> Judy,
> I got my CDI furler and new forestay in and installed. The question is,
> what is the optimal mast rake for the P-15? I can not find this piece of
> information. Can you or anyone else help me?
>
> Richard
> P-15 Sirocco
> TIEHH
> Department of Pharmacology
> Texas Tech Medical Campus
> 3601 4th Street
> Lubbock Texas 79430
> 806 743 2425 xt 232
> 806 743 2744 fax
Hi Richard,
I don't know much about the P15's, but here are a few ideas.
A good place to start is by setting your new forestay the same length as your
old forestay. If the rigger made it right, it would be the same as the old
length if the turnbuckle is adjusted to be halfway between its shortest
length and its longest. If it's a newer P15, you could call the factory to
ask for the information if you think there was a problem with your old
shroud. Or maybe someone with the same type rig you have can tell you what
length the forestay is.
I'd guess that the mast should be perpendicular to the waterline, for
starters, or perhaps a few degrees of rake. (But somebody else correct me if
I'm wrong on the P15)
That should be good enough for a decent rough tuning. Be sure to put cotter
pins in the turnbuckle once you have the length set correctly. It can, and
will, rotate while you sail or trailer, maybe even coming undone at the
proverbial "worst possible moment."
For fine tuning, which is very important, you've got to go sailing. Pick a
day with moderate conditions (about ten knots of wind) where you're not
overpowered or underpowered. Go sailing at slack tide or a location with
little current. Make sure the boat is properly trimmed fore and aft
(floating on her lines properly). Sail with a modest heel (about 15 degress
or whatever angle is "right" for the Potter 15)
Sailing close-hauled in 10 knots of wind with modest heel, with proper
fore-and-aft trim, the boat should have a very slight tendency to head up on
its own. You should have to pull lightly on the tiller about 3 degrees to
windward to keep her on a straight course. (Before you go out, mark the
centerline and 3* to either side of the centerline of your boat on the
cockpit seat somewhere for comparison)
This is called "weather helm." Boats are designed to have a slight weather
helm, usually 3*. It makes then safer, because they will round up if you get
yourself in trouble. It also gives you a slight "feel" for the tiller while
you sail. And a slight weather helm when you're sailing close-hauled
improves your leeway-resistance by producing lift to windward. Too much
weather helm makes you turn the rudder too far to compensate, and it acts
like a brake.
If the boat doesn't have a tendency to go upwind on it's own, or has a
tendency to head downwind (called lee helm), then you need to lengthen the
forestay a bit. Four or five turns of the turnbuckles will rake the masttip
back an inch or so. One inch is a lot, so resist the temptation to do more.
This moves the center of effor of the sails aft compared to the center of
lateral resistance (from the keel, chines, skegs, etc) and helps turn her
nose upwind. (Also check the port and starboard shrouds to make sure they're
still properly tensioned; as a rule of thumb, you should be able to move them
an 1-1.5 inches from their neutral position by pulling lightly on them with
two or three fingers.)
If you have to pull the tiller past 3* to keep her on a straight course, then
you have too much weather helm. Lengthen the forestay a few turns of the
turnbuckle to move the sailplan's center of effort forward. This will reduce
the weather helm.
(In this generalized procedure, I'm assuming there's no special procedure
unique to the P15, like setting the swing keel at some special angle that
affects the balance of the boat. P15-ers, chime in here with your knowlege!
I'm also assuming that you don't have a backstay. )
Hope this helps answer your question. If it wan't clear, or you have more
questions, please ask.
Best regards,
Judy B.
Judith Blumhorst, DC
HMS18/P19 Fleet Cap'n, Potters Yachters
1985 WWP19 #266 Redwing
(Rigged so a petite woman can solo)
Sailing on SF Bay, CA
(5-35 knot winds, 2-4' chop, 2-6' swells, and currents up to 6 knots)
Visit <A HREF="http://members.aol.com/jblumhorst/HomePage/index.htm">Judy B's
West Wight Potter Pages
</A>
and <A HREF="http://songbird.com/potter_yachter/">The Official Web Site of
the Potter Yachters
</A>