[quote=George1067]Rob
To get down haul to work really well wen wind picks up diamond tension is important , You can get a Loose gauge for about $80.. on ebay .. I am able to sail in high winds very well wen adjusted properly .. It is very simple .. Very important to flatten or make sail fuller flatter heavier air fuller light .. I send you line on mast rake setting etc from Bob Curry who was North East t Champ .
Sorry about the plagerism Bob, but I do get asked for this all the time...
Tuning: NACRA F17 SW
Nacra F17 Aluminum Mast Tuning Guide. Effective date: June 20, 2008
The information provided comes directly from months of testing and sailing.
By Bob Curry, 2004 2007 NACRA F17 North American Champion
Rudder Alignment
Rudder alignment should be set to 1/32”to 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 castingand
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 ¼” 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 ¼” 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 ¾” 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 ½” 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:
34-38, until 15 knots
38-41, from 15 to 25 knots
41-43, from 25 plus
The aluminum mast is very stiff fore/aft and flexible sideways.
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 theboat performs better with the tight shrouds.
Too tight and the mast won’t 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.
Have a great sailing season!
Bob Curry
sailbobcat@aol.com[/quote]
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