Originally Posted by taezow
I don't know what type of sail this is or how to fly it.
It has these two blocks and sheets
in the sail bag.
I have a new to me 27 Searunner
Yes it's a spinnaker. (Speedoo is wrong on one point: Trimarans don't need spinnaker poles, as they have enough beam to keep the sail open when sheeted to the amas.) Not enough detail in the images
to tell if it's an asymmetric
or symmetric -- the corner with the sailmaker's label is the tack, so the edge leading up to the head
from there would contain a luff rope
or cable if it's asymmetric
As to the purpose of the lines -- please post another image that shows more detail about the turning blocks and how they are attached to the two lines with blocks attached. They could be sheets, or they could be used to attach the lower corners if the sail is symmetrical.
You could have two separate sheets or one long mid-attached sheet, and those would lead outside your shrouds to turning blocks on the aft portion of the amas, then lead into the cockpit
optionally through cleats
or stoppers, then to a cockpit
used to adjust the sail under load. The head is attached to a separate spinnaker halyard
that exits the front of the mast
above the genoa
the two lines with blocks could be downhauls to attach to the clews and each one would attach at an ama bow with turning blocks leading aft then another turning block leading to the main hull
and cockpit. If asymmetric
the sail will have only one tack and one clew -- the two lines with blocks could be your sheets.