I have a 1990 Hobie 18 Magnum that I absolutely love (actually my fourth boat) and the wing rivets are coming loose on the port side at the front crossbar end. I know they have to be redrilled and replaced, but should I perhaps use aluminum rivets (4) because everything around it is aluminum?

W

I would use Monel rivets. You can do a search on "Monel" and you'll come up with quite a bit of discussion. They are not reactive with the aluminum like the stainless will and they are much stronger. On the other hand if you have a good grade aluminum rivet and it is pulled tight you shouldn't have any problems for a very long time (if ever). Its the movement that does fastners in.

Clayton

I think saying that monel is "not reactive with aluminum" is overstating the case. Monel is slightly less reactive via galvanic corrosion with aluminum (potential of 0.56 volts) vs. stainless (potential of 0.64 volts). If the parts being attached are stainless, I don't see a huge benefit for monel. A little sealant of some sort to limit the electrical connection between the stainless and the aluminum is a good idea.

You should get a good idea what kind of rivets are in there when you drill the old ones out.

Check out McMaster Carr. They are a great resource for parts like rivets. They don't carry marine gear but for basics like fastners they are a great resource

http://www.mcmaster.com/

go to page 3114 of the catalog. I really like the high-strength 18-8 stainless rivets. The 1/4 inch rivets are great for re-riveting Hobie 16 castings and crossbars.

ABSOLUTLY NOT ALUMINUM rivets. There is not enough shear strength. That is why stainless and monel are used.

Matt, I guess a good question would be what do you guys use as original equipment? Stainless or Monel?

This is true for most aluminum blind (pop) type rivets such as you might buy from a hardware store or home center, but not all. Textron/Cherry makes aluminum blind rivets that are very strong; nearly as strong as a solid high-alloy aluminum rivet. Solid Al alloy rivets are stronger than typical SS blind rivets. Cherry Max rivets are pricey at .50-$1.00 each rivet, but well worth the cost in certain situations. You will probably not be able to pull them with a normal mechanical hand puller if bigger than .125" dia. Air/hydraulic is the only way. Cherrymax rivets are available in both 5056 Al alloy and Monel. Sometimes small lots show up on ebay or at surplus stores.

http://www.textronfasteningsystems.com/aerospace/html/product/rivets.htm#BulbedCherryMAX

Jimbo

Now I know: Thanks, Guys. I'll drill them out today and figure out what the best size would be. I may have to go up a size since there was some movement on the wing...

Wyatt

Wyatt, there are inserts that the rivets fit into. They're great if the holes are slighty worn. The inside end of this insert is closed so they also keep the water out. I get them from the local Hobie dealer. Because the you have to stretch that as well as rivet you may want to test one to make sure it pulls all the way.

Oversize rivets are available from some manufacturers for holes that have been worn or misdrilled bigger than the 'nominal' allowance. Oversize rivets are a little bigger than the nominal size but nowhere near the size of the 'next size up' rivet.

Jimbo