easy way to pull up well set anchor

[Dieseldude]

Originally Posted by jtsailjt

Pulling at an angle does not create any more force, it just changes the direction of whatever force you can generate comes from.

True, changing the direction of application of a force does not increase that force. Depending upon what direction the flukes are driven in, direction can have an effect that can be an advantage or disadvantage though.

[valhalla360]

Originally Posted by jtsailjt

Pulling at an angle does not create any more force, it just changes the direction of whatever force you can generate comes from.

Actually, it can.

Example: take a 4ft piece of rope and put a 5lb weight in the middle. Grab the ends in each hand and lift the 5lb weight:
- Hold it up with your hands 2 ft apart. Assuming you are a healthy adult, probably not a problem.
- Try and hold it up with your hands 4ft apart so the rope is perfectly straight and horizontal to the ground. No matter how much force you apply, you won't be able to get the rope perfectly straight. The reason is when completely straight and horizontal, the rope can't provide a vertical force component to lift the 5lb weight. The closer you get to straight, the more force it takes.

So you are lifting the same weight but it takes many times as much force applied to the rope as you get the rope close to straight.

Pulling the anchor line to vertical, cleating it off and then driving forward with the motor creates a similar effect (turned 90 degrees from the example). When the anchor line is perfectly vertical, it can't generate a horizontal resistance to stop the boat moving forward. The result is any forward force, translates into substantial vertical force before it gets out of alignment enough that it can generate a horizontal force to stop the forward motion of the boat.

So the closer you get the anchor line to vertical, the more force vertical force is created from a relatively small horizontal force.

So if you try simply pulling straight up and there isn't enough wave action to have the rise & fall of the boat pull it up, you can apply a very small forward force to create a lot of vertical force on the anchor line and break it free.

[Dieseldude]

Originally Posted by valhalla360

Actually, it can.

Example: take a 4ft piece of rope and put a 5lb weight in the middle. Grab the ends in each hand and lift the 5lb weight:
- Hold it up with your hands 2 ft apart. Assuming you are a healthy adult, probably not a problem.
- Try and hold it up with your hands 4ft apart so the rope is perfectly straight and horizontal to the ground. No matter how much force you apply, you won't be able to get the rope perfectly straight. The reason is when completely straight and horizontal, the rope can't provide a vertical force component to lift the 5lb weight. The closer you get to straight, the more force it takes.

So you are lifting the same weight but it takes many times as much force applied to the rope as you get the rope close to straight.

Pulling the anchor line to vertical, cleating it off and then driving forward with the motor creates a similar effect (turned 90 degrees from the example). When the anchor line is perfectly vertical, it can't generate a horizontal resistance to stop the boat moving forward. The result is any forward force, translates into substantial vertical force before it gets out of alignment enough that it can generate a horizontal force to stop the forward motion of the boat.

So the closer you get the anchor line to vertical, the more force vertical force is created from a relatively small horizontal force.

So if you try simply pulling straight up and there isn't enough wave action to have the rise & fall of the boat pull it up, you can apply a very small forward force to create a lot of vertical force on the anchor line and break it free.

All that the example of the weight on the rope between hands shows is that the applied direction of the same magnitude of force has an effect. With hands close together, the vertical force transmitted to the weight is greater due to the the initial steeper angle of the rope. Lengthen the rope, and the vertical force as a ratio to the horizontal force is less. A greater portion of the force is doing the unproductive work of stretching the rope. Your arms are providing the same magnitude of force in both cases. This is similar to the distance between the fulcrum of a lever and the load against which the lever is working. Shorten the distance, and more of the applied force is transmitted to the load. Lengthen the distance and less of the force is transmitted to the load. In physics, you do not get something for nothing, you can only optimize something that you already have.

[seandepagnier]

Originally Posted by valhalla360

Actually, it can.

Thank for trying to explain. The gain is huge. I pull in 3-4 ft on the second anchor and it pulls the first one up a few inches.. so you can imagine the mechanical advantage. It is very easy to pull up anchors this way.

In physics, you do not get something for nothing, you can only optimize something that you already have.

a vague statement that happens to apply to many things not only physics.

Even the OP, who has no engine and relies on sculling claims he can get his boat moving at 2 knots and if his boat weighs at least a few tons, the energy it would impart to his anchor ride far exceeds any static force his arms can impart. So what am I missing that makes this be a useful technique for most cruisers?

The boat is moving 2kn. I lock off anchor. The boat just stops. The anchor doesn't really move. I would have to do this many many times over to break the anchor that way.

Using a winch should apply more static force than most engines. This should be true on most boats. So winching a second anchor would be the most powerful way to pull up on a stuck anchor for most boats even if they did have an engine.

Then there is cycling the engine on just for 2 minutes to unstuck an anchor ?! seriously its bad for engine to run short bursts. You only need 10-20 seconds of thrust to break out anchor, much better use case for electric propulsion.

[valhalla360]

Originally Posted by Dieseldude

All that the example of the weight on the rope between hands shows is that the applied direction of the same magnitude of force has an effect. With hands close together, the vertical force transmitted to the weight is greater due to the the initial steeper angle of the rope. Lengthen the rope, and the vertical force as a ratio to the horizontal force is less. A greater portion of the force is doing the unproductive work of stretching the rope. Your arms are providing the same magnitude of force in both cases. This is similar to the distance between the fulcrum of a lever and the load against which the lever is working. Shorten the distance, and more of the applied force is transmitted to the load. Lengthen the distance and less of the force is transmitted to the load. In physics, you do not get something for nothing, you can only optimize something that you already have.

There's a reason I said, pull until it's perfectly straight and horizontal...

Yes, it is demonstrating the impacts of angle on force multiplication.
- With your hands together pretty close to all the tension in the rope is being applied vertically lifting the weight. It's going to be pretty much 5lb plus the weight of the rope (divided by 2 as there are two ends lifting)
- As you get closer to straight and horizontal, there is less vertical component to the tension in the rope, so the tension in the rope must be greater to generate the 5lb lifting force. (in practice the rope will stretch and eventually break before it's perfectly straight and horizontal).

The example is a reverse of the anchoring to demonstrate why the tension in the rope increases.

When anchoring, the force (tension) in the rope is being applied by the sea bottom (which you are hoping will fail) against the buoyancy of the boat near the bow. Assuming you cleated it off once perfectly vertical, the only outside force you are applying is a small force forward on the boat with results in a large increase in the vertical force on the line.

Depending on the actual angles involved, a small 50lb forward force on the boat, can translate into thousands of pounds of additional tension in the anchor line...most of which is a vertical lifting the anchor shank, which hopefully breaks the anchor free.

Yes, there is a bit of stretching involved but unless you get significantly out of vertical, it does increase the force far beyond the forward force you apply with the motor. If you time it right, even the momentum of pulling the boat up to the anchor and quickly cleating it off may be enough to break it free due to the force multiplication of applying a horizontal force to a vertical anchor line.

[rslifkin]

Originally Posted by seandepagnier

Thank for trying to explain. The gain is huge. I pull in 3-4 ft on the second anchor and it pulls the first one up a few inches.. so you can imagine the mechanical advantage. It is very easy to pull up anchors this way.

a vague statement that happens to apply to many things not only physics.


The boat is moving 2kn. I lock off anchor. The boat just stops. The anchor doesn't really move. I would have to do this many many times over to break the anchor that way.

Using a winch should apply more static force than most engines. This should be true on most boats. So winching a second anchor would be the most powerful way to pull up on a stuck anchor for most boats even if they did have an engine.

Then there is cycling the engine on just for 2 minutes to unstuck an anchor ?! seriously its bad for engine to run short bursts. You only need 10-20 seconds of thrust to break out anchor, much better use case for electric propulsion.

A winch giving more pulling power than a typical small sailboat auxiliary is probably true. But it doesn't necessarily take a lot of force to get a well buried anchor out, sometimes you just need to sustain the force long enough for it to dig its way back out of the bottom.



I absolutely agree that short term uses like that are an excellent use case for electric propulsion. But for the boats out there in the world without it, you use whatever tools you've got, and generally go for the fastest or easiest option. Plus, in some cases you may be in an anchorage that requires a few minutes of motoring to get out to a spot where you can hoist the sails anyway, so firing up the motor to get the anchor up is no big deal (think an anchorage with a narrow entrance and the wind aligned to the entrance, so somewhere between impractical and impossible to sail through the entrance).

[valhalla360]

Originally Posted by rslifkin

A winch giving more pulling power than a typical small sailboat auxiliary is probably true. But it doesn't necessarily take a lot of force to get a well buried anchor out, sometimes you just need to sustain the force long enough for it to dig its way back out of the bottom.

I absolutely agree that short term uses like that are an excellent use case for electric propulsion. But for the boats out there in the world without it, you use whatever tools you've got, and generally go for the fastest or easiest option. Plus, in some cases you may be in an anchorage that requires a few minutes of motoring to get out to a spot where you can hoist the sails anyway, so firing up the motor to get the anchor up is no big deal (think an anchorage with a narrow entrance and the wind aligned to the entrance, so somewhere between impractical and impossible to sail through the entrance).

Actually, motoring forward on a vertical anchor line will typically generally create far more tension in the anchor line than a typical winch can apply. Plus most winches risk damage from heavy overloading trying to break an anchor free...typical practice is to cleat the line off once it's vertical.

While the OPs kedging process will work, it's certainly not easier for the typical cruiser who can simply motor forward for a few seconds on a vertical anchor line.

Switching to electric propulsion is unlikely to consider this very limited use case. Even if you plan to immediately deploy the sails as long as it isn't the only use, there will be no harm running the diesel long enough to break the anchor out on rare occasions.

[rslifkin]

Originally Posted by valhalla360

Actually, motoring forward on a vertical anchor line will typically generally create far more tension in the anchor line than a typical winch can apply. Plus most winches risk damage from heavy overloading trying to break an anchor free...typical practice is to cleat the line off once it's vertical.

While the OPs kedging process will work, it's certainly not easier for the typical cruiser who can simply motor forward for a few seconds on a vertical anchor line.

Switching to electric propulsion is unlikely to consider this very limited use case. Even if you plan to immediately deploy the sails as long as it isn't the only use, there will be no harm running the diesel long enough to break the anchor out on rare occasions.

I think winches in this context was referring to kedging against another anchor with a big primary winch, not using the windlass (which isn't designed to pull at maximum power continuously). But yes, motoring against the anchor is absolutely much easier.

[Dieseldude]

Originally Posted by valhalla360

Actually, motoring forward on a vertical anchor line will typically generally create far more tension in the anchor line than a typical winch can apply. Plus most winches risk damage from heavy overloading trying to break an anchor free...typical practice is to cleat the line off once it's vertical.

While the OPs kedging process will work, it's certainly not easier for the typical cruiser who can simply motor forward for a few seconds on a vertical anchor line.

Switching to electric propulsion is unlikely to consider this very limited use case. Even if you plan to immediately deploy the sails as long as it isn't the only use, there will be no harm running the diesel long enough to break the anchor out on rare occasions.

Motoring forward on a vertical cable may tend to rock the anchor out of the mud, since an anchor normally sets at an angle to the mud line. The lateral force will offer some leverage against the angle at which the anchor has set. But overall, applying propulsion power to a vertical cable is the least optimum because propulsive power is horizontal. An angular pull using engines will actually transmit more vertical component to the cable. At 45 degrees, the horizontal and vertical vector components are equal. But if using the windlass, a vertical cable will transmit the most windlass force to the anchor because the windlass force itself is vertical. Of course, a windless will have much less power than will most engines. But then there is propeller slippage when working against the heavy resistance of a firmly planted anchor.

[valhalla360]

Originally Posted by Dieseldude

Motoring forward on a vertical cable may tend to rock the anchor out of the mud, since an anchor normally sets at an angle to the mud line. The lateral force will offer some leverage against the angle at which the anchor has set. But overall, applying propulsion power to a vertical cable is the least optimum because propulsive power is horizontal. An angular pull using engines will actually transmit more vertical component to the cable. At 45 degrees, the horizontal and vertical vector components are equal. But if using the windlass, a vertical cable will transmit the most windlass force to the anchor because the windlass force itself is vertical. Of course, a windless will have much less power than will most engines. But then there is propeller slippage when working against the heavy resistance of a firmly planted anchor.

I don't think you are grasping the physics.

If the anchor line is near vertical, that horizontal force from the propulsion results in a vertical force many times the horizontal force.

Looked up and static bollard testing is somewhere in the vicinity of 25lb per HP, so a 30hp motor should be capable of somewhere around 700lb horizontal force. 100lb is likely to correlate to idle speed.

If you apply 100lb horizontal force with the motor. If the angle of the line (90 being vertical) is:
- 45deg ~ 100lb vertical force and 100lb horizontal force on the anchor shank.
- 85deg ~ 1143lb vertical force and 100lb horizontal force...
- 88deg ~ 2664lb vertical force and 100lb horizontal force...
- 89deg ~ 5730lb vertical force and 100lb horizontal force...
- 89.9deg ~ 57,000lb vertical force (of course in practice, the line is likely to stretch allowing the boat to move forward and changing the angle)

In principal, if you throttle up the motor, you can multiply the above vertical forces by 7. Bigger concern with a vertical line is not applying so much power you drag the bow under or break something.

A winch suitable for a 30-35ft boat may max out at 600-1200lb, so no, it's not going to generate anything close to the vertical force you can get by putting the boat in forward over a vertical anchor line.

[boat driver]

seriously, this is an interesting discussion by persons who do not read.
no engine, so don't mention. Stuck anchor. the rest still lacks lets see, winches available?
sculling oar?
lots of ways to get anchor up if one just thinks how it got there.
easy to make multiple purchase tackle for one.

[Linesledaft]

Just use a trip line to avoid that situation. I set one if I know the bottom is fouled.

[Putt-Putt]

AH yes, grasping the Physics can be a problem.

Often using an analogy proves useful. Let's try.

Here's the set up.

You and your girlfriend are out in the 4x4 for an early rutting season frolic in the backwoods. On the way home you get stuck, big time. You're now a mud slinger.

Not to worry, you grab the 15' chain, spool out the 100' of cable on your new (cheap) winch, sling a large fir tree 100' away with the chain, shackle on the steel cable and signal the girlfriend to tighten the cable. The cable is drawn bar tight, and the winch stalls. The truck goes nowhere.

Half way back to the truck, feeling frustrated you do your best WWE impression of a bounce off of the ropes. Dusting yourself off from the obligatory face plant, you notice that the cable has now drooped. Something must have moved! It wasn't the tree, is was the truck, about an inch and a half.

Retighten, lunge, another couple. Rinse and repeat a dozen times and you're free.

The important parts here are you must use inelastic components, (almost nothing is truly inelastic but steel is way better than nylon) the 100' (the longer the better) bar tight to start with and 2 fixed points. (the tree and truck)

Two paycheques later you replace the winch with a real one, a month later the girl replaced me with a new guy who had a bigger........errr, truck.

Yep, I was the guy with the welts! That was 45 years ago.

From my read of your system you are lacking at least the steel and the 2 fixed points. Feeling that it works may be its only virtue.

My rudimentary engineering skills reveal that if somehow you could apply a 100# force horizontally to your 45º rode, the forces at the anchor shank are 25# both vertically and horizontal.

Think about it, if 100# horizontal resulted in 100# both vertical and horizontal at the anchor, where did the addition 100# of force come from?
If that worked and you could commercialize it, your riches would make Musk look like a pauper.

Then again, except for the girl part, I could be all wrong.

[valhalla360]

Originally Posted by boat driver

seriously, this is an interesting discussion by persons who do not read.
no engine, so don't mention. Stuck anchor. the rest still lacks lets see, winches available?
sculling oar?
lots of ways to get anchor up if one just thinks how it got there.
easy to make multiple purchase tackle for one.

99.99% of cruisers do have an engine, so very relevant.

But even using sails, a sculling oar or even just timing it as you pull the boat up to the anchor line, getting it vertical and then applying a horizontal force is a great way to break out an anchor.

Assuming you aren't solo sailing, using the dingy motor could achieve a similar result without the hassle of setting a 2nd anchor. It's a fall back option but way down on the list of options.

[Dieseldude]

Originally Posted by valhalla360

I don't think you are grasping the physics.

If the anchor line is near vertical, that horizontal force from the propulsion results in a vertical force many times the horizontal force.

Looked up and static bollard testing is somewhere in the vicinity of 25lb per HP, so a 30hp motor should be capable of somewhere around 700lb horizontal force. 100lb is likely to correlate to idle speed.

If you apply 100lb horizontal force with the motor. If the angle of the line (90 being vertical) is:
- 45deg ~ 100lb vertical force and 100lb horizontal force on the anchor shank.
- 85deg ~ 1143lb vertical force and 100lb horizontal force...
- 88deg ~ 2664lb vertical force and 100lb horizontal force...
- 89deg ~ 5730lb vertical force and 100lb horizontal force...
- 89.9deg ~ 57,000lb vertical force (of course in practice, the line is likely to stretch allowing the boat to move forward and changing the angle)

In principal, if you throttle up the motor, you can multiply the above vertical forces by 7. Bigger concern with a vertical line is not applying so much power you drag the bow under or break something.

A winch suitable for a 30-35ft boat may max out at 600-1200lb, so no, it's not going to generate anything close to the vertical force you can get by putting the boat in forward over a vertical anchor line.

Thanks Valhalla, not trying to knock your theory, but I would have to see a vector diagram to see how a lateral force applied to the upper end of a cable would result in strong vertical force on it. Is this because tension is tension, and independent of applied direction? I do know that if I want to lift a weight on a rope, I get better results for my efforts by pulling straight up than I would by pulling sideways. This can be shown by simple vector analysis.