Plastic Under Fittings

[lockie]

When I've removed my mast winches and a couple of other fittings to service or replace, I notice that they have been installed with a sheet of thin plastic between the body and the mast/boom. This makes lots of theoretical sense from an electrolysis point of view. But what I'm wondering is whether it's a good idea in practice, compared with a good layer of Duralac? Would any plastic do?

lockie

[Marksman]

Hi Lockie

If the origianals are not reusable I would get some thin sheet mylar to replace them. I would also "wet install" the fasteners using a good non hardening, removeable 3M sealant like you would use on thru hull fittings. I have friend who installed steps on his mast using stainless screws with no sealant and now they are permanantly fused to the aluminum mast. If you prevent moisture from sharing the joint with the two metals they should be removable next time.

My .02

[anjou]

I swear by Duralac. Its been used in most if not all aluminum aircraft for well over half a century, so is well proven and tested.

[lockie]

I'll certainly be using Duralac on the screw threads. Just wondered if using plastic is common.

lockie

[Blue Stocking]

The poly-whatever snap=on top for canned peanuts, coffee, and the like, make fine shims.