I am seeking info or recommendation on material selection and fabrication of some spacers.
Our 35 yo
portlights, no great shakes to start with, are giving up the ghost. Lord only knows their make. Some are heavily corroded and compromised, they need to go.
I found Vetus units (PM-141 CE-A1) that fit this cut out, but the cut out is a bit rugged. I am not sure of the tolerance requirements for the Vetus lights but have read (on CF) they want 1 mm tolerance. The new units have a narrower bezel and do not bolt through the
steel. This means the old bolt holes will be partially exposed. Inside there is a 1/4” ply backer to the
steel. The
corrosion took place where the inner ring touched the
wood. They
cabin wall is 4mm thick, the lights will accommodate up to 1” thickness. The lights clamp to the
hull, no drilling required. I have 2 lights on order for a trail, should arrive this week. Need 12 altogether. 2+10.
The exposed holes are a problem. I could fill them by welding them shut. PITA. But I could also have a 1/8” spacer made that covers these holes. Tuis spacer would be outside of the
hull under the lights rim.
Inside I may need an additional spacer, between the
wood and the
interior rim. This would give the lights rim a more firm basis to clamp onto.
QUESTIONS:
1: What is the actual, practical tolerance for a Vetus portlight? PM-141 Vetus gives no guidance but says to cut out with an oxyacetylene torch. (Yikes)
2: Comments on the outer ring material. I was thinking first some grey polypropylene because that is what my Porta
Boat is made from and it seems totally impervious to UV. Better options? However I could use
aluminum, get it CNC cut.
3: Comments in the inner ring material. Similar to above; plastic or
aluminum?
4: Do I even need an inner ring would the wood be good enough? I am leaning away from this because of past
corrosion where the aluminum contacted the wood.
5: Regarding existing corrosion. I had the lobster guts out a couple of hears ago, cleaned them and rebedded. My only thought is that when I cleaned the inner ring of the existing lights I removed some kind of protective coating (anodizing?) that allowed them to corrode when reinstalled.
Any other comments or
advice would be appreciated.
Remember: steel
boat, Vetus is the only one (I can find) that marches the existing cut outs.