On my 1978 Nacra 5.2, a padeye on the rear tramp crossbar has pulled out. The padeye secures the heavy metal lines that run between the crossbars, hold the jib blocks, and serve as hiking straps (not sure what those lines are called.)

The area around the (former) padeye rivet looks badly corroded; the hole is hogged out and irregular. The other padeyes on both front and rear crossbars look like they have similar corrosion. I'm guessing it's galvanic.

How can I fix this? Can the damaged sections of bar be cut out, rewelded, drilled, and reriveted? Or is the whole crossbar a loss?

I've only had the boat a few months, sailed it twice, really looking forward to it, and so this is scary. It looks like similar corrosion has damaged the rudder crossbar attachment points -- I lost the rudder crossbar on the same trip. Maybe there's more corrosion elsewhere. Not so good.

Hoping for some reassuring advice,
thanks,
-Alex

The corrosion will mostly (if not exclusively) found very close to where dissimilar materials meet. Mostly you can "repair" the problems you talk about simple by repositioning the eyestraps and fittings. Often moving it 5 mm up or down (1/5 inch) or to the side is enough for several more years of secure fittings. In other cases simply rotating the fitting so the new holes for the rivets are at least 5 mm away from the old hole is a good approach as well.

So basically reposition the fitting a little and drill new holes and use new bolts/rivets is the solution.

Wouter

I guess you could use washers also?

You can also, depending on the padeye, drill out the holes to the next larger size rivet and reuse. To prevent the corrosion from happening (you are right, it is galvanic) you can use like metals or keep the metals separate. Since it sounds like the padeye sees a decent amount of stress I would not use aluminum rivets. You can use stainless steel with a rivet cover over it so it keep it away from the aluminum crossbar or you can use a Monel rivet. If you need to locate a place to buy the Monel rivet, here are a few mail order places: Jamestown Distributers or McMaster-Carr or Fastenal and finally Robnet.

Good luck and don't worry. You will be sailing soon.

I second above post. Might even be able to use original holes if you use aluminum sleeves. Mos def use stainless rivets, probably with steel monels as they pull tighter.

Me too. Drilling out and bigger often works well and replace with like metals. Has never come back to bite me.

Well, I measured it today, and the hogged-out hole and surrounding corrosion is about 3/4" in diameter, so I don't think that going to the next-size larger rivet will help that <img src="http://www.catsailor.com/forums/images/graemlins/wink.gif" alt="" /> Shall I just leave that corrosion, and drill/rivet an inch or two away?

Hobienick, you referred to a rivet "cover", and WindyHillF20, you referred to a "sleeve". The closest thing I could find was what Murray's Marine calls a "Rivet Casing": 6-10 (3/16 x 1/2) Part #19-5020, @ $0.70/ea. Is that what you are talking about? Looks to be for re-riveting a 3/16" rivet that has suffered minor hogging out of the hole, instead of going to a 1/4" rivet, and sounds like exactly what I need to replace all the other suspected weak padeyes (but obviously not the big one!)

About Monel metal, looking at the galvanic series, monel is much closer to stainless steel than it is to aluminum, so I don't see how monel rivets will cause any less corrosion than stainless. I've seen references to installing rivets "hot" or "wet" (what does that mean?), or with some "Goop" as an insulation barrier, but I don't know where to find that.

Thanks for the reassurance and advice, guys.
-Alex

Not needed. 5 mm (1/5 inch) is the minimum (reposition) distance you should use but more 10 mm (1/3 inch) is point less.




That is not the point of using Monel rivets. Plain alu rivets are too weak to hold any significant amount of force that is not perpendicular to the rivet itself. Monel rivets are much stronger and will hold up. Stainless steel rivets are much stronger still but also alot harder to pop right. Most often you need a large special tang for pure stainless steel rivets. And as Monel is also halveway between alu and stainless steel in galvanic corrosion it is a good compromise material.

I used done alot of riveting with monel (I build my own beach cat) and I can assure you that monel rivets is what you need.





Goop is an insulator so that the two dissimilar materials don't touch and as such can't corrode in the galvanic sense. I've done both (insulated and non insulated) on my boats in the past. Personally I found the corrosion to be quite slow even if you don't used an insulator. My spinnaker poles have held up non-anodised and non insulated for 5 years already without any significant corrosion and I store my boat on the beach and in the salty winds for 6 months a year.

So I decide to use the insulator on items like the mast as I want that to survive for 20 years or so. But I often "forget" it on spi poles and boom and other parts that are easily replaced for low costs and often break in some way of manner before 10 years has passed.

If you want to use an insulator then look for duralac, that is specially made for this purpose.

Wouter

Stainless rivets will work fine - you definitely need something stronger than aluminum for those jib lead cable padeyes. You can also use screws and nuts if you wish (glue the nut on the end of a stick to get it started). Stainless rivets do require a bit of hand strength to set, but you can look at it as a hand strength exercise. I set 48 stainless rivets on the Team Seacats N20 when I rebuilt it last year using a run-of-the mill hardware store rivet gun. In order to get it seated well it is important, when setting any rivet, that you keep good downward pressure on the rivet to hold it flat against the outer surface..stainless rivets are especially sensitive to this.

I always put something under the rivet (even aluminum rivets) to seal them up and provide some barrier. 3m 5200 will serve this purpose well and while I'm not sure about how much it prevents the two metals from electrically connecting, it does prevent water from getting in and sitting in the joint. Once you've set the rivet, you can clean up the 5200 with mineral spirits for a very nice clean smooth look. You can get 3M 5200 in most Wal-Marts in the boating section.

rivet casing is the correct term. I like Jakes idea of sealing the edges with 5200. I was able to buy a long arm rivet tool at Northern for less than $20.00. It can pull the stainless rivets tight without breaking your wrists.

Check out this stuff. A friend who works for JSI building spars showed me this stuff.

http://www.tefgel.com/

Jake:

From what dealer told me when I was talking about reseating my hulls on my 17, 5200 is PERMANENT fix. He is going to use 4200 (or whatever the 4000 series number is), that way if I need to fix anything in the future I can get it apart.

Just my 2 cents,

Doug

There are products out that allow parts glued-sealed with 5200 to be removed.

It doesn't work well when the 5200 is under a large protected surface, like a beam. Trust me, I've seen an I20 deck broken after a week of trying to remove a beam that was seated with 5200 using every ointment and/or spiritual fix we could dream up.

Don't seat beams with 5200 or 4200. Wax the aluminum beam with mold release and use epoxy or polyester resin infused with a filler. You can dam up the edges with clay or rope-type window caulk putty. Your hull socket will be perfectly fitted to the beam AND you can remove it and reinstall it without messing up the joint or having to deal with un-removable sealants. Besides, why would you fill the joint, that you are trying to firm up, with a flexible compound?

Weren't we talking about rivets though?

Jake is right, I work for an airline and what is causing the corrosion is the different metals that come in contact with each other. At work when we put two different metals together we use a sealant between them. When you use the ss rivets dip them in some rtv silicone to help prevent the contact between the metals. Water acts as the electrolyte to cause the corrosion. The less water touches the metal the less corrosion.

airborne