Outhaul Design


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Bill Balme
Bill Balme
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When the sails begin to slat in light air plus swell, we suffer from one of the blocks of the Outhaul which reside within the boom, slamming against the boom with a resultant rifle shot crack! It's quite disconcerting and certainly deprives one of sleep!

When I removed the outhaul a week or two ago (first time I'd removed it) I found that the construction was a 6:1 block and tackle affair, and that the distance between the two block was long - as I've tried to show in the attached photo. The line is then brought back to a clutch in the cockpit where a winch is available.

I am considering changing the arrangement in two possible ways and would welcome advise along the lines of; "No don't do it! or go with number 1 - or some better approach I've not thought of!"

Option 1 would be to arrange it so that the two blocks are much closer together - that will move the aft block closer to the mast, and therefore when the sail slats, the momentum in the aft block will be significantly reduced - hopefully reducing the noise.

Option 2 would be to eliminate the block and tackle entirely and use the winch whenever I need to adjust the outhaul. (I rarely have to use the winch to make an adjustment.)

Bill Balme
s/v Toodle-oo!

Dick
Dick
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Hi Bill,
I lean toward option #1 with the thinking largely along similar lines. My thinking is as follows.
If I am correct in reading your well labeled photo, that is a lot of line to make what are likely, given fairly modern sails, are quite modest lengths of mainsail clew adjustment (6-8 inches maybe) to achieve the needed variations in sail shape. I also assume that the rifle shot noise is made by the aft-most block when the boom jumps violently when the sail slats. I suspect that the forward block may make some noise, but far less as it is closer to the pivot point, the gooseneck, and therefore less susceptible to “whipping” back and forth.
One possibility which I think could be easily executed would be to decrease the throw (the distance from block to block) to just a few inches longer than needed and then to move the blocks forward toward the gooseneck. This would leave the “design” intact while adjusting the elements that enact the design.
Executing would entail: shortening or eliminating the pennant going from the forward block to the forward end of the boom near the gooseneck. Then add the now shortened-throw pair of blocks and figure how much to lengthen the pennant going from the aft block to the outhaul car where the mainsail clew is attached. This should now probably be of wire or high modulus line. And you should end up with a lot extra tension adjusting line.
In this way, both blocks would be much farther forward, near the boom’s pivot point and unlikely to whip around making the offending noise.
As I see it, there was never a reason to have such a long throw between blocks: this decision set up the noise you referred to.
Please let me know how this works. I am aware there are a couple of assumptions made and things I was unsure about.
My best, Dick Stevenson, s/v Alchemy
As an aside: annoying, especially unexplained, noise, even if not overtly offending should always be explored as it usually means chafe, something is poorly designed or something is going (gone) pear shaped. For example, in this case, if let go on, I would suspect, in time, damage to the block
Dick
Dick
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Hi Bill,
Another thought:
Alchemy has a similar design, but we always have the boom “triangulated” which prevents the boom from jumping around (the sails still can slat annoyingly in the conditions you described). This is done with a b&t arrangement to the side deck which, with the mainsheet, effectively stabilizes the boom. I consider the boom as the most dangerous gear on the boat and immobilizing it is a safety issue. Even close hauled with the boom strapped down tight, without triangulation, the boom can jump around a surprising amount and strike a head that might happen to be close. I suspect this arrangement contributes to our not being bothered by gear movement inside the boom.
My best, Dick
Bill Balme
Bill Balme
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Thank you Dick! Option 1 it is! That's certainly the simplest option in my mind. I think I'll end up looking for a maximum of 12" adjustment, but will probably plan for the blocks to be about 24 or 36" apart - otherwise I fear they may develop more friction and have a tendency to not lay well in the boom. I'm thinking 10mm 12-strand Dyneema should be plenty strong enough

With regards your boom restraint - do you essentially maintain three control lines on the boom at all times? Two side deck b&t's as well as a standard mainsheet?

I do use a b&t to the side deck when at anchor to stop the boom moving, and I occasionally have employed it while the main is slating - but with minimal success, since the main will slat whether or not the boom is rigid. I can't say I've noticed if it quieted the blocks though...

Bill Balme
s/v Toodle-oo!

Dick
Dick
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Hi Bill,
Sounds like a plan regarding the outhaul.
With regards to the side deck 4-1 b&t arrangement, yes, there are 3 control lines attached to the boom at all times (2 side-deck lines and the sheet): the side deck lines are brought back to the cockpit through brakes allowing for easy control at all times. The windward line is always slack (not braked) while the leeward b&t is always firmed up. The farther from close hauled we are sailing, the more this arrangement serves as the boom vang (and preventer until the boom end is over the side of the boat where an offshore preventer is used that goes to boom end). (We have no other vang.)
I believe I have written elsewhere in these pages in greater detail about this arrangement. Tell me if not found.
My best, Dick
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