Short tacks or long tacks for best VMG?

[Stu Jackson]

The truth is I could use the nav station mounted GPS for VMG, but I don't think an instantaneous VMG readout is going to inform tactics very effectively.

I like the "20 degree cone" concept. Does that mean a cone extending from the target back towards the starting point, and tack when you reach the cone (for shorter tacks as you near the target)?

1. VMG is "overated!" Wow, I'm gonna get some bad mail on that one! Now you tell us you do have VMG... It's great for local buoy racing with marks relatively close together (a mile or two). Mark VMG is great when you get closer to them. It's also a great teaching tool, because it is rare to find even the first upwind mark exactly "in the wind" which was your OP. But you might remember earlier VMG discussions on this board where there are two VMGs: one to the first mark (or destination) and one to the wind, usually measured a few thousand miles out on a projected waypoint dead upwind. What you're essentially asking is how to use VMG going upwind to get there fastest. I have not yet been able to distill 10 years of racing experience into two paragraphs, and while you're not specifically asking for that, it really is the answer, but I'll try: Set a windward VMG, set a mark VMG, sail the long tack first, and account for current and drift and your own leeway.

2. For cruising, yes. For racing, sometimes not because of #1.

But, as mentioned, conditions usually change during the day.

That's as best as I can sum it up. Just for fun, you might enjoy digging into a yacht racing strategy book, which would give you much more detail and be applicable to your goals.

PS - One of the reason that most sailing websites, being boat-specific or general, do not have "Racing Discussions" is that most racers I know don't give away their "secrets," except in the strategy books I mentioned earlier.

PPS - I admire you for considering sailing instead of motoring directly into the wind. Motoring into a wind is the most uncomfortable way to travel I've ever heard of, including a cross country trip having your mother-in-law in the back seat! Sailing upwind is pretty fun, balancing the boat makes it perform as it was designed to do, a lot more comfortable, and a lot faster sometimes if you do the math (VMG = faster on a longer course).

Have a great time.

 

[jviss]

jviss,
Good to see a fellow Westporter. I trailer but that is my favorite departure point. I was looking at Block for this weekend as well. I was going to put in at Galilee. Sunday looks iffy for a V25 in Block Island sound although the wind would be on our back. I like the seat of the pants claim. I calculate the closest angle with the current wind and try to plan my tacks to as few as possible with the final destination in mind. It sounds like you have that down with the last one bringing you in to the harbor. Leave the math home. Mathis not fun...sailing is. Good luck and have fun. That's a good cruise. PS: I navigate with Navionics on my DroidX. Nothign fancy. Boat pic is on the beach at Horsneck Point. KB

Yes! You should say hello if you're passing by. We're on mooring number 209.

I'm thinking with the tides, and the wind prediction we might just head the other way. If we leave WP at about 7:30 a.m. Saturday we should be in Edgartown by 1:00 p.m., faster if the wind swings into the South.

 

[jviss]

1. VMG is "overated!" Wow, I'm gonna get some bad mail on that one! Now you tell us you do have VMG... It's great for local buoy racing with marks relatively close together (a mile or two). Mark VMG is great when you get closer to them. It's also a great teaching tool, because it is rare to find even the first upwind mark exactly "in the wind" which was your OP. But you might remember earlier VMG discussions on this board where there are two VMGs: one to the first mark (or destination) and one to the wind, usually measured a few thousand miles out on a projected waypoint dead upwind. What you're essentially asking is how to use VMG going upwind to get there fastest. I have not yet been able to distill 10 years of racing experience into two paragraphs, and while you're not specifically asking for that, it really is the answer, but I'll try: Set a windward VMG, set a mark VMG, sail the long tack first, and account for current and drift and your own leeway.

2. For cruising, yes. For racing, sometimes not because of #1.

But, as mentioned, conditions usually change during the day.

That's as best as I can sum it up. Just for fun, you might enjoy digging into a yacht racing strategy book, which would give you much more detail and be applicable to your goals.

PS - One of the reason that most sailing websites, being boat-specific or general, do not have "Racing Discussions" is that most racers I know don't give away their "secrets," except in the strategy books I mentioned earlier.

PPS - I admire you for considering sailing instead of motoring directly into the wind. Motoring into a wind is the most uncomfortable way to travel I've ever heard of, including a cross country trip having your mother-in-law in the back seat! Sailing upwind is pretty fun, balancing the boat makes it perform as it was designed to do, a lot more comfortable, and a lot faster sometimes if you do the math (VMG = faster on a longer course).

Have a great time.

Stu,

On the "overrated" comment, I think I understand what you are saying, and perhaps we agree. My view is that what a cruising sailor wants is a VMG indication that has is a long-term average; say, over a few tacks, at least. It should then be resettable. That way you could try a few short tacks, see what you get, then a couple of long tacks. But, an instantaneous VMG indication, such as a GPS will display, is utterly useless, in my opinion. I know exactly what my instantaneous VMG is when I'm sailing a particular COG and speed.

It would be great to have a chartplotter that maintains and displays an upwind VMG so you could adjust your tacks accordingly. One of my great disappointments is that while chart plotting software gets better and better, and cheaper and cheaper (and even free), they all aim to do the same thing, and no one yet has taken the path less traveled and developed one specifically for sailors (that I know of, anyway). In addition, none of them seem to take into account during route planning the tides and the wind predictions, even though this information is available to the program and displayed! For example, why can't the software allow me to enter a departure time and date, and add the effects of the currents along the way to determine ETA, etc.? I guess it's asking too much for it to display the true wind (from predictions) and allow you to plot a beat to windward, and use the polars for your boat. If there is such a chart plotter, please let me know!

BTW, I'll be trying out PolarView NS on the Mac this weekend; usually use Maptech Offshore Navigator on a Windows machine.

 

[Benny17441]

Why limit the options to motor or sail? If speed is of essence why not motorsai? It will add to the pointing ability of the craft and will allow longer tacks while remaining closer to your rhumb line. It also helps diminish loss of speed during tacks.

 

[Warren Milberg]

Who cares? Don't forget, you are sailing a sailboat presumably on a relatively short cruise. You are not racing a powerboat, so lay back and enjoy yourself. Keep sailing in the general direction of your destination until you can't, then turn on the iron genny.... If you have to get to Block Island by a certain time, perhaps sailing there is not the best idea. I can't see how it matter how many tacks it takes.

 

[RichH]

Most current GPS do include VMG functions; albeit hidden from the mathematics adverse.

The function is called Estimated Time of Arrival (ETA) ... to a waypoint. Its not as precisely accurate as a dedicated VMG output, but can be 'reasonably close' especially during the early stages of each tack leg.
Especially in Block Island Sound and the mouth of Buzzards Bay where the currents swirl and come from non-intuitive directions (up to ~90° from 'expected'), simply follow:
Read ETA on one tack, tack over and read the ETA on the other tack ... choose the tack with the 'best ETA'.
When rechecking later on and near the original rhumb-line, 'reset' the waypoint to the exact same waypoint as before (to reset the 'origin' of the 'present' boat position) and again compare the ETAs, etc.
When tacking to compare, you will have to wait for a few minute until the GPS 'recomputes' and 'settles down' to more accurately compute the new ETA ... eg.: sail on each tack for a few minutes after 'resetting' your current position. Do keep reasonably close to the original rhumb-line.

 

[Bill Roosa]

If you are going by ocean route then, and forgive me if I don't get it, why not just aim for the destination? If you are "cruising" the I agree with Warren you should not be in that big a hurry as you have planned your route and the only reason to go fast is to avoid some weather system. Which is even more reason to just go directly to the destination.
I guess I'm confused because on a long "cruise" you will not be able to account for the wind shifts over the course of a few days so trying to figure out the "best" tack to get max VMG is really kinda silly. You would want to be steering around the bad weather and not concerned about the destination as much.

 

[dugout]

Stu,

It would be great to have a chartplotter that maintains and displays an upwind VMG so you could adjust your tacks accordingly. One of my great disappointments is that while chart plotting software gets better and better, and cheaper and cheaper (and even free), they all aim to do the same thing, and no one yet has taken the path less traveled and developed one specifically for sailors (that I know of, anyway). In addition, none of them seem to take into account during route planning the tides and the wind predictions, even though this information is available to the program and displayed! For example, why can't the software allow me to enter a departure time and date, and add the effects of the currents along the way to determine ETA, etc.? I guess it's asking too much for it to display the true wind (from predictions) and allow you to plot a beat to windward, and use the polars for your boat. If there is such a chart plotter, please let me know!

BTW, I'll be trying out PolarView NS on the Mac this weekend; usually use Maptech Offshore Navigator on a Windows machine.

This is a different question. Maxsea does graphic predictive routing based upon forcasted weather based upon performance or comfort. Performance Routing or Weather routing and it is based upon your boats polars. It even gives recommended sail changes.
http://www.youtube.com/watch?v=n59S_dNcaJQ
Start 2:20 into the video to see it demo this function.

It exists but its generally not used for little 25 mile day sails. Westport MA to Cape May NJ would be different. The weakness is predictive weather. Localized predictive weather still falls far short of useful info on short courses. Simply compare buoy reports to forecast and you will understand why.

OKHAM has provided this data for many years but the systems are dated and generally oriented to around the buoys.

 

[Stu Jackson]

VMG

Here's old discussions with some good links to VMG:

http://forums.catalina.sailboatowners.com/showthread.php?t=134024&highlight=VMG

http://forums.catalina.sailboatowners.com/showthread.php?p=633553&highlight=VMG

This one is pretty long but good: VMG for Dummies

http://www.wingsailor.com/html/vmg___gps.html

 

[Clark]

Wing on Wing . .

I've got a follow up question.

Which will finish faster: A boat without a spinnaker or whisker pole sailing wing on wing versus an identical boat gybing back and forth on broad reaches?

(I was watching the local race last night and I would've place my money on the gybers!)

IF the winds are strong enough to make hull speed while W/W, that is the fastest technique. So, it depends on your boat. If the winds are very light, I think I recall Don advising it for then as well. All other times, it is supposed to be better to gybe down wind but it requires intimate knowledge of your boat and how best to utilize your sail plan.

 

[Stu Jackson]

The only way to answer that question is to check the polars for your boat.