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Old 17 November 2014, 04:39   #1
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Alloy hull, which fixings??

Hi guys, currently arranging where things are going to live on my boat but can't figure what fixings will be best. Hull is alloy but I believe stainless bolts and rivets are stronger than alloy ones, but will having these stainless fittings promote electrolysis or other deterioration problems..
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Old 17 November 2014, 16:33   #2
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Electrolysis

Yes always best not to mix metals where ever possible with alloy hulls but the problem will not be that bad if using ss, the boat is not left afloat and rinsed off with fresh water after recovering. If it were me I would go and see your local yacht mast rigger, explain what you are doing and see if you could scrounge a handful of his rivets. With the bolts, if using ss, I would use nylon or similar washers / grommets and ensure there is no metal to metal contact. But I though you Kiwis had lots of experience with alloy boats so there must be an abundance of local advice and help. Oh….. and I assume it is a rib hull not sib with floor boards but you have posted in the sib section.

Jon
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Old 17 November 2014, 17:14   #3
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316 stainless is standard. Then add zincs to address corrosion just as you would with any other boat. If in fresh/brackish water you might consider manganese anodes as zinc isn't sacrificial enough and different aluminum alloys might end up being preferentially corroded (e.g. in your engine or remote from the zinc).

Aluminum bolts are: 1) not really available 2) 1/3rd weaker and will need to be massive to compensate.
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Old 18 November 2014, 07:44   #4
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Ended up using alloy rivets at this stage, thanx for you advice
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Old 18 November 2014, 16:40   #5
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Keep an eye on those aluminum rivets. They tend to weaken with stress.

jky
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Old 20 November 2014, 14:25   #6
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Aluminium rivets

Agree with JKY. I think a rigger would have given you Monel ones and some Duralac or similar compound but perhaps that’s a bit OTT as we don’t know what you are attaching to what. Hope it works out fine.

Jon
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Old 20 November 2014, 18:00   #7
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Yea thanx guys, I used some high quality alloy rivets to fix a strap to support my fuel cell. Looking at shear strength I think I'm going to be fineClick image for larger version

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Old 21 November 2014, 06:44   #8
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Pretty much what I did on my SIB (a few times.) Eventually the rivets break the heads off, presumably from repeated stress. Hopefully you have better luck.

jky
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Old 21 November 2014, 07:34   #9
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If I have any issues I will go straight to stainless, I don't see this strap moving anytime soon tho.
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