Monel Rivets, Paste etc

[SAWDOC]

My end of boom fitting needs some TLC neccessitating its removal and replacement. I have read several comments about the requirement to use monel rivets with paste when replacing mast or boom fittings. And then (the joy of this forum!) there is always the contrary view stating that ordinary rivets work grand and do not corrode. Can anyone comment from experience on the merits of one over the other?

 

[NickiCrutchfield]

I've always used monel rivets and that black stuff. No one I've spoken to has said anything but to use it. May well be hype, but for the little bit more money, less corrosion potential in the boat has to make sense.

 

[macd]

Depends on what the various bits are made of and what loads are likely to be applied. In low-to moderate-stress applications, using 'normal' (aluminium) rivets to join ally to ally (or anything non-metallic to ally) seems to me to make sense. But then I'm not a metallurgist. Suggest you ask Vyv Cox of this parrish, who is.

 

[AngusMcDoon]

Your boom fittings were likely originally attached by monel rivets, so to be safe, use them. They cost about £1 each in small numbers.

Coating them with corrosion stopping goo is a good idea, Duralac being the commonest stuff at about £12 a toob. It's horrible sticky stuff that gets everywhere, but seems to do the job.

Unless you are Geoff Capes, you will need a decent riveter - monel rivets are hard to pop. The standard B&Q type popper won't do. Get a lazy tong rivetter, about £15 from Amazon or Ebay. Silverline is a budget make that seems to work. Still be prepared to puff and grunt to pop 'em though, and be prepared for the bang when they go.

My end of boom fitting needs some TLC neccessitating its removal and replacement. I have read several comments about the requirement to use monel rivets with paste when replacing mast or boom fittings. And then (the joy of this forum!) there is always the contrary view stating that ordinary rivets work grand and do not corrode. Can anyone comment from experience on the merits of one over the other?

 

[Marsupial]

there are "various" problems with rivets and masts, even if its an ally mast and you use ally rivets the purity of each metal is probably going to be different and one will sacrifice itsself. Monel is "non reactive" allegedly, and very strong when compared to ally rivets, so use them if you can get them. What ever you use put some duralc past on everything and at least the rivels wont fail through corrosion.

Same rules apply if you are trying to put a stainless fitting on a mast, monel rivets and duralac paste and everything will be fine.

 

[vyv_cox]

My end of boom fitting needs some TLC neccessitating its removal and replacement. I have read several comments about the requirement to use monel rivets with paste when replacing mast or boom fittings. And then (the joy of this forum!) there is always the contrary view stating that ordinary rivets work grand and do not corrode. Can anyone comment from experience on the merits of one over the other?

Although I have not carried out any analysis it appears to me that every rivet in my 25 year old mast and boom, as fitted by Selden when they were made, is aluminium. I can see that if applying a stainless steel fitting to an aluminium mast it would make sense to use monel, being more noble than either. However, corrosion assumes the joint to be always wet, which would not be the case if a sealant were to be used. In the case of your boom end fitting, if it is like mine, you are joining aluminium to aluminium, so rivets of the same material should be fine.

Additional info - when I needed to drill out the rivets holding the end cap on my boom I replaced them with Rivnuts and bolts that can be removed very easily in future.

 

[pete]

If you do decide to use standard ally rivets watch out for the mild steel mandrel rusting away inside.

Pete

 

[jpthegp]

My general rules are - if rivetting stainless to ally, use Monel, and apply Duralac paste to rivets ant the fitting.

Ally to ally - use ally, unless more strength is needed - but then usually the fitting will be SS. No paste needed.

Ally to ally but more strength - monel with paste.

I totally agree with the laxy tong rivetter need - you need loadsagrunt and the bang as the rivet pulls is impressive!

 

[rhills]

Ally to ally - use ally, unless more strength is needed - but then usually the fitting will be SS. No paste needed.

I recently had the mast out of my 39 footer for repairs to a corroded section. The section concerned had a SS fitting attached with SS Self-tappers into the aluminium. Eventually, the aluminium had corroded around the whole SS fitting, not just where the screws were.

As a result of that experience and advice here from wiser heads than mine, I use Duralac whenever I have SS in contact with aluminium regardless of the fastener.

I agree about Duralac being awful sticky stuff. A couple of tips I've found useful - when working with it, I use disposable rubber gloves and I squirt a dollop from the tube into a small plastic bag (I collect the ones my chandler the little bits he sells in). You can then dip rivets/screws into the bag, or invert part of it if you need to smear something with Duralac. Works especially well if you're doing stuff up the mast.