1827 May 3, 2002
Gil & Judy,
The matter of helm pressure is often more a matter of sail balance than of the minor adjustment of rake.
Your rigger has stated correctly that the rake is basically preset and there is little that can be done other than tensioning the rig. The installation of a turnbuckle at the lower end of the forestay will help you balance the tension between the backstay and the forestay better but neither will effect rake very much. Additionally, forestay sag will detrimentally effect your upwind ability depending upon how full the sail has been cut, the forestay turnbuckle will certainly help in this.. My experiences, aboard Sea Quill found me design, my own 120% Doyle, cruising headsail with very little draft forward (but a full-hoist) and the upwind performance and ability to gain a few degrees was quite dramatic.
The ASW II is possibly one of the best balanced boats I have ever sailed or owned (that includes hundreds of deliveries in all kinds of conditions). My solution has always included the most important decision of selecting the properly sized headsail, for the conditions, as primary. The headsail trim is then adjusted to conditions. If trimmed with deeper draft (lead car, a bit forward) during higher wind conditions any sailboat will find itself over-powered and steer to weather (round-up). Move the lead car aft to flatten the lower part of the sail while twisting off the power aloft in higher winds. This setting lowers the tendency to round-up (weather helm). Set the mainsail with much the same idea in mind. The ASW II happens to appreciate judicious positioning of the traveler. Rarely will I power-up the main (centering the traveler car or positioning it slightly upwind of center) until lighter air (under 12 knots apparent) but find the average up-wind, boom angle indicated for adequate de-powering just about the time the outhaul is directly above the inboard edge of the cockpit locker seat. Once a comfortable, visual-dihedral (complimentary leech curves of the jib and main are achieved the helm is generally just a bit weather. With both sails drawing well, then balancing the helm to near neutral with the mizzen sheet drawn tighter until the desired helm is reached you will find your ASW II steer itself up-wind... without the benefit of any steering mechanism or helmsperson... (800 miles from the Virgins to Bermuda, in my boat, with but 20 minutes on the helm was very pleasant). A ‘slightly’ over trimmed mizzen will tend to keep the bow upwind. If she still rounds up, ease the mizzen ever-so-slightly so that the mizzen just begins to luff, thus dumping off the power at the stern).
Finer adjustments of the outhaul on both the mizzen and the main will deepen the draft by easing or flatten the sail when drawn tighter. My new Doyle main was designed without sail slugs (outhaul slide only) at the foot and even better sail-shape options appeared.
In any case before engaging the wind vane, auto-pilot or helmsperson, the trim must be found to achieve an almost neutral helm first. The Cape Horn will be happier and so will you.
Hope my experience helps.
1833 May 4, 2002
Dear Paul, thanks for the detailed course which prolongs my experience, but I have the following questions:
Mainsail Traveler: I have one only, and I assume that the preferred position in your sample case would be windward of center, do you suggest the traveler to be at or above the cockpit seat rimline in your example?
Mizzen: I don’t quite see how tightening a bit the Mizzen can help neutralize the slight weather helm, unless you are well above the best laminar flow. Later, you rightly advise letting it luff to counteract residual "round up" or weather helm. I agree to the latter, and am ready to be enlightened on the former.
Bert de Frondeville
1834 May 4, 2002
Dear Gil: I have too observed that below 8-10kts head winds, the Seawind IIK tends to need some lee helm, one spoke is about right, and can be increased to two in even lower 6-8kts wind. The boat steers at best 60 degree off the wind under those conditions, and any slop clobbers her because of her large shoulders.
The Cape Horn allows to set the helm at a reasonable preset angle (neutral helm) as you "pull the shift", so that I found it effective even under the above conditions, as long as you have 5+kts apparent wind and 2.5-3kts water speed.
In typical offshore configuration, I carry 6 diesel jerricans on deck so I may have 500N of motoring range. I used most of it in my first leg NY-Azores, and refilled, then never tapped that reserve again!
Kind Regards, Bert dF
1836 May 4, 2002
Perhaps my more exhaustive trim solutions were slurred... the business schedule and the commissioning schedule lately have found my tongue tied and my fingers leading my key board astray..
Tighten of the mizzen will bring the bow upwind, conversely easing allows the bow to fall off in most conditions. However if the dominant effort, on a beat or close reach, is the headsail, by deep draft built mostly into the forward 1/3 of the sail or excess fullness from the lead car being too far forward, this draft will tend to draw the course upwind, ‘lifted’. No amount of mizzen can help this condition.... but, if the headsail and main are trimmed to conditions most boats have a bit of normal, weather helm. Ease the main sheet until the luff edge back-fills a bit first. Once this is accomplished you approach LEE or Neutral helm and a bit of mizzen shall bring her up again. Most vanes or auto pilots cope better with a very slight amount of weather helm.
The main traveler (consider my main is quite differently cut than most ASW II’s I have seen) generally likes to be just to leeward of center in most up-wind conditions of 12 knots or more. I power up the sail in light air, on upwind points, by adding twist and fullness by moving the mainsail traveler upwind of center and easing the sheet some.
1848 May 11, 2002
Thanks to you and Bert for the advice and discussion on the finer points of sail trimming for the SWII. We sailed to the west end of Vieques on Thursday. Spent the night and had a nice dive on Friday morning before sailing back to Roosey Roads. The wind was the typical Caribbean 15 - 20 out of the east so we had a chance to try some of your suggestions. And it worked! We did find that minor trim adjustments affected helm pressure - much more than on our past boat - so guess we just needed to become more familiar with the SWII. The other thing is that, on our passage from Florida, the wind was so light that we should not have been surprised at the tendency to fall off. Looking back on it, we have to say we are pleasantly surprised at the light air performance. There were times when the wind was so light we were amazed to find that we were moving through the water at a steady 3 knots. On the overall passage we only averaged 100 miles/day - pretty slow. I still wish we had a turnbuckle in the forestay but guess we can live without it.
Gil and Judy
A Mast Tuning Guide - The Light Version
Mast tuning is simple if you remember a couple of basic principles. If you understand these principles, you can tune just about any mast.
The first principle, and probably the most important, concerns tuning the mast athwart ships. The diagonal shrouds, lowers and intermediates, always pull the mast to weather at the spreader where they terminate. The spreaders, on the other hand, due to the compression from the wires going over their tips, push the mast to leeward. In order to tune a mast, you need to establish a dynamic balance between "pull" of the diagonal and the "push" of the spreader.
The second principle is that the length of the headstay controls the rake of the mast, i.e., the amount that the mast is aft of plumb in the boat. Masts, in general, should always have at least a small amount of rake, they are usually designed for one to two degrees of rake. The feel of the helm is the ultimate test of the rake. Making a mast more vertical will help weather helm and more rake will help to correct lee helm. This is a bit of a simplification, but after all this is the "light" version of mast tuning.
The third principle is that most masts should have a slight "prebend" over their length with the headstay firm from a minimum of backstay load. Prebend can be visualized best by stretching the main halyard down the aft face of the mast. The maximum distance that the back of the mast is in front of the halyard is the prebend (you should take into account any offset that the position of the main halyard sheave causes). Prebend can be attained by tightening forward lowers, chocking the mast forward in the collar at the deck, moving the mast step aft (on a keel stepped mast), or lengthening the headstay. The amount of prebend varies from about 1" for a single spreader deck stepped mast to 6" for larger keel stepped spars.
The last principle concerns the amount of tension in the rigging. As a general rule, when the rig is fully loaded up (top end of the #1), the leeward shrouds should be beginning to appear to slacken. They can be deflected by hand, but not swinging loose. This will approach optimum general rig tension for most normal boats. Individually the wire tensions should be higher in the lowers and uppers than in any of the intermediates.
The tuning sequence that has worked the best for us is to start by centering the spar in the boat athwartships with the uppers. We tighten the uppers slightly. Next the lowers are adjusted so that the mast at the lower spreader is centered on the masthead. Sighting up the sail track is the best way to determine this. If the mast has multiple sets of spreaders, then the intermediates are adjusted next starting at the upper spreader. When the mast looks to be in column from the deck to the tip, then rig tension can be applied (chock the mast sideways and fore and aft now if it is a keel stepped mast- make sure the step position is correct for the required prebend). We add additional tension by adding equal numbers of turns to each side of the turnbuckles in the same sequence that we first used. Make sure that the turnbuckles are lubricated with heavy lubricant to prevent galling and damage to the threads. Check to see if additional adjusting of the shrouds is necessary as you add tension to the rig. Check the headstay to see if the rake of the mast is correct. Check the prebend. Tension the backstay and see if the mast remains straight under load. That should conclude the dock tune portion of the setup.
A Few Hints
1. If the tip of your mast seems to fall off, and your uppers are fairly tight, try loosening the intermediates.
2. Check the rake of a mast by tying a heavy object to the main halyard and measuring the offset from the back of the mast. Subtract any sheave offset present.
3. Make sure to do the final tuning of the mast when sailing. Make sure that the mast remains straight athwart ships. Check that the mast bends forward in the center (the reason for prebend).
4. Check to make sure that the bottom of the mast is square athwart ships, and for a keel stepped mast that the mast is straight through the deck. If it is not, the mast will be forced into an S bend that is impossible to tune out. We usually tune a keel stepped mast with the deck chocks out and shim the mast sideways after the mast is straight athwart ships. Mast steps and mast collars are rarely exactly on the centerline of the boat.
5. Use a steel tape run up the pole lift or main halyard to get the mast vertical in the boat.
6. Always pin and tape turnbuckles and cotter pins after tuning. Be sure the cotter pins are taped so that the sharp ends are covered to protect people and sails.
Well, there it is, twenty-five years of experience condensed into one and one-half pages. Now you should be ready to tackle tuning any mast. In fact, I hear there are some openings for riggers for the next America’s Cup.
Buzz Ballenger, Pres.
Ballenger Spar Systems, Inc.
1053A 17th Ave., Santa Cruz, CA 95062
408.462.2890 Phone, 408.462.2124 Fax