How to stop swing on mooring
- Thread starter hdhr289
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TS,
What's the difference between mooring & anchoring? The mechanics remain the same. the bow is hooked to a line, the only difference is in scope. In anchorages, in calm conditions & maybe some tidal currents, a shorter scope works better to reduce swing. Doesn't this also sound more like a mooring set?
CR
What's the difference between mooring & anchoring? The mechanics remain the same. the bow is hooked to a line, the only difference is in scope. In anchorages, in calm conditions & maybe some tidal currents, a shorter scope works better to reduce swing. Doesn't this also sound more like a mooring set?
CR
Another 'trick' to dampen swinging when on a mooring or anchor is to use a bridle ... a 2-part pendent attached 'back-from-the-bow' and so arranged that the 'connection' to the mooring pendent is AT near the waterline and 'under the bow'. How it works is that when the boat begins to swing, one side of the bridle will tighten or take up strain before the other side and will 'tend' to keep the boat straighter to the wind.
This is a mooring/anchor technique that is becoming more common in the 'hurricane' prone areas; and, many boats who moored/anchored this way in St. George harbor in the island of Granada during hurricane Ivan didnt wind up beached on shore as did the majority of boats which did not.
The mechanism with the bridle, affects a 'function of stability', especially for boats with high freeboard
Here's a diagram of how the bridle is attached ... and needs 'chocks' or hawse holes to prevent chafe and other boat damage. You also have to pull the bridle in under the bow so that the bridle is fairly taught. The bridle in effect lowers the angle of the rode. Not all boats will have their 'swing' dampened, you have to do a trial before you use this method:
This is a mooring/anchor technique that is becoming more common in the 'hurricane' prone areas; and, many boats who moored/anchored this way in St. George harbor in the island of Granada during hurricane Ivan didnt wind up beached on shore as did the majority of boats which did not.
The mechanism with the bridle, affects a 'function of stability', especially for boats with high freeboard
Here's a diagram of how the bridle is attached ... and needs 'chocks' or hawse holes to prevent chafe and other boat damage. You also have to pull the bridle in under the bow so that the bridle is fairly taught. The bridle in effect lowers the angle of the rode. Not all boats will have their 'swing' dampened, you have to do a trial before you use this method:
My two cents
In a mooring field or at anchor, as long as most are swinging together, its not a bad problem. After sitting out in a couple of small hurricanes, I have a 5lb mushroom anchor that I lower from the stern until it hits the bottom, give it a couple of more feet of scope and tie it off. It doesn't stop the swing but slows it down considerably. It just dampens the swing.
I might try the stern anchor setup, looks interesting.
In a mooring field or at anchor, as long as most are swinging together, its not a bad problem. After sitting out in a couple of small hurricanes, I have a 5lb mushroom anchor that I lower from the stern until it hits the bottom, give it a couple of more feet of scope and tie it off. It doesn't stop the swing but slows it down considerably. It just dampens the swing.
I might try the stern anchor setup, looks interesting.
Here is a little offbeat solution I played with for a while, had some limited success.. for your "entertainment", Ill post what I tried..
I had a Mac 26S on a mooring a few years ago and in some wind conditions, it would do some fairly wild swinging, even somewhat violent banging in higher winds. I tried a bunch of stuff and never did really solve the problem. I had tried a riding sail or sorts but found that in gusty winds, it did almost nothing. Im guessing that anyone who has success with a riding sail is in much steadier winds than I had. What made the most difference (but still didn’t completely solve the problem) is at least a little interesting.
I had sat on the boat and observed the pattern it makes in the swing and the illustration below shows what I saw at least on my boat.
The swinging occurs because the boats center of resistance in the water is behind the boats center of resistance in the air and this is not stable when the bow is pointed into the wind as the bow wants to fall off. This is what caused the boat to go from "1 to 2" in the diagram above in the first place. Add to this the lift of the hull and you get everything needed for an unstable system.
One thing I noticed is that the bow of the boat moves a LOT during the swinging. Also, if you add some drag to the stern, you tend to move the underwater center of effort backwards and this exaggerates the instability caused by the the air center of effort being forward of the underwater center of effort.
So I added under water DRAG at the BOW as this does two things which in theory at least should be positive. It moved the underwater center of drag forward which helps with the initial stability problem and it also dampens the bow movement. Interesting that a second anchor off the bow also tends restrict the bow side to side movement.
I had added the drag bucket shown in the pictures below and would just clip it to the bow eye strap. Since you’re trying to move the boat underwater center of effort forward, the rudder and outboard should both be out of the water and I found this did help.
As mentioned, the drag bucket didn’t completely solve the problem but it made way more difference than the anchor sail off the back or any sort of offset bridle arrangement I had tried.
I had a Mac 26S on a mooring a few years ago and in some wind conditions, it would do some fairly wild swinging, even somewhat violent banging in higher winds. I tried a bunch of stuff and never did really solve the problem. I had tried a riding sail or sorts but found that in gusty winds, it did almost nothing. Im guessing that anyone who has success with a riding sail is in much steadier winds than I had. What made the most difference (but still didn’t completely solve the problem) is at least a little interesting.
I had sat on the boat and observed the pattern it makes in the swing and the illustration below shows what I saw at least on my boat.
The swinging occurs because the boats center of resistance in the water is behind the boats center of resistance in the air and this is not stable when the bow is pointed into the wind as the bow wants to fall off. This is what caused the boat to go from "1 to 2" in the diagram above in the first place. Add to this the lift of the hull and you get everything needed for an unstable system.
One thing I noticed is that the bow of the boat moves a LOT during the swinging. Also, if you add some drag to the stern, you tend to move the underwater center of effort backwards and this exaggerates the instability caused by the the air center of effort being forward of the underwater center of effort.
So I added under water DRAG at the BOW as this does two things which in theory at least should be positive. It moved the underwater center of drag forward which helps with the initial stability problem and it also dampens the bow movement. Interesting that a second anchor off the bow also tends restrict the bow side to side movement.
I had added the drag bucket shown in the pictures below and would just clip it to the bow eye strap. Since you’re trying to move the boat underwater center of effort forward, the rudder and outboard should both be out of the water and I found this did help.
As mentioned, the drag bucket didn’t completely solve the problem but it made way more difference than the anchor sail off the back or any sort of offset bridle arrangement I had tried.
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On my 07 H-36 did swing a lot until I added 100' chain and now I swing very little and don't even notice the swing any more and sleep very good knowing we are secure with good holding with my 35lb delta and 100' chain.
I did try a anchor sail once and did not think it helped much.
Nick
On my 07 H-36 did swing a lot until I added 100' chain and now I swing very little and don't even notice the swing any more and sleep very good knowing we are secure with good holding with my 35lb delta and 100' chain.
I did try a anchor sail once and did not think it helped much.
Nick
Because if you are on a mooring, in a mooring field, and put out extra anchors, you're gonna have boats around you highly upset when you swing differently than they do, if for no other reason.
The bridle suggestion from Rich H makes the most sense from what I've seen.
And I understand his problem. My boat "Hunts" also on a mooring or at anchor, Fulll keel, cutaway forefoot- it's just a fact of life.
And at least he has an appropriate make of boats- a Hunter-grin
Yes the newer Hunters do that. On a mooring it should not be a problem but at anchor it may may pull your anchor out with a resulting anchor drag if it fails to reset. A riding sail might be a remedy but if you do do not have a backstay you are back to square one. Just make sure you have enough swinging room and keep an anchor watch in winds over 20 knots.
Kind of to summarize:
1. Something off the back - Good: Stops YOUR swing Bad: May allow others to swing into YOU!
2. Bridle - needs definition: Rich's or my link? Rich's is a short bridle used by many skippers with all chain rode to basically avoid chafe and . Compared to my link which I originally got from a Pardey book which consists of running a MUCH longer line from the bow rode (either chain or rope) to a sheet winch and essentially deliberately "cocking" the boat one side or the other.
3. Sail "stuff" - get a boat with a mizzen or haul up one of those aft stay things.
4. Find a big enough or empty enough anchorage...
Any other ideas? Beats trying to cut down your freeboard.
1. Something off the back - Good: Stops YOUR swing Bad: May allow others to swing into YOU!
2. Bridle - needs definition: Rich's or my link? Rich's is a short bridle used by many skippers with all chain rode to basically avoid chafe and . Compared to my link which I originally got from a Pardey book which consists of running a MUCH longer line from the bow rode (either chain or rope) to a sheet winch and essentially deliberately "cocking" the boat one side or the other.
3. Sail "stuff" - get a boat with a mizzen or haul up one of those aft stay things.
4. Find a big enough or empty enough anchorage...
Any other ideas? Beats trying to cut down your freeboard.
Although not much help on a mooring, it is a Hunter "design feature", the slow oscillation helps work the anchor deeper into the bottom
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