Gennaker height

HoffaLives · #1 (**permalink**) 09-05-2007

Our Cs 36T came with a 3/4 oz gennaker and we are figuring out how to use it (never having had one before.) The tack has a cloth device attached that apparently wraps around the furled headsail, but it also has a line for adjusting the height of the sail. What is this adjustment for? What are we looking for when we adjust the height? We did a beam reach with it the other day in light winds and she hit 8.5 knots. What's the maximum wind angle one should sail with this sail?

sailingdog · #2 (**permalink**) 09-05-2007

The cloth device allows the sail to tack around the furled headsail. ATN makes one called the Tacker, which may be what you have. There should be a line that attaches to the base of the forestay, to keep the tack of the Gennaker the proper height off the deck.

The maximum wind speed and angle are really dependent on the cut of the sail. I would say that you probably shouldn't use it in more than 14 knots apparent wind, as a rough guess. If the sail has a label from a loft on it, it would be well worth calling the loft and asking them some questions about the sail. Chances are likely they'll have some records of the sail and what specifications it was made for.

TejasSailer · #3 (**permalink**) 09-05-2007

We're really not very experienced with a Gennaker and are still learning, but we run a line from the cockpit, under the anchor roller to the tack of the Gennaker, to control the height.

BTW, both the ATN (for the tacker) and North Sails (for a sock) have videos on the web.

HoffaLives · #4 (**permalink**) 09-05-2007

Thanks very much for the information and the videos. The one from north sails especially shows me how to go about it. Can't wait to get out again and try it (the first time was such a mess with halyards on wrong side of jib sheets, spinnaker sheets improperly located etc.)

TejasSailer · #5 (**permalink**) 09-06-2007

As for the mess you describe, we've yet to successfully rig and launch correctly twice in row.

I forgot to mention some on-line articles, and it took me a while to find the URLs. Several are listed on http://cruisingresources.com/downwind_Sails

Some of the links are dead, but if you enter the title in google, you might find it elsewhere.

Here are some SailNet Articles
http://www.sailnet.com/forums/seamanship-articles/29095-trimming-your-asymmetrical-spinnaker.html
http://www.sailnet.com/forums/gear-maintenance-articles/19794-using-asymmetrical-spinnaker.html

There is another article I'll keep looking for that explains how to rig the lazy sheets outside the stay but inside the sail. The sail is a bit harder to gybe, but avoids running over the sheet.

RichH · #6 (**permalink**) 09-07-2007

The cloth device you describe (probably) allows the tack of the Gennaker to slide up and down on the furled headsail. Alternative devices to do the same thing: Parell beads, ATN "tacker", etc.

If your questions is: How high above the deck do you set the tack of the Gennaker (asymmetrical)?
Answer is: On a set/specific course, slowly ease the spinnaker sheet until the luff edge of the spinnaker begins to 'curl' ... and watch exactly where that 'curl' in the luff starts .....................
The goal (for that angle/course) is to have the 'middle' of the spinnaker luff 'break/curl' in the middle or slightly higher than the MIDDLE of the luff forward edge. If the luff 'breaks/curls' high up near the head of the spinnaker; then, the sail is being flown 'too high' and you should tension the tack line and bring the sail down closer to the deck. Conversely if the luff breaks/curls below the midsection, then the tack line is holding the sail too low and it should be eased .... until the sail breaks/luffs/curls in the middle or slightly above the middle.
Second consideration (dependent on wind strength and sea-state .... the higher the tack line allows the spinnaker to 'rise' the more unstable the sail will become.... unstable to wave action versus the boat and unstable to just a few more degrees of wind shift. Generally the lower sailing angle downwind (down to about 135deg) you sail the higher you carry the tack; conversely, the higher the sailing angle (up to a close reach if the sail is so cut) the lower the tack is held. ..... but the 'key' for good basic sail efficiency and stability is getting the sail to 'break/luff/curl' in the middle of the luff ---- and the that is controlled by the tack line attached to the tack of the sail.

The above is whats known as an 'elementary' setting/shaping and once you master that and how to control ......... the ultimate step is to get most of the 'lift' out of the spinnaker so that the sail begins to LIFT the boat's bow out of the water and not just 'push' the boat downwind, etc. ........ . :-)

tenuki · #7 (**permalink**) 09-07-2007

Rich that is an excellent description!

Another way of thinking about it is that the downhaul/tack line lets you adjust how deep or shallow the genaker is 'cupped' while the sheet controls the angle (simplified but an ok starting point IMHO). The size of the gennaker is fixed, so is the height of your mast, the tack line lets you cup and uncup the sail to fit conditions. Remember back to your experiments with aerodynamics as a child with your hand out the window of a traveling car? genaker adjustment is the same thing don't make it too complex.

HoffaLives · #8 (**permalink**) 09-07-2007

A fellow in the bar told me that the adjustment is essentially for racers where every 1/2 knot counts and cruisers can just set it and forget it rather than running another line aft. Opinions?

tenuki · #9 (**permalink**) 09-07-2007

Quote:

Originally Posted by HoffaLives

A fellow in the bar told me that the adjustment is essentially for racers where every 1/2 knot counts and cruisers can just set it and forget it rather than running another line aft. Opinions?

ok, but... where do you set it? You can't get away from understanding how it works... Besides, knowing sail shape helps in important things for cruisers like early detection of changing wind conditions, etc. I really don't think cruisers should practice being bad sailors. Ok, maybe you aren't constantly tweaking everything like in racing, but you should know how to set a sail correctly and for a genaker that involves using the tack line. Gosh, when you were a kid you probably spent hours with your hand out the window in curiosity, why be lazy now?

Cruisers can be really really good sailors (who may even be good racers). Cruiser does not equal poor/lazy sailor, it is merely someone who isn't racing at the moment.

RichH · #10 (**permalink**) 09-07-2007

Simple answer .... the tack height should be set to that the sail is at its most STABLE setting. If its unstable, or grossly unstable .... you can wind up with the kite tightly wrapped / hourglassed around the headstay, etc. within the blink of an eyeball. Proper setting helps avoid this.

For Cruising you can 'conservatively' set .... low tack; and, sheet pulled in more than normal ... but then the leech can become unstable and the sail become easily 'backwinded', etc. because its now 'powered-down' and somewhat flattened.