Thread: Unstayed aluminium mast

A 3 mm extruded aluminum mast wall, will require a huge diameter on most boats with a free standing rig. You could get by with 3 mm on a moderately sized (8 m or less) boat, but it would have to be well stayed to keep it from buckling and folding in half. Do you have a specific design in question with a 3 mm, unstayed mast? What's it's base diameter and approximate taper?

Par - Thanks for your interest.

I was deliberately being vague hoping to prevent the usual Junk Rig knocking fraternity. I am building a 17 foot trimaran daysailer. Just to be me, I am trying to put a Junk Rig with unstayed mast on this boat, and have read other posts where a unstayed 3mm aluminum tube, doubled at the partners is sufficient for very large rigs. I cannot find the link now, but he mentioned putting this rig on a (from memory on a 30 ft Wolftrap - whatever that is) I am no professional boat builder, but I came to the conclusion that if he could use this rig on such a large vessel, I should get away with it using about half the sail area.
Any thoughts on this???

Without rigging spec's it's a tough thing to say, but unless the mast had substantial girth (diameter) then I can't imagine any rig, junk or other wise being hung free standing. Someone is mistaken or can't read a ruler properly, as 1/8" wall thickness is quite thin for a 30' boat's free standing stick, again unless it had a 12" diameter base (maybe bigger).

a quick look at Goldspar AU website suggests 3mm is way too thin for a free-
standing mast.
Goldspar light poles, flagpoles, goal posts, spars & masts - yacht
The only one I can see on their stock list is for the Finn, & that has 4.5mm
walls for 114 sq ft sail on a 64mm base.

You would need something much stronger to cope with the higher stability of
the tri, and its larger sail area. Why not contact Goldspar or another mast
maker to see what they think. From memory, they also do, or have done the
unstayed masts for Norwalk Island Sharpies. Their larger sails would be nearer
your spec, although again, the NISs heel easily, spilling wind (and stress).
cheers
AJ

Thanks all. I guess it is back to the drawing board