Originally Posted by Jake
Originally Posted by sierracat
Originally Posted by Jake
I'm pretty sure that Nacra once marketed a widened 5.5 as a factory available 18 square if I remember that correctly. You may have some sort of combination of the two.

But, yes, if you intend to use that sail, you are definitely going to need a boom. Note that if you can put a strop around the boom to the mainsail so that the mainsheet loads are directly transferred to the sail, and only use the boom to support an outhaul adjustment, you can go with a much smaller (and cheaper) material for a boom (like most of the catamarans available today do).


Thanks Jake,

Hoping some others chime in on this, but what were you thinking regarding boom specs? Build my own (like the beams) rather than try and source a nacra original? Perhaps 2" 6061 Aluminum tube, maybe 0.0625 wall thickness? How about a gooseneck assembly? The old main beam had a rudder gudgen fitting attached facing aft, I suspect this was how the boom was attached when this was an 18sq. My sail doesn't come all the way down to the tramp at the tack, so I would need something a little higher on the mast. Maybe getting ahead of myself here, but throwing some ideas around.


Nothing says that the sail has to meet the boom at the goosneck...they could be three feet away and the boom angled upward if need-be...but, that takes up a good bit of real estate to get across the boat and having the boom up higher on the mast is definitely desirable.

BTW, sunfish masts will make an operable boom (or spin pole) and they're typically cheaper from a sunfish dealer than you can get the same extrusion from a metal wholesaler.


A Sunfish mast is a 2 1/4" section. Fairly heavy section. The booms are 1 1/2" and are used for spin poles and booms.

I made a boom using a 2" section. I found a aluminum cap that fit. It might have been from a Holder 14 boom. If you have access to a lathe you can make one easy enough. I got a shroud anchor bolt from a Hobie 18 or 16 and installed that in the cap. I had what is called a super goose which was for a Hobie 18 boom. This is an aluminum fitting that the eye of the shroud anchor bolt will fit perfectly. This same fitting attaches to the goose neck fitting on the mast. Simple and strong. I believe that fitting is still available from Murray's. Google "Hobie super goose" I will try to post a couple pic's if you like.

Have Fun