5200, 4200 or something else ref rubrails

[DCatSea]

I should know the answer to this, but age and alcohol have taken their toll, SO:

Some of you may know that one of my (several, as usual) big tasks this layup is to replace the antiquated, and possibly not-rubrail, rubrail on Mazboot.
Thanks to Tego (Cheers, Ben) I now have 70 plus feet of a rubrail that will fit AND do the job it's supposed to do, i.e. rub, without too much damage to the ancient craft.

Several oracles have told me that it looks as if some past PO's idea of rubrail is really the underlay for rubrail without the good stuff on top. I definitely concur.
The hull/deck joint is sound, and I don't want to disturb it so my proposal is to take the new rubrail and just fit it over the existing "not-rubrail".

Questions:
1) Has anyone done this before?
2) I propose putting a large-ish bead of something like 4200 between the two layers. I think that something that doesn't "go off" would be better. Does anyone have suggestions as to what might do the jobs of a) securing the rubrail, and b) providing a soft buffer betwixt old and new?

This will be done upon my return from UK, where I will be generously applying the annual "grandpa scares the grandkids" thing. (Now 2 new great grands to scare before they get much older).

Have a Great Christmas.

Doug

[Burton]

I've done rubrails on a number of boats and re-done hull to deck joints on two. Hmmm. I think there is wisdom in studying what the components are of each rail, existing and the added. For instance, is their expansion and contraction in heat and cold going to match with the old rail and for whatever bonding agent you use? A rubber rubrail soaked in a tub of hot water stretches like crazy! If rubber, how much "stretch" should it have? In addition to the expansion and contraction issue, another question is adhesion. Will chosen adhesive adhere to the substrate rubrail and new rubrail? Probably good to read the technical specs on all of it, if possible. Is there a substantial means of clamping until adhesive is cured? (One can't have enough clamps, ever...) After using lots of 5200 and having to try to remove some of it... I pretty much try to avoid it. Clean up is no fun for the squeeze out, either.... taping off to catch the excess really helps for whatever you use. However, 5200 has its place. What about Plexus? Of question is the fact, as I recall, that 5200 is not photochemically resistant. Of course, that may not be a factor as only the edge of the adhesive will be getting the sun. I'm not sure I follow the type of rubrail added. If the two-part kind, mechanical fasteners are the way to go for the inboard rail, then covered with the insert. Perhaps more info on details will help the pro's on here give better advice than I can offer. Best of luck!