Hi,

The Swedish guy here ;-) . If you want to add a jib it will work with a self-tacking Infusion or another F18 ditto. I have done this to our 10" wide 5.5 . See image below where a Hobie Tiger mast is used.

As I see it, it would be easiest to share the forestay load with a third centered Dyneema forestay and a low Dyneema bridle(Liros Static 4 or 5mm) at ca 1´ 2" heigth. You might have to lengthen the side forestays and shorten the top snout, as the jib luff is 19´ 7". If you are lucky, it will fit without altering the side fore stays, as the 18SQ mast is almost 2´ higher than the F18 mast.

If we assume 220lbs total static forestay tension, let the center stay take max 80lbs and the side forestays split the rest. Tricky, but it will work, if you have a Loos to check tensions. Don´t know how much sag you will get in the jib luff, though.

For next years 5.8 Frankencat build, that Jeff refers to, I bought a pair of 18SQ beams, but had to return them as I found them all to weak to use for 2 persons. Designed and built new 10.5" inch wide ones. First opted for a pair of 6.0 hulls, but changed to the 5.8s from the same source, as they where in much better shape. Also bought a Tornado self tacking jib instead of the 49er mentioned in the link below.

https://www.catsailor.com/forum/ubbthreads.php/topics/288287/re-taipan#Post288287