Maximizing VMG on downwind leg of race

[stickinthemud57]

Now that I have started racing, I'm torn on which strategy to use on the downwind leg - dead run or broad reach?

Research seems to indicate that in the case of most boats, a broad reach provides better Velocity Made Good.

Thing is, the 26S is not "most boats". It is far lighter than other boats of its size, and drag can be minimized by raising the centerboard when running dead downwind. Also, the centerboard, being much narrower than a keel would be on a boat its size, is going to allow more side-slipping on a broad reach than dead downwind, having a negative effect on VMG.

Experience, of course, is the only way to sort this out, and my 26S seems to achieve the best VMG going dead downwind. I base this on three experiences.

In a "Fun Race" (a casual cruise along a set course to the restaurant on the other side of the lake), I was able to pass a 36' keelboat flying a spinnaker flying only my main and Genoa.

In a recent race, on the downwind leg, I was able to pass a 30' keelboat even as my foredeck crew was having trouble setting the whisker pole.

Also in a recent race, a 36' keelboat which had been gaining on us peeled off on a broad run and jibed back toward the mark. We stayed on the dead run and beat them to the mark. It seems to me that had they stayed on the downwind course they would have passed us and beat us to the mark.

Each of these situations was in very light to light air. In some cases I was employing the vang, in others not. In no instance was I raising the centerboard.

My questions to those with insight are:

1. Given that running dead downwind appears to be giving me an advantage (at least in light air), should I just stick with that, or am I sacrificing VMG with that approach?
2. Does raising the centerboard really help that much? It seems that it presents very little surface area when compared to that of the hull, but on the other had it does create some turbulence.
3. Do you think that the choice to run downwind or on a broad reach will depend on the wind speed?

Thanks in advance for your thoughts!

 

[jon hansen]

do you want to win races? it's all about the wind speeds on the course. put you vessel in stronger winds and you'll win every time.

you did not mention the wind conditions over the entire course at all. there is no valid answer to your questions. again, you want to win sooner than later?

buy this book. read it. it will answer all your questions.

post photos of your trophies

 

[markwbird]

Generally, off wind is faster up to a point. That point being when the wind is very strong allowing you to do hull speed or better at DDW. In light wind sail at an angle. Try experimenting with a handheld gps that shows the VMG. Do the trig and figure out how much faster you have to go for each 5 degrees off of DDW to make up for the increased distance. Then you will have a rule of thumb to go by.

 

[Davidasailor26]

A polar diagram is what you’re after for the “authoritative” projection of best-case boat speed and VMG. Unfortunately those are hard to come by for the 26s. The suggestions above are good ones to find out what would work best do your boat. I’d add that I’ve had some success with being wing-on-wing with the pole but still on a very broad reach, not DDW. The pole holds the jib out well enough and you get just a little extra apparent wind from being above DDW. So I’d include that option in your experiments.

Also, the centerboard, being much narrower than a keel would be on a boat its size, is going to allow more side-slipping on a broad reach than dead downwind, having a negative effect on VMG.

One clarification - When you’re going below a beam reach slipping sideways is actually bringing you closer to your target than going straight ahead, so it’s increasing your VMG, not decreasing it. There may be other good or bad effects to the leeway, but all other things being equal it is more direct.

 

[stickinthemud57]

A polar diagram is what you’re after for the “authoritative” projection of best-case boat speed and VMG. Unfortunately those are hard to come by for the 26s. The suggestions above are good ones to find out what would work best do your boat. I’d add that I’ve had some success with being wing-on-wing with the pole but still on a very broad reach, not DDW. The pole holds the jib out well enough and you get just a little extra apparent wind from being above DDW. So I’d include that option in your experiments.

One clarification - When you’re going below a beam reach slipping sideways is actually bringing you closer to your target than going straight ahead, so it’s increasing your VMG, not decreasing it. There may be other good or bad effects to the leeway, but all other things being equal it is more direct.

True, no luck finding a polar diagram for the 26S.

Are you suggesting poling the foresail to the same side as the main (basic broad reach), or vice-versa (wing on wing)?

I see your point regarding side-slipping. Thanks for correcting my thinking on that.

 

[Davidasailor26]

Are you suggesting poling the foresail to the same side as the main (basic broad reach), or vice-versa (wing on wing)?

Still wing-on-wing sail configuration, but with the apparent wind angle more forward. My jib starts getting shadowed by the main around 135 degrees apparent wind angle. I try not to sail 135-140 degrees apparent. From 140 through 185 (5 degrees by the Lee) I can carry the jib wing-on-wing with the pole. So if sailing to the mark would have me at, say, 160 degrees I find wing on wing with the pole to Windward is best.

 

[Knuttle]

There is another factor that must be consider when you are deciding between a broad reach and downwind. Think of it like this. When you are sailing down wind you are sailing on the hypotenuse of a triangle. In choosing whether to go downwind or a broad reach, you must consider the sum of the distances of the two legs and the distance of the hypotenuse; and the speeds that can be made on the reach and the speed that can be obtained going directly down wind. Or the speed gained by reaching must be great enough so the extra distance is covered in less time than the down wind run.

An example if the sum of the distance on the two sides equals 2.5 miles, and the distance for going down wind is 2 miles. You can maintian a speed of 8mph on the down wind run, to beat the boat on the down wind run, the boat on the broad reach must achieve a speed great that 10 mph 2.5mile @ 10 mph = 2 mile @ 8 mph = 15 min

 

[shemandr]

[QUOTE="stickinthemud57, post: 1752444, member: 1517732.
...Does raising the centerboard really help that much? It seems that it presents very little surface area when compared to that of the hull, but on the other had it does create some turbulence.... [/QUOTE]
I don't think it's about turbulence - although there will be some. I think it's about friction. Less friction = more speed. You wouldn't drag a line in a race. For racing you try to optimize everything that will contribute to speed and minimize all that doesn't.

 

[Tedd]

Generally, off wind is faster up to a point. That point being when the wind is very strong allowing you to do hull speed or better at DDW.

Adding to that: After sailing a Mac 26S for several years, my experience has been that this point is reached at a lower wind speed than with a typical 26-foot keel boat. My 26S could exceed hull speed on a dead run (wing on wing) with only about 12-15 knots of wind. The 26S is very light and has (according to Macgregor himself) a hull form that is biased a little bit toward planing.

However, once you hit about 7 knots (half a knot above hull speed) it does become a bit of a balancing act. Not exactly "death roll" territory, but it can dart out from under you if you don't pay enough attention. That on its own is an argument in favour of broad reaching.

 

[stickinthemud57]

Still wing-on-wing sail configuration, but with the apparent wind angle more forward. My jib starts getting shadowed by the main around 135 degrees apparent wind angle. I try not to sail 135-140 degrees apparent. From 140 through 185 (5 degrees by the Lee) I can carry the jib wing-on-wing with the pole. So if sailing to the mark would have me at, say, 160 degrees I find wing on wing with the pole to Windward is best.

This makes it dawn on me that apparent wind direction can come into play sailing downwind. That qualifying term is important.

On my first race, where I had a coach (the now-owner of Sail Warehouse, as I came to find later) had me on just such a run as you describe - wing on wing with the foresail to port and with the apparent wind about 20 or so degrees off the port stern. That was another revelation to me when I realized that properly poled, the airfoil is still formed, but with the airflow running leech to luff.

 

[stickinthemud57]

However, once you hit about 7 knots (half a knot above hull speed) it does become a bit of a balancing act. Not exactly "death roll" territory, but it can dart out from under you if you don't pay enough attention. That on its own is an argument in favour of broad reaching.

Would you mind elaborating on this? What do you mean by "darting out from under you"?

 

[Tedd]

Would you mind elaborating on this? What do you mean by "darting out from under you"?

An unintentional gybe, basically. When you're above 7 knots in the 26S it's planing somewhat, and that reduces directional stability a little. If you've ridden motorcycles, it's a bit like going from lots of trail to just a little bit of trail. It's not difficult to manage but you do have to pay extra attention. If you're planing like that in following seas it can turn sideways on you. I should say that this only happened once, and it only happened because of lack of attention at the helm. It's not something you should be overly concerned about, just aware of.

It helps to retract the swing keel part way when running downwind. When I first started sailing the boat I didn't do that because I thought it was just about reducing drag. I didn't feel it was important for the kind of sailing we do. But actually the main reason for doing it is that it moves the center of lateral resistance aft, which improves directional stability.

 

[BarryL]

Hello

if you are racing in the jam class (jib and main) the it’s usually faster to sail directly towards the mark. Without a spinnaker you can’t sail fast enough to make up for the additional distance sailed. So, head directly to the mark. Do use a whisker pole to make the headsail work. Do sail wing and wing to project as much sail area as possible. Do ease the halyard and outhaul. Do everything you can to make the boat go. Raise the centerboard. Get crew weight aft or forward or whatever is fast for your boat. You need a good gps to show the vmg to the mark.

have fun

barry

 

[stickinthemud57]

An unintentional gybe, basically. When you're above 7 knots in the 26S it's planing somewhat, and that reduces directional stability a little. If you've ridden motorcycles, it's a bit like going from lots of trail to just a little bit of trail. It's not difficult to manage but you do have to pay extra attention. If you're planing like that in following seas it can turn sideways on you. I should say that this only happened once, and it only happened because of lack of attention at the helm. It's not something you should be overly concerned about, just aware of.

It helps to retract the swing keel part way when running downwind. When I first started sailing the boat I didn't do that because I thought it was just about reducing drag. I didn't feel it was important for the kind of sailing we do. But actually the main reason for doing it is that it moves the center of lateral resistance aft, which improves directional stability.

Interesting perspective on the utility of raising the centerboard. Like I said before - little gems in every response!

On our little lake, boat wakes take the place of open water rollers when it comes to messing with ones trim, so point well taken!

 

[stickinthemud57]

You need a good gos to show the vmg to the mark.

have fun

Not as up on the lingo as I would like to be. What is a "gos"?

 

[BarryL]

Sorry. GPS. Corrected above. The crew and driver should be watching. Make a small change, see if VMG goes up or down. Adjust accordingly.

Not as up on the lingo as I would like to be. What is a "gos"?

 

[stickinthemud57]

Ah, was guessing that might have been it. Thanks for the clarification.