You're certainly correct about wanting to build it yourself. The cost of a custom fabricated arch is likely to run into thousands of dollars. But the skills needed to cut, bend and weld material, not to mention the time it might take is also considerable.
You may want to consider buying
something used. I live in Florida
, and there are, literally, tons of this stuff laying around in boatyards
, marine salvage
centers, craigslist, etc. Something that came off someone's go fast boat or sport fisherman might be just right for your needs with only a little cutting and fabricating to adapt it. All you have to do is find it before it goes to the recycler or land fill. The fact that it may come already festooned with antenna
mounting tabs, lights, radar
platforms and rod holders is a bonus!
I once asked a local marine engineer/fabricator to build a combination stem head
fitting/anchor roller for my 30 Arpege. After a week of studying on it, his estimate was $4500. I laughed in his face. He came down to $3000. A month later I bought a custom fabbed anchor
roller off a 50 foot trawler
for $35 at a nautical flea market, drilled a few holes in it and bolted it on. Ten years and three hurricanes later it's still working and looking great.
Someone else suggested molding your own from fiberglass
. That would certainly be doable if you have time and a place to do it. It wouldn't be terribly difficult to mock up exactly what you want in plywood
, PVC, and bondo and create a mold
or form to layup
glass and epoxy on.