Tripletach

16sq mast rotation controls advice.

28 posts in this topic

Hi Guys. I have a nacra 16sq which I only bought a few weeks ago and I am fairly new to sailing. I've just realised it should have some sort of mast rotation controls on it and it doesn't or I haven't set it up. Could someone enlighten me on how to set up mast rotation control on the 16sq? Many thanks.

Share this post


Link to post
Share on other sites

16 sq mast rotation

The mast rotation setup on most 16 sq's is really simple, there have been a number of minor changes over the years but regardless most work the same way.

On the bottom of the mast is the rotator (mostly refered to as a spanner) this is at the very bottom of the mast and faces forward (don,t bother turing it around to de-rotate the mast up wind like a taipan or a class as it doesn't work on the standard 16sq rig) It is usually held in place with a riviet on either side that also holds the mast base in place, sometimes there is a second set of riviets to stop it pivoting downwards when in use, more common is a short rope tension strop that runs uo to a saddle on the front of the mast, this is there to stop the spanner pulling down and touching the front beam when the mast is rotated.

The front beam should have 2 small turning blocks on its top face about 200mm either side of the mast ball, these are usually fitted with a stand up spring so that they are standing vertically when not in use, there should also be 2 cleats on the front beam to secure the rope from the mast spanner, the position of these cleats vary greatly from 1 boat to the next due to personal preferance but they all do the same job. On some boats there is also a small turning block near the very ends on the front beam to allow the rope to be pulled from anywhere and still pull it through the cleat (not every boat has these as they again are personal preferance).

Some people rig the rope with a 2 to 1 advantange onto the spanner by tying 1 free end of the line to the base of the upstand block and then going out to the spanner and then back through the upstand block (again this is personal preferance, you don't really need the 2 to 1 as there is not a lot of load to pull on the mast rotation).

The simplest and most common setup uses a single continuous line ( 5 or 6mm line is plenty) tie 1 free end the end of the mast spanner (there should be a bridging piece inside the narrow end furtherst from the mast to stop it getting pulled back along the spanner) pass the other end of the line through the upstand block on the same side of the boat that you tie the line to, go through the upstand block and then along through the cleat on the front beam (if there is a turning block near the end of the beam go through that next) then pass the free end of the line under the foot of the sail to the other side of the boat and go back through the cleat and then through the upstand block and tie the free end to the mast spanner. Now when you pull and cleat the rope on the Starboard side the mast should rotate towards you and be cleated to hold it there (it will rotate to aout 90 deg or until the spanner is pointing directly along the front beam). When you uncleat it it should swing back to neat the middle, the same should happen when you pull and cleat the line of the Port side.

If the line is to short it can get caught while tacking or gybing and not allow the mast to rotate freely, if its to long it gets washed back along the tramp and tends to get tangled with the downhaul or traveler rope, its better to have it slighlty to long and cut it back to the correct length after its setup.

The mast rotation spanner does not do a lot when you are sailing upwind, the mast rotation angle upwing is mainly set by the outhaul position, as a rough guide this should be set with the blocks hanging directly below the middle bolt securing the track to the sail (this can vary due the conditions, the condition of the sail and battens as well as a number of other factors but this is a good starting point) When sailing upwind the mast rotation should not be cleated, when you pull main sheet tension on the mast will rotate to the correct position, in light winds and sloppy condtitions you may want to lock it in position between the port and starboard lines but most of the time let it find its on position even it it pumps a little going upwind.

The mast rotation spanner may need a pull onto the new tack after you have tacked in some conditions, when this happens the mast does not rotate full onto the new tack and looks like it is pointing straight ahead, check that the rotation line on the old tack is not cleated or jambed, pull the rotation line on the new tack to get the mast to swing around, this usually happens when you have a soft dimond wire setup and lots of downhaul on as you tack. Once the mast has come around make sure its not in the cleat or you will forget about it during the next tack and you will end up with that lovely tell tail bruise in the sail where the spreader tip tries to punch through it on the new tack.

The mast rotation is used for downwind sailing mostly, when you are sailing downwind ease the outhaul all the way out, this will bag up the sail and force the mast to rotate nearly all the way around to 90 deg anyway, the traveler and mainsheet should be set for the conditions and angle you are sailing, the mast can be pulled around to the full rotated position and cleated there. When you gybe make sure to release it from the cleat or you will end up with that lovely bruise in the sail again. There should not be alot lot of load on the rotation line when you are pulling it around to cleat, if it is heavily loaded it usually means something is wrong or the line on the other side of the boat is either cleated or stuck on something.

If this doesnt make sense let me know and I will get some pics of the setup on my boat next time I go out.

Good luck on your new 16sq, if you need help with anything else just send me a message or put a post on CatSailor.

Corey

Share this post


Link to post
Share on other sites

Hi Corey,

Thanks a million for the detailed reply. I appear to have the cleats fitted to the front beam but not the turning blocks. I peeled off some tape on the front beam at approx 200m from the mast ball and found some old rivet holes which must be where they are fitted. I will source some and rig it the way you have described.

Thanks again

Pete

Share this post


Link to post
Share on other sites

I managed to find a couple of pics of the front beam area of my old boat (#29)

You can see the mast spanner sticking out in front of the mast with the yellow tie to stop it getting pulled downwards, the mast rotation control rope is the white and blue fleck rope running to the upstand block and then lying along the tramp in the photos. This control line then runs along to the cleat you can see near the beam strap, my boats have an extra block near the outer end of the beam so that i can rotate the mast by pulling the control line from anywhere on the tramp.

Hope this helps.

Corey

post-14851-13778265593662_thumb.jpg

post-14851-13778265593943_thumb.jpg

Share this post


Link to post
Share on other sites

Hi Corey,

That's a great help, thanks. I also see how you had the dagger boards set up too which is different to mine and a lot better idea. I gather the bungee attaches to the forward stay shackle? Also, what is the black rope running from aft through the turning block mid way between the beams and running across the tramp? Is it the rudder pull down rope?

Cheers

Pete

Share this post


Link to post
Share on other sites

Yes thats right Pete, pulls the rudder down from each side of the boat.

Share this post


Link to post
Share on other sites

The centreboard setup on the earlier boats had that system to hold the boards up, the shock cord loop ran to a hook that was rivited to the top of the deck about halfway forward towards the forstay tangs. They changed this setup to the same style used on the 5.8 somewhere around the 50 to 60 sail numbers, the other system is the same as the 5.8 and uses side loaders that have a black foam covered tube that pulls the board over towards the side of the case to keep it up or down, the same down haul system can still be used but it takes a bit more of a pull to get them down. The older stlye works really well when its setup properly, if you position the saddle that is rivited to the tramp track just behind the centre of the board when you pull the rope it pulls the board backwards slightly and it slides easily down through the case, dont worry about mounting a block there as the rope passing through a saddle and up to the s-s eye that is cast into the handle area of the board works fine.

The black rope running forward along the deck is to pull the rudders down, the rope runs through a cleat that is mounted on the deck just if front of the back beam, some boats have it mounted on the white gelcaot section between the beam and the deck insert and some have it mounted on the deck insert itself, its much better mouted in the white gelcoat section as this area is stiffer and stronger than the deck insert, also if its to far forward you will end up kicking it when getting in or out off the wire or worse still you will end up sitting on it which is really uncomfortable, the rope runs through a hole that passes through the back beam to a pulley on the end of the downhaul rope on the rudder, it goes through this block and then returns to a saddle mounted above the hole on the back side of the beam, this gives you 2 to 1 to hold the rudders down, (this system is sometimes refered to as the Piggy System, the explaination of why its called this will require a long and involved history leason), this system is much more user friendly than the original sytem that was mounted on the top of the rudder arms and most Nacra's are now setup with the Piggy System, most of the Nacra's in South East Qld fit a rubber bungie or spring system at the beam end of the system to help absorb the shocks from hitting jelly fish, these things wreak havoc on rudders (some of the A's at Humpybond endup with broken rudders and damaged rudder stocks from hitting these bloody jelly fish - Hey Leon). At the other end of this same line I pass it through a block and then go across the trmap to repeat the same system on the other side, this means you can pull either rudder down from anywhere on the tramp. My current boat has a slightly differnet setup as I am playing around with a sytem that will let me pull it down from on the tramp or on the wire using the same rope (will let you know when I get this worked out).

You will find the boat a lot more responsive if you fly the windward rudder when sailing down wind, also I pull the windward board up until the tip is flush with the bottom of the boat and have the leeward board about halfway up, some people have the both all the way up and some leave them down, see what works best for you. If you pull them to far up you will get a lot of turbulance in the bottom of the case at it will slow you down, you will hear and feel it if you pull them to far up.

Some people fly the widward rudder also when going upwind, this can make the steering more responsive, but dont forget to put it back down before you tack or the boat will park itself head to wind during the tack.

I find it useful to have all the control lines different colours to make it easier to grab the correct one at a mark rounding or when they have been washed all over the place during a race in a bit of breeze.

If you have any other 16's or 5.8's sailing near where you are check ou the setup they are using as a lot of the systems are the same.

What is the sail no. of the boat that you have got, this may give us a clue as to how it would have been setup in the past as there have been a few subtle changes over the years.

Hope this helps.

Corey

Share this post


Link to post
Share on other sites

Thanks again Corey for the info. I owe you a beer or 2 if we meet some day.

Pete

Share this post


Link to post
Share on other sites

I have so far rigged up the mast rotation control, dagger board pull down rope and rudder pull down system. I have the old style rudder pull down system. Sail No is 55. Hoping to get out this weekend and try it all out. Cheers.

Share this post


Link to post
Share on other sites

Hey Corey - how many times does the sail downhaul pass through the lower eyelet? I have nmine set up to go through once but your seems to go twice - or am I seeing it wrongly?

Share this post


Link to post
Share on other sites

The standard setup only has the rope go through the lower eye once.

The top eye should have the double down haul blocks on an s shaped hook, with a double block on each side of the sail.

The rope then makes the purchase system on one side of the sail, then passes through the lower eye to make the purchase on the other side of the sail.

Most sails have the rope simply pass through the eye and continue on the other side of the sail, some older sails may have a small block bolted through the top of the eye on both sides of the sail, we used to do this to reduce the friction of the rope passing through to the other side, with more modern ropes and low friction coverings this is no longer needed as most ropes will run freely through the eye, make sure the downhaul rope you are using is not to large in diameter as it will not run freely through the system and will not release easily when you need it to.

The really old setup for the original Mylar sails only used a single block on each side because if you canked on to much downhaul all it did was pull the seams apart on the sail, when they changed to the Dacron sails most people added additonal blocks so that you have double blocks on either side of the sail, the dacron sail responds to more downhaul differently to the mylar sail.

I took some pics of the deck setup on my boat last week when I sailed with the new square top but didnt take any of the downhaul setup, we have our State Tiltles over the Easter Long Weekend so I can get some pics of it if you like and post them on here, if you need any other pics of how the boats are genrally setup let me know and I will get some pics over the weekend.

On a slightly differnet subject i have included a couple of pics of the latest protype square top, this thing is really sexy on the boat.

I couldn't get any pics of it with sheet tension on or while sailing because all the A Class guys normally at the club had buggered off to the lake as it was blowing 20 to 25 from the South East on the day.

post-14851-13778265694996_thumb.jpg

post-14851-13778265695353_thumb.jpg

Share this post


Link to post
Share on other sites

Hi Corey,

Interesting to see the down haul line go through the lower eye. I got 2 sails with my boat and one has the sweeper professionally cut out so they must have had to modify the downhaul as there is only one eyelet on this sail. What they have done is cut a slot in the bottom of the mast and installed a pulley wheel on each side of the slot. The downhaul line passes through here to link each side which would normally go through the lower eye. This way the downhaul can stay permanently rigged when you take the sail on and off. Seems to work well. [ATTACH=CONFIG]748[/ATTACH]l

post-24064-13778265695851_thumb.jpg

Share this post


Link to post
Share on other sites

Thanks Corey,

I appreciate the answer. It looks as though I have it right based on your description.

How would you rate the new square-top?

Martin

Share this post


Link to post
Share on other sites

Here are a couple of pics of the standard downhaul setup used on most of the boats, there is a differnet option that sometimes gets used, this was borrowed from the setup on some of the 5.8's and does not have the cleats on the mast, instead the downhaul cleats are on the side decks near the side stays.

I have also attached a couple of pics of this setup, Guy's boat #310 (which is currently for sale) has this alternative setup, the last fall of the downhaul passes through the front of the tramp to a couple of blocks mounted on the rear face of the front beam, there is then a 2 to 1 purchase under the tramp which passes under the tramp and up through an eyelet along the side of the tramp to the cleat on the side deck. There are a few advantages with this type of setup, the mast is a bit cleaner, and the downhaul is easy to adjust as the cleat is literally at your feet. There are a few potential disadvantages such as when it really blows you have to go forward to get the downhaul for adjustment and you cannot easily switch masts with other boats that use the standard setup, I also think the mast may be a little restricted in its ability to rotate while the downhaul is loaded.

I have put a few details about the new square top sail in the other thread about this sail.

hope this helps

Corey

post-14851-13778265701118_thumb.jpg

post-14851-13778265701319_thumb.jpg

post-14851-13778265701511_thumb.jpg

post-14851-13778265701711_thumb.jpg

post-14851-1377826570191_thumb.jpg

post-14851-1377826570211_thumb.jpg

Share this post


Link to post
Share on other sites

I realise this is an old, old thread but are any of the gents that posted in this thread still about?  I have a couple of questions.

Thanks

MG

 

Share this post


Link to post
Share on other sites

Yep, still about (from time to time) may be able to help answer your questions.

 

 

Coremeister

Share this post


Link to post
Share on other sites
11 hours ago, Coremeister 2 said:

Yep, still about (from time to time) may be able to help answer your questions.

 

 

Coremeister

 

Brilliant.  Let me knock up a sketch and upload it.

 

Share this post


Link to post
Share on other sites

Just wondering if you could please provide some advice on how I rig the mast adjuster on my 16 sq.  (Mast adjuster in front of mast.)  

From the photos you've posted above I can nearly make out what’s going on but not quite.

If you look at the sketch I've attached I'm wondering that if I'm siting port side;

- do you rig the mast adjuster starting at [A] then through [ B ] then cleat off through [C] or

- do you start at [A] then through [D] and then cleat off through [C]?  (And vice versa if I were sitting on the starboard side. [A-B-E] )

The reason I ask is because if I'm siting as shown in the sketch the mast is usually rotated around too much to the port side as shown on the sketch in the mast marked (1).  My understanding is it is more efficient if it were in position (2). 

BUT to rotate the adjuster clockwise from (1) to (2) I would need to change sides whilst the boat is in motion if it's rigged [A-B-C] & [A-D-E]  which obviously you can’t do.  If it were rigged [A–D-C] I can rotate it clockwise from the port side but that looks like an awkward setup.

Does the rope pass through the little upstands and then cross behind the mast [A – D – C] or do you set it up [A–B-C] before you head off the shore?

Sorry if this has been covered above and I’ve missed something.

 

 

Mast rotator.pdf

Mast rotator.jpg

Share this post


Link to post
Share on other sites

I will try to find a couple of pics of the standard setups.

As in the previous posts there have been a few minor variations over the year's, not acounting for non standard setups that tend to show up on older boats.

What sail number is your boat ?

I will get some time over the weekend to answer in a bit of detail

 

Corey

Share this post


Link to post
Share on other sites

Thanks Corey appreciate it.  My sail number is 25.

 

Share this post


Link to post
Share on other sites

The standard setup for a forward facing mast rotator on a 16sq is rigged as per your sketch A-B-C, there are a couple of minor variations to this, most people tie the rope end to the base of the upstand block that is on the beam at B then loop through the rotator at A (dont worry about using a block here as it only gets in the way and the rope passes smoothly over the round material of the rotator anyway, this will give a simple 2:1 system that is easier to uncleat). Then back through the block at B to the cleat on the beam at C. Again a common variation is to then continue the same rope back across the trampoline (under the toe strap) to then become the system on the starboard side, make sure you leave a bit of slack in the system as you dont want it to have to run through the system each time you tack or gybe as it will get caught and cause grief. 

As per your sketch above the sail and mast shown as incorrect is actually correct, the mast rotator generally does nothing when going to windward and is only used when running downwind to over rotate the mast, this seems a little odd at first when compared to boats such as A Classes, Taipans or even F18's and F16's  (or any others with a wing profile mast and boom) the Nacra mast is more of an elliptical profile a behaves a little differently. The mast rotation when going upwind responds more to the position of the outhaul car, it will find its own angle based mostly on this and the shape and tension of the bottom battens.

When running downwind the mast is over rotated  and cleated on the windward side, with the outhaul car released to the end of its track, this has the effect of adding draft to the sail which helps to run deeper, some people don't bother with running the rope but still keep the rotator in place to allow you to "pop" the sail in light winds, they can still over rotate the mast downwind by putting their knee against it to hold it there, when there is enough breeze to warrant not sitting near the front beam they simply don't worry about it, I prefer to still keep it cleated even in these conditions as it stops the mast pumping from the boats motion in waves. 

The sketch you show as correct is correct by the text books and will deal with things such as maintaining attached laminar flows and angle of attack, this is critical on boats such as A's and F18 that carry wing masts, even more critical on things such as Americas Cup boats with solid wing mast/sail setups, it does not directly carry over to the Nacra system, we have played around with the ideas with both the dacron sail and the newer square tops, up until mid way through the last nationals I had my mast rotator facing backwards and rigged to allow mast rotation control upwind but still allow over rotation downwind, at previous Nationals one of the WA boats has played around with a modified system similar to that used on the F18 Infusions (I think Andrew has gone back to the normal setup). I was finding that by de-rotating the mast upwind the boat would foot off with good speed but would not maintain height to windward, and when the breeze was up and I had plenty of downhaul on the mast would flick towards the center and tend to stay there, this would really kill the height and the only way to get it to go back was to drop the downhaul and rotation control and start the process again which was not fast compared to the fleet. On the lay day i put the mast rotation back to facing forward so that I could lock the mast around slightly over rotated going to windward to stop it centering, my boat seems to do this more on on tack than the other, haven't figured out why as yet. As stated in earlier posts, over the years plenty of people have played around with various systems to control mast rotation, some are successful in some conditions and others make very little difference over the entire wind range, because of this most people end up going back to the standard system which works well over the entire wind range. The mast rotation makes the most difference when running downwind and as such it is more important to have a system that allows you to over rotate when running down wind. 

If you feel inclined to play around with any ideas with your boat please keep us updated as to the success, if Andrew has any pics of his modified F18 system that would be a good starting point as it did look kind of cool and also functional but may mean you need to have and additional eyelet fitted to your trampoline.

If I can be of further help just let me know.

 

 

Corey 

 

   

Share this post


Link to post
Share on other sites

Thanks heaps Corey.  There's a load to digest here.

Let me have a read of it all and I'll get back to you.

Many thanks.

 

Share this post


Link to post
Share on other sites

So Corey if I'm reading that correctly you're putting a knot in one end of the rope so it's held at B and then it passes up through A back to B and then Cleats off at C.

So effectively B -> A -> B -> C.

Is that right?

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now