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Rope for gybe preventer on 30ft boat

8K views 19 replies 9 participants last post by  tdw 
#1 ·
I have a gybe preventer I've been using on 25ft boats, a 50ft length of about 400lb breaking strain rope with a 400lb-rated snap shackle on the end. I can't remember the exact type of rope I bought but it's quite stretchy.

At the time I bought it, I thought stretchy would be a good thing. But now I think it means that, if it were to snap, there would be tremendous recoil.

So I have two questions :

What breaking strain would be ideal for a 30ft boat? and

What type of rope would be ideal?
 
#3 ·
Odd alright, don,t use a gybe preventer myself but sailed on a 32ft sloop a couple of years ago in rough weather round the Isle of White, UK.
As far as I could tell the Gybe preventer was much the same as the headsail sheets, 5/8" or there abouts. Attached to the end of the boom and could be rigged fairly handily by some clever mechanism I didn,t take much note off.
There was a recent thread about Gybing with was a lot of discussion about a gybe brake, seemed a safer bet to me.
Safe sailing
 
#4 ·
At the time I bought it, I thought stretchy would be a good thing. But now I think it means that, if it were to snap, there would be tremendous recoil.
The Idea of the Preventer it to keep the BOOM for making that Fast swing to the other side of the Boat so Stretch is not wanted, make the preventer the same as the Main Sheet as the load can be the same.
 
#6 ·
So Mark...Did you get that boat? You keep on posting tantalizing questions...

fwiw my preventer used to be a fender line - but have moved to a 1/2" nylon double braid (8,000lb?). Would also be interested in more experienced sailor "best practices".

Thought about the brake, but want to keep things simple and clutter-free. Otherwise too many lines!
 
#7 ·
Hi Paul,

The situation is that I test sailed the boat, and the survey is tomorrow. Until the survey is completed satisfactorily, I don't want to count my chickens before they are hatched, so to speak.

When the transaction's completed I'll post a pic or two.

I have fender line for the gybe preventer right now so it sounds like I need to get something stronger, or a boom brake! A boom brake might not be much more expensive than 60ft of 8000lb rope!
 
#8 ·
Mark,

On another site sometime ago, there was a discussion on what to use as a preventer. Most seemed to favor a stretchy line to absorb the intial shock of the wind getting on the back side of the sail in a jibe...the thought being that you wanted to minimize the shock on the sail and rig, while at same time preventing that high speed acceleration and immediate stop on the other side associated with the gybe. There are two issues here...first the unexpected acceleration of the boom across the boat which could hurt or kill someone, and second, the damage associated to the sudden stop of the sail and boom at the end of the gybe. A strong line that isn't going to break will prevent the sling shot effect that you are concerned with. Some stretch in the preventer will lessen the shock. I haven't had reason to test it, but based on that discussion, I also use 1/2 inch double braid nylon rated at 8600 lbs breaking strength on a 32 ft. boat. A second area of concern was whether the preventer should be attached to the outward end of the boom, or at some midpoint on the boom. There was no consensus here, although the end of the boom seem to be slightly favored, but many with mid boom travelers attach to mid boom (I use mid boom). Most preferred leading the preventer line on each side forward through the bow cleat and then back to the stern cleats so that the preventer can be controlled from there.

Perhaps some of the bluewater sailors on this site can give better guidance.
 
#9 ·
We had a thread going on this last year but I'm damned if I can find it now. The Wichard was mentioned and I threw in the thing we use which is a climbers thinga me whatsit. Someone else then suggested a climbers thinga me whatsit with horns. It is rigged and works in much the same fasion as the Wichard but at 10% of the price.

I've not found the horny wee beastie as yet but the gelded version has worked for us within reason. I say within reason cos I've not had need to do a crash bang in over 20 knots.

Anywho .. to answer the OQ ... we use sheet line. Stretchy would be a worry I would have thought.

 
#10 ·
"A second area of concern was whether the preventer should be attached to the outward end of the boom, or at some midpoint on the boom. There was no consensus here, although the end of the boom seem to be slightly favored, but many with mid boom travelers attach to mid boom (I use mid boom). "

On another discussion it was suggested to have a line, attached to the boom end, ending in a bowline at the mid-boom point. Some shock cord would hold it to the boom when not in use. You could attach your gybe-preventer's shackle to the bowline.

What do you think?
 
#12 ·
CMI rescue-8 descender
Cmi Gear Rescue 8 Black AL Better/stronger ones are available in plated steel.

TDW - the one you show if the loop slips 'over' it will jam tight. The 'ears' on the rescue-8 prevent this.
Rich, good man, thank you. I'm still trying to find one of those horned or eared versions. We've not had a problem with ours but I take your point and better to be safe than etc etc.

Looking at the Wichard it doesn't look a great deal stronger than either what we have now or the CMI so I doubt stronger is required. One point though, when used as a boom break the lines go through the descender very differently than when it used for climbing, most importantly it is also used upside down.
 
#13 · (Edited by Moderator)
My preventer is a long bit of 6mm rope from one stern cleat, along to the amidships cleat, up to the mainsheet fitting on the boom and down the other side and back.

At the boom fitting i have tied a loop and the loop is attached to the fitting with a couple of turns of 4 mm line that should have a breaking strain of a few hunderd kilograms.

I bought a mountaineers "descender" like the photo of the red one in the posts above for about $10 but I have stopped using it as this system is simpler and beter.

The idea is not to stop the boom flying across under all circumstances. It is to stop it flying across at the same time as the boat gybes accidently (a second or 2 later is fine). Or to stop the boom coming across from a wave and rolling etc. :)

I want the 4mm line to break before the boat is pinned down aback.

In the video below you can see how mine is set up - its not in closeup, but you'll get the idea :) Its the light coloured lines either side of the main sheet at the boom. I am running pretty deep downwind and you can see the boat rolling so this is where a preventer is good. Not so you can sail by the lee with thumb in bum and mind in neutral!



I can't get the YouTube video to embed properly :( Can someone tell me how?

Mark
 
#15 ·
I can't get the YouTube video to embed properly :( Can someone tell me how?

Mark
No. Its a secret. Unless you know the secret handshake. :p

Click on "Embed". That opens up a box with the vid details, select all that. Copy. Paste into your SailNet reply.

I can do it, so being an Australian is not an excuse. :)
 
#14 ·
My two cents:

- stretchy is good as it absorbs dynamic loads, IMHO
- stronger is better, just make sure you can release the preventer easily and in a controlled manner when you have to
- snap shackles are quick and convenient, but they break at the most inopportune times (like, in the middle of an uncontrolled jibe), so if you're going to use one go oversized. (I have a snap shackle on one side and I tie a knot on the other because the shackle broke)
- I prefer end-boom preventers as you're less likely to break the boom, especially if you drag the boom in the water as you roll to and fro, which happens sometimes in downwind sailing when the seas get up

My preventer is set up with a line port and starboard from the cockpit to big blocks on the bow and from there outboard back to the shrouds where the lines are attached when not in use. There is a single, stretchy line attached to a bail at the end of the boom that is long enough to run to the gooseneck where it's cleated off when not in use. To rig the preventer join the port or stbd line to the one on the boom and tension it from the cockpit. The disadvantage of this set up is that you need to reset the preventer after a jibe/tack.

In sizing the line....go to a good rig shop and ask what they recommend (and why).
 
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