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Jethrow

Thoughts on mast rotation controls

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Hi all

I'm looking to simplify my mast rotation controls.

At the moment it's not connected to the boom at all so the rotation is controlled by an adjustment to the spanner and then separate over-rotation lines on either side.

I have to use the over-rotation controls as a lock to stop the mast flicking around in choppy water but it makes tacking complicated with all the adjustments that need doing and undoing.

Yes, pics would help but I don't have any on hand at the moment.

Thanks in advance

Jethrow

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Boomless deck sweeper, then the rotation will be self setting in most conditions. Do you know a good sailmaker?

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It used to have a boomless deck sweeper, about 15 years ago, before it became trendy.

I cut it off... :lol:

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I'm really hoping that someone pipes up with something brilliant. On my G-32 rig I have the tiller facing forward and a centerline tether to limit rotation. I also have side controls to induce rotation and lock the mast when it's choppy. The only time I used the side controls, I poked the spreader through the main when I gybed before releasing the control.

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Russell,

I have the same concerns re side controls to induce rotation. When I sail a friends boat with that feature we never remember to let it off.

Looking at putting a system to induce rotation  on my boat I bought a couple of those pivoting clam cleats that release when the load gets too high.

There is an adjustment screw to fine tune the load triggering the  release. Hoping that with the correct purchase and cleat setting I can get them to release when I forget to do it.

 

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Not brilliant - but it works.  Spanner facing aft and mostly hidden under the mast and sail tack area is a better solution than tiller/spanner facing forward,  just asking for trouble - like catching headsail and reacher sheets when tacking/gybing. Also easy to trip over.

And if necessary, you can run the spanner sheets aft to cockpit and have cam cleats close to hand. And you can lock the leeward spanner sheet to stop mast rotating in sloppy seas, killing sail power and drive. But remember to let it off when tacking.

JacquesGrouchospanner - Copy.jpg

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Yeah, it's the whole "Letting it off before tacking" that's bringing me undone. ;)

You don't look like you've got a purchase in the system above? Do you just set your mast at a particular angle or am I missing something in the photo?

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Stiff bottom battens and if necessary an inhaul along with the outhaul on your boom.  Compression in the batten will force the mast around but still allow it to rotate back.

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Russell, Scarecrow, has it. If the out haul/inhaul tension is correct you shouldn't need to cleat it and the foil will self-correct,

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^ Nup, wrong.

My gooseneck is inline with the sail track and the mast is so stiff with so little luff curve that it has no effect.

Sail shape is excellent for the boat so inhauling to give more batten pressure is undesirable.

 

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Another image, shows spanner setup with slightly more clarity. It's a double purchase system which is locked off on the spanner. But you could have three purchase lines per side and run each final single sheet back to cockpit.

If your main sheeting system is slightly aft of main sheet track, then tension will always push mast rotation round to the correct spanner set position.

redmastspanner copy.jpg

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3 hours ago, Jethrow said:

^ Nup, wrong.

My gooseneck is inline with the sail track and the mast is so stiff with so little luff curve that it has no effect.

Sail shape is excellent for the boat so inhauling to give more batten pressure is undesirable.

 

That's why you have to go to a stiffer batten.  Stiffer batten inhauled to match the current sail shape will apply more load to the track.

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Put your rotation controls onto the redundant jib winch on the windward side. That way, it has to be let off before the tack [To get the new jib sheet on]

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I like your thinking there VMG but no usable winches on the boat, just purchase.

I think I just need better memory! :lol:

I have had a thought about a cam based snubber rather than a locking purchase, I'll post pics if it works

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12 hours ago, SCARECROW said:

That's why you have to go to a stiffer batten.  Stiffer batten inhauled to match the current sail shape will apply more load to the track.

Yeah, I see what you're saying but there's just not enough offset between the batten & the gooseneck compared to the mast pivot to balance the loads I'm talking about.

We saw something like maybe 50+ kg's when the current lock snapped and a new crew tried to grab it in a particularly bad washing machine chop. It just tossed him across the boat, sail cloth and battens can't hold that.

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16 hours ago, teamvmg said:

Put your rotation controls onto the redundant jib winch on the windward side. That way, it has to be let off before the tack [To get the new jib sheet on]

I love the simplicity of that suggestion.

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Something that worked well on one boat I ran, was to work out the limits of how much rotation you want to allow with a stopper knot and run the tension backwards.  Basically just set up so you ease the windward side down to where you want it set, have the leeward side with just enough slack to put the mast straight.  Once you are on the new tack, blow the adjustment and let the mast down to the stopper knot and you've got your maximum rotation you want.

Worked well, as the mast on that boat had a tiller arm through bolted to the front.  At the end of the tiller were a pair of 4:1 blocks port and starboard, hung on a U-bolt.  That put them a foot or foot and a half ahead of the mast, with the line leading and down to the deck with blocks on pad eyes with a cam cleat behind each.  3-4 feet to each side. It had some leverage to work it without having a spaghetti, or an 8:1 tackle.

The tiller also gave you a pretty good visual indication of what was going on up there from the helm.  

We used to break the bottom battens at the batten car, but never broke them again after glassing them back together with some biax in epoxy.  We cut a dado down a 2x4 long enough to back up the batten and set it to size...   Ground the scarf into the batten over a few inches and laid it into the dado with a piece of mylar packing tape in it and then built up the first 5-6 inches out of biax strips cut so one axis lay in as uni in epoxy and let it set up under tight clamp pressure.  Never broke it again...  Theory being that the straight unidirectional extruded batten has no strength except in tension...  Adding a little fiber going different directions by the batten car gives it a little bit more strength when the boom rises and tries to jam the batten through the mast track.  You get a stress riser, and the fiber bundle explodes...   We had end of boom sheeting with a 10 foot long traveler and sending the traveler down meant less batten popping than easing the mainsheet.  The boat didn't have a vang of any sort as we were running for charter.  

Cheers

 

 

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