MONEL VS STAINLESS STEEL RIVETS QUESTION

Can anyone help by discribing the difference...I am working on my H17 and Hobie calls for Monel rivets, I have always used SS rivets in the past on my Prindle. SS rivets are more expensive, but locally available. Is there a difference in strenght, performance, metal compatability??? What is the Monel??? a special alloy??? one down side I see is it has a standard steel pin, that would rust.



Any input would be appreciated!!

Hi,

Unlike Stainless Steel, Monel is mostly Nickel (67% Ni, 30% Cu, 1.4% Fe). Some Mocel alloys (Monel K-500 for example) can be much stronger than 18-8 or 316 stainless steel. However, the monel rivets I've seen availalbe are actually weaker than the 316 Stainless rivets. (See McMaster.com pages 3069 and 3070 which lists the shear and tensile strength of both). And yes, the monel rivets have a carbon steel shank I don't see the advantage of monel over stainless.

Stronger is not always better. What is the sacraficial element in the design? The fuse, so to speak. Making something else stronger than it should be may make something else realatively weaker in the assembly. Bear in mind that some things are meant to break so that others don't.

Is there any part on the cat with rivet failure a design consideration?

Just consider what the failure modes are. If the rivet goes, what is the severity of the failure. If the rivet does not fail but the next item in the chain does, and has a worse consequence... you get the picture. Heck, the rivet may already be the strong link in the chain and this conversation is moot... Just give it a moment of thought, that's all.

Hi, Steve,

Is Monel less apt to galvanic corfrosion when attaching stainless fittings to Aluminum masts? I realize it's customary to put some kind of layer between the fitting and mast; but doesn't the rivet contact both? So which do you use, stainless or aluminum? I one heard "monel" is okay in direct contact with both Al and Fe. Zat true?



Ed

Hi Ed,



Unless there are large loads, I often use aluminum rivets. With any rivet, I always use a generous amount of 5200, 4200, life-caulk or equivalent in the hole and under whatever fitting I am attaching. (never silicone - it doesn't hold up).



Monel is slightly less reactive with the aluminum regarding galvanic corrosion, but I don't like those rusty mandrels that get left behind. See Galvanic Corrosion Potential Chart:

http://www.pemnet.com/design_information/galvanic.html



Just my $.02 worth.



Steve



P.S. Where were you guys Sunday? We had 6 boats, perfect wind and water and ran two great buoy races with no sea grass, nasty power boaters, etc. Coming to Shelter Island??

Thanks for the input....I think I am going to just use stainless with sealant around them.



Thanks



Mike

Silicon seems to use a acetic acid solvent (vinegar smell) and that is why you cheap stainless fittings rust bloom when sealed with it. Incidently, vinegar works when you are trying to get that epoxy off your hands. (Silicon sealant probably makes a bigger mess, but ty it and let me know.)

My understanding is the monel won't react with the alum. like the stainless. As to the shank being steel. I have found the ones that are not steel tend to break off before the rivet is fully drawn tight. If you don't like the rusting shank, Neatly dab your 4200 there.