NOTE: this was a topic in the pdracer discussion group and was originally a question for a production fiberglass boat, but the information directly applies to the pdracer.
Question: I need some advice. I have a Newport 16 (also called a Neptune or a
Gull).
I have one set of sails. It looks pretty standard. The main has battens,
but it doesn't stick out too much. The jib does not extend back past the
mast.
Does anyone know the process to design light air sails for a
pre-exisiting, discontinued boat? How about a storm rig?
Answer:
As an ex-sailmaker, you have hit on one of my favorite topics. Forgive
my disorganized ramblings, but here are some options for you.
The easiest way to power up your boat in light air is with a genoa. For
this, you will need to add fair leads or trim blocks somewhere aft of
the shrouds. On a Neptune 16, that probably means on the cockpit
coaming. For true adjustment, you might want to add a set of genoa
tracks and cars, but this is
Puddle-Duck-Do-It-Yourself-For-Less-Than-$50-If-Possible so:
Forget what I said above, and go get out your tape measure. A flexible
tape is best. Step the mast and tie your tape measure to the Jib
halyard and hoist. Measure the maximum luff dimension from head to
tack.
Now measure the maximum leech dimension from the head to one of your
stern cleats. Be sure the tape is taken outside the shrouds.
Now pull the tape down and measure the maximum foot dimension from the
tack to the stern cleat. Be sure the tape is taken outside the shrouds.
This will give you triangle that the actual sail must fit inside. Note:
this is not the finished size of the sail.
OK, now you must make an accurate scale drawing of the triangle. Mark
off a couple of inches on the luff to allow for stretch, the halyard
shackle and the tack fitting, and make a mark on center of the line that
now represents the luff of the sail.
Next, draw a line from the point representing the stern cleat through
center of the luff. This is the approximate sheeting angle of the new
sail.
Allow room for a block to be tied to the stern cleat and pick a point
somewhere along the sheeting angle where you will be comfortable seeing
under the foot of the sail and make a mark on the sheeting angle. This
will be the clew of the sail. Draw lines from the clew to the tack and
from the clew to the head. This is your sail!
Now all you have to do is build it, but there are many articles on
construction, so I won't go on.
You can also power up your boat in light air by going to a masthead
genoa. Simply add a jib halyard on the masthead and follow the same
steps above. You will have to tack the sail around and outside of the
forestay, but that is no big deal.
(Disclaimer) Note: your boat does not have a backstay, and the shrouds
do not go to the masthead, so do not fly such a sail in any breeze, or
you risk damage to your mast, and possibly to yourself and your crew.
You could also use your existing fairlead and add a bowsprit to get the
added sail area.
If you are ambitious, you can build (or have a sailmaker build) a max
roach, full battened catamaran style mainsail, but that is a lot of work
to get right. For inspiration, look at pictures of any beach cat. You
can copy these with probably four battens, and you have no limit on
roach since you have no backstay to get in the way.
A storm jib is roughly 25% of the fore triangle - that is half the luff
and half the foot of your non-overlapping working jib. It will usually
be set on a pennant to raise the tack off the deck enough to allow a
breaking wave to pass underneath without filling the foot of the sail
with water.
A storm trysail is roughly 25% or less of the mainsail. They are
usually rigged to be set on a track that runs parallel to the regular
mainsail track, or in lieu of that, you have to take the main down
completely and use the standard track. Trysails are meant to be used in
conditions where you wouldn't want the boom crashing around, so are
designed to trim to blocks that are usually mounted on the stern such as
spinnaker blocks or snatch blocks tied to the stern cleats. It is
expected that the mainsail has been securely furled on the boom, and the
boom has been lashed to the deck.
The materials we use for making polytarp sails and such are not suitable
for storm sails, and you should consult a sailmaker if you are seriously
are considering taking your boat in conditions that would warrant them.
However, you are likely to never encounter conditions that would warrant
a true storm jib or storm trysail (let us hope!) If you are out in
conditions that get above 25 knots of breeze, I recommend you drop the
main and sail home under jib alone. If you routinely sail in a windy
area, you might want to add a deep reef to your mainsail. You can also
have a reef added to your jib. A professional sailmaker should be
used, and it should cost less than $75 per sail for a boat of your size.