Sealant for bedding?

[Quandary]

In a contribution to the recent thread on corrosion in alloy steering pedestals, Vyv (whose advice I hold in high regard) recommended using Sikaflex 291 as an alternative to Duralac etc. when bedding ss. machine screws etc into alloy.
I recently used the same product very successfully to seal my persistently leaking iron gutter joints at home and some leaked from the cartridge into the gun. The tube and the gun are now inseperable so the adhesive quality of 291 is considerable. It makes me worry that using this adhesive/sealant as a bedding or separator may mean that components can not be released, though it certainly should be durable, and it outperforms most stuff in a wet environment.
Is it perhaps better to use a silicone or acylic sealant for this purpose, because they release easier and can be removed and replaced at reassembly, either would be preferable to Duralac, which is very difficult to apply evenly and then to clean up and is one of the messiest products you can try to use?
I would welcome advice on this because one of my lower priority winter projects might be to dismantle and reassemble the steering pedestal and hoop while it is still possible before it all siezes together.

 

[neilandshiv]

I've been using Arbokol 1000 for variety of jobs.
Good sealing and you can get stuff apart and its easy to clean up the excess.
Bloke at Shamrock Quay told me they use it between keels and hull on boats!
I've use it for hatches and bow roller fitting, between teak fittings and fibreglass deck,
and will be using to reseat genoa track.
hope that helps
neil

 

[vyv_cox]

There's no doubt it's an excellent adhesive. My son tells a tale of a yacht whose keel was bedded with Sikaflex 291 (?) prior to launch. Something was found to be wrong when the boat was back in the water, it was taken out again, keel bolts loosened but the keel remained attached when the hull was lifted. It took considerable effort to separate the two.

Despite that, I have bedded window frames, windlass, cleats, fairleads, chain plates and just about everything else with Sikaflex 291. It has never been particularly difficult to remove them later. I find that, unlike the keel example in which the pull was normal to the joint, introducing a wood chisel into the joint on one side exerts an angular force which easily separates the two faces. I would expect a strong 'lean' on a steering pedestal would easily remove it from the cockpit floor.

 

[Quandary]

Sikaflex 291

If I put it on the threads of the countersunk flush headed ss machine screws in the (perhaps vain) hope of isolating the stainless steel from the alloy will they ever come out again though.

 

[pvb]

I would welcome advice on this because one of my lower priority winter projects might be to dismantle and reassemble the steering pedestal and hoop while it is still possible before it all siezes together.

I'd stick with Duralac. Although it's a bit messy to use (I use meths to clean up), it will prevent corrosion and it will allow subsequent disassembly. Glueing stuff together with Sikaflex is an inferior option.

 

[vyv_cox]

I'd stick with Duralac. Although it's a bit messy to use (I use meths to clean up), it will prevent corrosion and it will allow subsequent disassembly. Glueing stuff together with Sikaflex is an inferior option.

To be fair to myself I didn't recommend Sikaflex as an alternative to Duralac. I was suggesting that keeping the water out of the bolt recesses on top of a steering pedestal flange might be achieved using a plug of Sikaflex. My approach to combatting corrosion is firstly to exclude the water. If that can't be done avoid all the consequential stuff, like galvanic couples, corroding metals etc.

A nice example worked by colleagues: Most North Sea platforms have sea-water fire fighting systems. On many of them the nozzles and valves originally installed were brass and they began to corrode and fail in increasing numbers. One platform replaced all theirs with bronze ones, at a blindingly outrageous cost. The solution proposed and implemented by my colleagues was to add small valves as close to the main outlets as possible. Fresh water was back-filled through these, completely arresting the corrosion.