Hi John,
I am in the process of finishing my ladder back mahogany helm chair and can offer a bit of advice. I will post photo's shortly of my work.
First I found a used old fighting chair that I purchased from "The Sailorman" in Fort Lauderdale for $250. It was a bargain as they were wanting $450. It was in rough shape. After removing the vinyl from the armrests and taking off the aluminum hinges I used a heat gun and stripped off all the old varnish and sanded it down to bare wood. The hinges were in rough shape from years of salt exposure and had to be replaced. I went to see the people at "Bluewater Chairs" in Fort Lauderdale and was fortunate in that they sold me a set of used chromed bronze hinges for $250. New stainless hinges cost around $500 a set (if they will sell them to you). The used hinges were in very good shape and I only had to clean them up and polish them. I was going to have them re-plated but it would have been cost prohibitive. The hinges were not an exact fit so I used a dremel and a sander to shape the seat to the form of the hinges. I then drilled out any old holes in the seat and back and filled them with wood dowels, sanded it down and then preped the wood for 3 coats of west marine epoxy, sanding between each coat. This sealed the wood from water intrusion. I then put on 6 coats of Epifanes varnish, sanding with fine sand paper between each coat. (cost of sand paper, epoxy, and varnish was approximately $100). I purchased new 316 stainless steel screws for the hinges and drilled new holes and assembled them. I am now in the process of getting new seat and back vinyl cushions made as well as new arm rests upholstered. I am not sure of the cost yet but expect it will be around $400).
I am using my existing helm seat pedestal and chair mounting hardware as it is in excellent shape and heavey enough to manage the additional weight (the new seat will weigh about 75 pounds compared to around 25 pounds for the old seat.
So when all is said and done I will be into this for about $1000. I think even if you build a chair yourself and you have to buy the wood that is what it will cost you.
So far (without the cushions and armrest) I am very please with the outcome and a little surprised by the cost. I though it could be done for less but I did not have the supplies that I needed hanging around.
I will send a few photos later today. I would suggest that if you are in South Florida that you drop by "Bluewater Chairs" their product is absolutely stunning (at about $7,000 per chair).
Mark
Lake of the Woods
1989 40 DC