stanchions will be plenty strong enough! Mine is an aluminum Colvin Gazelle with sockets welded to the bulwarks and pipe inserted for the stantions. The lifelines
are plastic coated and tread through holes drilled in the pipe. The tops are capped and the bottoms left open. Another scheme I have seen is rings of 3/16 round welded to the outside of the pipe. In any case, the same pipe and socket arangement is used with a bent piece that has a pully on the end and extends out horizontally almost three feet as an anchor
davit or cathead. The anchors are 75# fishermans. I would bet that you could easily hoist that 450# guy by them!
If you have access to 5000 series aluminum for your portlights
and anything else it will do much better than 6000 series in the salt environment
. Especially if you don't protect it with paint
. With any aluminum your biggest problem will potentially be with galvanic corrossion. If you don't want the crusty corrossion of your aluminum you will need to keep stainless from being in contact with it. Stainless is at the opposite end of the scale and everywhere there are stainless bolts, even on painted aluminum, on my boat there is the crud. They will all be replaced with hot dipped (not plated) galvinised steel
. Both zinc (galvinised) and mild steel
are very close to aluminum and although they can rust themselves they don't eat the aluminum through galvanic action. Loss of material on your aluminum stantion bases might not be that big a problem if you build them heavy enough but on my hull
I would rather not have any stainless giving up the aluminum's electrons!!
Aside from galvanic corrossion there is poltice or crevass corossion to consider wherever oxygen is kept away from the material. (Same with stainless-ever notice the rust coming from under chainplates?). The oxygen allows the creation of a layer of protective aluminum oxide. Without it aluminum corrodes. By painting (directly after sanding
to get the paint
to adhere to the aluminum and not the oxide that has formed) the undersides of the bases and bedding them the best you can this can be minimized. Exposed bare aluminum is very corrossion resistant so long as it is exposed to the air but will show light white crust with time no matter what. A quick scrub with a scotchbright pad or 'green scrubby" from the supermarket makes it shine again. There are chemicals that work wonders also-witness an acid wash on my aluminum livestock trailer after 120K miles each year and it looks like new again! On small parts
(I used to manufacture packframes) wire brushing seemed to do wonders for a longlasting finnish. Might of had something to do with smearing the surface of the material but they seemed to stay shiney and not crust with time.
Do you have any pics of your aluminum portights? Want to offset your costs a bit and sell a few?