Dragged Our Rocna Today

[noelex 77]

Originally Posted by Dockhead

As far as I'm concerned, a real improvement in anchor alarms would be a feature in our plotters which would allow us to define a safe zone, like the guard zones on radar. We point the cursor at the point where the anchor is, and define whatever circle we like around that. Would be simple for Raymarine or Furuno to come up with -- one day of one programmer's time, I think.

Good idea.
Some GPS units allow a remote point to be set as the centre of the alarm radius. This is much better than the more common situation where the GPS uses the boat position as the centre of the alarm radius.Not as good as a guard zone, but defiantly a feature worth looking for if you use the anchor alarm, and you should.

[MarkJ]

Originally Posted by noelex 77

Good idea.
Some GPS units allow a remote point to be set as the centre of the alarm radius. This is much better than the more common situation where the GPS uses the boat position as the centre of the alarm radius.Not as good as a guard zone, but defiantly a feature worth looking for if you use the anchor alarm, and you should.

OpenCpn is letting me do this with 2 points. You can either be within them, or outside them, of one of them.
The other day I set one near where the boat was at 50 m radius, and the other I set near the shore (actually onshore) so the line was in the bay, so if I dragged too close to the danger area I would get an alarm.

I thought quite nifty!

[ActiveCaptain]

Originally Posted by Dockhead

For a meaningful increase in functionality and precision of an anchor alarm, I think you need to have the ability to set up some kind of guard zone around any point you put your cursor on, not necessarily where your GPS antenna is. That will eliminate the need to physically position your boat over the anchor and make people much more likely to use it. If you can vary the shape of the guard zone to account for any special obstacles, then that would really be great. Maybe your gizmo does that; I don't know.

I'm not sure I understand the difficulty. With my technique, you configure how far back the GPS is located at the time you drop your anchor. There will actually be a couple of selections available in case you're using a GPS on the phone that moves (click on bow, cockpit, etc). When you drop the anchor, you press a single button. Now it knows where your bow is and where the GPS is and can eliminate the GPS location error. A really nice check is that it gives a constant read out in feet as you deploy rode and pull back. So if you've let out 100' of chain and the display shows 120', there's probably a problem and you know it immediately.

[Dockhead]

Originally Posted by ActiveCaptain

I'm not sure I understand the difficulty. With my technique, you configure how far back the GPS is located at the time you drop your anchor. There will actually be a couple of selections available in case you're using a GPS on the phone that moves (click on bow, cockpit, etc). When you drop the anchor, you press a single button. Now it knows where your bow is and where the GPS is and can eliminate the GPS location error. A really nice check is that it gives a constant read out in feet as you deploy rode and pull back. So if you've let out 100' of chain and the display shows 120', there's probably a problem and you know it immediately.

Well, IF your phone has a precise GPS receiver (?), and IF your system allows you to hold the phone in your hand as you drop the anchor over, and press one button to fix the anchor location, THEN that's pretty cool -- a good improvement. Besides that, if it all runs on your phone then you can keep the phone next to your bunk, another advantage.

You are thus eliminating BOTH the more serious problem of the distance between your boat and your anchor, and the less serious problem of the location of your GPS antenna. That's pretty cool, if I understood you right.

But it would depend on your phone having a GPS as precise as your on-board one. My own phone (a Nokia E90) does not have such a precise GPS. Maybe some newer phones have WAAS and so forth built in?

[ActiveCaptain]

Originally Posted by Dockhead

But it would depend on your phone having a GPS as precise as your on-board one. My own phone (a Nokia E90) does not have such a precise GPS. Maybe some newer phones have WAAS and so forth built in?

I'm concentrating on iOS at first because the tools are great for developing there. But yes, you have the idea. And when you're in your stateroom at night, you'd click on stateroom to correct for the pre-configured GPS distance there.

You're quite right - many phone GPS's aren't good enough. The iPhone 3GS is unacceptable - at least it gives an HDOP to tell you how unacceptable it is. I've done a lot of iPad testing and it is acceptable even below deck (although not on a steel boat). I'm hoping that the iPhone 4 will have a similarly improved GPS - they're using the same chipset as the iPad but I haven't gotten my hands on one yet.

The problem with OpenCPN as an anchor alarm is that I have no way to run a laptop (even a small one) in my stateroom - it's just impractical. I wouldn't want to even think about the power requirements of running it all night long either. My iPad will definitely run all night and my iPhone with an external battery (solar chargeable) will also run all night. They easily sit right next to me while I sleep and wake me up if they go off a foot from my head.

[cchesley]

Somehow, all this talk of anchor alarms seems to miss the point. I guess it's ok for you computer geeks but, sheesh, making sure you have your phone/computer/gizmo next to you in bed and calculating all the 'corrections for anchor position, cabin location, etc, etc seems somewhat foolish or paranoid.

I learned long ago that just because something CAN be done with electronics or computers doesn't mean it really adds value. Perceived value maybe but there are so many steps and assumptions that are made that it kind of takes the fun out of it. What happened to going cruising? Most nights at anchor, you really won't have to worry about dragging anchor anyway. If you do need to be concerned, I'm not so sure that relying on all these calculations is really very reassurring. When in doubt, keep an anchor watch!

Let's see, I don't trust my anchor, so I dive on it, and then I set my anchor alarm because, well, I can and after all, I don't trust my anchor (or anchoring job) but somehow I do trust my phone and oh, wait, there's no cell signal here??? now what do I do? Where does this stop?

(but I do 'get it' that it's all fun for the tecknogeeks, I just hope you don't really bet the farm on this stuff)

[ActiveCaptain]

Originally Posted by cchesley

I don't trust my anchor (or anchoring job) but somehow I do trust my phone and oh, wait, there's no cell signal here??? now what do I do? Where does this stop?

It probably stops right before condemning something before you really understand it. There's no cell signal needed and that's probably the start of the misunderstanding you have about what is possible and useful.

There are many reasons and enjoyments arrived from being on a boat. No one's enjoyment is any more important than any other's. Some want to completely unplug and get away from everything in the real world. Others want to tinker with their toys as a way of having fun. Neither is better or worse.

[mikereed100]

In choosing an anchor for the new cat I have been considering the Raya, Rocna and Manson. Raya was in front due to lighter wieght and lack of a hoop but it seems the company has gone TU, leaving Rocna and Manson. There are 2 things about the Manson that IMO give it a slight edge; the sharpness of the tip and the size of the hoop. There may be no advantage to these things in the real world, but it may be that a pointier tip will penetrate weed better and a larger diameter hoop would be less likely to pick up mud.

Maybe Mark (Colemj) would be willing to buy a Manson and anchor in the same spot during a gale in the interests of science?

Mike

[Dockhead]

Originally Posted by cchesley

Somehow, all this talk of anchor alarms seems to miss the point. I guess it's ok for you computer geeks but, sheesh, making sure you have your phone/computer/gizmo next to you in bed and calculating all the 'corrections for anchor position, cabin location, etc, etc seems somewhat foolish or paranoid.

I learned long ago that just because something CAN be done with electronics or computers doesn't mean it really adds value. Perceived value maybe but there are so many steps and assumptions that are made that it kind of takes the fun out of it. What happened to going cruising? Most nights at anchor, you really won't have to worry about dragging anchor anyway. If you do need to be concerned, I'm not so sure that relying on all these calculations is really very reassurring. When in doubt, keep an anchor watch!

Let's see, I don't trust my anchor, so I dive on it, and then I set my anchor alarm because, well, I can and after all, I don't trust my anchor (or anchoring job) but somehow I do trust my phone and oh, wait, there's no cell signal here??? now what do I do? Where does this stop?

(but I do 'get it' that it's all fun for the tecknogeeks, I just hope you don't really bet the farm on this stuff)

Well, it's not just technogeekian mastu**ation, it's a real concrete need. It's a way to get desparately needed sleep at anchor. "If in doubt, just keep an anchor watch" -- just. You're short handed, you had a hard passage today, you've got another one tomorrow -- well, no problem, just stay up all night and watch the anchor. I wish you many pleasant anchor watches.

No, I don't trust my anchor. I have never trusted any anchor, even if I have dived on it. I have dragged too many times over the decades, and these incidents are the closest things to real disasters I've ever had sailing.

So I commend Active Captain on his work and hope that more progress is made. A really good anchor alarm would really improve life on board.

[Dockhead]

Originally Posted by ActiveCaptain

I'm concentrating on iOS at first because the tools are great for developing there. But yes, you have the idea. And when you're in your stateroom at night, you'd click on stateroom to correct for the pre-configured GPS distance there.

You're quite right - many phone GPS's aren't good enough. The iPhone 3GS is unacceptable - at least it gives an HDOP to tell you how unacceptable it is. I've done a lot of iPad testing and it is acceptable even below deck (although not on a steel boat). I'm hoping that the iPhone 4 will have a similarly improved GPS - they're using the same chipset as the iPad but I haven't gotten my hands on one yet.

The problem with OpenCPN as an anchor alarm is that I have no way to run a laptop (even a small one) in my stateroom - it's just impractical. I wouldn't want to even think about the power requirements of running it all night long either. My iPad will definitely run all night and my iPhone with an external battery (solar chargeable) will also run all night. They easily sit right next to me while I sleep and wake me up if they go off a foot from my head.

Can't you run OpenCPN on your iPad? My laptop will run all night (Sony TT) on batteries, and it will run indefinitely off a small inverter at the nav table. Maybe the key to all of this is to get an accurate GPS signal into the laptop, iPad, or phone from an external GPS receiver.

How about this for an idea: Why not mount another GPS antenna (they're cheap) on the bow pulpit? Connect it to your laptop at the nav table, then remote desktop (by WiFi or Bluetooth) to your phone, iPad, etc.? Then all you need is a button programmed on your phone to place a mark on the chart in CPN. You can then set whatever zone you want on the laptop. Then you keep the phone or whatever next to your bed, and you can see on the screen how you're swinging, and it will give you an alarm if you stray out of your zone. You eliminate the antenna placement problem because the antenna doesn't move around with you -- it's always on the bow.

[colemj]

Originally Posted by mikereed100

There are 2 things about the Manson that IMO give it a slight edge; the sharpness of the tip and the size of the hoop. There may be no advantage to these things in the real world, but it may be that a pointier tip will penetrate weed better and a larger diameter hoop would be less likely to pick up mud.

I don't think the spear tip on the Manson makes much of a difference. The Rocna was buried deeply in the weeds, given how much weed came up with it. I just think there wasn't any substrate of significance underneath it.

Is the hoop larger on the Manson? They look about the same to me. (pic from Sailfasttri) I suspect any difference wouldn't be significant in practice.

Originally Posted by mikereed100

Maybe Mark (Colemj) would be willing to buy a Manson and anchor in the same spot during a gale in the interests of science?

Absolutely I will. I await the grant money for the study...

Mark

[ActiveCaptain]

Originally Posted by Dockhead

Can't you run OpenCPN on your iPad?

No, you can't. Doubt you ever will. It would be a total re-write. The iPad uses the same frameworks as the iPhone and software is written in Objective C.

There probably are some laptops that can run for 8-10+ hours on batteries. But I wonder if they can be powering a GPS (or worse power-wise, talking to it via Bluetooth) all night. There's also a size issue. A phone is really the perfect thing.

Originally Posted by Dockhead

How about this for an idea: Why not mount another GPS antenna (they're cheap) on the bow pulpit?

Sure, that's possible. That will remove the GPS location error. But so will a little trigonometry with a procedure for capturing the GPS location when the anchor is dropped. Having a single GPS wired or wireless also means that only a single device can be connected to it and something has to be powering it. Most current Bluetooth GPS's will run for 10-20 hours on a battery charge.

One other nice feature is that, especially if you have 2 phones (husband/wife, etc), the second phone could be monitoring the anchor from onshore. That would require an adequate cellular signal but it sure would be nice to know how far the boat was pulling back from the hook when you were walking around town having lunch.

[Vasco]

Originally Posted by cchesley

Somehow, all this talk of anchor alarms seems to miss the point. I guess it's ok for you computer geeks but, sheesh, making sure you have your phone/computer/gizmo next to you in bed and calculating all the 'corrections for anchor position, cabin location, etc, etc seems somewhat foolish or paranoid.


()

Like cchesley I can't understand all this. What happened to good old fashioned seamanship. Check weather, check conditions, stay alert (even when sleeping)when it's honking keep an anchor watch. Actually I rely a lot on my wind generator. We sleep in the aft cabin and the KISS is close by. When it really starts humming I get up and have a look.

Following is a true story. A bunch of us were anchored off Cumberland Island, GA. Blowing a bit. I saw a Tayana 42 slowly dragging down on my buddy's Whitby42. Called my buddy on the vhf and warned him. Next thing I know the Tayana (upwind of the Whitby) is on the same channel claiming the Whitby is dragging, and that's why they're closer!! The Tayana eventually reanchored. Doesn't end here though.

Next morning the Tayana is getting a lesson on the vhf from his buddy on how to set the anchor alarm on his Garmin. The buddy tells him how to set it and to leave it on when they leave the anchorage to test it. The Tayana then asks "do I leave my anchor down too"? This is a boat that has come from Maryland. I don't know how he made it to Georgia. I swear this is a true story.

[Auspicious]

Originally Posted by Vasco

Check weather, check conditions, stay alert (even when sleeping)when it's honking keep an anchor watch.

Vasco's valid points notwithstanding, I've given up on using anchor alarms. Now I just turn on a GPS track and watch the swing pattern on either the chartplotter or laptop with the display zoomed all the way in. It provides much more meaningful information than the on/off anchor alarm.

[skipmac]

Back to the original subject, bought a new Rocna (20 Kg for 42' boat) last fall for the trip down the ICW to FL. Anchored out most of the way including one night when a pretty nasty thunderstorm blew in about 1:00 am and never moved an inch.

Got to the St Johns River in FL and dropped anchor off of Green Cove Springs and every time I backed down on the engine to set the anchor I slowly backed across the river. Let out about 100' of 3/8" chain (that's 30 meters to MarkJ) in about 7' depth and was still dragging when I backed down at full power.

Since it was very calm with nothing in the forecast I finally gave in. Next day met a couple of friends at the local dock that had been anchored there for a while who confirmed everyone had the same problem, no matter what kind of anchor. Apparently there is really, really deep, soft, silty mud with no hard bottom so as deep as your anchor can go you will still be in fairly soft goo.

Wondered if a large Danforth type would work there?