David Flynn

I would check with a rigger to confirm, but, my experience would suggest that a halyard diameter of 5/16-3/8” would be totally fine if polyester rope was being used. In terms of loading you could actually go smaller, particularly if high modulus (dyneema) rope was used but the halyard would become difficult to hold on to. The same is true for spinnaker sheets. On racing boats will use 1/4” or 5/16” spectra/dyneema core line, but, for cruising applications, standard polyester of slighter larger size fore ease of handling makes the most sense. Length for spinnaker sheets is typically twice the length of the boat. I hope that helps!