Nacra 5.5 Mast Rotation :: Catamaran Sailboats at TheBeachcats.com

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Nacra 5.5 Mast Rotation

thebda

Rank: Lubber

Registered: Mar 14, 2018

Last visit: May 15, 2021

Posts: 22
Posted: May 10, 2018 - 11:41 AM

Here's a rough sketch of how my mast rotation is setup. Initially I set it up to do a 180 at the block to give me 2:1 on the line and allow to adjust mast rotation from the high side. The problem I'm running into is that the 4mm line I have is slipping in the cam cleats (the lines cross over so you can adjust from the high side, not sure if this is correct) and a 6mm line won't fit through the tighter side of the block I'm using to cross over (but will on the opposite side since it's wider). I believe these blocks and cams are all from the factory so not sure how it's supposed to be setup. Also do you guys usually have both mast rotation lines tight to stop the mast from rotating in light winds or do you just set them to limit total travel in each direction and leave them from tack to tack so one is always slack.
Dogboy

Rank: Mate

Registered: Mar 19, 2004

Last visit: Nov 21, 2024

Posts: 964
Posted: May 10, 2018 - 12:14 PM

Whenever you're sailing, the mast should always be able to rotate at least 45 degrees or so off of the centerline. The only case where you might want the mast locked on centerline would be if you're just bobbing around in light wind and the mast keeps banging back and forth.

I believe the way those NACRA rotators are intended to work is that they can either be set up to limit mast rotation (upwind) or pulled in from the opposite side to induce rotation (downwind). IMO, it's a bit of an over-complex system. The rotators on most boats are lead behind the mast and the line terminates either on the boom or is routed through a grommet in the tramp and lead out to cleats on the hulls. A much simpler system.

sm
P.M.

Rank: Mate

Registered: Jan 14, 2004

Last visit: Sep 25, 2024

Posts: 866
Posted: May 10, 2018 - 03:29 PM

You have it backwards. You should reeve the sheet to "induce rotation". The 5.5 is boomless. Rotator arm forward of the mast.

Rarely will you need to adjust rotation on this boat. The gains will be had from an over rotator downwind which it looks like you have illustrated.

Inspect this picture for proper set up. It's in my album. The rotator will act as your turning block. Dead end the sheet on the beam.

https://www.thebeachcats.…c85cb1d7950d4ee3447cd898

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Philip
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thebda

Rank: Lubber

Registered: Mar 14, 2018

Last visit: May 15, 2021

Posts: 22
Posted: May 10, 2018 - 03:45 PM

OK, so we're trying to enduce more rotation in the mast on downwind and just let it go on upwind, not try and flaten it out (assuming it's within a reasonable distance, 80 degrees or so)
P.M.

Rank: Mate

Registered: Jan 14, 2004

Last visit: Sep 25, 2024

Posts: 866
Posted: May 10, 2018 - 04:11 PM

Sounds like you're just learning the boat, or the boat is new to you. I suggest you just leave the rotator sheet off for now. With a boomless main, mast rotation will tend it's self via mainsheet tension.

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Philip
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Dogboy

Rank: Mate

Registered: Mar 19, 2004

Last visit: Nov 21, 2024

Posts: 964
Posted: May 10, 2018 - 07:37 PM

You should be able to either induce or limit rotation depending on how you tension the adjustment lines. If you’re setting it to induce rotation, you have to make sure you remember to release the adjustment line before you jibe or the mast won’t rotate to the new side and you run the risk of breaking battens and possibly the mast if it’s windy enough.

sm
nacra55

Rank: Mate

Registered: Nov 02, 2004

Last visit: Aug 07, 2023

Posts: 626
Posted: May 10, 2018 - 09:33 PM

I'm with Philip, leave the mast rotation alone if your new to the boat. Forgetting to uncleat it in a jibe can be very bad as Dogboy said.

That said, the rotator arm should point forward and be rigged to cleat on the high side, it's a boomles rig.

Rigging the rotator: On the windward side there should be an eye strap in front of the cleat toward the mast. The rotation line dead ends there with a stopper knot, go thru the eye strap toward the mast, thru the hole of the rotator then back to the cleat on the windward side. Then across the tramp and tru the cleat, to the rotator then back to the eyestrap and dead ends with a stopper knot.

If you have the triangular rotator, the line should go from the eye strap forward and across the mast to the hole on the far side of the rotator arm.

Some sailors hang a pair of single blocks off the rotator so the line runs smother.

Sheet tension is key for flattening the main and most of the time there is no need to use the rotation upwind. In choppy seas, you can use the rotator to lock down the mast so that it won't rotate (not shake the air out of your sails). Down wind you can induce rotation so that your mast has a smother entry into the wind by rotating the mast to 90 degrees, but don't forget its on when you jibe. The heavier the air the more damage.

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Ron
Nacra F18
Reservoir Sailing Assn.
Brandon, Mississippi
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nacra55

Rank: Mate

Registered: Nov 02, 2004

Last visit: Aug 07, 2023

Posts: 626
Posted: May 10, 2018 - 10:02 PM

Your picture looks like your using the barber hauler cleats too. The barber hauler cleats are used from the high side but are across the boat by the cheek blocks on the end of the beam.

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Ron
Nacra F18
Reservoir Sailing Assn.
Brandon, Mississippi
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bradinjax

Rank: Mate

Registered: May 10, 2016

Last visit: Oct 22, 2024

Posts: 226
Posted: May 10, 2018 - 10:37 PM

I have owned 3 or 4 cats without mast rotation adjustments and 1 or 2 that had them. I have very rarely found mast rotation adjustment to be of significant importance. It is pretty much the last thing on my proper trim checklist.

In boats that had a boom it seemed more important. In boats that were boomless I could still often get proper mast rotation for conditions with cunningham and main sheet tension unless my forestay tension was way too loose or too tight.

Often on boats with mast rotator adjustments proper forestay tension for wind conditions usually solves the problem. Adjust according to conditions. More forestay tension for higher wind.

Quick rule of thumb for proper forestay tension: after forestay is set use hands to turn mast both left and right easily to about 45 degrees relative to hulls. If it turns to stiff resistance one way more easily than the other you have side stay length problems. This will get you in the ballpark.

Brad in Jax
Andinista

Rank: Mate

Registered: Aug 18, 2003

Last visit: Dec 13, 2023

Posts: 880
Posted: May 11, 2018 - 06:23 AM

P.M.

Inspect this picture for proper set up. It's in my album. The rotator will act as your turning block. Dead end the sheet on the beam.

https://www.thebeachcats.…c85cb1d7950d4ee3447cd898

Better to remove the mast base pin, in case the mast falls, which happens once ore twice in a lifetime but actually happens.
Andinista

Rank: Mate

Registered: Aug 18, 2003

Last visit: Dec 13, 2023

Posts: 880
Posted: May 11, 2018 - 06:58 AM

For boomless boats you need to uncleat the line on each turn. The rotator is rarely used so the chances to forget to uncleat are high. And that is a good reason not to use if not necessary. I love mine to lock the mast when not sailing. i.e on the trailer, when I leave the boat on the water. If you race maybe it gets more use but still not all the time. Different story if there is a boom, not just different rotation setup but different forces and interactions too.
thebda

Rank: Lubber

Registered: Mar 14, 2018

Last visit: May 15, 2021

Posts: 22
Posted: May 14, 2018 - 08:37 PM

Thanks for the input, I uncrossed it and tried it last weekend, I used a lot more out haul (or in haul, whatever the car is that pulls the mainsheet connection towards the mast) to help flatten the main when I sheet in. The barber hauler uses a separate set of cleats on the front beam I just left them out for simplicity.