Hobie Nick wrote:
The use of SS, Monel, or aluminum rivets is dictated by the loads the rivets will be seeing. For low load situations, use aluminum rivets in the aluminum crossbars. For high load situation you need to use either Monel or SS. Monel will not corrode aluminum but is more costly than SS. Using stainless rivets or screws will require isolating the SS from the aluminum. I have found that Tefgel works really well for this application. It does not glue the connection together like Lok-tite nor does it leave a mess behine like silicone.
Harder metals do not corrode softer metals. It depends on thier relationship on the galvanic chart. For example, titanium is very hard but does not corrode aluminum.
You should choose your fastener by what is appropriate for the situation. Often blind fasteners are used where threading thin walled materials is ineffective, you do not have access to use a nut, or if you do not plan to remove the fastener. Machine screws are used if you need to be able to remove the fastener.
You've made some great points in your reply. Thank you. Most people do not have the knowledge (or inclination) to alter their own boat by leaving any mods to their dealer. Hopefully anyone that has read both of these posts will benefit if they live in rural areas far from their dealer.
My choice of machine bolts is based on the fact that fittings will wear out as time goes by. Why change something that has proven itself to me for many years on much larger vessels than a 13 foot roto moulded Catamaran?
Have a 'Whale' of a day...http://www.youtube.com/watch?v=Ndppa4Vj37E
Best Regards, Hobie Nick