This boat, called Kura (Maori for red feather) is the first frame I built, for Jack's Flyer Cat tubes (19" dia. x 15 ft. long). For tight, rocky water, I wanted a narrow rig with a low center of gravity, and this has been the ticket. For materials, see the list in the first (pictureless) post.
This one has welded double-rail corners from Sid's sports. The rear bay (covered by a deckboard) fits a 70 qt. cooler. The two side decks (for dog comfort) are PolyMax kennel floor.
The 90° drops are 1" nominal steel conduit with sections of chainlink toprail braised on to fit the Speedrail joint (at the top). At bottom, they're bolted inside the lower frame tubes with 1/4" machine screws and acorn nuts. The floor is a 2' x 4' PolyMax panel framed in wood, with aluminum bar and channel reinforcement. Relatively light, but rigid. And you can pee through it.
The wood components add stiffness to the frame. The oarstands are bolted onto mahogany plywood recycled from old cabinets, while the seatboard is solid mahogany doused with epoxy resin. The board has a nice flex and the seat is a steel-framed type from NRS. The wood parts are fastened with u-bolts and acorn nuts (always cap the end of a bolt—an exposed thread will slice you open like a razor blade).
Kura, on Deso in 2005, with an extra gearframe up front. One advantage to this sort of frame is adaptability. It can be set up differently for every trip, with the rower front, rear, or center. For added cargo, I built simple frames of top-rail with bolted conduit corners (no drops) to fit York Packs. Two York Packs drop in, with 3 gal. jerrycans on either side. Cooler in the rear, with a pad for seating
That's it for me. Your turn, amigos. Invent, or die.