Snatch block for misc. use? - SailNet Community
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post #1 of 16 Old 02-21-2010 Thread Starter
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Snatch block for misc. use?

Forgive me if I use the wrong nomenclature, but after googling last night I think what I'm looking for is a snatch block. I'd like to have a block/pulley setup that I can use to hoist things easier. Like dealing with the dinghy, or I saw somebody on the dock using one to go up their mast. Can anybody recommend a general purpose setup for me? I tried looking on ebay for an old wood one, that would be cool, but I really have no idea what I'm looking for. If I have 2 pulleys in the block at the top, do I have 1 at the bottom? I guess I should have walked over and talked to the guy on his mast to see his setup.

Any ideas? Where to buy?

Thanks!

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post #2 of 16 Old 02-21-2010
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You have a few things going on here, so I'll break it out:

1. i wouldn't use a snatch block when my life depends on it. A snatch block's sides open to allow insertion of a line without threading it from the end. Mostly used for running rigging applications like spinnakers. I'd a use a traditional captive Harken or Schaeffer block. No wood.

2. Assuming that you weigh 200#, you need at least a 4:1 purchase to cut the load to something manageable if going up the mast. Even with 4:1, that means that you're pulling 50# on each pull. That can get to be a lot. Assuming that you have a tang on the single block at the bottom (where you are sitting), you'll have 4:1... but I would try to go to 5:1 or higher.

3. Unless you plan to hold the line in your teeth when you get to the mast head , you need a cleat on the lower block, so that means a built-in cam cleat in the block.

Summary: There are better, safer ways to get to a masthead. I personally use a traditional bosun chair and get a helper to hoist me up.

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post #3 of 16 Old 02-21-2010
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A snatch block is like a regular block but instead of you having to find the end of the line and pass it through the pulley the block opens up, splits in half, so you can put it on a line in the middle.

West Marine sells them along with most other marine stores.

What you may be referring to is a handy billy.
This is two blocks with one or more pulleys each that when connected with a line give you a mechanical advantage.
If you look a traditional boom vang setup you can get the idea.

Yes two at the top and one at the bottom is a standard configuration.
You will need a becket somewhere however which is just a loop that lets you tie off the line.

Using a halyard to haul this deal to the top of the mast then you can use the mechanical advantage to haul yourself up is a common practice.
You need a lot of line.
For example if you have two pulley's on top and one on the bottom block with a becket you will have 4 to 1 advantage but for a 50' mast would need over 200' of line.

Also you have to be very, very car full of the blocks used and the line used if your life is on the line, literally.
Unless you are very comfortable in rigging such things you may be better off with a commercial solution like Top Climber etc.
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post #4 of 16 Old 02-21-2010
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Quote:
Originally Posted by Sabreman View Post
3. Unless you plan to hold the line in your teeth when you get to the mast head , you need a cleat on the lower block, so that means a built-in cam cleat in the block..
This is a really important point but I personally would never trust a cam cleat with my life, they slip, the line could be wet or slimy, the teeth worn etc.

I would tie off the line to whatever the bottom block was tied off to, probably the harness.

The other issue is that folks who do this take other precautions:

1. They know the rig and the condition of all the parts including spreaders. If something goes wrong and you can't go up or down it can be a puzzle as to what to do. Don't ask how I know this. If the rig has not been inspected in years you don't go up it period.
2. You never use the shackle on the halyard. Use a bowline.
3. Make sure someone else is around.
4. Bring a light line with you so someone on the ground can tie off the tool you forgot.
5. Bring a short length of line or special strap to tie yourself of to the mast when appropriate.
6. You may need to rig some kind of foot stirrup if you need to get to the very top of the mast as the blocks and halyard and sitting posture may not get you high enough.
7. And of course you test all this stuff out three feet off the deck before you go all the way up.

If you are going to just have someone winch you up you need two helpers. One to winch and one to tail
even if you have a self tailing winch.

Last edited by davidpm; 02-21-2010 at 11:19 AM.
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post #5 of 16 Old 02-21-2010
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Umm... I seriously doubt it is a snatch block you want.

The snatch block is a great block for changing the position of things line spinnaker sheets, but not something I'd generally recommend for hoisting dinghies or going up the mast. A snatch block is really useful for altering the lead of a line without requiring the line be re-reeved, since a snatch block can be placed on a line without requiring the bitter end be passed through it—through use of a swiveling or hinged cheek plate.

A snatch block looks like this:



What you're probably thinking of is a block-and-tackle, which would be far more useful for hoisting dinghies or for pulling oneself aloft. As for how many sheaves you'd need on either end, it depends on how long a rope you have and how much mechanical leverage you're looking to get.

The greater the mechanical advantage, the longer a rope you will need—a four-to-one block and tackle needs a bit more than four times the length of the greatest height it will be used on, a six-to-one requires SIX times the height. For a 35' mast, a 4:1 would require 150' of line, a 6:1 225' or so.

You can buy a block and tackle in many places. A good source for a 4:1 block and tackle would be to buy a Garhauer Boom Vang setup.



If you're going to use a block and tackle to lift yourself aloft... I'd second the precautions that DavidPM has pointed out. I'd also point out that you'll probably want to have a bag, bucket or pouch attached to the bosun's chair or harness that you can tail the block-and-tackle line into. If you do not do this, and merely let the line fall to the deck—you may find that when you want to come down, that the line is snagged on the deck hardware and that you are effectively trapped aloft.

Using the proper terminology would really make communicating much easier.

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Last edited by sailingdog; 02-21-2010 at 11:24 AM.
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post #6 of 16 Old 02-21-2010 Thread Starter
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I'm learning the terminology as fast as I can!

So I'm not looking for a snatch block after all, just a block and tackle. I like the boom vang setup. I'm just looking for a general purpose setup, for hoisting the dinghy aboard, or if I had to lift something heavy for whatever reason. In a pinch I could go up the mast with it, but that's really not what I'm asking for.

Thanks for all the good advice. I'm usually the guy who learns about tailing the block and tackle line in to a bag/bucket/pouch the hard way.

Is that boom vang setup overkill for just hoisting a dinghy? Is there a more economical alternative?

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post #7 of 16 Old 02-21-2010
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Remember if you're using it to go up the mast at 5 to 1 that's over 200' of line on a 40' mast. Set up properly it works well and this is basically what I use.

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Quote:
Originally Posted by n0w0rries View Post
I'm learning the terminology as fast as I can!
I'd highly recommend you get Dave Seidman's book, The Complete Sailor. Cuts the learning curve quite a bit, and I have it as required reading for new crew who want to learn to sail aboard my boat.

Quote:
So I'm not looking for a snatch block after all, just a block and tackle. I like the boom vang setup. I'm just looking for a general purpose setup, for hoisting the dinghy aboard, or if I had to lift something heavy for whatever reason. In a pinch I could go up the mast with it, but that's really not what I'm asking for.

Thanks for all the good advice. I'm usually the guy who learns about tailing the block and tackle line in to a bag/bucket/pouch the hard way.

Is that boom vang setup overkill for just hoisting a dinghy? Is there a more economical alternative?
How heavy is the dinghy?? The boom vang setups from Garhauer are quite reasonably priced for sailboat gear.

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her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

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post #9 of 16 Old 02-21-2010
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post #10 of 16 Old 02-21-2010 Thread Starter
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My dinghy weighs 90lbs per the specs. I don't sail it much, and it has a nice boom vang (picture below)--this should answer nicely?


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