Spent a lot of time on my rings for the portholes this weekend. I know the plans call for plywood, but I really wanted to use regular wood (fir for me). I cut them, shaped 'em up very nice, sanded them and drilled one of them out to check before continuing. I really thought with that thickness it would be able to withstand a little bit of pressure. I was mistaken. It cracked along the grain plane on each end as I cranked down the screws a little. The last time I made a silly mistake, I was able to make some pretty decent lemonade. I don't see that happening here. I guess I'll have to get some decent plywood and try again. Hopefully I won't have to buy a whole sheet of it. Are most of you using plywood?
I used some opening stainless portholes on my boat but I had to add ply rings on the inside of the cabin to make the cabin sides thick enough for the portholes to work out. I think it turned out good. You may have to either go with ply or lam some lumber together to keep it from splitting
Keith
Quarter inch plywood worked well for me. Make sure that you put lots of spar varnish on them before installing. Mine are 4 years old, and they are showing that I didn't put enough coats on them during construction. Guess bright work aways needs lots of annual attention anyway.
Greg
Did you cut the porthole rings from a single wide board?
Or piece them together from six or eight segments?
Make up some wooden rings that exactly mimic what you want in a ring (inside or out), including flanges, rabbit for the glass, etc. Then make a plaster mold of this. Coat the mold with release wax or powder then mix up some epoxy and give the mold a quick wipe with goo. Allow to get tacky then mix up a thickened batch, using bronze or brass dust (lots of it) as the thickening agent (you need some micro fibers to prevent the metal particles from sagging). Spread this into the mold, covering all surfaces, let get tacky. Apply some fabric reinforcement and more goo, until you've built up the inside to the desired thickness. Pop it out of the mold and you have a plastic ring, which happens to look just like what you want (a bronze port), but it can't turn green. Protect it with some polyurethane, varnish or automotive clear coat and drill mounting holes. Another option is to skip all the metal filler thing and just cast up a ring with goo and fabric, then paint it with metallic spray paint.
It'll weigh a fraction of the real thing, look fine, is home made with materials you probably already have and you can make several exact copies after the mold is built.
You can also make "loaded" parts this way. I made a custom mast band for a friend who wanted to have some flag halyards on his motor sailor. He priced out a custom bronze mast band with a couple of eyes and he didn't want to spend a few hundred on having one welded up. We made the band from wood, cast it as a single piece, then cut the mold in half on the band saw. We very carefully applied fabric reinforcement around the eyes, so the strand orientation was in the direction of the load and cast the two half's as described above. We popped them out of their molds while in the "green" stage of the cure and carefully aligned and bonded them together with thickened epoxy. They were painted with a can of Rustoleum spray paint and it was screwed to the mast head. It works fine and looks great. I wouldn't use it to hoist a boson's chair, but it could have been reinforced with carbon and Kevlar, which would have made it strong enough for a stemhead or chain plate.