Question: I would like a large roach, but how can I be assured it won't interfere with my backstay?

Answer: Information about the backstay location is essential for the sail designer, if we are to ensure that a large roach goes free of the backstay.

The three critical dimensions are as follows:

1. Lower Backstay position - With the boom horizontal, measure from the back of the mast to the backstay along the top of the boom.

2. Masthead Crane, horizontal offset - Estimate the horizontal length of your mast crane (from the back of the mast to the aft end of the crane where the backstay is attached).

3. Masthead Crane, vertical offset - Estimate the vertical distance from the top of the mainsail to the upper attachment of the backstay.

Note that even with moderate / normal roach size, the room under the backstay on some boats can be pretty tight, so whenever possible, I like to have this information regardless of the sail / roach size.