Rivets or Screws

[Mike Sibley]

I plan to install a traditional boom vang on a Pearson 365 but am unsure about the attachment points at the base of the mast and on the boom. Aluminum is soft, so I assume the attachment points are the weak link in the system. Is it better to attach connection hardware with rivets or machine screws? If rivets are used, I assume that it would be best to use 1/4 inch stainless steel rivets. If screws are used, I assume I would tap for 1/4 inch or 5/16 inch screws. Also, would a heavy eye strap (attached with two rivets or screws) be sufficient or will I need something heavier that is attached with four rivets or screws? Any suggestions would be greatly appreciated.

[SabreKai]

Screws allow for removal, rivets are permanent. The next thing to consider is the thickness of the material you want to drill and tap. If you want to go with 1/4 inch, consider that you will only have 2-3 threads in the material. I'd be wanting a material thickness at least as much as the diameter of the machine screw I was putting in, so I'd say go with the rivets.


Sabre

[Weyalan]

Rivets are not permanent. It is not a big job to drill-out rivets and re-rivet. Monel rivets are good for this type of application. If you decide to use threaded fasteners, it might be worth considering using helicoil inserts. Whichever way you go, make sure that you use an appropriate barrier-coating between the steel and the aluminium; Duralac being one such coating. If you don't, the steel will cause the alloy to corrode.

On our 40' boat the boom vang fitting and the goose neck fitting on the mast are attached with threded fastenings, not rivets, with helicoil inserts. However other fittings ion the mast and boom use rivets.

[duncan_ellison]

Anyone here used Riv-Nuts for this application ?

These are like a cross between a rivet and a helicoil insert, you use a tool like a rivet gun to squeeze up the threads which then lock into the hole making a permenant thread very tightly fixed to the hole.

I have some of these in Stainless and was considering using them to attach ancillary stuff to the mast so that it could be easilly removed.

With a bit of tef-gel between the riv-nut and the mast, I can't see any downside. With the right sized drill, you can even drill them out to replace them.

Duncan
S/Y TALISA