SailNet Community - View Single Post - Sailing upwind in Cat/sloop
View Single Post
  #1  
Old 08-04-2010
Jeff_H's Avatar
Jeff_H Jeff_H is offline
Moderator
 
Join Date: Feb 2000
Location: Annapolis, Md
Posts: 6,445
Thanks: 3
Thanked 64 Times in 47 Posts
Rep Power: 10
Jeff_H has a spectacular aura about Jeff_H has a spectacular aura about Jeff_H has a spectacular aura about
Sailing upwind in Cat/sloop

I apologize in advance to the fellow who PM'd, me with this question but regretably my answer was too long for a PM. I thought this might have enough general interest that I put it here. Out of respect for their privacy the question has been altered so that hopefully the specific person and boat is not identified. I also apologize because much of my answer was copied from an earlier post that I had written for some other similar discussion in some other sailing forum.

The questions was: I have just purchased Canadian crusing design built between 1986-89 (not a Nonsuch), that is almost a catboat, with mast far forward, large main, fractional rig and a small jib that just fits between forestay and mast and which self-tacks. The boat is widebeamed and I've found it doesn't point that well. I'm getting 65 degrees tack angles. Is there anything I can do to the trimming or sail configurations (i.e oversized jibs, etc.) that might improve the upwind performance?



My response is that it is a little difficult to answer this question without knowing the boat and seeing how the person sails her. I am also not familiar with the specific model in question so I am guessing a bit and talking in perhaps broader generalities than might be ideal.

That said, this boat was not unique.The 1980's was a period when a lot of manufacturers hoped to cash in on the popularity of the Nonsuch. Manunfacturers as diverse as C&C, Freedom, Hunter, Herreschoff Catboats, and Pearson, built 30 foot or so catboats with freestanding, or nearly freestanding rigs, many of which also tried to add spinnakers or jibs.

In most respects, these were reasonably good boats in terms of nice accommodations, easy handling and reasonable performance. To one degree or another, a short coming of almost all of these catboats was some reduction in windward performance.

This shortcoming derived from a number of common causes that are imbedded in the design concept of many of this style of boat. First of all, most of these boats offered moderately shoal draft fin keels. While better for windward performance than a full keel, these long fins tended not to point especially high as compared to deeper draft/ shorter chord fin keels, plus they also make a lot of leeway.

Most of these boats had a lot of wetted surface. While part of the cleverness of the Nonesuch was that that Ellis had carefully modelled his hull form to minimize wetted surface, few of the clones seemed to be as careful. Lots of drag requires lots of power to overcome and so many of these boats had to be 'driven off' rather than pinched. In other words, om order to over come all of these design issues, these boats were typically sailed so that the helmsman does not try to point as high in order to optimize the speed part of the VMG equation.

Next comes the rig. Important to sailing upwind consistently well is maintaining good airflow over the sails. Freestanding rigs (which I assume your boat is and apologize if I am mistaken) have several inherent problems when it comes to beating. In a general sense, to make up for the lack of shrouds, they tend to have much larger diameter masts, and these tend to throw a big wind shadow. To a minor extent, the mass of turbulance being shred off these larger diameter masts is like sailing in bad air all the time. Some like the Freedoms had carbon fiber masts of a smaller diameter, but some used what were essentially heat hardened, spun aluminum light poles which were heavy and had a very large diameter.

Upwind, it is important to keep the sail shape steady as well. Because free standing spars tend to be by their very nature more flexible than stayed spars, there is a tendancy for the forestay tension to vary and with it the headstay sag to vary as well, this automatically changes the angle of attack and lead angle on the jib, disrupting the airfliow over the sail. Similarly, the head of the mast flexes as well, opening and closing the leech, loosening the halyard tension and flattening and rounding the sail with each cycle. Its disruptive to the sail shape and airflow, which are also bad things for upwind sailing.

Even so, tacking through 130 degrees is excessive. What makes matters worse is that I am assuming that this angle is being read off of the compass courses and not off the GPS and so does not include leeway.

Anyway, getting to the heart of your question. First of all, because of the large amount of wetted surface on these boat, if you want toi go up wind, a clean, smooth bottom paint is extremely important. Ironically more so than on a race boat.

I would then next start with the jib. First of all, the jib should have a row of telltales roughly 18 inches from the leading edge and there should be one set (one on erither side of the sail) that is roughly 25% from the top, 25% from the bottom and one last set in the middle. If you don't have them make them and put them on. These can be made with 8" lengths of yarn or musical cassette tape taped to the sail.

When going upwind I would spend time on the foredeck and watch the sail to see what it does. Have the helmsperson slowly turn up towards a luff and then fall off. The windward teletales should all start to act up at the same time. Tall blade type headsails are very sensative to sheet lead angle and self tacking jibs rarely have proper sheet leads. If the telltales at the head or the foot 'break' first then the sheet lead is wrong. Some of self tacking jib systems permit lead adjustment but most don't.

If you can adjust your lead and the head of the sail breaks first then the lead needs to be moved forward to pull downward and use more of the head of the sail. If the bottom of the sail breaks first then move the lead aft.

If you can't adjust the lead at the sheets, then you are stuck going with the traditional method of raising the tack of the jib above the deck with a pennant. If the windward head telltale of the sail is breaking first, then add a short length of line to raise the tack of the jib above the deck further. If the bottom is breaking first and there is no penant then the sail is probably shot.

If the jib is on a boom, there are no easy answers other than to get a sailmaker to look at the sail and see if it can be recut.

The next issue is the length of transverse motion of the jibsheet lead. If the motion is too wide, then you cannot point. You can look at ways of keeping the jib traveller from swinging as far.

While improving the Jib lead can help a lot, I am afraid that adding a genoa probably will not do you much good.

Then move onto you mainsail. The big issue here is getting a tight enough leech to point without stalling the sail. In this case, telltales in the trailing edge of the sail near the batten pockets can really help. Upwind, the outhaul halyard should be reasonably well tensioned. Ideally the traveler and mainsheet are set so that the boom is roughly on the center line of the boat, and the trailing edge of upper teletale is roughly parrallel to the boom (sight up the sail from below the boom.) The trailing edge Telltales should be flying and the sail should not be luffing. Too tight and the sail will stall, too loose and you can't point. Moving the traveler above the centerline and easing the sheet will allow the upper batten to open up if it is cocked to windward and dropping the traveller and tightening the sheet will move the batten to windward relative to the boom. Play with this and you should see both your speed and pointing angle improve.

Most of these catboats were sold as being easy to sail and so had primitive sail shaping gear so you are somewhat limited in what you can do beyond that. With good hardware you can often get good performance upwind even with old and blown out sails. But in the absense of good sail shaping gear, the sails take a real beating and there is nothing much you can do about it. This means that sails have a shorter lifespan on boats like these and they will have a bigger impact on upwind performance than on more conventionally rigged designs. In other words, if you really care about good upwind performance, you may need new sails. Uh! I hate being the one to say that.....

Regards,
Jeff
__________________

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Curmudgeon at Large- and rhinestone in the rough, sailing my Farr 11.6 on the Chesapeake Bay
Reply With Quote Share with Facebook