hi all, winter project on my nacra 5.2 is to try swapping my old 6:1 harken mainsheet system with an equally old ronstan 7:1 system from a tiger shark (18" paper tiger)
i see that many use "S" hooks to hang the top block from the boom hanger and was wondering what loads i should be calculating for buying an S hook and also for making a pigtail to bring the blocks closer together (so i can use the same mainsheet length), 100kg/220lbs? enough?
Last edited by erice; 08/28/0904:21 AM.
eric e 1982 nacra 5.2 - 2158 2009 weta tri - 294
-- Have You Seen This? --
Re: S - hook for upper mainsheet block to boom
[Re: erice]
#189316 08/28/0904:30 AM08/28/0904:30 AM
100kg? How hard do you pull on the mainsheet? 40 - 50 kgs at least, multiply by 7 and then multiply with Pi as a safety factor
5mm or 6mm.
Now why do you want to go for an S hook? If you sail/race a lot and rigging time is very important it makes sense. If you are not stressed while rigging, a shackle is better in my opinion.
Re: S - hook for upper mainsheet block to boom
[Re: Rolf_Nilsen]
#189317 08/28/0904:33 AM08/28/0904:33 AM
50kg x 7 = 350kg plus safety factor 50kg so i need an S hook rated to 400kg, close to a 1000lbs.....
the only S hooks i can see are rated to about 100kg and the snap shackle people post pics of seems identical to the 1 in the shops i see rated at 120kg.....
the shackles that are doing the job now are probably only rated to 120-150kg, divide by 5 - means either i am pulling less than 30kg, possible, or the shackles are very conservatively rated and are working very near their rated values...
edit....i see the muurays snap shackles on pg31 are rated to 1000lbs
I use the same snap shackle as Tony, but to be clear I use it between the main and the boom. My sheet blocks are attached to the boom with a regular shackle (the one you need a screwdriver to open) as I almost never remove them.
Re: S - hook for upper mainsheet block to boom
[Re: erice]
#189336 08/28/0907:53 AM08/28/0907:53 AM
I've had an s-hook straighten out on me and I've seen one other do the same. I feel like the snap shackles are too heavy (unless you can afford the titanium versions) and I just go with a regular shackle now. Keep it simple (and reliable).
Jake Kohl
Re: S - hook for upper mainsheet block to boom
[Re: Jake]
#189369 08/28/0909:07 AM08/28/0909:07 AM
i asked a similar question (or responded to one) a while back. i had many people tell me the s hooks can bend under stress... i said i have never seen that and i have used mine for years...
Guess what.. they were right.. when i upgraded to an 8-1 i bend the hook. BUT there was a larger hook that i was using and it never bent.
I used a snap on the bottom blocks and the s-hook to the boom. I have removed it and now just use a shackle (i spliced a pigtail)
Last edited by andrewscott; 08/28/0909:08 AM.
Re: S - hook for upper mainsheet block to boom
[Re: pepin]
#189380 08/28/0909:45 AM08/28/0909:45 AM
I use as well a loop of 3mm double braided dynemma with a plastic ball at the end. It certainly holds more than 500kg and you can open it with gloves.
I had 4mm dynemma (single braid) spliced around the boom bail (where the upper blocks attach) and it lasted 3 sails before it broke from the rubbing. Next time i will have to use a shackle on the bail.. but i felt that kind defeated the puropose... granted the bail is not smooth.. its a flat piece of stainless...
Re: S - hook for upper mainsheet block to boom
[Re: Smiths_Cat]
#189408 08/28/0911:56 AM08/28/0911:56 AM
Watch out with the little plastic balls. I don't trust them anymore since I used one at the spinnaker tack (pass a loop through the tack and slide the ball through): I saw it explode in pieces under load.
I now use a small dyneema loop I spliced. It took me while to get the damn thing right. It has a sliding eye on one side which is closing up under load, and a turk knot variation on the other side to get through the eye. Like the attached image (sourced on the net, mine is not that neat!)
All the rope manufacturer sell you those loops for a small fortune but explanations on how to do them properly are non-existent...
Last edited by pepin; 08/28/0912:01 PM.
Re: S - hook for upper mainsheet block to boom
[Re: erice]
#189424 08/28/0902:35 PM08/28/0902:35 PM
50kg x 7 = 350kg plus safety factor 50kg so i need an S hook rated to 400kg, close to a 1000lbs.....
the only S hooks i can see are rated to about 100kg and the snap shackle people post pics of seems identical to the 1 in the shops i see rated at 120kg.....
the shackles that are doing the job now are probably only rated to 120-150kg, divide by 5 - means either i am pulling less than 30kg, possible, or the shackles are very conservatively rated and are working very near their rated values...
edit....i see the muurays snap shackles on pg31 are rated to 1000lbs
Correct, I did an experiment with an oversize suitcase scale to see how much I cna actually pull, 30kgs is good, at 38kgs I tore the skin off my hands ( dam forgot about the gloves ), using legs as well I could get low 40's but and this is a big but, it was in ideal conditions and I'm sure on a boat would be less.
Good fun experiment to do though.
Re: S - hook for upper mainsheet block to boom
[Re: waynemarlow]
#189427 08/28/0902:42 PM08/28/0902:42 PM
When I sailed the new Viper in July it came with the Dyneema hank to attach the upper block to boom. It worked very nice and is light weight. I do like that setup.
Philip USA #1006
Re: S - hook for upper mainsheet block to boom
[Re: Jake]
#189488 08/29/0911:07 AM08/29/0911:07 AM
Alec and I had an S-Hook straighten out on us on the 6.0 at the beginning of a C-100 in a blow. Sheet in, get on the wire, BANG! Hook straightened. Don't recall it being a wimpy hook either. In that blow, not much left to do but limp into a cove while things flogged. I tend to use snap shackles a lot, but in most cases I use regular shackles now. Crew gives me crap for making sure they're tight, too.
they are easy to make.. the biggest issue is making sure the knot doesn't come undone... which is unlikely. I made some myself and tested with a 32:1 block set up and damn near broke my deck and the blocks and the "softie" was fine. There is no way that the force would exceed this on one of our boats. Abrasion can be an issue but provided there are no sharp edges then there shouldnt be an issue
Re: S - hook for upper mainsheet block to boom
[Re: pepin]
#189660 08/31/0910:01 AM08/31/0910:01 AM
Watch out with the little plastic balls. I don't trust them anymore since I used one at the spinnaker tack (pass a loop through the tack and slide the ball through): I saw it explode in pieces under load.
I now use a small dyneema loop I spliced. It took me while to get the damn thing right. It has a sliding eye on one side which is closing up under load, and a turk knot variation on the other side to get through the eye. Like the attached image (sourced on the net, mine is not that neat!)
All the rope manufacturer sell you those loops for a small fortune but explanations on how to do them properly are non-existent...
Very cool... the one in the image doesn't appear to have a lock stitch.. i take it you add a lock stitch?
Re: S - hook for upper mainsheet block to boom
[Re: ]
#189717 08/31/0901:54 PM08/31/0901:54 PM
Very cool... the one in the image doesn't appear to have a lock stitch.. i take it you add a lock stitch?
For a straight bury (which that looks like), I'd add a lock-stitch. A self-secured eye (such as a brummel splice) wouldn't need it. I'd also taper and bury the end of the button knot.
Regards, Eric
Re: S - hook for upper mainsheet block to boom
[Re: Isotope235]
#189719 08/31/0902:01 PM08/31/0902:01 PM
which part are you saying to lock stitch? can't do a brummell splice or lock stitch on the splice because because you need to loosen the splice when it goes over the knot and to be able to undo it
Last edited by PTP; 08/31/0902:03 PM.
Re: S - hook for upper mainsheet block to boom
[Re: PTP]
#189722 08/31/0902:23 PM08/31/0902:23 PM
![[Linked Image]](http://bosunsupplies.com/images/157-0.jpg)
