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Measuring real and apparent wind

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Voyager
Master Marine Consultant

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USA
5389 Posts

Initially Posted - 09/12/2009 : 08:53:34

Quite often we get out on the boat and we find that the wind speed is not exactly what we counted on. Sometimes too little so we have to motor sail, other times more wind than we expected, so we have to shorten sail.

We can use the Beaufort Scale to estimate wind speeds, and some sailors are very adept at doing that.

Now I don't have an anemometer on the mast top to measure wind, mainly because it's too damned expensive, plus its a pain to wire up. But I sure would like a way to measure actual and apparent wind on the deck of the boat.

I've seen the handheld propellor type wind meters in the catalogs, and I understand that they are pretty accurate. One problem for me is something that small is likely to get mislaid, lost or dropped, even overboard at one point or another.

They mainly appear to cost over $100, so its a thing that is too fragile or risky that I would be quite p.o.ed about losing.

What do you use to measure wind speed? I've seen windvane type gizmos that you point into the wind, and a lever moves along a wind speed chart pasted on the side, and you read speed off the chart. They're dead simple, and so are inexpensive.

Are these things anywhere near accurate?, or would I be better off trying to see whether the wavelets are cresting occasionally or very often (Beaufort)?

Bruce Ross
Passage ~ SR-FK ~ C25 #5032

Port Captain � Milford, CT

Edited by - on

John Russell
Master Marine Consultant

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USA
3444 Posts

Response Posted - 09/12/2009 : 09:40:02

Santa brought me a handheld last Christmas. The name is escaping me right now but, I'll update when it comes to me. I like it. It has a built in electronic compass for assessing wind direction or bearings and a thermometer. It averages wind and gives gust speed. I think Santa paid around $110-$125. Guess the elves could't figure out the electronics.

Got it!!! [url="http://www.speedtech.com/yfuojq521455/WIND-METERS/WM-200--WindMate™-with-Wind-Direction-and-Backlight/p-110-445/"]WM-200 WindMate™ with Wind Direction and Backlight [/url]

Edited by - on

DaveR
Master Marine Consultant

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USA
2015 Posts

Response Posted - 09/12/2009 : 10:39:54

It seems to me that if the windex is fooled by the movement of the boat, so will a hand held meter. I've considered these things pretty much useless (especially in winds less than 8 knots or so) and look to onshore aids (flags) to give me a real estimate. Am I wrong?

Edited by - on

Steve Milby
Past Commodore

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USA
5904 Posts

Response Posted - 09/12/2009 : 14:28:30

My boat has an expensive masthead anemometer and apparent wind direction indicator, installed when new by the original owner. The wind speed quit working, but the wind direction still works. I never found the wind speed useful, but the wind direction is sometimes useful for steering, especially when the bimini is up and I can't see the masthead Windex. IMHO, the wind speed isn't worth the cost of repair.

The only time the wind speed might be useful is when you're first trying to decide which size jib to raise. It might be somewhat helpful then, but a handheld would serve the purpose and be much less expensive. If you're trying to decide whether to reduce sail area, you shouldn't need a WSI to make that decision. The boat's angle of heel and the tiller pressure will tell you when to reef.

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Dave Bristle
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Djibouti
10005 Posts

Response Posted - 09/12/2009 : 14:59:49

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Steve Milby
 ...The boat's angle of heel and the tiller pressure will tell you when to reef.<hr height="1" noshade id="quote"></blockquote id="quote">...as in, "The time to reef is when you first think about it."

You're not gonna find a "true" wind speed indicator unless it's something that is integrated with your GPS so it can do the geometric calculation using your course and speed-over-bottom. If it exists, you can guess the cost. (Hint: Too much.)

I had a cheap plastic lever gizmo that essentially told me what I already knew, probably within +/-10% or so. But so often, what you measure when standing still at the dock is not what's out there, especially if the wind is off-shore. When you're out there, the boat (and your gut) tells you when you should make changes.

Edited by - on

delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Response Posted - 09/12/2009 : 16:22:53

I've got a Kestrel that'll give me wind speed in either instantaneous, average, or highest, plus temp, barometric pressure & elevation (sea level!), wind chill, dew point, relative humidity, and time (which is basically useless since it doesn't keep good time). I think Rita paid $180 for it for my birthday a couple of years back.

As noted, it tends to get lost, but it is handy for speed, as opposed to direction. My wind bird got blown off in a storm a while back and we haven't dropped the mast since to replace it.

While I think the Kestrel is a cool toy, I'm not sure it really helps me with sailing, it's more a confirmation of what I already know, plus it's kind of fun to play "how hot is it?".

They make little pitot tube anemometers that you can pick up for less than $10, they're probably accurate enough for what you're trying to do. I think I've seen them at WM, but also at places like Target in their sporting goods department.

Edited by - on

bigelowp
Master Marine Consultant

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USA
1786 Posts

Response Posted - 09/12/2009 : 18:42:50

I have both a mast head windspeed indicator "instrument" (Raytheon) and a Furlex direction indicator and a hand held @$50.00 West Marine Special wind speed guestimate. The Raytheon gives me interesting but often misleading information, the Furlex tells me where it's all coming from and the hand held confirms what I already know. All are useful . . . but need to be combined with your comfort level and knowledge of boat and local area. In order of need I would rate the Furlex first, the hand held wind speed second and the Raytheon "instrument" third -- Together though they help a lot!

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Voyager
Master Marine Consultant

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USA
5389 Posts

Response Posted - 09/13/2009 : 06:16:12

Initial indications sound like, well you spend a lot or spend a little, but you really never know for sure what the wind speed is exactly, so I guess I will continue to use the old stand-by:
Wet a finger, look at the trees, look at the waves, check your angle of heel and check with Rear Admiral Beaufort:
http://www.coastalwindsports.com/BeaufortScale.html

This is a pretty cool website in its own right, if you're into kites and suicide!

Edited by - on

JimB517
Past Commodore

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USA
3285 Posts

Response Posted - 09/13/2009 : 14:32:51

I bought a cheap $30 yellow plastic wind meter from Amazon.com. It is super accurate. It can measure the speed of you walking down the hall (about 3 knots). I calibrated it in the car on a calm day and it was correct up to 20 knots, it will read to 70.

I learned a couple of things: I was radically over estimating wind speed using seat-of-the-pants guestimate methods (ie. guess 20 when its really 10).

My boat begins to get overpowered hard on the wind with the 155 up and full main at 12 knots apparant.

It hangs on a laynard around my neck.

I use it all the time at the dock and in a race.

Edited by - on

delliottg
Former Mainsheet C250 Tech Editor

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USA
4479 Posts

Response Posted - 09/13/2009 : 15:27:22

This is the one I was thinking about (click the photo):

[url="http://www.amazon.com/Meter-Wind-Dwyer-Instruments-METER/dp/B0019H84JW/ref=sr_1_3?ie=UTF8&s=automotive&qid=1252880185&sr=8-3"]

[/url]

You can get them for about $20 on Amazon. No batteries, nothing to go wrong, twin scales, 0-10 & 10-66 MPH.

Edited by - on

britinusa
Web Editor

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USA
5404 Posts

Response Posted - 09/13/2009 : 16:00:36

We have the Raymarine TriData system that includes wind speed, direction and can also show actual or relative wind direction (at least that's my impression, it's all magic!)

Anyway... we have seen 30+ knots of wind on it but have had it while moving at 70mph, but that's with the mast down.

The biggest problem we have is the need to fix the deck connector so often. Flimsy wire breaks in the connector. the Receptical seems fine.

The admiral pipes up as soon as wind speed get's to 18knots. We're probably reefed before then.

Paul

Edited by - on

Prospector
Master Marine Consultant

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Canada
3159 Posts

Response Posted - 09/14/2009 : 06:36:27

Why do you care about "actual" wind speed?

I sail to apparent wind. Downwind th ewind feels light, upwind it feels strong. The "real" wind only matters in that it is either building or dropping, oscillating, or steady, and I sail to it. Also, th ehandheld wind meters will still only give you apparent wind, unless you throw someone overboard, and have them shout out the readings as you sail away. (Bring lots of crew)

our masthead instruments were very finicky. They rarely worked, and since we lost them on our summer vacation, I haven't worried about getting them replaced. They are low on the priority list.

Get good telltales on your sails, sail to them, and your results will be just as good.

Edited by - on

redviking
Master Marine Consultant

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USA
1771 Posts

Response Posted - 09/15/2009 : 06:37:16

I bought one of these for cheap for my C25 years ago and it really is a decent little toy.

http://www.weatherconnection.com/product.asp?itmky=441601&s=froogle

Lysistrata has instruments upstairs and now that I've gotten used to knowing what's going on, I could never go back.

Classic conversation between wife and I on downwind run in 4-7 foot seas - running at almost 8 knots with winds approaching 25 knots. Wife: "Maybe we should reef - it's blowing 24." Me: "wake me up when it is blowing 25." "It's blowing 25." "Wake me up when it's blowing 27." "It's blowing 27." "Alright, I'll be right there to help put a reef in."

sten

Edited by - on

HeelinPatrick
Navigator

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USA
102 Posts

Response Posted - 09/15/2009 : 07:42:47

Looking at the water on the lake, and the trees, and flags and all that is about all I need to determine what sails to put up. What would be great is knowing what it will be blowing later in the day, especially for shorter races.

Now, I do call the airport on occasion when on the water, they give previous 15 minute data, which states average wind speed and peak wind speed. I use that and compare it with weather.com predicted hourly windspeeds, and what I see on the lake. Since forecasters don't give the wind strength in things like slight white caps forming and trees lightly rustling, need to have an idea what a given mph means for conditions on the water. So, knowing the actual wind compared to what you see is useful in that respect. Plus, when bragging, you can say, "man, it was blowin 25 out there!" I debated getting a handheld gizmo, but a new 135 genoa is higher on the shopping list.

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Stu Jackson C34
Admiral

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844 Posts

Response Posted - 09/15/2009 : 17:11:00

The Beaufort Scale is very helpful because it describes water conditions that "track back" to wind speed without needing any devices: http://en.wikipedia.org/wiki/Beaufort_scale

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Voyager
Master Marine Consultant

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USA
5389 Posts

Response Posted - 09/15/2009 : 17:33:48

Ok, so here's what I was talking about. Yesterday, the NWS called for 5-10 kt winds blowing from the northwest to start, then veered to west later on.

According to actual buoy wind measurements, it was blowing 12-14 with 18 knot gusts.

I really got knocked around by the gusts and the waves. Waves were 2-3 ft, short and steep and most were breaking. When beating, I had to ease off in puffs and was heeling around 15 degrees most of the time. Because of the waves and puffs, I could not do more than 3.2 kts VMG on a reach according to the GPS.

Today, the NWS predicted 5-10 kts out of the west, just like yesterday. Today, the wind seemed a little less fierce, and remained pretty steady, no gusts. The waves were about 1ft, with an occasional crest. Even close hauled, I was heeling at about 10 degrees, and was making between 4.8 to 5.2 kts VMG.

According to the weather radio, actual wind speeds were about 8-10 kts with no gusts.

It was what I'd call smooth sailing.

As I said up above, you can spend a lot of money, but you really can't get much better wind info than looking at the waves and checking the radio. I think I'll try one of those cheezy yellow plastic wind gauges.

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Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 09/15/2009 : 20:14:39

Bruce, what do you mean by VMG? My calculation of VMG to windward says if you're sailing at 45 degree off the true wind (pretty high), a VMG of 5.2 knots means your actual speed is about 7.3 kts. That's pretty good for beating in a C-25!

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brrit
1st Mate

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80 Posts

Response Posted - 09/16/2009 : 05:37:29

I find myself in the same position as you Voyager. I have the masthead system installed, but it is in need of repair. I'm too cheap to have it fixed and haven't had the chance to climb up the mast.

As a result, I've love a handheld unit that wouldn't cost an arm and a leg. My sailing skills are still developing and, honestly, I just don't trust myself with assessing the wind speed. I'll have to check out some of the handheld units suggested here and see what I can find.

Great thread!

Edited by - on

HeelinPatrick
Navigator

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USA
102 Posts

Response Posted - 09/16/2009 : 06:43:20

I'll add this too, I've studied the weather report, vs. what actually happened that day. The weather (www.weather.com is what I use) tends to aim on the high side for wind speed (sensationalism), and the wind they say is the gust wind. And this is the hourly prediction I'm talking about. If you look at the forcast for the day itself, it might say something like 20-30 mph winds. But if you look at the hourly forcast, one hour out of the day might be predicted at 21 mph, and the 21 is most likely the gust rating, and 12-15 mph might be what it is actually blowing. That's weather.com's way of peaking people's interest in my opinion. On their site, wind speed isn't a big deal, temperature, humidity, cloudiness take a higher importance it seems.

I found this somewhere, unfornately, it doesn't cover where I am, but maybe some of you:
http://windmapper.com/?Loc=MW
And actually, checking it again, the Lincoln Airport is on it, maybe I will start using this as well. Anyone else use this?

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Steve Milby
Past Commodore

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USA
5904 Posts

Response Posted - 09/16/2009 : 07:27:34

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Dave Bristle
 Bruce, what do you mean by VMG? My calculation of VMG to windward says if you're sailing at 45 degree off the true wind (pretty high), a VMG of 5.2 knots means your actual speed is about 7.3 kts. That's pretty good for beating in a C-25!

<hr height="1" noshade id="quote"></blockquote id="quote"> In Bruce's post he referred to his VMG readings, as observed on his GPS. I don't think you can take GPS speed readings too literally. The 5.2 reading was undoubtedly the highest reading observed, might have been momentary, and might have been aided by current or other factors. Moreover, I commonly see the speed readings on my GPS jump around as much as a half knot or more, when I know the boat's actual speed hasn't changed that much that rapidly. You have to take those readings with a grain of salt, and view them as a sort of average. If you're getting consecutive readings of 4.7, and 5.3, and 4.9, and 5.5, and 4.8, then you have to consider your boatspeed is actually somewhere around 5.0 kts, more or less. Mr. Garmin would like us to think his GPS is as accurate as the Hubble telescope, but I think it still has a ways to go.

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Stu Jackson C34
Admiral

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844 Posts

Response Posted - 09/16/2009 : 07:55:16

The ONLY way to answer the VMG question is to have Bruce tell us what he was using as a waypoint. In many cases, sailors use the true wind direction and then plot a waypoint say 1,000 miles away, to get VMG for the wind direction, as compared to just using the next closest buoy, for example, as a waypoint. So, Bruce, what was it?

Edited by - on

Renzo
Admiral

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USA
621 Posts

Response Posted - 09/16/2009 : 08:31:08

Go out on the water. Raise the mainsail. turn off and raise the outboard motor. Trim the mainsail for a beam reach or a close reach and check your knot meter, with a little practice you can then judge what sail combination will suit you best. example: Less than 2kts raise the 155%, 3.5 kts use the 150%, hull speed on the main alone put in a reef then raise the 110% jib. It's all a matter of what you're comfortable with, the actual speed of the wind doesn't matter.

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jerlim
Master Marine Consultant

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USA
1484 Posts

Response Posted - 09/17/2009 : 11:07:00

We've got the same meter as Sten, it's accurate when measured in a moving car - and at that price is not too bad if lost to Neptune... While the ability to determine the best sail plan, based on your own observation of the conditions is really important, the meter does allow you to quantify wind speed for reference, as well as bragging rites - as in OMG, it's blowing 22 gusting to 28!!

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JimB517
Past Commodore

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USA
3285 Posts

Response Posted - 09/17/2009 : 11:36:54

It helps you make decisions when standing on the dock prior to heading out. It is hard to feel the difference between 15 knots and 20. The boat will know the difference however! In the latter case you'd probably want to hank on the 110 jib and maybe consider the 1st reef before heading out.

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redviking
Master Marine Consultant

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USA
1771 Posts

Response Posted - 09/17/2009 : 11:41:38

Knowledge is power and I am amazed at how many people guess when they are floating, but wouldn't dream of guessing when they are cooking, making beer, working on a car, or shopping for the wife. knowing the difference between 15 and 20 could make a difference in making the right decisions.

sten

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Renzo
Admiral

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USA
621 Posts

Response Posted - 09/17/2009 : 13:12:08

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by redviking
 Knowledge is power and I am amazed at how many people guess when they are floating, but wouldn't dream of guessing when they are cooking, making beer, working on a car, or shopping for the wife. knowing the difference between 15 and 20 could make a difference in making the right decisions.

sten
<hr height="1" noshade id="quote"></blockquote id="quote">

A little extra chili powder never hurt anything.

Letting the brew age another week might make it stronger.

I think the springy do-hicky belongs to carborator.

If ya buy the wife a bigger bra maybe she'll grow into it.

Seriously,It's great to know for sure and exactly how much the wind is blowing, but if you don't, it's easier (and safer)to change sails up than it is to change them down. I love instrumentation when it's working, but I try to keep my guessing skills sharp just incase.

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