Finally getting around to installing one on my Nacra 5.7. It would seem the " best" way to do this would be pull the mast base, and install with a compression sleeve nside the mast. This, I think, will also be a royal pain as I'm sure the base is pretty well welded on after 20+ years. Curious to know how these are installed by the factory on Hobies, Nacra, Etc. Are the loads light enough that a sleeve on the inside is just overkill? Any other mounting related issues I should be aware of?
Thanks
Chris
Mast Rotator
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Posted: May 08, 2012 - 08:33 AM
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Posted: May 08, 2012 - 08:46 AM
I'm confused, did your 5.7 not have a mast rotator. So prior to this install you're mast did not rotate at all?
Here is a link to some Hobie 18 mast base photos.
http://www.hobiecat.com/f…ewtopic.php?f=13&t=42441
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ALLEY CAT 1984 RED LINE HOBIE 18 MAGNUM
Sail # 10505 or 277
San Diego, Ca
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Posted: May 08, 2012 - 09:52 AM
The base casting will pop off with minimal effort.
Here's a pic of what I found inside a 1991 mast.
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Posted: May 08, 2012 - 10:04 AM
That's perfect - thanks. Forgot the rotator would be so close to the base. Doesn't look like it has or needs a compression sleeve inside.
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Posted: May 08, 2012 - 10:15 AM
That one doesn't have it, but that can't be the original bolt. It spent some time in the ocean but that looks like the titanic. I seriously doubt it's stainless. IDK if they need a compression sleeve, but obviously they work without one just fine.
Either way, pop the casting off and see what you're working with.
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Posted: May 08, 2012 - 11:01 AM
OK, two things--
Don't forget the compression tube, or you'll be sorry. The stainles bolt will corrode the hole in the aluminum mast and it will eventually break. The Hobie kits come with a reinforcement plate and a compresion tube. Even if you THINK you don't need it--use it.
Next thing: how are you going to rotate without a boom? On the A cats, we have a control on the front beam on each side and you have to remember to release it when jibing. It's pretty ugly if you don't. The older style that has a jam cleat on the boom just didn't work very well.
If you are still boomless, the forward facing rotator would probably be the better rout for you. However, if you use the one pictured above, you can put it behind the mast and run the control lines around the mast. -
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Posted: May 08, 2012 - 11:04 AM
I have an '84 5.7. You do not need a sleeve, no need to remove the base, unless you want to reseal it...the only purpose of the sleeve would be to prevent compression, & deforming the mast extrusion. You are not going to tighten the bolt down that far, in fact the mast rotator will tend to drop down, you will end up attaching a small bungie or line to hold it horizontal.
Visualize what happens during mast rotation. (Hold the mast, then move the rotator arm from side to side) The loads the rotator bolt will place on the extrusion will not try to squeeze the extrusion walls together, they will try to elongate the holes. If can be a powerful force, just try to reduce rotation on a windy day. Mostly the mast will do its own thing just fine on this setup. Downwind you may want to induce more rotation, & on very light conditions you can lock the mast in one spot. That will help prevent the mast banging to/fro & shaking the wind out of the sail, not to mention driving you nuts. It is also very useful when raising/dropping the mainsail if you cannot park your boat directly into the wind. You can pull the mast direct into wind, then cleat, it makes raising the sail much easier. My boat is geared up from my dock, & is rarely ever directly into the wind.
One CAVEAT, if you cleat the rotator, you must remember to uncleat it first, & allow the mast to swing. The manual says you can break the mast if you forget it. I have forgotten if a few times, if you ever tack, then wonder why you are moving so slowly, see if you forgot to uncleat the rotator line. It totally destroys the airflow.
That bolt IIRC is 5/16" SS. Just do it up enough to remove slop from the rotator arm, don't try to crank it down.
This is an early photo & is rigged poorly. I believe Ron (Nacra 55) showed me how to do it correctly. Run it as a continuous line. Start by tying to one padeye(visible just inside the cleats on beam) then through the end of rotator arm, then through cleat, around behind mast, through other cleat, to rotator arm, then finally to other padeye & tie off, or dead end with stop knot. That will give you a 2:1 purchase.
You can see how the rotator hangs down, I added a small piece of line from end of arm up to diamond wire to hold the arm horizontal.
Edited by Edchris177 on May 08, 2012 - 11:08 AM.
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Posted: May 08, 2012 - 11:29 AM
Thanks for all the replies. it would seem if the rotator was mounted up high, a compression sleve would be imperative. Being just an inch or two above the base, maybe not so much as the base should carry the compressive load.
The main goal for me, if not the only goal, is to settle down the mast in light winds. More than likely I'll end up rigging it as shown above, which looks great. I've toyed with the idea, however, of just rigging some form of a friction line through it that would prevent the mast from dancing around in light winds/calm, but still rotate normally when the sail fills normally. Think this might work? I do like the idea of rotating the mast for rigging though - hadn't thought of that...
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Posted: May 08, 2012 - 12:13 PM
I tried adding shock cord to my 5.5 the day I crashed it. It was to be a preventer line for the jib sheet (I have the inverted triangle rotator) but it added too much friction to the rotator. I'm fairly certain I would have fine tuned it and kept it, but I only had one outing with it as it was and it sucked.
My 5.5 upwind didn't need the rotator at all -- it would rotate and give a great entry shape just from the tension of the sail.
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Posted: May 08, 2012 - 01:19 PM
Run the bungee preventer from the bow tang to the diamond wire, around the front of the mast, around the other diamond wire and back to the bow tang on the other hull. This keeps the jib sheet from wrapping around the forward facing positive rotater. Put some plastic clips on it so you can remove it so that the sun won't eat it up.
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Nacra F18
Reservoir Sailing Assn.
Brandon, Mississippi
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Posted: May 08, 2012 - 02:27 PM
Yeah, I've got/had the preventer on all of my boats that ran a jib -- I'm very familiar with the typical setup (and had the typical setup on the 5.5)
However, on my 5.5 with the wide rotator, I connected the rotator line to the opposite side of the rotator (so the rotator lines crossed each other under the rotator) which exposed the corners of the rotator, and the jib sheet would catch on it constantly. I added a single shock cord that ran from the main beam to the rotator corners to hid them from the jib sheet. That's the shock cord that added friction -- it didn't make the mast resist being rotated, though, because it ran through blocks as one continuous line.
I wanted it this way as I could get more rotation downwind than I could by pulling the close corner to the beam.
Hopefully that makes sense.
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Posted: May 08, 2012 - 09:09 PM
on my N5.8's, i turned the rotator to the back of the mast overhanging the tramp. it's fastened thru the base casting so no need to do a compression sleeve.
i had 3 grommets placed in my tramp. the first one is just a little farther back from the end of the rotator and in the center of the tramp (see photo).
the other two are at the sides of the tramp, one on port and one on starboard. they are just in front of the grommet where the trapeze bungee exits the tramp. mount a cam cleat on top of the hull just in front of the trap bungee, facing toward the grommet in the edge of the tramp.
so here's what to do....... run one continuous line from the port cleat, down thru the port grommet and under the tramp to the center grommet. come up thru the center grommet and thru a small single micro block that is attached to the back end of the rotator, then go back down thru the tramp and underneath to the starboard grommet. come up thru the starboard grommet and run the line thru the starboard cam cleat.
the line does not tie firmly to the rotator but can be pulled from either side to adjust the rotation of the mast. when sailing, one side has to be cleated in order to pull the rotator toward the grommet in the center of the tramp, but you can pull it from the windward side which is where you want to be.
on this cat, my photo only shows the center grommet and mast rotator without the micro block, lines or cleats. i will try to take some photos of the complete arrangement on my other cat when i get it set up.
this works slick and doesn't add a bunch of slack lines and hardware to your tramp.
jon
Edited by arch on May 08, 2012 - 09:51 PM.
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Posted: May 09, 2012 - 12:46 AM
This setup is common (in overall design if not execution) on the Inters...probably more boomed boats as well.
I don't think I understand using it on a 5.8, though. I'm glad it works for you.
Looking at it I think I might move my cleats back to the helm on my inter. Thanks for the pic.
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Posted: May 09, 2012 - 08:15 AM
i'll try to get some pics of my actual complete setup on my 5.8 in a few weeks and repost them here. the older 5.8's are boomless, as you know, so they can't lever against a boom to control mast rotation like the Inters. that's why i did it this way.
my cam cleats are on the hulls between the helm and crew so either one can adjust the rotation. when i had an Inter18, and was sailing solo, i had a hard time reaching and adjusting the rotation lines cause the cleats were just behind the front crossbeam, so moving them back would be a great idea!
jon
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Posted: May 09, 2012 - 08:31 AM
All 5.8s are boomless. It seems to me like you should have a block on each side under the tramp that your rotator line goes through, that allows you to cross them under the tramp and pull the opposite line, since you want to induce rotation, not limit it.
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Posted: May 09, 2012 - 09:10 AM
That's right. All boomless rigs you want to induce rotation, especially off the wind. On rigs with booms the rotation is induced due to compression from the mainsheet on the boom, so you want to limit rotation. It's sometimes easier to understand if you look at the mainsheet angle in relation it's anchoring point. With booms it is pulling the anchor point forward, and on boomless it is pulling the clew back.
I think I covered this in detail awhile back. With the stock forward rotation on the boomless rig, you can actually over rotate (induce) and limit rotation. It is a very clean set up and uses one continuous line. I think there is a photo in my album.
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Posted: May 09, 2012 - 12:22 PM
No need for a rotation limiter on a boomless rig, sheet tension and outhaul handle that. You need positive rotation for light and heavy air and off wind. Phillip and I have both talked this to death.
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Ron
Nacra F18
Reservoir Sailing Assn.
Brandon, Mississippi
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