Hi
Rather than start a new 'boom' thread, I thought I'd add my thoughts here.
My original boom solution on my AI in 2015 was similar to Walt's, except that it was more basic and allowed furling:
https://www.hobie.com/forums/viewtopic.php?f=32&t=54212 I used Prusik loops to attach the (fishing pole blank) sprit boom to the base of the mast, to attach the main sheet pulley to the boom, and to attach the clew to the boom. This meant no tools were needed, and that I could slide the clew down the boom to allow furling with the boom attached (Prusik knot at mast base allows the mast to rotate while the boom does not).
In its last iteration also routed the mainsheet along the boom before coming down to a pulley on a traveler (mounted on the forward cross bar) then going back to the helm. This created a sort of vang effect that helped keep the boom-end down in downwind conditions.
However, the boom still lifted a bit too much for my liking, and as I sail my AI as a monohull, an aka mounted vang wasn't an option. I also didn't like the fact that I couldn't furl the sail downwind without retracting it, not always possible in challenging conditions
Fusioneng's twin boom idea mentioned earlier in this thread appeals, with the front of the curved booms being held by a rope suspended from a mast topper to allow furling, but I wanted something easier to fabricate, so after I saw Sidney Herreshoff's 1934 Amphicraft arrangement (
https://3.bp.blogspot.com/-QGoO-KWjUpg/WHgXNlp078I/AAAAAAAAT1A/kmPnSrhQbKcST29Su1SNcQDco2_MvDGwwCLcB/s1600/Amphicraft%2BKent%2B1.jpg I decided to copy it, but without the two horizontal ropes locating the crossbar to the boom (so I can still furl the sail)
Here's the result (finished yesterday):
https://youtube.com/shorts/Srye_9GeUpw?feature=shareI've used fishing pole blanks again for the crossbar and booms, and used the fishing pole alloy screw-in end-plugs to mount short lengths of cord to join the boom ends together and join the crossbar to the booms. The two vertical ropes at the ends of the front of the booms lead down to a single carabineer on a loop at the mast base that allows mast rotation, while I used the Hobie spinnaker mast topper to attach the top ends of the ropes clear (to clear the sail.)
With the 1m crossbar keeping the booms well apart, I don't seem to need Herreshoff's two horizontal ropes locating the crossbar to the boom side to side to stop the sail touching the booms (or the bars used to the same effect on the Fulcrum Speedworks foiling UFO catamaran)
I really like the fact that I will still be able to furl and unfurl the sail downwind without having to bring the mast back to the cockpit (I've used a 2:1 pully set up to maintain clew tension):
https://youtube.com/shorts/sQP-ls3GKbs?feature=shareHopefully we'll have good weather tomorrow so I can try it out