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Old 04-03-2015, 11:03 AM   #21
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Originally Posted by Xsbank View Post
The radio tower mentioned is likely not bathed in salt water.
Neither are my boat's windows but they do get spray on occassion--definitely not soaking in salt water. The aluminum trim is original and looks great (particularly where SS hardware has been used) and the trim is close to 35 years old. Boat has always been in a saltwater environment. Windows were recently pulled and re-sealed with butyl (original butyl lasted decades before leaking).

Interesting thread...
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Old 04-03-2015, 11:51 AM   #22
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Stainless steel screws are the proper thing to use. Get the 318 steel ones, Jamestown has them, instead of 316. Wrap them with Teflon tape and put a dab of silicone in the holes if you like. Don't use bronze, brass, or aluminum.
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Old 04-03-2015, 12:50 PM   #23
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Originally Posted by Vashon_Trawler View Post
Neither are my boat's windows but they do get spray on occassion--definitely not soaking in salt water. The aluminum trim is original and looks great (particularly where SS hardware has been used) and the trim is close to 35 years old. Boat has always been in a saltwater environment. Windows were recently pulled and re-sealed with butyl (original butyl lasted decades before leaking).

Interesting thread...
Sounds like the screws were properly bedded.
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Old 04-03-2015, 12:57 PM   #24
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The screws on my Hatteras are all monel. The window frames are 39 years old and the aluminum windows show little if any corrosion at the screws. Aluminum and stainless don't mix, tef-gel helps but no guarantees. My sailboat masts always isolated stainless from aluminum with vinyl tape or nylon sleeves. There are nylon sleeves specifically made to protect stainless rivets in aluminum. You could rivet your windows with aluminum rivets. They drill out easier than removing corroded screws. If it were my boat I would opt for monel screws. I don't know where they are on the periodic table compared to aluminum, I just know they have held up for 39 years of salt water on my boat.
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Old 04-03-2015, 01:14 PM   #25
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Very surprised that your aluminum frames are held by Monel screws. Monel is further from aluminum on the galvanic table than even copper, bronze, or brass which we all have seen the results of when in contact with aluminum in a salt environment. Is you boat in fresh water or washed down after each use?
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Old 04-03-2015, 02:51 PM   #26
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It's 39 years old

Quote:
Originally Posted by Brooksie View Post
Very surprised that your aluminum frames are held by Monel screws. Monel is further from aluminum on the galvanic table than even copper, bronze, or brass which we all have seen the results of when in contact with aluminum in a salt environment. Is you boat in fresh water or washed down after each use?
I've had it for the last 5 years, sails in salt rests in fresh, most of the last 20 years. The previous owner kept the boat in Portage Bay Washington in fresh water. The boat has been all over the place in salt water as far south as Guatamala. I've heard it rains a in Washington and it certainly did in Saint Helens. Down here the sun does more damage than anything. I was told the original screws in the whole boat were Monel. They look like it when I remove them. The window screws I haven't needed to remove yet! I could be mistaken as I really don't know, they just look the same color as the monel screws I've removed. Hatteras actually colored trim screws to match moldings and such.
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Old 04-03-2015, 04:37 PM   #27
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I think there may be some confusion between the corrosion in the aluminum when in contact with a stainless fastener, usually evidenced by a bubbling in the aluminum surface around the head of the screw, and crevice corrosion of the screw itself due to water intrusion. Monel is less prone to the latter, but should still be properly bedded with something like Tef gel to protect the aluminum from the former. We did a glass re-bed of almost all the windows on my Hatteras, and for the life of me I can't remember if the screws were monel or bronze, but we did bed them when we put the frames back on. The idea of using rivets for this purpose frankly horrifies me, what a mess!
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Old 04-03-2015, 07:04 PM   #28
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In my opinion, and based on a lot of years' experience with float planes (aluminum) in a salt water environment (PNW), Scary's post 24 is right on the money. I would never trust any sort of insulating gel or paste because the threads of the fastener are going to make metal-to-metal conact no matter how much of the stuff you smear on there or pump into the hole.

If one absolutely has to use stainless fasteners to hold aluminum components, the nylon sleeves mentioned by Scary are the only reliable way to go in my opinion. Even insulating tape seems iffy to me because of the potential for the fastener threads to cut through the tape and make metal-to-metal contact with the aluminum.

I believe the best things to use when fastening things to aluminum or fastening aluminum to things like a cabin side, particulalry in a salt environment, are either aluminum fasteners or galvanized steel fasteners, which are what is generally used in the assembly of the float systems for a floatplane (but not the floats themselves).

The problem with using galvanized fasteners is that the galvanizing disappears with time--- it serves the same function to the steel fastener and the aluminum comonents the fastener is fastened to that zinc anodes serve to a boat. So they have to be inspected at specific intervals and replaced when the galvanizing starts going away, otherwise the steel fastener will start to rust.

Windows in a boat don't seem to me to be a strength item. So I would think aluminum fasteners, be they screws or rivets as Scary suggests, would be the way to go.
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Old 04-04-2015, 10:03 AM   #29
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Just use Tef Gel or something else to help isolate the SS fasteners and be done with it.

For decades builders and riggers have been doing just that. And as you can clearly tell by the testimonials posted here, it works over the long term.

Galvanized fasteners on a boat in saltwater!?
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Old 04-06-2015, 01:11 AM   #30
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I would like to thank all here for having a discussion about something i was about to ask about, but was beaten to the draw. I am in the process of rebuilding a swim platform I built for my old Trojan cruiser. The swim platform uses a welded aluminum frame covered with King Starboard. It has served me well over the years, but it has never experienced salt water. I bolted it to the transom with 316 Stainless 3/8" bolts. I can't really say I have experienced any corrosion around the stainless bolts but I do know that aluminum is a sacrificial anode material of choice in fresh water. I hope the Californian makes it to salt water in the next year or two so I wasn't sure what to do about fastening it to the transom. Use the same SS hardware? I was considering asking here but you all beat me to it. I started wandering about connecting the aluminum frame to my bonding system, but quickly concluded that would be the same as using it as a sacrificial anode. Not Good. But the stainless hardware bothered me. My new plan: switch the 3/8' 316 Stainless bolts out for 1/2" Aluminum bolts. The aluminum is weaker at 37,000 psi tensile vs 70,0000 psi tensile for the 316 SS, but the larger size 1/2 vs. 3/8 comes real close to the same overall strength in the end. A Happy Ending. With somewhere close to 24 half inch aluminum bolts holding it to the transom it will be more than adequate and not make me worry about corrosion. It amazes me how much one can learn here by reading the experience of others. The old Trojan was 10' wide beam and the new (to me) Californian 34 LRC is 12' wide. although both boats transoms have a radius, they are not the same. So my plan is to cut the old swim platform in half and spread the halfs to the new wider width and weld a new aluminum section in the middle. In doing so I can adjust the end pieces to better match the Californians transom radius. It is my hope to put together a story about the project in the future.
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Old 04-06-2015, 01:51 AM   #31
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Quote:
Originally Posted by Capt.Bill11 View Post

Galvanized fasteners on a boat in saltwater!?
I'd never use galvanized fasteners on a boat. But they are the solution on a floatplane where the strut and spreader bar systems need very strong fasteners but stainless steel cannot be used.
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Old 04-06-2015, 08:28 AM   #32
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I agree with N47 but those plastic washers are hard to find especially for recessed screws.
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