tracking/tacking angles

[ikrieger]

I just wanted to pose a question out there as I feel I'm not getting the most windward performance out of my boat.

I've looked at my tracks on the gps after sailing and it seems i should be getting better angles when sailing close hulled. I've been trying to improve my windward performance but no matter what i do or wind/water conditions I can't seem to improve my upwind performance. When tacking I look at the compass then tack and try to hold course near 90 degrees off my previous course. The boat can hold this angle on the compass after gaining speed but when viewed on the gps tracks the angle is actually 110-120 degrees, definitely not 90 degrees. Is this due to drift/leeway or just bad sailing. I know there are many variables that can improve windward performance like wind, the sea, rig tuning, sail trim, condition of sails, etc. etc. Just wondering if anyone has suggestions. I'm going out this evening maybe there is something I can try?

[lshick]

The 90 degrees that is often quoted is usually heading-to-heading, not COG-to-COG. So if you're getting 90 degrees h2h, you're doing pretty well. (Whether that will give you your best VMG to windward is a separate question.)

If you add maybe 7 degrees on either side for leeway, that puts you in the range of maybe 105 degrees COG-to-COG at best.

On our Valiant 42 with windvane steering, we figure on 120 degrees COG-to-COG, because we hate to pinch.

[jackdale]

The 90 degree is a rough guideline; as is the 60 degree gybe angle.

It could be both leeway and current. Are you watching your jib telltails? Your sail trim? Bad sail trim will not produce optimum sail angles.

In addition, if you are pinching, you will make more leeway.

Another thing to try: watch your VMG on your GPS. You will need to set a waypoint which is directly up wind. Check your VMG after you sails and get on your tack. Watch what happens when bear away and head up.

Does the degree of weather helm make any difference?

Can you get the polars for your boat?

Lots to experiment with.

Jack

[paulk]

As you suggested, there are a lot of variables involved with tacking angles. What kind of boat are you sailing? How old are your sails? Were they cut for racing or for cruising? On a Soling with new racing sails, we would expect to tack through 60º, heading to heading, in a steady breeze. On a Catalina 30 with 20 year-old sails blown out from years of cruising, 120º might be normal. Current, the angle waves are hitting your bow, and how much heel you have can also impact your headings. The trick is to do the best you can with what you have and have a good time doing it. If you can make improvements... that's changing the variables.

[sailak]

Checking GPS tracks with my boat I was getting right at 90 degrees on a starboard tack and about 95-100 degrees on a port tack. Winds were 15-17 with seas 2-3 feet, I was hand steering using telltales on the jib and the windex for guides. The traveler and mainsheet were eased some to reduce heel.

Could a rigging issue cause the difference in angles?

Omega 36, fractional sloop with 100% self-tacking jib, fin keel.

[Jeff_H]

120 degrees course over ground from tack to tack is obscenely bad. As Pauls says there are a lot of factors but a properly sailed, reasonably modern boat in moderate winds and moderately flat seas would typically show a something less than 90 degrees betweeen tacks on the compass and roughly 90 degrees COG. The angles get wider in light air and narrower in a breeze.

SailAk. I have no idea what you are saying. If I read what you are saying you tack to tack is 185 (90 + 95) to 190 (90 + 100) degrees, in other words beam reach to beam reach. Something is wrong with your numbers or else you are in a lot of current.

Jeff

[sailak]

Originally Posted by Jeff_H

SailAk. I have no idea what you are saying.

Sorry. The 90-95 was the COG angle between tacks. Right at 45 off the wind on either tack.

[bheintz]

ikrieger, as others have mentioned, the type of boat makes a big difference in sailing characteristics.

For example a Neptune 24 will react very differently than a Melges 24.



Specifically, for the Neptune 24, it appears that the center of effort of the sail area is fairly far forward. You might find it beneficial to lengthen your headstay a bit to increase weather helm.

Remember the Mainsail is for pointing and the Genoa is for power. Upwind you want the Leach of the main just tight enough to that the Leach tell tails are still streaming. (too tight the leach/battens will hook, too loose and you're giving up pointing ability) When you drop the traveler, ease the mainsheet, or the vang you are de-powering the Mainsail, and reducing weather helm.

[ikrieger]

To answer some questions: My boat is a Neptune 24 with centerboard.

When I posted this question it was after sailing with 110 jib and full main in 15 knot wind 2-3 foot seas. I trim the tell tails so all are flying straight back including the main. I put the traveler to leeward and pulled the outhaul tight as i can to flatten at 15k and above. I'm on lake erie so there is no current. I seem to be able to tack through at about 90 degrees and hold that course but even when holding that course i still seem to get a wider angle than 90 on my gps tracks.

All my sails are cruising sails in fair shape and the main is particularly in bad shape with some missing battens...i know i know....

I would consider my rig tune to be adequate but not perfect. the leeward shrouds have some slack when sailing. I try to make the backstay tight.

Maybe a new mainsail will give me an improvement.

[bheintz]

Originally Posted by ikrieger

the main is particularly in bad shape with some missing battens...i know i know....

Maybe a new mainsail will give me an improvement.

In the mean time, I'd try to get some new battens. Some Marines Chandlers sell untapered batten stock in bulk lengths -- a sailmaker can also sell you some at a reasonable price.

Probably what you are experiencing is leeway, which can be 4 to 8 degrees on some boats.

Also 90 degree tacking angles are usually given as an example to those new to sailing because it is easier to conceptualize: 100+ is not unheard of racing in extremely light wind.

Ultimately, your progress upwind is the goal (also known as VMG, CMG, SMG on the GPS). Set a waypoint significantly upwind and try different angles to the wind (90, 95, 100, 105, etc) and see how your boat speed increases and monitor your CMG. You will find different results for different wind strengths and sea states.