OK, I have just about wrapped up my frame building project, so I thought it would be a good time to share some ideas and pics.
I started out with the idea of bending up a tubular frame, welding in some aluminum diamond plate for the side decking, and welding spuds to the side pieces that I could snap-pin the cross bars to for a break down frame. Some wise people on the Buzz suggested that it would be a good idea to make the frame adjustable, and to not weld it together.
I took their advice, went back to the drawing board, and designed a fitting that would be adjustable, support double side rails, have a means to support/fasten the side decking, and quickly disconnect from the crossbars with snap pins, while keeping the side assemblies (fittings, double rails and decking) together as a unit.
After many hours on my CAD, and a few different versions, I came up with something I liked. I purchased some stock, fabricated some tooling, and machined the fittings. Here is what I came up with:
Fittings on the double rails:
With side decking (I'm still waiting for the stainless fasteners to hold the decking down):
The cross bars can be used as double side rails for a day frame setup. (I have a drop bag that fits the front bay, and will make a plywood or HDPE cover for it.):
Someday, if I buy another raft that has different tube spacing, all I will need to do to make this frame work is to fabricate another set of crossbars. And if for some reason I want to completely change the layout, it can be done easily.
It has been a fun project, and I am very happy with how it turned out.
Thanks for looking!