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
Hi Eng,
I've just sent an e-mail to Bob for an updated verion of these tips as they are now 18 months old, i'll post as soon as i get them... BTW, i sailed the proto when Ross put it together, great boat, the new one should be awesome. Rigged the mast yesterday (same section as the F18 and the main has a bigger square top and looks HUGE), at the factory and will put the platform together tomorrow, can't wait to get her on the water, will let you know what she's like after the first sail...
Cheers,
Leroy
Tell Roscoe to finish mine before yours <img src="<>/cry.gif" alt="cry" title="cry" height="15" width="15" />
Just kidding mate, he's still got a fair way to go on mine.....
Hey hang on whats happening to my I17 wings, that I ordered URRRMMM last mission beach nacra nationals?????
<img src="<>/laugh.gif" alt="laugh" title="laugh" height="15" width="15" /> <img src="<>/laugh.gif" alt="laugh" title="laugh" height="15" width="15" /> <img src="<>/laugh.gif" alt="laugh" title="laugh" height="15" width="15" /> <img src="<>/laugh.gif" alt="laugh" title="laugh" height="15" width="15" /> <img src="<>/laugh.gif" alt="laugh" title="laugh" height="15" width="15" /> <img src="<>/laugh.gif" alt="laugh" title="laugh" height="15" width="15" /> <img src="<>/laugh.gif" alt="laugh" title="laugh" height="15" width="15" /> <img src="<>/laugh.gif" alt="laugh" title="laugh" height="15" width="15" /> etc etc..... <img src="<>/wink.gif" alt="wink" title="wink" height="15" width="15" />
Wasn't that the North Queensland titles?????
Is that
THE
leapin Leroy Brown? Look forward to seeing the new beast on the water.
Below is an updated tuning guide I put together after the 2008 North Americans. If I were to sail the boat, this is exactly how I would run the set up. In combination with Curry's guide you should have a good starting point.
Tuning and sailing techniques for the F-17SW
Boat set up:
Mast: The boat seemed to perform well through a wide range of conditions, from 2-20knots with the mast set at 1 5/8” of spreader rake and tension from 37-42 on the newer loose gauge. I recommend a tension of 39 for most every condition up to 18 knots. Above 18 knots, increase tension to 42. The boat does not respond well to more tension. Maximum depower can be achieved with down haul as long as your mast has at least the above mentioned tension. Tension below 39 should only be used for heavier skippers or in very bumpy, light conditions.
Rake: The Rig should be raked approximately 14 inches behind the attachment point of the upper rudder arm.
Tension: As tight as you can get it with one man hanging from the trapeze. Never tension your rig with the main sheet.
Spinnaker: The luff should be adjusted to be a tight as possible. No more than 45 degrees of twist should be allowed when grabbing and twisting the luff with one hand.
On the water:
Beating: The new rig likes to depower early! Do not hesitate to pull on the downhaul and rotator. Maximum power is with your mast rotator pointing between your rear beam and side stay, closer to the side stay but not pointing directly at it. The carbon rig is notorious for over sheeting in lighter breeze however it is almost not an issue with the SW rig. Always keep your main tension tight the blocks should always be directly over each other, never any deflection between the top and bottom main sheet block. Once you are on the wire and begin to depower keep as much tension as possible. Once you’re on the wire you should also prepare to begin depowering steps. 1) Increase downhaul, assuming that there are no wrinkles in the sail, increase down haul tension by 50%. Trim your down haul for the consistent breeze and use the main to depower in gusts. 2) Mast rotation should be brought back once you have increased the downhaul. I recommend mast rotation at the leeward edge of the tramp pocket stitching. 3) As the wind increases continue to increase down haul. A 180 lbs skipper should have max downhaul in 15 knots! 4) After you have reached max downhaul (two hands and all your strength) move your mast rotator further aft, maximum mast rotator depower is recommended at 2 inches inside the outside edge of the tram pocket stitching. Play the main! Boat speed can be hugely increased by consistently playing the main. Do not keep it in the cleat and pinch in the puffs!! The best method is to anticipate the puff, have you main uncleated and release sheet as you head up slightly. The gust should be completed with an adjustment back to proper course and adding tension back to the main. In conditions gusting above 18 knots I recommend droping your traveler 6-8 inches.
Running:
Set your spinnaker first! Do not release downhaul or mast rotation until your spinnaker is up and sheeted. Whoever has the spinnaker up first has the advantage. One the spinnaker is flying release all down haul and mast rotation. If you are not flying a hull you should position you body just ahead of the dagger board sitting on the tramp. I do not recommend raising a dagger board, you will lose more trying to adjust your boards up and down then you will gain from the minor reduction in drag, unless conditions are very light. Additionally the leeward board should remain down to facilitate flying a haul as low and early as possible. Main tension should be eased slightly from close hauled and 6-8 inches of traveler should be used in all conditions except for extremely light winds where less main sheet tension should be used. If the wind is not strong enough to induce maximum rotation use a positive rotator or your foot on the boom to achieve it.
As the wind increases you should move back on the tramp. I always sit just inside the hull on the tramp in conditions up to 10 knots. Do not “wild thing “the boat. It is only beneficial to do so if you understand the mark. In conditions over 10 knots you should be sit as far out on the hull as possible leaning back. You will be able to fly the hull don’t worry. You are using this body position to facilitate maximum forward acceleration from the spinnaker. Forward acceleration is more important than vertical lift. Jibe the boat with speed, if you slow down going into a jibe in breeze you are much more likely to flip the boat coming out of the jibe, this sounds risky but it works. Stay in clear air and keep an eye out for the puffs!
Hi Chris,
Thanks for that, all sounds pretty logical... And yes Aido it is me... Hopefully be on the water this weekend, if not it will be a couple of weeks because i'm interstate next weekend...
Cheers,
Leroy
What is the technique for tacking in light air with chop? Do I go to the back of the boat or stay by the dagger or in front of the dagger?
Does the spin luff tension change with different wind conditions?
In really light conditions and flat water does it pay to have a bit less mast rotation (than to point to the dagger) to reduce drag? (2-4 knots of wind)
Luff tension on the chute should always remain the same unless you need to reach for some reason, in which case you can loosen the tension slightly.
It light breeze, when you are sitting on the hull it pays to talk the boat just far enough back to get the tips of the bow out of the water at the water line. This will reduce drag in the tack. Move back forward as quickly as possible.
It does not pay to rotate back in light air. Set the main up for maximum air flow around the mast. You are not trying to reduce drag, you are trying to increase lift in light air. However, never over rotate to winward. I would say max rotation on the wing mast in any condition would be the side stay or slightly behind. You can mark your tramp with stitching or white paint to give you rotation reference point rather than eyeballing the angle.
POOP, won't be on the water this weekend, boat not ready and bank is stuffing me around.... Interstate next weekend for 5 or 6 days, so it'll be 15th at the earliest, DAmn thats frustrating...
Enginineer, tx for exelent guide, I have a question however:
What doe you mean by
the intersection of the front of the bridle tang and the hull.
?
Is that where the bridle is attached to the hull?
Kind regards,
Martijn Balhuizen
Hi Martijn,
I wish!!! Bob Curry has compiled this information. I would say that is what he means. He is a great guy, email him if you need further clarification sailbobcat@aol.com
Do you sail F17 in europe?
We have now 2 inter 17 Nacras at our club. I will post some pictures on Monday.
Chocko
Yes, I sail an I17 in The Netherlands Europe. (I sail a Inter20 as well with crew, but always have loved the I17, and really like the fact that I am free to sail whenver possible). I started Hobie 16 , Hobe17, Inter17 (old), Inter17 (newer).