slam' of the lazytong and the danger of pinching yer fingers .

 

[Z SPARS UK]

Monel Rivets

Monel Rivets will only corrode on Carbon, all spar companies use Monel rivets.

 

[VicS]

Monel Rivets will only corrode on Carbon, all spar companies use Monel rivets.

I know the Monel wont corrode, but why don't the Monel rivets cause corrosion of the aluminium in the same way that stainless fasteners do.
The galvanic series predicts that they will.

 

[vyv_cox]

I agree Vic, I can't see any reason why Monel and 316 SS should be any different when it comes to galvanic reaction with aluminium in seawater. See this page which seems to confirm that.

I can only assume that there are other factors that mitigate against SS for such rivets.

 

[john_morris_uk]

With the mast steps arrived and my having been on the boat yesterday I have some definitive figures for the rivets I require.

The holes in the mast steps are 5.2 mm inside diameter when I measured them with a digital caliper (not the 5 mm that the Force Four assistant measured with his ruler) This sounds like 5 mm clearance to me and so I require 5 mm monel rivets, not the 4.8 mm rivets I thought I needed.

The mast wall thickness is 5 mm as far as I can measure, and the steps are made of 2 mm plate, so allowing two diameters length extra for pulling up, it appears I need 5 mm by 17 mm monel rivets.

This doesn't allow for the very thin nylon washer that goes between the mast step and the mast, but I assume that won't make any difference once the thing is pulled up tight?

My main problem now is that none of the suppliers that people have kindly indicated to me supply 5 mm rivets - they all seem to quote for 4.8 mm rivets. If I use them, there would be a .4 mm clearance which seems a bit much for something I am trusting to stand on 16 metres up in the air.

 

[VicS]

I have pop rivets labelled 5mm - 3/16"

Some aluminium ones that came from B&Q ( with the Stanley brand name on the pkt) and some Monel ones that came from Force4 (with the Holt brand name on the pkt)

Both when measured are in fact 3/16" or 4.8 mm.

So very likely if you find nominally 5mm ones they will only measure 4.8mm !

Drill out to take 1/4" rivets and use aluminium ones ???
They have a shear strength of 460 -700 lbs depending upon the grade.

 

[Honey]

Caution

Just a word of warning before you start...... A previous owner of my boat fitted these steps and obviously fitted them with the mast down. (Not easy to do with the mast up) but failed to appreciate the angle caused by the baby stays such that one of the steps about half way up is unuseable unless the baby stay is slackened off!