Conference unifix::sailing

Hi Ron:

If you buy the Loos tension gauge, it comes with an instruction pamphlet 
describing some guidelines.  Their recommendation is a twist on what you've 
heard.  "Enough but NOT TOO LOOSE" is what they say.  The reasoning is that 
a loose rig bounces around too much and the resulting impact forces on the 
fittings are much higher that their recommended static forces are.  Plus a 
loose rig "works" when sailing in choppy water which is disconcerting.

If you're not interested in using the guage, set the upper shroud tension 
to that the leeward shroud does not go slack when sailing close hauled in 
20 knots of apparent wind.  Set the lowers so that the mast tip stays straight 
or bows slightly to leeward at this wind speed.  Setting both uppers and 
lowers firm to the touch will generally do this.  If not, take incremental 
half turns tighter until you achieve it.  

How tight you set the lowers compared to the uppers depends on the wind 
conditions and how performance oriented you are.  Loose lowers get more 
drive at low wind speeds because the mast will bow to leeward at the 
spreaders giving a fuller main.  Tight lowers cause the mast tip too fall 
off spilling off air at higher wind speeds.  The gain in low wind 
performance is marginal.  The increase in comfort and reduction in heeling 
from tight lowers is sigificant on a fractional rig.  If I were sailing 
with my family, I'd keep the lowers tight.

Forestay and backstay tension are interrelated.  Adjust the forestay 
turnbuckle to give enough rake for the amount of weather helm you like to 
have.  Longer forestay = more helm.  To adjust the backstay, sail close 
hauled in the same 20 knots apparent as before, trim your main so the top 
batten is parallel to the boom (mainsheet very tight), and tighten the 
backstay so all the slack is gone but the top batten is still parallel to 
the boom.  This will give good pointing in most conditions and minimize 
headstay sag in a breeze.  Too much headstay sag causes poor pointing and 
too much healing in a breeze.  Again, this emphasizes control and safety 
when it's windy.

When in doubt, err on the tight side.

- gene

    
    I borrowed a tension guage this Spring and spent one evening getting
    the stays to the recommended tension.  Getting the tension in all the
    lowers to match took much more time than expected, but the improvement
    in pointing this year was remarkable.
    
    No matter whether you're cruise- or race-oriented, the time spent on
    the rigging is well worth the effort.
    
    

    When first stepping the mast, would you have the stays loosely attached
    to the spreaders, set the tension on the stays, then tighten the
    connection to the spreaders?
    
    Gregg

    WINDSONG has one section side stays or shrouds with the upper stays
    being one run of wire from the deck to the mast passing through a
    fitting at the end of the spreader. I found out the hard way that there
    should be little or no tightness on that fitting. At least for stranded
    wire, any tightness will cause a pinching and pinching causes unwanted
    additional stress and the wire BREAKS! And we all know what happens
    when the upper shroud parts during rough weather, that's right the
    lower shroud give ups. "I hate it when that happens" cause nobody is
    left holding up the mast. 
    
    Fred the-one-with-a-whole-new-appreciation-for-rigging-tension/setup.

    RE: .4
    
    Are you saying that the stay (shroud) should be free to move withing
    the fitting? And that the fitting is merely keeping the stay at the end
    of the spreader?
    
    Gregg

    The answer I got from the Marine Surveyor assigned by my Ins Co when
    the mast took its swim, was, "just 'snug' enough to keep the speader in
    position". He explained that I should be able to move the spreader with
    only moderate force.
    
    It all seemes reasonable to me, but without thinking it through, I was
    the one who originally tightened them down to the point that they would
    NOT move. I could not even pull the remaining end out of the spreader
    after it broke. IT was tight. Obviously hind sight says TOO tight. 
    
    The fitting at the end of my spreader is a hard rubber one with a small
    "u" bolt with one side treaded and a nut. If I tighten the  nut just
    enough to compress the lock washer, I can still move the spreader but
    only with pressure. I do not think that once the mast is up and tension
    adjusted to the stay, that the spreader is going to move. Before I
    stepped the mast but with the upper stays in place, I lined the
    spreaders up so that the outboard ends were about one inch  above being
    perpendicular to the mast. 
    
    If this does not agree with what other know or think, PLEASE jump in.
    
    Of course this whole issue is more critical to the trailer sailor who
    typically steps their mast mre than once a season.
    
    Fred. who-has-to-replace-2-nuts-discoverd-missing-from-OB-motor-bracket!
    	Yesterday was an exciting sail for a number of reasons.

    
    re: 1" above perpendicular
    
        'course, that depends on the rig.  You want to bisect the angle
        the shroud makes around the spreader.  Usually that's about 7
        degrees above perpendicular but you can figure it out exactly
        by taking a photograph & doing a little geometry.

    I thought of bisecting the angle, but this would require more upward
    movement of the spreaders than the spreader bases attached to the mast
    would allow. My logic was that something above perpendicular to the
    mast would tend to hold the spreaders in place and still provide the
    required transfer of force.
    
    Fred

If the spreaders bisect the angle of the upper shroud, then moving the 
spreader up or down (assuming the shroud is tight) requires stretching 
the shroud, which requires a lot of force. Thus the load imposed by the 
tight shroud will keep the outer end of the spreader from moving either 
up or down. When the shroud is slack (eg, the shroud is the leeward 
shroud when sailing to weather) the outer end of the spreader must be 
kept from moving by somehow fixing or clamping the shroud to the end of 
the spreader. Not much clamping force is needed. 

As the spreader moves downward, there comes a position where the shroud 
will no longer need to stretch as the spreader moves downward. At this 
position the shroud load will force the spreader further downward, 
resulting in a loss of shroud tension and possible loss of the mast. So, 
bisecting the angle is rather desirable. The spreader doesn't have to be 
much above horizontal to achieve this.

    If the goal is to keep the lee shroud just short of looseness
    when reaching in a good wind, does this imply that if you have a
    soft boat then perhaps a slightly larger diameter shroud wire would
    be better?
    
    I'm thinking of buying an old 505. The new ones ($15,000) have cored
    hulls with kevlar and epoxy skins. They are extremely stiff and
    apparently run very high rig tensions. The old ones (like I can
    afford) are a lot softer and can't hold nearly as much tension.
    Thus they are not competitive in decent fleets.
    
    Clearly on a reach the bending of the system is partly due to rigging
    stretch and partly due to hull bending. If I have a soft hull, would
    it make sense to try to compensate for it by using slightly larger
    than normal shroud wire? I would keep the tension as low as
    possible, but hopefully the reduced stretch of the windward shroud
    would compensate to some degree the softer hull.
    
    This would be the opposite of the "you've got a soft boat so you
    need lighter wire" theory.
    
    I guess maybe the real question I'm asking is "how much does the
    windward shroud wire stretch on a dinghy under normal conditions?"
    
    Doug.

    re .10
    
      doubt they stretch at all. Ussually a light boat flips over and you
    practice the dog paddle. ;>)
    
       Snug the puppy up and forget about it. I learned a lot time ago to
    skip the bells and whistles and concentrate on sailing the big picture.
    Got of box of garbage I had bought and then took off.
    
       Maybe some low stretch halyards will make up for your wires as you
    get a bit more kick out of each puff.

    I bought an old 505, and it has a crude mast ram at the partner.
    What it really is is a wedge that can be pulled down between the
    front of the mast and the foredeck, thus forcing some straightness
    into the lower part of the mast and thus allowing fullness in the
    lower part of the sail.
    
    It's ugly as sin, basically. All the cool new boats have rams (aka
    "struts") that reach up from the foredeck to a car on the mast. By
    pulling the car down or up you can push the mast aft or forward
    to control bend in its lower half.
    
    But the deck on this boat is very thin plywood--a ram would punch a
    hole right through it. One option is to use blocks, which is what I
    probably will end up with. Another option is to use lower shrouds,
    which I'd like to investigate a bit.
    
    As I understand it, "lowers" would go from the mast at boom height
    back to the shroud chainplates. This would put them at perhaps a 30
    degree angle from horizontal. Pulling on the lower shroud would pull
    back the mast and accomplish the same thing as the ram, although
    only in one direction.
    
    Does anyone have experience using lower shrouds on a small boat?
    
    Thanks.
    
    Doug.
    
    

I have got lowers on my Old Javelin. As you mentioned lower shouds can only pull
the mast straight. They also add to the problem of a pre bent boat, amplifying
the effect of the shouds of bending an old boat athwartships. If they are being
used with a pre bent rig then as I understand it lowers will work, because as
you let them off to increase bend the mast will naturally bend. Applying more
Forestay tension should also induce more bend. One advantange of lowers is that
they pull at the correct point on the mast. Mast rams (not struts) push and pull
at deck level which sometimes cause 'S' mends in the mast.

Matthew 

    I wonder if you could take a minute to explain exactly how your
    lowers are rigged? What size wire? Is there a single pull line or
    one for each side? Are the two shrouds connected somehow to maintain
    the setting equally between them? How do they hook onto the mast?
    
    Adding lowers to my boat would be a bit of an engineering problem
    because none of the stuff is there at this point. One question is
    whether the engineering difficulties of lowers vs blocks at the
    partner is worth it.
    
    I'm still not clear on exactly why you need lower mast bend control
    at all, anyway. Isn't this really a sail shape issue? If you want to
    flatten the sail, pull on more vang; the sail should be cut to make
    the flattening take effect over the whole sail and not require two
    adjustments (or more if you include outhaul and cunningham). Or is
    this a case of the 505 people going overboard in adjustability?
    
    How about if I just block the mast so that, with the sail unrigged
    but the shroud tension adjusted for the conditions, the mast just
    touches the block at the front? This is what is suggested in one book I
    have...
    
    Thanks for any hints...
    
    
    Doug.

With older boats it is often worth sitting down and thinking about whether a
piece of rigging is worth the Money,time and effort, against the amount of speed
you expect to gain from it. Trying to reduce the weight as much as possible and
replacing old sails for new ones that match the mast are probably the most
benificial. Obviously you have to ask the question "Is it worth spending  money
on new sails for an old boat." 

When you see the amount of speed difference between 505's and that most of the
fast ones are highly adjustable then I suppose that all the adjustment is
needed. Some boats have matrixes drawn on the fordeck with wind speed across the
top and the settings down the side.

Lowers. can be adjusted while sailing with a lot more ease than adding or
removeing mast blocks. My lowers are attatched to U bolts located on the side
tanks near the bulkhead more or less on line with the shrouds. The anchor point
could be on the same fitting as the main shrouds. Attatched to the U bolts are
swivel blocks. On the mast at about gooseneck height is a double spinaker pole
eye fitting, fitted with very strong rivits. This fitting has two more blocks
hanging from it. Attatched to one side of the mast rack is a another block. I
used 3-4mm wire rope to create a 2-1 purchase between the mast and deck blocks.
The tails of the wire purchase system come together half way between the double
spinaker fitting and the mast foot , running down the front of the mast. At this
point they are attatched to a none stretch rope that goes throught the block on
the mast rack and runs aft onto a large purchase system (similar purchase to the
rig tension) which is under the CB case. The tail of the purchase system is then
routed from the floor of the boat up through the CB case to a swivel cleat.
Which can be adjusted from  either side. 

Well I hope that wasn't too boring.

Matthew

    Not boring at all. Thanks for the info.
    
    Question: Do you adjust this very much on the course, or is it
    a wind speed issue that can more or less be set once at the beginning
    of the race and then left alone? Obviously mast blocks would be a lot
    of hassle if they have to be removed upon every change from beat to
    reach, but if the lower setting only needs one setup per race, it
    doesn't seem worth the extra hassle and hardware.
    
    I basically prefer simplicity if possible...
    
    Doug.

You hear different stories about how much people use the mast struts/lowers.

If one went sailing in very light airs and had flattened the mainsail
accordingly and then the wind picked up. One would be able to powerup the rig
with reletive ease by pulling on the lowers. 

Some people just pull on rig tension and set up the strut/lowers  to just take
up the slack, mainly to pull against the force from the kicker. This is probably
done on land before the race.

I suppose like all bits on the boat that adjust the shape of the sail, its trial
and error to find which possition/s the sail likes the mast in.

Extract from the 505 home page:

http://www.paw.com/sail/int505/fix-up.htm

Mast Bend Adjustment

Modern North American 505s use mast struts, fixed on the foredeck above the
watertight bulkhead,and fastened to a "car" sliding on a track riveted or bolted
to the mast, roughly at gooseneck height. Pulling down on the car forces the
mast aft at gooseneck level, while pulling it up forces the mast forward
inducing bend. This system works very well, but the same effect can be had by
using wooden blocks in front and behind the mast at deck level. The mast is
forced aft to straighten it for more power, is allowed to bend forward to
depower, and is forced forward to pre-bend for flatter sail shape in light air.
In addition, the mast is prevented from being pushed to far aft by pressure from
the spinnaker pole on a heavy air reach. This last point is important when tight
reaching in heavy air. If you do not have a means to prevent the pole
straightening - or even inverting - the mast, when a puff hits, the spinnaker
pole will start bending around the forestay and the main will become fuller,
both undesirable. 



Obviously lowers will not fight against spinnaker pole pressure.

Matthew