dunedin
Well-Known Member
Rope lashings often give a smoother and finer alignment - particularly as this one will vary as the boom swings
Mainsheet advice needed please!
- Thread starter James W
- Start date
Graham_Wright
Well-Known Member
He is right. It is well known and accepted in engineering circles. Ball bearings are fine for continuously rotating loads but they are a disaster for shock loads. The shock caused the balls to impact the races. Roller bearings are not quite so bad.
rogerthebodger
Well-Known Member
It does depend on the block having a swivel included. If not you are right a rope lashing may be better but rope of subject to chafe which I personally try to avoid
Laser310
Well-Known Member
i am guessing that the tail goes to a winch?
if so, it might be more purchase than is needed.
How far from the end of the boom are those blocks? obviously, the further forward, the more purchase you need.
the forward angle to the traveler doesn't help either...
in any case, fewer turns will mean less friction and you may not loose much of the effective mechanical advantage if you reduce the purchase a bit.
i agree with using a lashing or soft shackle for the twisted block, or anything that lets it align better.
if so, it might be more purchase than is needed.
How far from the end of the boom are those blocks? obviously, the further forward, the more purchase you need.
the forward angle to the traveler doesn't help either...
in any case, fewer turns will mean less friction and you may not loose much of the effective mechanical advantage if you reduce the purchase a bit.
i agree with using a lashing or soft shackle for the twisted block, or anything that lets it align better.
Laser310
Well-Known Member
I'm definitely swopping to dyneema, anything for a friction free life!
is there a clutch?
make sure you don't downsize so much that the line won't work in the clutch.
There are ways to deal with that problem in a halyard, but they are not practical on a sheet.
TernVI
Well-Known Member
The aft block on the boom looks to need moving forwards so the sheet doesn't touch the pram hood.
The forward block on the boom could be replaced with a 'fiddle block'.
The rope could be thinner or tapered.
The mast foot block is an issue as others have noted..
The deck organiser is a prime suspect.
If the rope is touching the deck at any point, that contributes an amazing amount of friction. Raising it on little strips of half round stainless can help.
Or raise the deck oraginser on a spacer.
I assume a mid -boom 7:1 sheet on such a boat is going to need a winch?
I would investigate using a much simpler tackle and a better winch if needed.
Unfortunately not much can be done cheaply.
The forward block on the boom could be replaced with a 'fiddle block'.
The rope could be thinner or tapered.
The mast foot block is an issue as others have noted..
The deck organiser is a prime suspect.
If the rope is touching the deck at any point, that contributes an amazing amount of friction. Raising it on little strips of half round stainless can help.
Or raise the deck oraginser on a spacer.
I assume a mid -boom 7:1 sheet on such a boat is going to need a winch?
I would investigate using a much simpler tackle and a better winch if needed.
Unfortunately not much can be done cheaply.
Laminar Flow
Well-Known Member
I would assume that all depends on the loads involved.
A 40' boat would likely have a 400 sqft main. Rigs are generally designed to a loading of 1 lbs/ sqft = 400lbs load on the main sail. I triple block = 1/3rd load per bearing = 133 lbs, which is peanuts by the way, and as far as I am concerned there is not really anything static on a sailing vessel; there is always some movement in a sheet. Consequently, there is no one locked pressure point on a sheave bearing.
BTW, I think ball bearing blocks are a fine thing.
James W
Well-Known Member
This is amazing, thanks to all for your ideas and input. Lots to think about.....
pvb
Well-Known Member
Absolutely right!
rogerthebodger
Well-Known Member
Here is the Engineering practice from SKF
Static loading sizing
SKF
The calculation for dynamic loading on ball bearings
SKF
Or take a ball bearing on a hardened plate the hit it with a hammer or put a heavy load onto the ll bearing.
This is exactly how the hardness of a metal is measured. Its call brinell effect
In the Brinell hardness test, an optical method, the size of indentation left by the indenter is measured. In contrast to the likewise optical Vickers method, which involves a pyramid-shaped indenter being pressed into a specimen, the Brinell method uses a spherical indenter.
Its
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Daydream believer
Well-Known Member
I would have called that a Rockwell hardness test & the technology came out of the ark so nothing rocket science being quoted there & proves SFA really.
What does prove things, is the practicality of actual use & most experienced sailors (whether part time prostitutes or not) know that decent quality high load bearing blocks, are far nicer to use than cheapo plain bearing. You can argue all you like but that is fact.
Obviously if they are not set up properly then no block will perform correctly. i would suggest that the OP's system is a prime example of cat's cradle. Perhaps he might be better to first consider the number of roves he really needs, then the size & quaity of block, giving due regard to loading. Then sheet type, (Those sheets are shot) diameter etc. the blocks need to be rigged to align themselves to the sheet loads at all boom angles & the OP needs to look for friction points at the organisers & rubbing points on the deck. The track car should be examined for free running, along with the pullies & control lines to it.
Finally the method of hauling the mainsheet & jamming it. An incorrect clutch, or poorly maintained clutch, will cause lots of friction. It will soon ruin the mainsheet or cause firring which will create friction elsewhere. Winches that have not been serviced for years do not help either.
So it is not just a case of throwing money at one item & i am sure that the OP has guessed this. It needs a full overhaul starting from scratch & it cannot really be done on a forum as easily as it can from on board.
Years ago, I rigged my last boat myself, after rebuilding it. I was quite proud of the job, until I saw an identical Stella, that had just been rigged by "Rig Magic" from the Orwell. I would suggest that the services of a proff rigger is sometimes well worth the expense
Where is Brent Swain when we need him?
What does prove things, is the practicality of actual use & most experienced sailors (whether part time prostitutes or not) know that decent quality high load bearing blocks, are far nicer to use than cheapo plain bearing. You can argue all you like but that is fact.
Obviously if they are not set up properly then no block will perform correctly. i would suggest that the OP's system is a prime example of cat's cradle. Perhaps he might be better to first consider the number of roves he really needs, then the size & quaity of block, giving due regard to loading. Then sheet type, (Those sheets are shot) diameter etc. the blocks need to be rigged to align themselves to the sheet loads at all boom angles & the OP needs to look for friction points at the organisers & rubbing points on the deck. The track car should be examined for free running, along with the pullies & control lines to it.
Finally the method of hauling the mainsheet & jamming it. An incorrect clutch, or poorly maintained clutch, will cause lots of friction. It will soon ruin the mainsheet or cause firring which will create friction elsewhere. Winches that have not been serviced for years do not help either.
So it is not just a case of throwing money at one item & i am sure that the OP has guessed this. It needs a full overhaul starting from scratch & it cannot really be done on a forum as easily as it can from on board.
Years ago, I rigged my last boat myself, after rebuilding it. I was quite proud of the job, until I saw an identical Stella, that had just been rigged by "Rig Magic" from the Orwell. I would suggest that the services of a proff rigger is sometimes well worth the expense
Where is Brent Swain when we need him?
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mikegunn
Well-Known Member
I’m afraid you’re wrong. A Rockwell “C” hardness tester uses an inverted pyramid shaped indenter. The size of the indent is measured as the average across the diagonals and calculated from a chart.I would have called that a Rockwell hardness test & the technology came out of the ark so nothing rocket science being quoted there & proves SFA really.
What does prove things, is the practicality of actual use & most experienced sailors (whether part time prostitutes or not) know that decent quality high load bearing blocks, properly rigged & set up, are far nicer to use than cheapo plain bearing. You can argue all you like but that is fact.
Where is Brent Swain when we need him?
Mike
Laminar Flow
Well-Known Member
As most things it depends also on the application.
For mast sheaves I most likely would not use ball bearings, nor would I use them for running backstays. Neither of these applications is particularly prone to shock- loading either, unless you run your boat into a low bridge.
I once built a nice set of teak faced triple blocks for running back stays. They were specked to the breaking load of 3/8th cable. Of course they didn't have ball bearings.
The first time I used ball bearing blocks I was blown away by the ease with which one could adjust the sheets. I doubt they wear out all that often and if they did they tend to be in places that are easily accessible.
For mast sheaves I most likely would not use ball bearings, nor would I use them for running backstays. Neither of these applications is particularly prone to shock- loading either, unless you run your boat into a low bridge.
I once built a nice set of teak faced triple blocks for running back stays. They were specked to the breaking load of 3/8th cable. Of course they didn't have ball bearings.
The first time I used ball bearing blocks I was blown away by the ease with which one could adjust the sheets. I doubt they wear out all that often and if they did they tend to be in places that are easily accessible.
pvb
Well-Known Member
The voice of experience!
Daydream believer
Well-Known Member
You would not use a Brinnel test on ball bearings , roller cages & the like because it is for soft material. that is why I assumed Rockwell.
But i am only into limited model engineering so I will bow to greater experience. & stand corrected
Channel Sailor
Well-Known Member
triple and single I would agree. But would not advise moving any of the blocks on the boom forward, unless the manufacturer (or a designer) of the boom says it would be ok. The boom size might be close to tolerance, so moving blocks forward could over stress it.
Also suggest a few options: swap for roller bearings instead of plain, The single aft block on the boom could be larger diameter. Swap out that deck tidy small diameter plain roller for something bigger diameter and maybe roller. Swap the foot block for a larger diameter and fix the swivel on it is it articulates properly. Wash the main sheet to soften it up.
I reckon this could be a quick fix, investigate if you can go down a size on the mainsheet line size, maybe use a hi tech product. It appears to be on a winch so handling might not be an issue.
The cleat on the bottom triple could have been original design before the spray hood was installed. I reckon that deck tidy was not originally for the mainsheet with that size of line.
The two blocks on the boom are probably there the spread the load across two rather small pop riveted D rings. That much purchase and on a winch could be a lot of load on one D ring mid boom sheeted.
savageseadog
Well-Known Member
Ball bearing blocks are the way to go for the most important sail control on the OP's boat, forget about it being over the top or anything better is better. I'd look very carefully at the diameter of the sheet line as well as the outer's condition which looks furry to me. Also look at the mast foot block which looks as if it should be better set up as already suggested, it needs to fully articulate, a spring would stop it from dropping down and possibly jamming when the sheet slackens.
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PetiteFleur
Well-Known Member
I also fitted ball bearing blocks with a jammer on my 33' boat - it made a big difference especially with a new mainsheet.
penfold
Well-Known Member
I agree with the majority view that ball bearing blocks will reduce friction loads, but be sure you're sitting down when you look at the price of BB blocks that size, never mind triple sheave ones! The sheet does look ready for replacement. The forward turning block might be usefully moved onto the shackle/eye on the mast foot, it will give a better lead. Does not having a kicking strap/vang not cause problems when furling the main? The one time I sailed with a mast furler it was very fussy about the angle of the boom when furling.
Norman_E
Well-Known Member
Are the fixings for the blocks riveted to the boom? if they are screwed to it I would move the forward double block to a point just aft of being directly above the traveller with the boom centred. Is that a 14mm mainsheet? If so change it for 12mm. I changed the original 14mm mainsheet on my 45 foot boat to good quality 12mm double braid and it made a big difference as far as friction was concerned. If you need to buy any new blocks I found Selden ones like these very satisfactory. Selden Plain Bearing Block 70mm PBB70