We did our fair share of light air racing this season. Most annoying were the times when the sea conditions were rolling and the rig / boom was flopping all over the place. It was very difficult to keep our speed up and I was wondering if securing the boom with a preventer would help or hinder our boat speed.
Preventer In Light Air + Boat Speed
- Thread starter Ducati
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That'd drive me nuts, too, but I'm not so sure any boat speed would accrue. But at least it'd be a lot quieter. 
We just take our cunningham line off the main (shackled to a line through the cringle) and hook it to a mainsheet boom bail, and run the bottom / mast end off to a shroud, bottom of the turnbuckle. The shackle at either end makes it very easy and a versatile double duty line. Easy to make and easy to undo.
No need to run a "true" preventer all the way to the bow.
We just take our cunningham line off the main (shackled to a line through the cringle) and hook it to a mainsheet boom bail, and run the bottom / mast end off to a shroud, bottom of the turnbuckle. The shackle at either end makes it very easy and a versatile double duty line. Easy to make and easy to undo.
No need to run a "true" preventer all the way to the bow.
Ducati,
You did not say what reach you are sailing on. If sailing on a broad reach with swept back spreaders you might risk an accidental jib. I would either tie up a preventer to the end of the boom to the toe-rail adjacent to the mast OR winc/cleat a boom brake line. I use a Walder boom brake for this.
You did not say what reach you are sailing on. If sailing on a broad reach with swept back spreaders you might risk an accidental jib. I would either tie up a preventer to the end of the boom to the toe-rail adjacent to the mast OR winc/cleat a boom brake line. I use a Walder boom brake for this.
In racing, a preventer is going to be a problem. Dumping a preventer in a hurry can be too slow a processes. We found the best way to hold the boom secure in light air runs and lumpy seas is with one crew member assigned to stand on the cabin top with his/her back to the boom. This crew member can also keep track of the incoming puffs as they approach calling the lifts and knocks in preparation for any gybes.
For light air purposes, it's quite simple to rig a semi permanent preventer by knotting a length of line around the boom, just behind the vang, and running the ends forward to blocks on each toe rail, then back to handy cleats near each side of the cockpit. You leave it loose, until needed. When you jibe... just uncleat the loaded side... reset if necessary on the other tack. 3 strand nylon line would be a good choice for shock absorbtion.
http://sailmagazine.com/boatworks/sails-and-rigging/boom_time/
http://sailmagazine.com/boatworks/sails-and-rigging/boom_time/
All good points made above.
I'd have a hard time predicting whether a preventer helps much in lumpy, no wind situations. It can certainly help keep you from going insane, but to stop the slapping of your main with a preventer, you will also compromise you sail shape. It's possible that, given the right wave direction and boat motion, that you could turn the rocking of your boat into a fanning motion for the main by having your main locked down in a particular position.
When cruising, shorthanded, or night sailing, I use a prevents for safety reasons.
My preventer is a 4:1 ball bearing, block and tackle, with a cam cleat on one fiddle block and snap shackles on both blocks. I can quickly connect it to any point on the boom, and the other end to almost anywhere on the boat, but most often to the toerail near the shrouds. It can be a spare main sheet if something fails, it can be a hoist for a MOB situation. At dock I use it to keep my boom perfectly steady (to avoid gooseneck squeek when sleeping below).
As noted in an earlier post, when racing, using a crewmember can be effective, if not quite as safe.
Chris
I'd have a hard time predicting whether a preventer helps much in lumpy, no wind situations. It can certainly help keep you from going insane, but to stop the slapping of your main with a preventer, you will also compromise you sail shape. It's possible that, given the right wave direction and boat motion, that you could turn the rocking of your boat into a fanning motion for the main by having your main locked down in a particular position.
When cruising, shorthanded, or night sailing, I use a prevents for safety reasons.
My preventer is a 4:1 ball bearing, block and tackle, with a cam cleat on one fiddle block and snap shackles on both blocks. I can quickly connect it to any point on the boom, and the other end to almost anywhere on the boat, but most often to the toerail near the shrouds. It can be a spare main sheet if something fails, it can be a hoist for a MOB situation. At dock I use it to keep my boom perfectly steady (to avoid gooseneck squeek when sleeping below).
As noted in an earlier post, when racing, using a crewmember can be effective, if not quite as safe.
Chris
If want to maintain boatspeed in lumpy condition .... consider what is happening during a roll tack where the boat is allowed/forced to maximum heel and the the mast rapidly allowed to become vertical (during the tack) ... the result is a boost of speed/power.
On the 'other side of the roll cycle toward max. heel the sail is 'working backwards', the camber is inverting and the apparent wind usually a massive 'header'. Like pulling a boom to windward to make an 'emergency stop' with the sail.
Then consider a sail prevented during 'rolly' conditions .. what happens on the 'down slope'? header on one-half the cycle, and lift on the opposite side of the cycle.
Without a preventer the 'cycle towards max. heel may be 'stopping the boat'. sail is operating backwards (camber inverted and drastically 'headed' by the apparent wind. .... essentially roll tacking on one side of the roll and 'reverse sailing' on the reverse roll = net sum ZERO.
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Another consideration, manually rapidly pulling in the sheets repetitively to 'fan' the sails then letting out the sheets to begin another 'fan' motion is illegal ... BUT can result in much greater boat speed ... and thats why 'ooching' is illegal.
So possibly put all the pluses together and eliminate the 'negatives' .......when the mast is going to vertical, begin to head up (like you do during a 'roll tack'); when the mast is going back to maximum heel (and the sail tries to invert & reverse camber) quickly bear off (with the minimum amount of applied helm pressure so the 'helming action' doesnt tend to stop the boat) to lessen the 'inversion' (hence lessening of the total forces which tend to stop the boat) and simply follow the mast head 'windex' with the sails to keep them 'as full as possible' until max. heel occurs and the repeat. This, probably, isnt illegal 'ooching' or 'manually fanning' the sails with the sheets, is propelling the boat 'solely' by wind power and therefore should be legal for your 'class'.
Then decide if a preventer is needed or not to get the maximum 'half roll tack', half bear off combination to gain 'maximum' out of the sails ..... decide if the preventer will keep the sails at a better average 'angle of attack' and with the most air flow across the sail 'unseparated' 'heel to leeward phase' part of the cycle.
Simple speak ... compare your VMG with a preventer on a steady/straight course VERSUS a combo of half roll tack/slight heading up PLUS bearing off to keep the apparent wind under control and with a more prolonged 'attachment' .... by FOLLOWING more the masthead windex *with the RUDDER/HELM* (and not using so much helm so it slows the boat by the steering action) as best you can. Probably almost all your competitors will be sitting there on a straight course bitching about all the 'slatting' going on .... and from what I discussed above 'may' keep you in longer periods of 'correct' apparent wind and if the additional steering 'losses' is less than the gain from increased correct flow across the sail .... a net GAIN.
if the above seems reasonable, do some pre-race trials, with or without a 'training horse' boat to see if this will or wont get your boat speed up in lumpy conditions. You boat and it natural period will determine how much or how little you need to S steer to keep the apparent wind across the sails 'longer'.
hope this isnt too confusing
On my lightweight, 'steers on less than a dime', planing sportboat ... I can usually gain by 'partly roll tacking' and partly/rapidly following the windex' when in rolly conditions - both upwind and down. ... but my crew/wife hated the constant in and out hiking per roll cycle when doing so.
On the 'other side of the roll cycle toward max. heel the sail is 'working backwards', the camber is inverting and the apparent wind usually a massive 'header'. Like pulling a boom to windward to make an 'emergency stop' with the sail.
Then consider a sail prevented during 'rolly' conditions .. what happens on the 'down slope'? header on one-half the cycle, and lift on the opposite side of the cycle.
Without a preventer the 'cycle towards max. heel may be 'stopping the boat'. sail is operating backwards (camber inverted and drastically 'headed' by the apparent wind. .... essentially roll tacking on one side of the roll and 'reverse sailing' on the reverse roll = net sum ZERO.
-------
Another consideration, manually rapidly pulling in the sheets repetitively to 'fan' the sails then letting out the sheets to begin another 'fan' motion is illegal ... BUT can result in much greater boat speed ... and thats why 'ooching' is illegal.
So possibly put all the pluses together and eliminate the 'negatives' .......when the mast is going to vertical, begin to head up (like you do during a 'roll tack'); when the mast is going back to maximum heel (and the sail tries to invert & reverse camber) quickly bear off (with the minimum amount of applied helm pressure so the 'helming action' doesnt tend to stop the boat) to lessen the 'inversion' (hence lessening of the total forces which tend to stop the boat) and simply follow the mast head 'windex' with the sails to keep them 'as full as possible' until max. heel occurs and the repeat. This, probably, isnt illegal 'ooching' or 'manually fanning' the sails with the sheets, is propelling the boat 'solely' by wind power and therefore should be legal for your 'class'.
Then decide if a preventer is needed or not to get the maximum 'half roll tack', half bear off combination to gain 'maximum' out of the sails ..... decide if the preventer will keep the sails at a better average 'angle of attack' and with the most air flow across the sail 'unseparated' 'heel to leeward phase' part of the cycle.
Simple speak ... compare your VMG with a preventer on a steady/straight course VERSUS a combo of half roll tack/slight heading up PLUS bearing off to keep the apparent wind under control and with a more prolonged 'attachment' .... by FOLLOWING more the masthead windex *with the RUDDER/HELM* (and not using so much helm so it slows the boat by the steering action) as best you can. Probably almost all your competitors will be sitting there on a straight course bitching about all the 'slatting' going on .... and from what I discussed above 'may' keep you in longer periods of 'correct' apparent wind and if the additional steering 'losses' is less than the gain from increased correct flow across the sail .... a net GAIN.
if the above seems reasonable, do some pre-race trials, with or without a 'training horse' boat to see if this will or wont get your boat speed up in lumpy conditions. You boat and it natural period will determine how much or how little you need to S steer to keep the apparent wind across the sails 'longer'.
hope this isnt too confusing
On my lightweight, 'steers on less than a dime', planing sportboat ... I can usually gain by 'partly roll tacking' and partly/rapidly following the windex' when in rolly conditions - both upwind and down. ... but my crew/wife hated the constant in and out hiking per roll cycle when doing so.
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