Vulcan versus Standard Rocna, SS v Galvanized
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Panope
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When you view power charts for your MARINE engine, be sure to ignore the "max power" (and torque) curves as it is impossible to load the typical boat engine to match the curve except at max rpm. The exception would be the case where a controllable pitch propeller is fitted.
What you need for the typical fixed pitch propeller/engine combination is the "propeller curve".
Steve
Note the large discrepancy between the Max power curve and the propeller curve in this example:
What you need for the typical fixed pitch propeller/engine combination is the "propeller curve".
Steve
Note the large discrepancy between the Max power curve and the propeller curve in this example:
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dhays
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psneeld
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Based on Fortress info, for a semi displacement hull of 50 feet in 40 knpt winds, your anchor has to endure about 3000 pounds of pull.
Their chart suggests about 200 shaft hp to simulate that.
Looking at the boat diesel charts, for about 100 prop hp per engine, 1600 to 1800 rpms should do it.
I think the holding power charts are a bit high, 3000 pounds is quite a lot....but if expecting yawing and pitching due to large waves, maybe not.
So if it were me, I might use 1500 rpm to back down and call it a day.
Remember Irv...this is just simulating the wind, not saying that you have to do it to get your anchor to hold.
But if anchored on a tuft of grass or a big rock, this might tell you whether you will break free.
Their chart suggests about 200 shaft hp to simulate that.
Looking at the boat diesel charts, for about 100 prop hp per engine, 1600 to 1800 rpms should do it.
I think the holding power charts are a bit high, 3000 pounds is quite a lot....but if expecting yawing and pitching due to large waves, maybe not.
So if it were me, I might use 1500 rpm to back down and call it a day.
Remember Irv...this is just simulating the wind, not saying that you have to do it to get your anchor to hold.
But if anchored on a tuft of grass or a big rock, this might tell you whether you will break free.
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Anchoring a boat is as much an art as it is a science. When we consider the different boats, different anchors and rode, scope, different bottom conditions, and current and wind, we can't count on a chart to insure we stay where we started the night before. Backing down at "X" RPM is meaningless.
I think experience tells you how hard to back down and for how long.
I think experience tells you how hard to back down and for how long.
Adding to the confusion:
Plan on your REVERSE thrust to be roughly 1/3 of FORWARD thrust.
Here are the numbers (measured with strain gauge) for my 40 HP engine:
OK, that's direct thrust. Now figure in the resistance of the flat transom and the angle of the rode to the anchor.
dhays
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FWIW, I have not used a lot of power to back down on my anchor in the North Pacific 43. On my sailboat with a 56hp engine, I would use a fair bit of its available power to set an anchor. The first time I tried that with my power boat out of habit, I pulled that anchor right out of the bottom. It only then dawned on me that it may not take as much with 380hp vs 56hp.
Bigsfish
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Scott
Thanks so much for the info. Your my new hero, drinks are on me in Ft. Pierce even if you hang out with the ladies.
I seem to remember I back down and raise the RPMs to about 1200 on each engine. I'll try boosting it to 1500 next time I'm out. The information is much appreciated.
Thanks, I owe you.
I must say I've gleaned a lot of good info from this forum
Thanks so much for the info. Your my new hero, drinks are on me in Ft. Pierce even if you hang out with the ladies.
I seem to remember I back down and raise the RPMs to about 1200 on each engine. I'll try boosting it to 1500 next time I'm out. The information is much appreciated.
Thanks, I owe you.
I must say I've gleaned a lot of good info from this forum
psneeld
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Many charts of data points with not much in real life reference.....so take the for what they are.
Not sure about reverse thrust versus forward.... as the prop would have a lot to do with it.
Certainly none of it is a 100 percent accurate, but certainly not meaningless.
It just gives a rough idea of how much hp might be required to simulate wind pull on an anchor and I have no idea if the chart accounts for reverse thrust losses.
It sounds about right to me and I have enough experience to feel comfy with it if you feel it is necessary.
Not sure about reverse thrust versus forward.... as the prop would have a lot to do with it.
Certainly none of it is a 100 percent accurate, but certainly not meaningless.
It just gives a rough idea of how much hp might be required to simulate wind pull on an anchor and I have no idea if the chart accounts for reverse thrust losses.
It sounds about right to me and I have enough experience to feel comfy with it if you feel it is necessary.
psneeld
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Scott
Thanks so much for the info. Your my new hero, drinks are on me in Ft. Pierce even if you hang out with the ladies.
I seem to remember I back down and raise the RPMs to about 1200 on each engine. I'll try boosting it to 1500 next time I'm out. The information is much appreciated.
Thanks, I owe you.
I must say I've gleaned a lot of good info from this forum
I wouldnt tiotally dismiss Steve, in fact he probably is the go to guy on much of this.
As I posted, all these charts have to be taken with a grain of salt .....yet learn a tid bit or two from each of them when coupled with personal experience.
Others.... yep.....ignore to the max....
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Panope
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OK, that's direct thrust. Now figure in the resistance of the flat transom and the angle of the rode to the anchor.
Ha! More variables to keep the discussion going.......
The "flat transom" comment reminds me of a relevant event from a couple years ago.
Prior to entering my marina on a particularly windy afternoon (38 kt. gust 45. NOAA), I needed to confirm whether or not reverse power could stop/hold the boat against the wind with the bow pointed directly downwind.
I tested this, moments after this picture was taken, in the open bay. The answer was: yes. The engine (in reverse) could stop the boat (GPS confirmed).
It was my impression that the 3 foot chop slapping into the flat transom was of little consequence. Rather, the force was predominantly windage.
I think we can infer that for Panope, full power reverse is equal to about 40 knots of wind. Of course any surges, veering, or snatches while anchored would increase the load to some higher value.
Next time you all are out in some wind, do the test yourselves. My guess is the higher powered boats will hold themselves, in reverse, against similar wind with not much more than idle power.
Steve
At time of this photo, I was progressing under storm jib only:
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From post 11..
I have a Delta SS on my port bow and a galvanized Boss on my starboard, I use the Boss about 95% of the time because it works so well ( it's really big).
Bigfish, in my humble opinion, you are seeking a solution to a problem you don't have. You've got a decent anchor, (see in quote), so just chuck it out, take up the slack with a bit of reverse if you must, then go make a cuppa tea, and chill out man. As you said yourself..."I'm amazed I only drug my anchor once in 40 years."
I have a Delta SS on my port bow and a galvanized Boss on my starboard, I use the Boss about 95% of the time because it works so well ( it's really big).
Wow, guys this is getting confusing. I never had this info I'm amazed I only drug my anchor once in 40 years.
Bigfish, in my humble opinion, you are seeking a solution to a problem you don't have. You've got a decent anchor, (see in quote), so just chuck it out, take up the slack with a bit of reverse if you must, then go make a cuppa tea, and chill out man. As you said yourself..."I'm amazed I only drug my anchor once in 40 years."
Bigsfish
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Peter B
Your probably correct but I need something to worry about. Not sure about the tea comment. ? Sometimes in the pursuit of knowledge we make problem where non existed. I was really trying to find out a proper reverse speed to maximize the setting of the anchor. Scott was nice enough to do the work and his answer was damn close to what I do. Lucky I guess.
Thanks.
Your probably correct but I need something to worry about. Not sure about the tea comment. ? Sometimes in the pursuit of knowledge we make problem where non existed. I was really trying to find out a proper reverse speed to maximize the setting of the anchor. Scott was nice enough to do the work and his answer was damn close to what I do. Lucky I guess.
Thanks.
My personal experience with life tells me that there's more resistance against the flat end than against the pointed end. That's the reason most boats are built with a pointed end and the reason we are told to tie the anchor to the pointed end.
All this talk of wind is fine of course, but in my area, tidal current is usually a bigger concern than wind. A two knot reversing tidal current is the norm in my area and it can be more. If I'm headed into the current, I have to do two knots with the engine just to stand still.
I know there are places with faster currents than that so current has to be a big concern for boater in t
Simple. It's the speed just before you pull the anchor out of the bottom!
I suppose it's best to slowly raise the speed to allow the anchor to set as you are pulling on it. And you need enough scope so you're not pulling it back towards the surface while you're trying to set it.
psneeld
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Irv
I think the fortress numbers are not really for setting the anchor as much as making sure it wont pull free in the conditions you are expecting.
So on a calm night, doing it may be overkill until say a thunderstorm builds, and having the engines online at that point might be worthwhile anyhow.
The clump of grass or rock scenarios are the reason I like testing the hold.
While the numbers are susoect from many points of view, they represent a reasonable approach to checking your set for the anticipared conditions.
But every boat has its peculiarities, so add in a little experience and go from there.
I think the fortress numbers are not really for setting the anchor as much as making sure it wont pull free in the conditions you are expecting.
So on a calm night, doing it may be overkill until say a thunderstorm builds, and having the engines online at that point might be worthwhile anyhow.
The clump of grass or rock scenarios are the reason I like testing the hold.
While the numbers are susoect from many points of view, they represent a reasonable approach to checking your set for the anticipared conditions.
But every boat has its peculiarities, so add in a little experience and go from there.
Nomad Willy
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How hard to back down when setting is probably the most dificult question that's ever been asked in anchoring. That is if you want the perfect answer.
With these variables, the bottom, the power and the anchor there is a very wide range of setting force that could be deployed.
A. For the backing down hard crowd when you stopped the action and decided you're set (pun intended) for anything you may have been in the process of breaking out so you'd have a very weak set.
B. For the moderate crowd you may have hooked a rock and when the wind changes out comes the anchor.
C. For the just give the anchor a little nuge crowd there's no guarantees either. The bottom may be such that after a bit of resistance breakout happens since there's a hard layer 4" down that the anchor can't penetrate.
One could argue that the best set would be no set at all as the wind or current will bring about setting slowly and it's common knowledge that the slower one sets the anchor the more effective the setting will be.
However we usually don't anchor in/on unusual bottoms so setting till the rode becomes a bit tight seems to work for most and one knows that the anchor is holding a fair amount of resistance. So we know our anchor is performing to some degree and with experience we know the boat will "probably" stay put.
A lot of us can say what we do and readers can pick a favorite method and hope for the best. Anchoring is always a "hope for the best" activity. I should throw in another variable never mentioned on TF to my knowledge and that variable is the skipper's attitude. I set my anchor and am fairly comfortable w it but many boaters are afraid of the variables that they may know little or nothing about. However one should have confidence in one's past experience. Or lack of it I suppose. To many knowing anchoring is an iffy activity excites them and offers a gambling challange that gives them great satisfaction. I know I've got some of that in me but if there's any unusual threats in the air for that night I set the anchor alarm so my gambling instincts don't go very far.
I don't think Marin Faure was much of a gambling man in anchoring. He applied considerable effort to insure there would positively be no dragging. He did drag once and subjected the offending piece of hardware (the Bruce anchor that came w his boat) to the most humiliating punishment imaginable .. eternal duty as a door stop.
But our degree of seeking adventure at anchoring varies a lot between us.
Add all those variables up, add some I missed and it's a wonder we usually anchor successfully at all.
With these variables, the bottom, the power and the anchor there is a very wide range of setting force that could be deployed.
A. For the backing down hard crowd when you stopped the action and decided you're set (pun intended) for anything you may have been in the process of breaking out so you'd have a very weak set.
B. For the moderate crowd you may have hooked a rock and when the wind changes out comes the anchor.
C. For the just give the anchor a little nuge crowd there's no guarantees either. The bottom may be such that after a bit of resistance breakout happens since there's a hard layer 4" down that the anchor can't penetrate.
One could argue that the best set would be no set at all as the wind or current will bring about setting slowly and it's common knowledge that the slower one sets the anchor the more effective the setting will be.
However we usually don't anchor in/on unusual bottoms so setting till the rode becomes a bit tight seems to work for most and one knows that the anchor is holding a fair amount of resistance. So we know our anchor is performing to some degree and with experience we know the boat will "probably" stay put.
A lot of us can say what we do and readers can pick a favorite method and hope for the best. Anchoring is always a "hope for the best" activity. I should throw in another variable never mentioned on TF to my knowledge and that variable is the skipper's attitude. I set my anchor and am fairly comfortable w it but many boaters are afraid of the variables that they may know little or nothing about. However one should have confidence in one's past experience. Or lack of it I suppose. To many knowing anchoring is an iffy activity excites them and offers a gambling challange that gives them great satisfaction. I know I've got some of that in me but if there's any unusual threats in the air for that night I set the anchor alarm so my gambling instincts don't go very far.
I don't think Marin Faure was much of a gambling man in anchoring. He applied considerable effort to insure there would positively be no dragging. He did drag once and subjected the offending piece of hardware (the Bruce anchor that came w his boat) to the most humiliating punishment imaginable .. eternal duty as a door stop.
But our degree of seeking adventure at anchoring varies a lot between us.
Add all those variables up, add some I missed and it's a wonder we usually anchor successfully at all.
sunchaser
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Is our method below an alternate or majority view? --
I idle back down on my anchor. This really stretches the road. Where we anchor, in 6 hours or less the tidal change will 180 the vessel and rode. If the predicted winds are for 40 knots I'm in a protected anchorage.
If worse comes to worse I have a good and oversized anchor that I know sets quickly and holds fast in 35 knots. With no serious backing down, in these winds Mother Nature does that for our vessel. Works for me and where we cruise. But shallow water East Coast is different.
I idle back down on my anchor. This really stretches the road. Where we anchor, in 6 hours or less the tidal change will 180 the vessel and rode. If the predicted winds are for 40 knots I'm in a protected anchorage.
If worse comes to worse I have a good and oversized anchor that I know sets quickly and holds fast in 35 knots. With no serious backing down, in these winds Mother Nature does that for our vessel. Works for me and where we cruise. But shallow water East Coast is different.
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Bigsfish
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WesK
"Simple. It's the speed just before you pull the anchor out of the bottom"
I used that same line when fishing for kings Fish with no leader, I would tell the guys you must set the hook just before you feel the fish strike. It works!
Scott
I agree. Any info from such a table is only a reference with lots of outliers. In a big storm I like to have the engines running!
"Simple. It's the speed just before you pull the anchor out of the bottom"
I used that same line when fishing for kings Fish with no leader, I would tell the guys you must set the hook just before you feel the fish strike. It works!
Scott
I agree. Any info from such a table is only a reference with lots of outliers. In a big storm I like to have the engines running!
Nomad Willy
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I bought an anchor from a fairly unknown manfacturer. He knew I was in SE Alaska and wanted me to be amazed at the performance of his product. Told me to go find a big fishboat and have then set the anchor and then try to pull it out. I passed on it (the pull out) but wondered how much hp applied it would take to pull it out. I have successfully used it in a 50 knot gale. Would anybody in the Puget Sound area be interested in a 2-300hp pull-out of an 18lb anchor? Would need a samson post or cleats strong enough for your full throttle stattic pull.
dhays
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One of the TF regulars (I can't recall who) described a technique some time last year that I thought was good.
He would set with just idle power, then shut down and have a beer, eat dinner or whatever for about an hour. This allowed the anchor soak. He then would go back and set the anchor with more force.
To me this made a lot of sense if you are in a situation where you have some force on the rode for that hour. It allows the anchor to dig in over time with mild force, then you set it deeper with the engine.
He would set with just idle power, then shut down and have a beer, eat dinner or whatever for about an hour. This allowed the anchor soak. He then would go back and set the anchor with more force.
To me this made a lot of sense if you are in a situation where you have some force on the rode for that hour. It allows the anchor to dig in over time with mild force, then you set it deeper with the engine.
Bigsfish
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Dave
I do something similar after the first set under mild reverse, wait about 15 minutes (set anchor alarms, turn off electronics, cover the bridge console, Echt ) and then power set the anchor. Seems to work. I don't know what it really does.
I do something similar after the first set under mild reverse, wait about 15 minutes (set anchor alarms, turn off electronics, cover the bridge console, Echt ) and then power set the anchor. Seems to work. I don't know what it really does.
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Yes, I get that, and with your spade type Boss, a back-down to set is probably a good idea, but the exact power needed probably does not need exactitude, is what I was getting at I guess. For my Super-Sarca, I just let the drag of the boat set it most times, unless there is no wind or current. Works well for that type in my experience.
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I don't think it was me that said that, but that tactic is the one I would recommend, and do, over and above what I just said above to BigsFish, if I was really concerned re the possibility of a weather step-up of consequence.
