- Oct 22, 2014
- 21,759
When the weather turns winter foul, do you?
The subject of preventers is focused on holding the boom in place so it does not sweep across the boat wacking crew heads, or carrying your crew off the boat, dumping them into the deep. It seems an easy fix. Just tie the boom to the side of the boat.
When you start to examine the methods and forces involved, many sailors will find the process challenging unless you are an engineer with a deep knowledge of mechanical engineering and a mastery of the sailboat design. One such individual is Kurt Zinsmeyer. His work on the "design of preventers" was recently shared on the Attainable Adventure Cruising website (morganscloud.com).
I found that on my 35-foot boat, the tension on the preventer would be 1040 lbs. I use a bow turning block, and the estimated Total Force at the Preventer Turning Block will be 2,053 lbs. A safety factor of 5-1 would need a line at least 5/16ths diameter with a breaking strength of 8100 lbs.
This depends on how my preventer runs from the end of the boom to a bow cleat, through a strong enough turning block, and back to the cockpit. If I shorten the line, reduce the size, or attach it to a mid-deck cleat, the forces increase exponentially. That is why preventers are not recommended to be secured to the rail or center boom amidships.
Of course, if you are waiting till spring, this discussion likely is moot. On the other hand, should you find yourself caught on the water sailing into a squall, using a preventer just come in handy.
It is worth discovering the use of this safety sailing tool
A. Immediately start packing your foulies and head to the boat for some excitement.
B. Pause over a cup of java/tea and wonder why you're hesitating. Am I getting too old for this?
C. Take one look at the wind and rain hitting the window pane, grab the comforter, pull it over your head, mumbling wake me next summer.
One of the joys of sailing is doing it when the waters are less crowded. If you are feeling the call to get your face sprayed with winter-chilled wind-carrying water as it rises over the bow and you see your bow dip into the next wave, then this thread is for you. The subject of preventers is focused on holding the boom in place so it does not sweep across the boat wacking crew heads, or carrying your crew off the boat, dumping them into the deep. It seems an easy fix. Just tie the boom to the side of the boat.
When you start to examine the methods and forces involved, many sailors will find the process challenging unless you are an engineer with a deep knowledge of mechanical engineering and a mastery of the sailboat design. One such individual is Kurt Zinsmeyer. His work on the "design of preventers" was recently shared on the Attainable Adventure Cruising website (morganscloud.com).
I found that on my 35-foot boat, the tension on the preventer would be 1040 lbs. I use a bow turning block, and the estimated Total Force at the Preventer Turning Block will be 2,053 lbs. A safety factor of 5-1 would need a line at least 5/16ths diameter with a breaking strength of 8100 lbs.
This depends on how my preventer runs from the end of the boom to a bow cleat, through a strong enough turning block, and back to the cockpit. If I shorten the line, reduce the size, or attach it to a mid-deck cleat, the forces increase exponentially. That is why preventers are not recommended to be secured to the rail or center boom amidships.
Of course, if you are waiting till spring, this discussion likely is moot. On the other hand, should you find yourself caught on the water sailing into a squall, using a preventer just come in handy.
It is worth discovering the use of this safety sailing tool