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Old 11-11-2010, 16:27   #1
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Boom 'Snubber / Preventer'

I hope "snubber" is the right term.

I want to rig a "snubber"/preventer on the boom of a Pearson C23.

This boat is "cat" rigged, i.e. single mast, dinghy style, keel stepped, in the bow, no standing rigging.

She performs really well on a reach, and also downwind, but with such an enormous single sail it is important to be able to hold the boom out, especially with following seas. (With no spreaders, or rigging, the boom will go as far forward of the mast as you wish, or dare!

As we use the boat primarily for day sailing, I had thought of dismounting the boom vang, and using it for a preventer.
Alternatively, I have been thinking of making up some sort of continuous line that can be used on port and starboard tacks alike.

Has anyone any ideas on this project?

Brian.
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Old 11-11-2010, 16:57   #2
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Originally Posted by beemister View Post
As we use the boat primarily for day sailing, I had thought of dismounting the boom vang, and using it for a preventer.
Although that's a common practice in dinghies, it's not recommended in larger boats. The problem is that when you need to jibe you'll be caught without a vang, and the result is that you'll sky the boom. Your rig might be just over the line for using this effectively, at least in anything beyond light air.

All you need to rig a preventer is a snatch block and an appropriate length of line.

The term "snubber," by the way, is more generally applied to a length of line used at anchor to absorb the shock of a chain rode.
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Old 11-11-2010, 17:33   #3
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Do you have a picture of your boat? Cat rigs often have problems with preventers because there is no good place to lead the line. You want to get it as close to perpendicular to the boom as possible to get the best mechanical advantage which means leading it as far forward as possible. On some cat rigs, the mast is all the way forward so you can't really lead a line forward. Since you can't put a line in tension to do it, that leaves you with being able to put something in compression which is definitely trickier.

Do you have shrouds or a freestanding rig? If you don't have shrouds, you can actually let the sail out past 90 degrees which will greatly decrease the chance of gybing.
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Old 11-11-2010, 18:00   #4
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Do you have shrouds or a freestanding rig? If you don't have shrouds, you can actually let the sail out past 90 degrees which will greatly decrease the chance of gybing.
Good point, but that all depends on the type of gooseneck.
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Old 11-11-2010, 18:10   #5
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I'll beg ignorance on cat rigged boats, but won't running with the sail in front of the mast (sailing by the lee) begin the "death roll" motion?
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Old 11-11-2010, 18:26   #6
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OK, Connemara is a sloop not a catboat.

But I use a preventer on a run to... umm... prevent a crash gybe.

Basically, you put a turning block on the toerail about even with the mast or maybe a bit forward, clip a line to the end of the boom, down through the block and back to the cockpit to a cleat.

Increasing or easing the tension on the line let's you adjust how far sternward the boom can come, while the main sheet keeps it from going too far forward. In my case, of course, the shrouds keep it from going too far forward.

If you need to gybe suddenly, you can still do it. You just cast the line off the cleat, turn, and then once things have settled down, re-rig the whole affair on the other side.

I actually find the trick is useful anytime the wind is much abaft the beam and a sea is running. It prevents the sail and boom from slapping back and forth as the wind force changes when the boat rises and falls.

Not my idea, of course, but I forget where I got it from.

Connemara
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Old 11-11-2010, 20:41   #7
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Bemister, I sent you a PM.

Steve
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Old 11-11-2010, 22:12   #8
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Good points, everybody!
I think you about covered all my problems....
There is no standing rigging, so no shrouds,
The mast is way forward, so getting the correct angle is difficult to say the least,

Thanks, Steve, for the boom brake idea, I will check tomorrow on the feasability of this, but I think the angles are all wrong...

Oh, and to make things worse, there is no toerail...
The boom goes out so far the main sheet lies on the safety line in light wind, (the traveler is at cockpit seating level, in front of the hatch.
The original design had the topping lift adjustment at the gooseneck end of the boom, that got changed right away!
Keep the ideas coming, I'll try to get some photos.

Thanks again.

Brian.
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Old 12-11-2010, 02:41   #9
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I use a long bit of 10mm line the middle of which is tied to the mainsheet fitting to the boom and then each side of line is run amidships around the amidships mooring cleat and back aft tied off to the aft mooring cleats.

At the middle attachment point I a bit of 4mm line doubled over so it will break before the boom

Actaully between the line and the thin line is a mountaineering figure 8 descender ($10) to act as a boom break, but the fixed method is better so I have tied off the Figure 8 thing and dont use it.
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