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Catalina/Capri 25/250 Sailor's Forums

Catalina 250 Specific Forum

Tacking; angle vs. wind speed graph

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jbkayaker
Captain

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USA
299 Posts

Initially Posted - 12/20/2010 : 17:03:30

Has anyone worked up a tacking angle graph for a Catalina 250 WK ? The tacking angle is the smallest when the wind is strong and noticeably larger in light winds. A graph would be helpful to have when racing or when deciding if you have gone far enough to make the harbor entrance without needing another two tacks.

Jim Butler

Edited by - on

Stinkpotter
Master Marine Consultant

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Djibouti
9080 Posts

Response Posted - 12/20/2010 : 22:48:17

What you're looking for is a "polar chart". I'm not aware of one being developed for the C-25 or C-250, particularly because 98% of their buyers don't race them. If you find a polar chart for a somewhat similar boat, it'll show you the most effective angles to a race mark at various wind speeds.

If you just want to figure out tacking angles to round a point or make an inlet with these boats, figure 95-100 degrees (a little past dead abeam) as the best you should expect to do. I generally allowed for more, and figured the additional boat speed from not having to pinch too much would compensate. I also had to allow for tidal currents... Plus, those two extra tacks when you find you aren't making your objective are generally not what you want.

Edited by - Stinkpotter on 12/21/2010 10:31:48

Arlyn Stewart
Master Marine Consultant

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2980 Posts

Response Posted - 12/23/2010 : 07:08:09

Warning... making a polar chart for the C250 might be too depressing.

I recall on one of my Great Lakes cruises, coming out of a channel into the open waters of Lake Huron. The destination was a harbor about eight miles straight into a strong breeze and four foot of swell.

Before making the turn after exiting the channel, I'd casually thought we'd make the harbor in just a few hours and have for a change a leisure evening as most of our cruising days are and had been fairly long ones.

The boat was driving well at 5-5.5 mph in the breeze that was just under that required to reef. We were on a tack toward open water and I noted the VMG... 1.3 Holy smokers, I switched screens on the gps, ETA was six hours to make eight miles. I figured that I had to be a bit confused in my initial observation that the destination was directly up wind. We switched to the other tack.... nope, the observation had been correct... the VMG number was allmost identical.

If we motored... we'd be there in 1.5 hours instead of six... we motored.

After the cruise while processing the log into a story, the math was done and again IIRC, the inclusive angle was something around 135-140 degrees or about a 68-70 degrees tack track while the pointing angle of the boat was likely the expected 45 degrees. That means the track was something like 20-25 degrees off the pointing angle. That means of course for those conditions that day, one had to sail well beyond the beam or an additional twenty five degrees past the beam angle to the mark.

Bottom line, the C250 water ballast and I expect wing keel as well suffer a lot of windage and leeway.

It all causes me to remember the old Hobie Cat racing days. My son and I raced a Hobie 18 having symmetrical hulls and dagger boards. When there were enough of each class the 18s and 16s raced in separate classes but occasionally we raced together and in a breeze I'll never forget how those little 16s would go to the windward mark. We'd all be pointing about the same 45 degrees but those 16s would track to their pointing angle and we couldn't.

Remember those Hobie 16s and Prindle Cats had asymmetrical hulls and in a breeze that lifted the windward hull almost completely out of the water, the leeward immersed hull was lifting them to weather and they could make a windward mark after reaching beam... the only sailboats that I've seen that could.

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Steve Milby
Past Commodore

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USA
5902 Posts

Response Posted - 12/23/2010 : 08:46:10

Polar charts sound good in theory, but I have never considered them a particularly useful aid. There is a lot of appeal in the thought that, all you have to do is sail at a certain angle to the wind in a certain windspeed, and you'll make the best VMG, but in sailing, nothing is ever as simple as it seems.

The accuracy of the data itself depends on the sailing skill of the person who compiled the data, and his thoroughness in collecting the data. Did he actually sail all the different angles in all the different windspeeds, or did he sail some of them and extrapolate the rest? In collecting the data, how accurate were the instruments that he used to determine boat speed and windspeed? Most polar charts were created by an anonymous person, and his sailing skills are an unknown quantity. Were his sails well-trimmed for each sailing angle? The information in a polar chart doesn't take into account the sailing conditions that might be affecting your boat, such as currents, waves and boat wakes.

I believe polar charts represent, at best, an educated guess as to the angle for your best VMG to a destination, but I believe the average sailor with a moderate amount of experience can make an educated guess that is equally valid. Thus, I doubt that they really offer anything useful to most sailors.

If you want to learn the fastest sailing angle to any given point, I think the best way to learn is to race your boat. By doing so, you'll be learning how your boat sails, with your hand on the helm and you trimming its sails, and on the waters where you sail. When racing, you can compare whether another boat, that is sailing alongside you on a slightly broader angle, is making better speed than you, and if so, whether it is making enough extra speed to compensate for the extra distance that it must sail to get to the destination. After you have experienced that 2-3 times, you'll know your own boat and your own skills better than a polar chart.

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Stinkpotter
Master Marine Consultant

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Djibouti
9080 Posts

Response Posted - 12/23/2010 : 10:46:51

Ya, I might have overstated things for a C-250... I suspect the C-25 fin does better, especially in larger seas which will slow the C-250 more each time it hits a wave. But remember, speed reduces leeway, and falling off a little and easing the sheets just a little increases speed. Thus, sailing what appears to be a <i>little</i> lower than the highest "point" can actually give you as high an actual track, with more speed. VMG on the GPS will tell the story.

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The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.