I received from West a pre-spliced spin halyard with wichard shackle that was 'custom' length as it was cockpit-led and longer than their standard ones. Due to the bracket/sheave arrangement in my spinnaker sock I needed a larger inside dimension on the halyard shackle than was provided on the new halyard. This led me to discover that my 3/8" Sta-set halyard, which is rated at around 4400 working lbs, has a wichard shackle that is rated at 2640 lbs. How do I determine the loading imposed by the spinnaker and whether that shackle is up to the task? Am I negligent to 'assume' that hardware that is incorporated into a 'packaged' halyard would be of a similar load rating? The symmetrical spinnaker is of mystery origin and make that came with the boat, (C&C 34). Replacement of the new shackle would require the removal of the 'bar' in order to get it out of the eye splice....its a nice job that they did....just seems, maybe a little undersized.
- Status
Observation, Not Answer
I was looking through my Defender catalog and noted blocks rated for 3/8 line have a similar breaking strength as your shackle. I think line needs to be more conservative due to wear, UV degredation, etc and also for ease of handling; I think 3/8 is the recommended minimum. I guess I'd call the distributor and ask, or just ask WM where they came up with that sizing. Rick D.
I was looking through my Defender catalog and noted blocks rated for 3/8 line have a similar breaking strength as your shackle. I think line needs to be more conservative due to wear, UV degredation, etc and also for ease of handling; I think 3/8 is the recommended minimum. I guess I'd call the distributor and ask, or just ask WM where they came up with that sizing. Rick D.
Try this
The tension is pretty terrific, as you'll find when you try to pull in the tack line under full spin. It's the other end of the halyard and is well into the thousands of pounds. Should it break, the spin goes in the drink and the halyard comes flying out of the mast, requiring you to rethread it down the mast. That's tough and may require dismasting. I suggest you replace the thing with the right equipment and sleep well at night.
The tension is pretty terrific, as you'll find when you try to pull in the tack line under full spin. It's the other end of the halyard and is well into the thousands of pounds. Should it break, the spin goes in the drink and the halyard comes flying out of the mast, requiring you to rethread it down the mast. That's tough and may require dismasting. I suggest you replace the thing with the right equipment and sleep well at night.
Working Load Versus Breaking Load
Equipment is generally rated as a working load limit, then there is a breaking load limit. The difference is the factor of safety. Somewhere in between is the limit at which the material will plastically deform (permanent deformation). My guess is the breaking load is about the same as the line load but the working load is half that. dave
Equipment is generally rated as a working load limit, then there is a breaking load limit. The difference is the factor of safety. Somewhere in between is the limit at which the material will plastically deform (permanent deformation). My guess is the breaking load is about the same as the line load but the working load is half that. dave
A Comment
Dale does not say what size his boat is, but my experience with a masthead rigged 30' Ron Holland racing boat was that it was only just able to support a heavy man at the masthead. Indeed one of the old IOR stability tests was to pull the boat down so the mast was horizontal and measure the righting force developed at the mast head. Well if a 30 footer was rated at about 250 lbs and, of course, spinnakers can do this also, then I would expect the spinnaker halyard tension to be measured in the low hundreds of pounds. I conclude the shackle will be more than adequate.
Dale does not say what size his boat is, but my experience with a masthead rigged 30' Ron Holland racing boat was that it was only just able to support a heavy man at the masthead. Indeed one of the old IOR stability tests was to pull the boat down so the mast was horizontal and measure the righting force developed at the mast head. Well if a 30 footer was rated at about 250 lbs and, of course, spinnakers can do this also, then I would expect the spinnaker halyard tension to be measured in the low hundreds of pounds. I conclude the shackle will be more than adequate.
Re: Don's Comment...
Follow up. I just looked at WM catalog, Master, 2003, Page 847. Sta-set X 3/8 is rated for the same as Sta-set 7/6. You might have Sta-set X. In any event the 4400 pounds you quote is for X. From the chart, it appears the line sizing is correct. However, note it is breaking load, NOT working load. That is a very different thing. Bottom line: I'd run that chute without angst. Rick D.
Follow up. I just looked at WM catalog, Master, 2003, Page 847. Sta-set X 3/8 is rated for the same as Sta-set 7/6. You might have Sta-set X. In any event the 4400 pounds you quote is for X. From the chart, it appears the line sizing is correct. However, note it is breaking load, NOT working load. That is a very different thing. Bottom line: I'd run that chute without angst. Rick D.
A suggestion!!
Have all your eye splices made as a long splice so that the shackle can be removed whenever you want without cutting the line. I've done this with all mine. To answer your question though, the shackle is more than up to the loading. I would have suggested that you down size the halyard for less friction in the sheeve and less weight aloft. A fast hoist on the spinnaker is very important.
Have all your eye splices made as a long splice so that the shackle can be removed whenever you want without cutting the line. I've done this with all mine. To answer your question though, the shackle is more than up to the loading. I would have suggested that you down size the halyard for less friction in the sheeve and less weight aloft. A fast hoist on the spinnaker is very important.
Thanks all...
Alan: The particular Wichard shackle that West used came with that retainer 'bar' that not only keeps it from falling free from the eye in a blow, but prevents it from being removed without surgery... or I'd have done that to begin with. (May still do it.) Rick: Yes, its Sta-set 'X', the stiff stuff that likes to kink up at inconvenient times... John D.: I had thought that the working strength was 50% of the breaking strength of line...(?) Don A: The masthead rigged symmetrical spinnaker came with the C&C 34,'(which was perhaps not made clear). For calculation, it would seem to me that the loading could be greater from aft (down wind / pitch pole) than from abeam (more heel)... Dave/Bill O. Between the lines in my original post, I was searching for a means to calculate the 'working load' of the halyard. If I can determine the working load, the breaking strength will be moot for both hardware and line....I'll definately sleep better. It was my local West rep that originally pointed out the difference in load capacity.... He placed a call to their rigging department and we are both waiting on an explanation of their hardware selection 'logic'. At any rate, it'll be trial by fire this weekend as the spin will fly free of the sock for the first time in at least five years... Thanks again to all.
Alan: The particular Wichard shackle that West used came with that retainer 'bar' that not only keeps it from falling free from the eye in a blow, but prevents it from being removed without surgery... or I'd have done that to begin with. (May still do it.) Rick: Yes, its Sta-set 'X', the stiff stuff that likes to kink up at inconvenient times... John D.: I had thought that the working strength was 50% of the breaking strength of line...(?) Don A: The masthead rigged symmetrical spinnaker came with the C&C 34,'(which was perhaps not made clear). For calculation, it would seem to me that the loading could be greater from aft (down wind / pitch pole) than from abeam (more heel)... Dave/Bill O. Between the lines in my original post, I was searching for a means to calculate the 'working load' of the halyard. If I can determine the working load, the breaking strength will be moot for both hardware and line....I'll definately sleep better. It was my local West rep that originally pointed out the difference in load capacity.... He placed a call to their rigging department and we are both waiting on an explanation of their hardware selection 'logic'. At any rate, it'll be trial by fire this weekend as the spin will fly free of the sock for the first time in at least five years... Thanks again to all.
Sheet Loading Formula
The “HARKEN” website includes some good information, including Genoa Sheet Loading formula: SL = SA x (V x V) x 0.00431 where: SL = Sheet Load in pounds SA = Sail Area V = Wind Speed in knots
The “HARKEN” website includes some good information, including Genoa Sheet Loading formula: SL = SA x (V x V) x 0.00431 where: SL = Sheet Load in pounds SA = Sail Area V = Wind Speed in knots
- Status