Csail
N/A
Is there any way to stop it, the boat is long keel but just rocks like mad compared to others in the anchorage.
Rocking at anchor
- Thread starter Csail
- Start date
M
MarkG
Guest
Have u tried the flopper stopper?
It appears to be a weighted bucket with the bottom cut out to form a one way valve, hung from the boom to one side or the other of the boat.
It appears to be a weighted bucket with the bottom cut out to form a one way valve, hung from the boom to one side or the other of the boat.
Talbot
Well-Known Member
Check that you have not overloaded the ends of the ship, as this will increase the probability of rocking.
FullCircle
Well-Known Member
If you use two road cones one inside the other but suspended about a foot apart, then hanging off the boom that will help damp the motion.
I assume (as does MarkG) that by rocking you mean rolling from side to side?
Or do you mean pitching, as Talbot is alluding to, which is movement from stem to stern?
I assume (as does MarkG) that by rocking you mean rolling from side to side?
Or do you mean pitching, as Talbot is alluding to, which is movement from stem to stern?
pcatterall
Well-Known Member
I have used just a bucket full of water on the boom. The bucket is heavy when out of the water and wieghs nothing when in and so damps the rolling. But also consider how to control effect of contrary wind.
BobE
Well-Known Member
If you have two Spinnaker booms.. ( Some of us use a two pole system!!)
A bucket of water on each rigged as far out as you can should make a significant difference... Buckets should be just in the water...
Cheers Bob E..
A bucket of water on each rigged as far out as you can should make a significant difference... Buckets should be just in the water...
Cheers Bob E..
Poignard
Well-Known Member
Under what sort of conditions? Maybe she is a bit "tender". Do you have a lot of weight high up? Or it could be a design thing. Have you asked other owners of your type of boat if they experience it?
saltwater_gypsy
Well-Known Member
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Sometimes it helps to rig a line from the anchor chain to the midship cleat. You can then adjust the system to bring the bows into the swell and convert rock and roll into upsy downsy.(that may not be the completely correct terminology!!)
rwoofer
Well-Known Member
I think you will find that no weight in the ends does the opposite. This is why racing boats take weight out of the ends - it allows the boat to go up and over waves with minimal effort, otherwise they would plough through which kills speed.
All down to the angular momentum.
All down to the angular momentum.
Salty John
Well-Known Member
I'm with Talbot on this one: Adding weight in the ends definitely leads to hobby-horsing. Moving weight from the ends to the centre, and low down, relieves hobby-horsing. This was always the case with my boats, anyway.
pcatterall
Well-Known Member
Arn't they both right?? less weight in the bow allows it to rise with rather than crash through waves when moving forward but will aid hobby horsing when at anchor??
cliffordpope
Well-Known Member
I think it depends on the weight in the ends in relation to the buoyancy at that point. If you have less weight than buoyancy then the boat will tend to pitch quickly, because there will be nothing to resist the upward pressure of each wave.
At the other extreme with excess weight over buoyancy you simply have a see-saw, but probably with a longer period than in the other case.
I always understood the optimum was for each section along a boat to have a rough balance of deadweight v. buoyancy.- ie if you sawed the boat up into a series of connected portions they would all float level, with no hogging or sagging.
At the other extreme with excess weight over buoyancy you simply have a see-saw, but probably with a longer period than in the other case.
I always understood the optimum was for each section along a boat to have a rough balance of deadweight v. buoyancy.- ie if you sawed the boat up into a series of connected portions they would all float level, with no hogging or sagging.
mikemonty
Well-Known Member
[ QUOTE ]
Arn't they both right?? less weight in the bow allows it to rise with rather than crash through waves when moving forward but will aid hobby horsing when at anchor??
[/ QUOTE ]
As usual there are no easy answers!
If the boat has little weight at the ends its motion (natural frequency) is going to be faster, so if it falls into phase with shorter waves it will pitch more.
If you have all your gear stowed at the ends its moment of inertial will be greater,its natural frequency lower, and it will pitch more in longer waves when it starts to get into phase with them.
So you can play tunes (or rather avoid harmonising!) - in a short chop move all your gear to the ends, and in a longer wave, bring all the heavy gear into the centre of the boat.
Arn't they both right?? less weight in the bow allows it to rise with rather than crash through waves when moving forward but will aid hobby horsing when at anchor??
[/ QUOTE ]
As usual there are no easy answers!
If the boat has little weight at the ends its motion (natural frequency) is going to be faster, so if it falls into phase with shorter waves it will pitch more.
If you have all your gear stowed at the ends its moment of inertial will be greater,its natural frequency lower, and it will pitch more in longer waves when it starts to get into phase with them.
So you can play tunes (or rather avoid harmonising!) - in a short chop move all your gear to the ends, and in a longer wave, bring all the heavy gear into the centre of the boat.
Talbot
Well-Known Member
[ QUOTE ]
I think you will find that no weight in the ends does the opposite. This is why racing boats take weight out of the ends - it allows the boat to go up and over waves with minimal effort, otherwise they would plough through which kills speed.
All down to the angular momentum.
[/ QUOTE ]
Thats what I said !!!!!!!!!!!!!!
I think you will find that no weight in the ends does the opposite. This is why racing boats take weight out of the ends - it allows the boat to go up and over waves with minimal effort, otherwise they would plough through which kills speed.
All down to the angular momentum.
[/ QUOTE ]
Thats what I said !!!!!!!!!!!!!!
rwoofer
Well-Known Member
I sounds like Mike Monty probably has the right answer. I got my understanding of this phenomena from Frank Bethwaite's book, High Performance Sailing, which is a bit dinghy orientated. He recommends in light winds with waves/swell that the crew move towards the ends of the boat to keep the rig as still as possible ie. to stop hobby horsing which kills the airflow over the sails.
Csail
N/A
sorry , should have been clearer, she is rolling side to side while at anchor. Forward sailing she sails through anything.
lw395
Well-Known Member
Anchoring with the keel in the mud works very well!
Seriously though, your two options are to try to change the natural roll frequency, by adding/ removing weight high up or low down or perhaps moving mass out towards the gunwhales.
Its going to be hard to make areal difference.
Or, add damping of some sort.
As an obscure possibility, try changing your anchor rode arrangement, maybe this is how wave energy is coupled into the hull? Try using a longer rode and/or a weight on the rode.
I found my boat much steadier with about 10kg of lead 5-10m down the (mostly rope) anchor rope.
Do other examples of the same design have the same problem? If not, focus on the differences, however small.
HTH, do let us know if you find an answer that works.
Cheers,
Seriously though, your two options are to try to change the natural roll frequency, by adding/ removing weight high up or low down or perhaps moving mass out towards the gunwhales.
Its going to be hard to make areal difference.
Or, add damping of some sort.
As an obscure possibility, try changing your anchor rode arrangement, maybe this is how wave energy is coupled into the hull? Try using a longer rode and/or a weight on the rode.
I found my boat much steadier with about 10kg of lead 5-10m down the (mostly rope) anchor rope.
Do other examples of the same design have the same problem? If not, focus on the differences, however small.
HTH, do let us know if you find an answer that works.
Cheers,
damo
Well-Known Member
I find that the bow on a longkeeler tends to pay off more easily, so you can end up across the wind and waves. Apart from the other suggestions, I have successfully used a riding sail (storm sail hoisted upside down on the back stay) to weathercock the boat, and also dropped a kedge astern to keep it in line with the wind. I have also been on a boat where the skipper hung a kayak from the swung-out boom.
