Submitted on September 20, 2004 by Michael Goddaert

Question: Hi Dan, We are currently developing a 56ft blue water cruiser and as
we are planning to maximize the roach in the mainsail in order to improve its efficiency, I was wondering if there is a specific maximum overlap (with the
backstay) in a single mast configuration?

I read some of the articles on Beowulf with its amazing looking sailplan but I
suppose they have a mizzen without backstay and the main backstay running aft
of the mizzen base, thus allowing such great roach without giving up the backstay
or needing any running backstays.

We are also thinking about maximizing the mast crane in order to get the backstay as far aft as possible. Would this help?

Thanking you in advance,
Michael Goddaert

Answer: Hi Michael, There is no magic number for the amount of roach that will fit through the backstay. It is safe to say that the more roach you have, the more
breeze it will require to get the sail through the backstay. Also, stiff battens
require more wind to blow through, and larger roach sails require stiffer battens, so the problem is compounded. The sail area of the Beowulf sails equaled 88% of
the area of a rectangle formed by the mast and boom, but as you pointed out,
there was no permanent backstay to interfere with either the main or mizzen.

A good way to determine the maximum roach for your sail is to start with the
notion that the sail must completely clear the backstay without touching when the first reef is in place. The first reef is then used for motorsailing so that the roach is
not slapping the backstay in relatively calm conditions when the boat might be
rolling a little. The second step is to determin where the reefs in the sail will be located, considering logical increments of sail area reduction and the reefed
location of the head of the sail relative to the diagonal shrouds and spreaders.
With the sail head drawn on your sailplan at the first reef position, you can measure down the luff to each batten location and then easily determin the Maximum length
of the batten to clear the backstay.

In very general terms, the second batten down should have more absolute overlap than the top batten, but the top batten will often have the most overlap as a % of
its length. Making the backstay crane longer doesn't have a big influence on the amount of overlap on the second batten down. It does have an influence on the amount and location of the mast bend. If you make the crane longer, you will probably have to add stiffness to the top panel of the mast, which means more
weight up high. In that case it is not a good tradeoff.

Regards,
Dan Neri

Email North Sails with your question today!

Go BACK to Solutions for Sailors Main Page.