We've got a total of 8 lovely old bronze portlights
mounted to the hull
of our boat which I'm in the process of removing and refurbishing. There was a bit of a design flaw with mounting of the portlights
in that they were mounted through the solid fibreglass hull
and through the 1/8" plywood
lining on the inside. All very well and good, except that the design of the portlights means they seal on the inside of the hull, not the outside. No doubt silicon was used in the past to seal the gap around the hull cutout and portlight frame, but it gave up the ghost long ago and the flaw in design is that once the ply gets wet (which it will because there isn't an effective seal between hull and ply) and starts to rot
it then turn allows more water
leakage (which eventually works its way down the inside of the hull and proceeds to rot
the bottom of the chainplate knees, but that's another story!)
Anyway, I'm thinking butyl tape could be the answer, as it maybe/perhaps/will ooze into the gaps between portlight and hull and hull and ply when the portlight is bolted back in place. The only problem is I don't recall
ever reading if this has been done or is advisable??? Oh yeah, some of these portlights can submerge temporarily on a decent angle of heel, just to add to the fun! Did I also mention they're opening types as well? Fortunately the window seals
seem to work pretty good!
On the subject of seals
, is EPDM sponge a good sealing rubber? I'm trying to source 1/4 x 1/4 sealing in Oz and not having much luck other than EPDM sealing in this size. The existing stuff is still in reasonable condition but is solid rubber and quite firm.