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Tuning: NACRA F17
Nacra F17 Carbon Mast Tuning
Guide.
Effective date:
June 20, 2008
The information provided comes directly from years of
testing and sailing.
By Bob Curry, 2004 / 2007 NACRA F17 North American
Champion
Rudder Alignment
Rudder alignment should be
set to 1/32to no more than 1/8 toe in.
With rudders down and locked, measure fore & aft on
the rudder, 12 down from the bottom of the lower casting
and level with the bottom of the stern. The tiller arm to
cross bar space should be equal on both starboard & port
sides before tightening the set screws.
Daggerboard/Rudder
Tuning
Careful tuning of the
daggerboards and rudders is important to prevent cavitation.
Rounding of the leading edge seems to be more important than
getting the trailing edge sharp. For the trailing edge,
thinning of the foil from about 1 forward to an edge about
1/16 thick seems to work best.
Daggerboards:
Upwind:
- Skipper sitting on the
side> Boards totally down.
- Skipper hiking almost on
trapeze > Boards totally down.
- Skipper on trapeze > Boards
totally down.
- Skipper on trapeze and full
cunningham > Raise the boards 6.0 up above the deck.
Downwind:
-Always raise the leeward
board about 12.0 up above the deck and the weather board
all the way leaving just enough board down to fill the trunk
below the hull.
-Mast
rotation always fully opened/released and enjoy the ride!
Rudder-rake/angle:
You turn the adjustable eye
that is screwed into the lower rudder casting 1 Ό out. You
measure
between the black rudder case
to the center of the adjustable eye.
This is a good starting point for most skippers.
Mast Set-up
Spreader-angle:
With 175 lbs on board,
recommend that you use 2 1/2 of spreader rake.
With 187 lbs on board,
recommend that you use 2.0 of spreader rake.
With 198 lbs on board,
recommend that you use 1 Ύ of spreader rake.
With 210 lbs and above on
board, recommend that you use 1 ½ of spreader rake.
Measure between the
mast-track and diamond wires.
Place a sail batten from wire
to wire and measure the
distance. It is
recommended not to use less than 1.0 spreader sweep.
Diamond tension:
To measure the tension of the
diamond wires, use a Loose & Co tension gauge which
you put onto the wire and let
go. (the expensive one with the two wheels)
This one gives you the most
accurate readings. The numbers that work on this tension
meter are:
32-36, until 15 knots
36-39, from 15 to 25 knots
39-42, from 25 plus
The carbon mast is very stiff
sideways and flexible fore/aft.
Mast Rotation:
- Skipper sitting on the
side= mast rotator pointing at middle of daggerboard case.
- Skipper hiking almost on
trapeze= mast rotator pointing at end of daggerboard case.
- Skipper on trapeze= mast
rotator pointing in the middle between rear beam and
daggerboard case.
- Skipper on trapeze and full
cunningham= mast rotator pointing at intersection of
rear beam and outside of the
hull. Lighter
skippers will not have this rotation so far back.
Move the rotation forward to open the top section of
the sail.
Rig Set-up
The NACRA F17 seems to like
a tight rig and the boat performs better with the tight
shrouds. Too tight
and the mast wont rotate downwind!
Mast Rake
Basic setting for now is the
upper screw of the rudder spring on the transom.
Or with a rudder attached to the boat and in the
kicked up position, 15-20 behind the transom measured on
the top of the trailing edge.
To measure, you take your
trapeze line and find the intersection of the front of the
bridle tang and the hull.
You swing the trapeze line to the back and hold it
against the transom or trailing edge of the rudder to see
where it touches.
Spinnaker
End pole: The end pole
snuffer system, I found the sail to stay powered up by
raising the spinnaker to full hoist and then using a 9-12
pigtail at the tack.
The spin works best when grabbing the luff and
rotating tightly to 90 degrees.
Always set your spin for a port rounding.
Midpole:
Have a great sailing season!
Bob Curry
Team Nacra USA, F17 #723
Questios: see
Ask Bob
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