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Old 18-02-2011, 14:45   #1
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Forestay Load Estimates

Hello all, I am in the process of converting my deck stepped mast to a tabernacle system. I am going to use an electric winch to raise and lower. I will need to use two blocks in my situation to allow for complete lowering to the deck. Mast weighs approximately 80lbs but I have no idea how much working load is exerted on the Forestay under sail so I am not sure of what load rating of blocks to get. All suggestions welcome.
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Old 18-02-2011, 15:12   #2
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I'm confused - what are you going to do with two blocks used for lowering the mast that would have those blocks somehow interacting with the loaded headstay when under sail?

As regards working load, figure it's 15-20% of the breaking load of the existing headstay, depending upon how much of a safety factor you want.

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Old 18-02-2011, 16:58   #3
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I am not clear how the load under sail relates to the hardware for lowering the mast.

Are you going to lower the mast underway and with sails up?

b.
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Old 18-02-2011, 17:01   #4
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The weight of the mast plus a suitable fudge factor.
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Old 18-02-2011, 17:32   #5
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I'm confused by your description too. But the forestay load can be estimated from the breaking strength of the backstay. Not from the forestay itself as they are often rather oversize because of torture from sail hanks ... and the inconvenience of having a rig fall into the cockpit.

Blocks involved with the backstay should be rated appropriately. Watch out for perhaps unexpected doubling of loads in odd block arrangements.
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Old 18-02-2011, 17:37   #6
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Use the diameter of the forestay to size the blocks. They are sized according to the max diameter line that will fit. You can go a few sizes up if you want to be safe. They don't have to be "sailing" blocks if you are only going to pull them out once in a while... You may want blocks designed for wire as opposed to rope, they'll probably have steel or aluminum shives instead of plastic.
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Old 19-02-2011, 11:38   #7
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Thanks for all the input. To try to clear the confusion on the block needs, my first block is going in place of my turn buckle to change vertical pull to horizontal lift, since this is actually below deck I need a second (temp) block for elevation so I will have enough lift instead of trying to plug the mast straight forward.
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Old 19-02-2011, 11:49   #8
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What size turnbuckles? Just look up the load rating for your turnbuckles then get a block with the same (or better) rating.
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Old 19-02-2011, 11:49   #9
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I guess I should maybe explain a little further the reasoning behind all of this. I have a 26.5 hunter docked in my back yard. I live on a river that leads to the Chesapeake but I have two bridges that I have to deal with, hence the need for easy up and down. Since it will only be sailed on weekends due to it's size I don't mind leaving the winch as the securing source of the Forestay. Hope this clears things up better.
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Old 19-02-2011, 11:51   #10
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Quote:
Originally Posted by callmecrazy
What size turnbuckles? Just look up the load rating for your turnbuckles then get a block with the same (or better) rating.
Thanks, great logic!
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Old 19-02-2011, 11:54   #11
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Schaefer Marine Hardware - Product Catalog

ouch! not cheap.
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