In case of interest, I just finished building the second version of a raised helm seat for my boat. (Admittedly, there are a few additional cosmetic things I might do, but not in an hurry.)
I think I have it down to where it’s pretty easy.
The seat looks like this:
The upper part is closed-cell EVA foam. It was sold to me as UV-resistant, and I hope that’s true. There’s an adhesive upholstery spray designed to hold fabrics to each other or hard surfaces. Although Starboard’s pretty slippery, it seems to have worked to spray both it and the bottom of the foam and then press them together when the spray was partially dried and tacky. After that, I put some weights on it and left it overnight. The attachment is strong enough that you can lift the entire thing holding it by the foam edges, with no sign of peeling.
At some point, both for UV protection and cosmetics, I may cover the white EVA foam with some Seadek mocha and black EVA decking material, which is what you see on the cockpit seats on either side.
The bottom part was made out of 0.75” Starboard, but could just as easily have been marine plywood or Medium Density Overlay board. I used Starboard only because my mechanical engineer stepson was kind enough to do the cutting for me, and he happened to have that material on hand. Being a mechanical engineer, he also was kind enough to do a pair of CAD drawings of the design:
Here’s my drawing of the pieces needed to build the base:
Although the text in this drawing says 30”, the pieces are actually about 29.6” long, but those details don’t really matter. The angle on the left and right top cuts is about 11-12 degrees.
With 0.75” top pieces and 1” foam, this makes a seat raised 4.25” above the cockpit seat. If you want a higher seat, either buy thicker foam or cut the vertical supports more than 2.5”. The 0.75” material thickness might be overkill; if you went down to 0.5”, you’d want to adjust the vertical piece height accordingly.
I hope folks find this useful. It puts the job in the range of something duffers like me can do (as long as you have a tool that will cut the angles correctly, or are willing to mark them and take them to someone who’ll cut them for you).
I’ll post a follow-up after it’s been in use for awhile to report how it holds up.
– Bob