Thimble necessary for mainsheet? - SailNet Community
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post #1 of 18 Old 02-17-2014 Thread Starter
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Thimble necessary for mainsheet?

I am finally replacing the 4:1 mainsheet system I have on my 1985 27' Pearson. The bearings fell out of what was probably the original Harken fiddle block. I'm replacing with a Garhauer 30-06 US and a 30-01 US combo (thanks to Guido at Garhauer for awesome help) for less than half the price of a comparable Harken system. The original setup had a splice (a clamp ) with a thimble on the standing end of the mainsheet where it is attached to the becket of the fiddle block+cam cleat assembly (see photo).

Is the thimble preferred/necessary to reduce line stress? Is there a better thimble to use than the teardrop shape? Finally, who do you recommend to do custom splicing? I am looking at Defender since they have good prices on rope, but they want $18 for a custom splice. I'm toying with the idea of buying a fid with the rope purchase and trying it myself, but don't know if I am up to the effort or challenge.
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post #2 of 18 Old 02-17-2014
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Re: Thimble necessary for mainsheet?

I can't really tell from the pic, but it seems that block could chafe right through an unprotected line. Probably why the thimble is used.

That thimble doesn't look spliced, but rather sewn, which is easier and ironically can be stronger.


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Re: Thimble necessary for mainsheet?

I disagree. The becket on that fiddle block is made of Marlon and has a radius for line. A thimble is not needed. You can attach the line to the becket with a bowline or anchor hitch. I prefer a short splice myself. If you ever chafe through the cover, you can always cut the splice off and tie a bowline. My mainsheets all wear out from overstress long, long, before the splice begins to show wear.

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Re: Thimble necessary for mainsheet?

Quote:
Originally Posted by GeorgeB View Post
....The becket on that fiddle block is made of Marlon and has a radius for line......
Well, I said I could not tell from the pic. You must know this about that piece, as I can't see how the pic helped. If you're right about it having a plastic radius, a knot would certainly be fine.


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Re: Thimble necessary for mainsheet?

The load and movement at that point in the line is so small it really doesn't matter. And as George pointed out the becket is large enough to spread the load some anyway.

In an absolute sence it probably reduces max load on the line by a few (2-3) percent. But it's lost in the noise.

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Re: Thimble necessary for mainsheet?

For what its worth, all knots will reduce the breaking strength of a line by a minimum of 30% to as much as 60%. I believe a bowline is in the 40% range.

Should be moot, as the specs for breaking strength of our lines considers the excess necessary for this.


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Re: Thimble necessary for mainsheet?

I've always liked the look of a nice splice, even when a knot would do. If need to remove, just make the eye longer and feed the eye thru the becket and the end thru the eye to make a loop.
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post #8 of 18 Old 02-17-2014 Thread Starter
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Re: Thimble necessary for mainsheet?

Thanks for the input guys. Here is a slightly better pic of the setup. You can see the thimble setup hidden partially by the mainsheet. The becket is very small in diameter and under load I imagine it will put some significant kink stress on the line. So who is a good source for custom splicing?
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post #9 of 18 Old 02-17-2014
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Re: Thimble necessary for mainsheet?

Get a fid and splice it yourself. Useful skill to learn and you'll soon save the price of the fid(s).

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post #10 of 18 Old 02-17-2014
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Re: Thimble necessary for mainsheet?

I've done splicing myself; it isn't that hard. You can also try ZZ4TGA (I hope I got his username right!)

- Jim
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