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Preventors do I need one

Jul 27, 2011
4,223
Bavaria 38E Alamitos Bay
A slightly back-winded mainsail from being off course, being held tight in place by the preventer will exert little force from momentum even in moderate air, as it should not be moving. I doubt it would pull anything out of the deck, etc., just carrying the static load. I suppose the bad act is where a very strong gust hits the boat from the lee side. Such as a williwaw when passing Pt Conception on starboard tack, on a broad reach, continuous wind from the NW. Still no shock loading, however.
 
Last edited:

dLj

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Mar 23, 2017
1,336
Hunter 30 Snug Harbor, Lake Champlain
I would rather attach a fender to a solid tubular system than a wire lifeline. I would rather attach the fender to to padeye with backing plate rather than the stanchion base. Even the connection of a chainplate would be a stronger connection than a stanchion.
What is the difference between connecting to the base of a stanchon and a padeye with backing plate, if the stanchon is mounted with a backing plate?

For sure, you need to use break-away points that won't rip your top rail off along with the stanchions in the solid rail application. You've mentioned several ways in an earlier post.

dj
 
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Likes: jssailem
Oct 22, 2014
13,888
CAL 35 Cruiser moored EVERETT WA
A sudden gust with a wind directional change. A squall. The change in forces as you slide off a 12 foot swell. The dipping of your boom in the back of a wave. All sorts of sudden changes can exert forces that if not controlled can make your day a bad one.
 
Mar 26, 2011
2,733
Corsair F-24 MK I Deale, MD
A slightly back-winded mainsail from being off course, being held tight in place by the preventer will exert little force from momentum even in moderate air, as it should not be moving. I doubt it would pull anything out of the deck, etc., just carrying the static load. I suppose the bad act is where a very strong gust hits the boat from the lee side. Such as a williwaw when passing Pt Conception on starboard tack, on a broad reach, continuous wind from the NW. Still no shock loading, however.
In fact, there is always a shock load from the sail filling on the opposite side.

In this case they broke a hefty Dyneema strop. Even in lighter winds, I suspect the force is much more than you think. I broke a preventer in just 20 knots once on my 34-foot cat. The line was a little old but looked capable. I only had it in place as a convinience. It was an eye opener, because it was a surprise.

The math says a preventer needs to be about as strong as you genoa hardware (it's been researched), which could be a little or a lot, depending on the wind.

Preventer broke, man dies.
Investigation Clipper Race Fatality
 
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Likes: Will Gilmore
Jun 25, 2004
242
Hunter 306 Pasadena MD
After reading about them for years, I rigged one for the first time on a solo trip last month when I had an all-day downwind run. It went from maybe 2/3 out on the boom, down to the mid-ship docking cleat (through the hole under the cleat) and back to the very sturdy arch. It has always seemed to me that the angle would be much better if it's run to the mid-ship cleat rather than to the bow cleat. Here's a picture. Comments?
preventer.jpeg
 
Mar 26, 2011
2,733
Corsair F-24 MK I Deale, MD
Wing on wing? Just don't do it. Slowest point of sail and dangerous.
Unless you are flying a chute, I will bet spending money it is the best VMG downwind for your boat as soon as hull speed begins to limit reaching, if you can set the sails properly (whisker pole). This is commonly misunderstood and as a result, most people aren't good at it. Whether it is dangerous depends on many factors; as I said, for me is it something I reserve for rivers too narrow for jibing. It's safe for that.
 
Dec 28, 2015
1,017
Laser, Hunter H30 Cherubini Tacoma
There is a boom brake listed on Craigslist Seattle/Tacoma if anyone local is looking for one
 
Oct 19, 2017
6,559
O'Day 19 Littleton, NH
Most of the time that I have wanted a preventer or used one when I had one, the wind was light and the waves were rolling. Without a stronger wind to keep the sails filled against the roll, a wave is what usually brings the boom swiping inboard on a down hill arc.

There are times when the preventer just keeps the boom from pumping in time with a short period roll.

-Will (Dragonfly)
 
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May 17, 2004
2,916
Beneteau Oceanis 37 LE Havre de Grace
I see wing on wing as a useful tool in the toolbox, and a preventer as a risk mitigation strategy for it. Where I sail in the northern Chesapeake the waves aren’t usually big enough to roll the boat much, and the wind switches are small enough that I accept the risk of WoW without a preventer. If I were sailing in waves big enough to dip the boom in the water I’d probably reevaluate those risks. I can set a whisker pole and carry it easily with a TWA of 155, around the same cutoff where the jib gets blanketed by the main. It works ideally from there to TWA of 175. The main won’t accidentally jibe until TWA of about 170 on the other side, so for me there’s an acceptable margin of error for rolling, wind switches, or momentary inattention.

Whether WoW is faster than reaching and jibing will depend on a boat’s polars, but it’s hard to find them for pure jib and main configurations. There’s a set at https://nakedsailor.blog/wp-content/uploads/2019/12/Hanse_388_Speed_Guide.pdf for a Hanse 388 that matches my experience with other boats pretty well, basically showing a slight advantage for WoW. Watch a Star class race and it’s pretty clear they favor WoW. Most PHRF non-spin races will show the same. And as thinwater points out there are times when a channel or other navigation restrictions make it the best tool for the job.
 
Dec 25, 2000
4,666
Hunter Passage 42 Shelter Bay, WA
Info on boom preventers from MD School of Sailing:
Boom Preventer
Must give this preventer rigging a try. Looks a bit more versatile than how I do it. With enough line perhaps set it up much like how a boom brake works. That way in a downwind tack change I can control the boom swing to the new tack. Our boat is too heavy for the boom brake according to the maker.
 
Jul 1, 2010
793
Seaward 25, Catalina 350 Erie, Pa
Concerning the discussions above mentioning anchor points, possible boom damage from hitting the water, boom damage from anchoring a preventer anywhere other than the end of the boom, etc... None of this really is an issue with using a boom brake or figure 8, as it gives away, if necessary but makes the jibe manageable. Here's a the article I found that originally gave me the idea to use a figure 8 on one of our boats:


As far as wing on wing, with a poled out genoa, we love that point of sail when conditions permit, and that's the direction we want to go. Set the autopilot, kick back and relax. Usually faster to the destination, anyhow.
 
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Mar 26, 2011
2,733
Corsair F-24 MK I Deale, MD
Must give this preventer rigging a try. Looks a bit more versatile than how I do it. With enough line perhaps set it up much like how a boom brake works. That way in a downwind tack change I can control the boom swing to the new tack. Our boat is too heavy for the boom brake according to the maker.
As opposed to simply centering the boom with traveler and mainsheet before or during the jibe? If it's blowing, particuary on large boats, center the boom first, then release rather quickly as soon as the boom shifts to prevent rounding up. Nice and smooth.
 
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Likes: jssailem
May 17, 2004
2,916
Beneteau Oceanis 37 LE Havre de Grace
If it's blowing, particuary on large boats, center the boom first, then release rather quickly as soon as the boom shifts to prevent rounding up. Nice and smooth.
That’s pretty much what we do with our mid-boom sheeting setup. We run with the traveler centered. Sheet in while turning DDW, when apparent wind is lowest. It’s ideal if you can slowly ease the sheet as the sail fills on the new side, softly “catching” the boom and slowing it as it gets to the new running angle.
 
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Dec 28, 2015
1,017
Laser, Hunter H30 Cherubini Tacoma
Must give this preventer rigging a try. Looks a bit more versatile than how I do it. With enough line perhaps set it up much like how a boom brake works. That way in a downwind tack change I can control the boom swing to the new tack. Our boat is too heavy for the boom brake according to the maker.
You can get some pretty big figure eights defenders to make your own
 
Dec 28, 2015
1,017
Laser, Hunter H30 Cherubini Tacoma
My issue with wing on wing is I can’t figure out how to keep my whisker pole from rubbing on my stay
 
Oct 22, 2014
13,888
CAL 35 Cruiser moored EVERETT WA
What about rigging a tweeker from the pole forward to the deck? It will keep the pole from getting to the stay.