Paul Thompson wrote:Personally, I'd stick to steel and aluminum. Your whole rig hangs from the masthead crane and it's not a place that I'd choice to experiment. While polycarbonate might be strong, I doubt that is abrasion resistance is very good or even just good.

I'll take your advice under advisement.  I'm inclined to disagree. I think you'd wear through metal a lot quicker.  PC is one of those plastics used as bushings.

Polycarbonate is the stuff they make bulletproof "glass" and the bubble windshields on jet fighters out of.  When I say it's bulletproof I'm not exaggerating.  It's way tougher than the aluminum mast will be.  It's not brittle, either - when it does give it slowly bends.  I saw a quarter inch sheet of it, years ago, that had been shot with a 38 special at about fifteen feet at the Kansas City police shooting range, and just had a small dent in it.

Jeff McFadden wrote:OK, I ordered 2" x 1/16" x 20 feet, 8 total.  That's 7 for the battens plus one to extend the yard.

The existing yard is 16 feet long, wood, inverted T section, with the existing sail laced to it.  I'm going to lace a 2" x 1/16" x 20 foot aluminum tube to the bottom of it, sticking out 2' on each end, and call it good.  If I find out otherwise I do.

Still got to move the step, finish (well, ok, make) the partners, make a masthead crane which I think I'm going to print out of polycarbonate on my 3D printer as an overlapping plug that stuffs into the top of my aluminum mast, overlaps the edges to provide a weatherproof seal, and either has the necessary bosses on it for hanging blocks, or a webbing "crown" with loops to hang soft shackles & blocks on.  Got the sail cloth and thread but I need to buy some plywood sheets to put on horses to use as a worktable for the layout and sewing.  Bought forest green Odyssey III sail cloth.

That sounds good, Not sure about 3D printing and polycarbonate as I do not know enough about it. One thing for sure, what ever you do regarding the masthead, it must be beyond doubt as if anything goes wrong there, you'll be at least chin deep in the brown sticky stuff.

Do be aware that while large diameters and thin walls are a good thing in terms of stiffness and keeping weight under control, it is possible to go to far. Thin wall tubes are more fragile than thick wall tubes and dents have a greater impact on structural integrity/strength. That being so, I'd not use a tube with a wall thiner than 1.5mm (1/16" or .062").

Also while light is in general good, a little weight is no bad thing as it will help the sail come down. Just, as in all things don't over do it. On LC I'm using 50mm diameter x 1.5mm wall x 16' on the main and 50mm diameter x 1.5mm wall x 12'6" on the foresail. Thats heavy but using the same batten size for both sail makes carrying spares easier and for my coming voyage I need near unbreakable battens, as I will not have access to unlimited spares. 

Jeff McFadden wrote:Would that be number 2 counting from the top or the bottom?  Do I need a heavier spar for a "boom" or is that just another batten as somebody, maybe Slieve, has said in the past?

Depending on its length (I need to measure) my existing yard may do.  It's wood and very heavy, but I'm rapidly approaching 20 grand in this ten thousand dollar boat and I'm getting stretched pretty thin.  I'd try to reuse my old battens but they're 1" plastic pipe, which I define as "not real."

No need to translate to Imperial measurements.  I'm getting to where it's the Imperial, not the metric, that drives me crazy.  Google will do the conversion in the blink of an eye.

Somewhere I failed to see the "b" dimension.  20 footers is what I can reasonably buy, so that will be it unless it seems necessary to go to 25 to get the extra inches for the one batten.

It's second from the top. No specific need to make the "boom batten" heavier but many do as a little weight here does not harm. However technically, it's just another batten. 20ft lenghts is fine, just cut them to size. 20ft fot the long batten is also OK, if you want the 2", just make wooden plugs to extend it 1" on each side.

The "b" is just standard PJR terminology.