: Hi all,
: Tom wrote few days ago he built boats using 3/4" (6061-T6) X
: .037 wall tubing Vs .049 and that he is still happy with them.

: So today I found these tubes for sale: 5/7" (18mm outer - 16mm
: inner) x .039 (1mm)
: and inserts .607 (15.4mm outer - 14mm inner) x 0.028 (0.7mm)

: There are also available inserts 5/8" (16mm outer -14mm inner)
: x .039 (1mm) but they will fit looser i think.

: Would you go for inserts .028 better fitting or .039 loose fitting?

I think you have those options reversed. .039 would be a tight fit: 16 mm OD tube going into 16mm ID tube gives you no slack at all. It might be difficult to fit these together. On the other hand, putting a 15.4mm tube into a 16mm tube gives you 0.6mm of play, which should be plenty of clearance for easy assembly (and disassembly if you are looking to build a folding boat). With all that said, the original specs were for .049 wall thickness, with the option of going down to .037. You are starting on the light side (.039 and going lighter still (.028). I'd look for a smaller diameter tube with a thicker wall than that for my inserts. Can you get something 13mm ID with a .049 wall? That would be about 15.5 or 15.6 OD, and strong. Or, I'd use hardwood dowels for the inserts. You could combine these ideas and use the lighter thinwalled tube, but epoxy a dowel inside it to stiffen and strengthen it.

Just my thoughts. good luck with your project.

PGJ