[Rhodes22-list] Mainsail slugs (was Mast Crane) (was Lou Moore)

[Roger Pihlaja]

Oh brother, problem solved!  The reason you don't put a slug on the
headboard is that the headboard is rigid.  The system needs the slight flex
of the cloth sails in order not to bind up as the length of halyard is
reduced as the mainsail is hoisted up the mast.  It's sort of the "universal
joint" in the system & putting a slug on the headboard took all the
flexibility out.  Never put a slug on the headboard.

Roger Pihlaja
S/V Dynamic Equilibrium

----- Original Message -----
From: "Rik Sandberg" <sanderico at earthlink.net>
To: "The Rhodes 22 mail list" <rhodes22-list at rhodes22.org>
Sent: Friday, March 19, 2004 4:34 PM
Subject: Re: [Rhodes22-list] Mainsail slugs (was Mast Crane) (was Lou Moore)


> Steve,
>
> Hmmm....don't need a slug on the headboard.....I too had (key word had) a
> slug on the headboard of the mainsail on my Flicka. It wore out and broke
> when we were down at Kentucky Lake last fall. the other slugs seem to be
> fine. I was wondering how to go about replacing it, but if this is right,
I
> shouldn't have to.
>
> Can you explain why a slug isn't needed on the headboard?? It seems
there's
> a lot of new stuff to learn when you go from a IMF main to a standard main
:-)
>
> Rik
>
>
> At 01:49 PM 3/19/2004, you wrote:
> >Lloyd
> >The slug in the headboard was the problem.  Didn't
> >need one there.
> >Steve
> >
> >
> >--- Lloyd Crowther <lcrowther at cox.net> wrote:
> > > Roger,
> > >
> > > Thanks for the prompt reply.  My problem was more
> > > that I couldn't get my
> > > Main all the way up rather than I couldn't get it
> > > down.  Before I had the
> > > 7/16" plastic, cylindrical slugs sewn onto grommets
> > > the sail maker later
> > > placed aft of the bolt rope along the mainsail's
> > > luff, I tied a slug to my
> > > halyard, tied a string to the lower part of the slot
> > > on the slug to pull the
> > > slug back down, and hoisted it up, no problem.  I
> > > took the sail to Quantum
> > > Sails Loft in Annapolis and asked them to put the
> > > slugs on.  When I tried to
> > > raise the sail, the topmost slug would bind about
> > > 3/4 t0 7/8 of the way to
> > > the masthead no matter what I did, lubrication or
> > > any thing else. I never
> > > had any problem getting the sail back down because I
> > > did all this in my
> > > slip.  I did take the precaution of looping a light
> > > line through the bottoms
> > > of the slug slots so if they twisted I could pull on
> > > the line to re-tension
> > > any slug that twisted.
> > >
> > > I just went down to the cellar and measured the
> > > spacing of the grommets they
> > > put along the luff (I cut the slugs off when I
> > > abandoned the whole exercise
> > > last spring) and found they were 18" on centers.  So
> > > I guess you have solved
> > > some if not all of my problem although I doubt that
> > > I pay all that money
> > > again to prove you right.
> > >
> > >   My thought was that as the sail got nearer the
> > > pulley in the mast. the
> > > halyard tended to pull the headboard, with its
> > > sewed-on slug, in towards the
> > > mast, relieving the pressure on that slug and
> > > allowing it to twist and bind.
> > > In any event, thank you again for your rapid and
> > > responsive reply, your
> > > knowledge continues to amaze me.
> > >
> > > Lloyd
> > >
> > > ----- Original Message -----
> > > From: "Roger Pihlaja" <cen09402 at centurytel.net>
> > > To: "The Rhodes 22 mail list"
> > > <rhodes22-list at rhodes22.org>
> > > Sent: Friday, March 19, 2004 5:45 AM
> > > Subject: Re: [Rhodes22-list] Mast Crane (was Lou
> > > Moore)
> > >
> > >
> > > > Lloyd,
> > > >
> > > > I used 7/16" dia. cylindrical plastic sail slugs
> > > on the luff and a 7/16"
> > > > dia. bolt rope on the foot.  Note: There are two
> > > styles of sail slugs in
> > > > common use, T-shaped & cylindrical shaped.  Each
> > > style is designed to be
> > > > used with the cooresponding slot shape on a mast
> > > and they are not
> > > > interchangable.  On Dynamic Equilibrium, the
> > > cylindrical style of sail
> > > slug
> > > > matched the configuration of the extruded slot on
> > > the mast.  If a bolt
> > > rope
> > > > works well in your mast slot; then, I would expect
> > > the cylindrical style
> > > > sail slugs are the correct ones for your mast as
> > > well.  However, I would
> > > > check to be certain.  7/16" dia cylindrical sail
> > > slugs are the same size
> > > as
> > > > came on the OEM standard sail.
> > > >
> > > > Here's a couple of tips you might try on the mast
> > > groove:
> > > >
> > > > Take a rag & moisten it with a good silicone
> > > lubricant like Dow Corning
> > > > Slipicone.  Run the oily rag up & down the length
> > > of the slot.  The
> > > > Slipicone will remove any accumulated crud that's
> > > built up in the slot,
> > > plus
> > > > it will also leave behind a silicone wax finish
> > > that is much more slippery
> > > > than the bare anodized aluminum finish.  Do the
> > > same thing with the
> > > plastic
> > > > slugs on the mainsail.  NOTE: Dispose of this oily
> > > rag by immediately
> > > > burning it OR soak it in water, put it in a
> > > plastic bag, & put it out with
> > > > this week's trash.  NEVER just leave it sitting
> > > around or it may
> > > > spontaneously ignite & start a fire.  I usually do
> > > this maintenance on the
> > > > mast slot at the beginning of the sailing season.
> > > >
> > > > While you are wiping down the slot, take special
> > > note of the location on
> > > the
> > > > mast if you feel any rough spots, dents, or burrs.
> > >  Go back and carefully
> > > > inspect those spots.  A dent or burr on the inside
> > > surface of the slot can
> > > > cause the bolt rope or sail slides to hang up.  A
> > > minor dent or burr can
> > > be
> > > > smoothed with 400 grit emery cloth.  A rough spot
> > > is quite often a
> > > build-up
> > > > of something like tree sap or bird droppings,
> > > which can be removed with a
> > > > product like Formula 409.  One year, I even
> > > discovered a mud dauber wasp
> > > > nest in the slot!  I was relieved to find the wasp
> > > nest because something
> > > > was absolutely jamming the mainsail at that point
> > > on the mast.  I was
> > > afraid
> > > > it was something really serious.
> > > >
> > > > While you are wiping down the sail slugs, take
> > > note if any of them are
> > > > damaged or have rough spots on them.  Repair or
> > > replace as required.
> > > >
> > > > After cleaning out the mast slot, take one of your
> > > sail slugs & run it up
> > > &
> > > > down the length of the slot on the mast.  It
> > > should move freely with no
> > > > binding anywhere.  It's possible the gap width on
> > > the slot on your mast
> > > has
> > > > a "tight spot" wherein the gap width is off spec
> > > too narrow.  This
> > > condition
> > > > can be repaired by forcing a wooden wedge into the
> > > slot in the narrow
> > > areas
> > > > to widen the gap.  Depending upon the length of
> > > the narrow slot region,
> > > you
> > > > might have to custom make this wedge to fit your
> > > situation.
> > > >
> > > > It's also possible that the sail slugs on the sail
> > > you tried were spaced
> > > too
> > > > far apart.  The sail slugs need to be spaced no
> > > more than about 12" apart
> > > on
> > > > center, or they tend to get cocked and bind up in
> > > the slot.  Also, the
> > > tiny
> > > > shackles that attach the sail slugs to the luff on
> > > the mainsail must be
> > > the
> > > > proper size.  If they are too short, the luff will
> > > bind on the trailing
> > > edge
> > > > of the slot.  If they are too long, they may allow
> > > the sail slug to become
> > > > cocked in the slot & bind up.
> > > >
> > > > Finally, I'm sure you already know this; but, I'll
> > > just mention it for the
> > > > sake of completeness.  No mainsail will drop down
> > > the mast easily if the
> > > > sail is under load.  This means the boat must be
> > > head to the wind, the
> > > boom
> > > > must be centered, with the boom topping lift
> > > supporting the weight of the
> > > > boom.
> > > >
> > > > If none of this works for you Lyoyd; then, I'm at
> > > a loss to explain why
> > > your
> > > > mainsail won't fall down the mast when the halyard
> > > is released.
> > > >
> > > > Roger Pihlaja
> > > > S/V Dynamic Equilibrium
> > > >
> > > >
> > > >
> > > >
> > > > ----- Original Message -----
> > > > From: "Lloyd Crowther" <lcrowther at cox.net>
> > > > To: "The Rhodes 22 mail list"
> > > <rhodes22-list at rhodes22.org>
> > > > Sent: Friday, March 19, 2004 1:27 AM
> > > > Subject: Re: [Rhodes22-list] Mast Crane (was Lou
> > > Moore)
> > > >
> > > >
> > > > > Roger,
> > > > >
> > > > > What size sail slugs do you use?  I tried 7/16"
> > > plastic sail slugs and
> > > > > couldn't even get the sail all the way up
> > > without it binding.  Don't
> > > have
> > > > > any trouble with  raising it with the bolt rope
> > > but it is a bear to
> > > furl
> > > > if
> > > > > your a single-hander.
> > > > >
> > > > > Lloyd
> > > > >
> > > > > ----- Original Message -----
> > > > > From: "Roger Pihlaja" <cen09402 at centurytel.net>
> > > > > To: "The Rhodes 22 mail list"
> > > <rhodes22-list at rhodes22.org>
> > > > > Sent: Thursday, March 18, 2004 11:35 PM
> > > > > Subject: Re: [Rhodes22-list] Mast Crane (was Lou
> > > Moore)
> > > > >
> > > > >
> > > > > > Peter,
> > > > > >
> > > > > > I modified the standard masthead with some
> > > aluminum bar stock & a MIG
> > > > > > welder.
> > > > > >
> > > > > > Look on the FAQ page for the tension settings.
> > > > > >
> > > > > > The way to measure maximum chord inches is to
> > > first load up the rig
> > > with
> > > > > the
> > > > > > backstays.  Then, run the main halyard down to
> > > the base of the mast &
> > > > tie
> > > > > it
> > > > > > off taut against the slot on the aft face.
> > > Then, using a bosun's
> > > chair
> > > > or
> > > > > a
> > > > > > step ladder to get up high enough on the mast,
> > > measure the maximum
> > > > > > chord-inches from the halyard to the slot on
> > > the mast.
> > > > > >
> > > > > > Note: If all you want to do is eliminate the
> > > headstay sag, the
> > > standard
> > > > > > backstay adjuster with the standard masthead
> > > geometry will do that.
> > > The
> > > > > > only real reason for the crane is to create
> > > clearance between the
> > > > > backstays
> > > > > > and the big roach of a fully battened
> > > mainsail.  You also need to be a
> > > > > > little conservative re the amount of roach in
> > > the mainsail.  Designing
> > > > in
> > > > > > too much roach will disrupt the balance of the
> > > sail plan by shifting
> > > the
> > > > > > center of effort (CE) aft, thus causing an
> > > excessive amount of weather
> > > > > helm.
> > > > > > Some of this weather helm can be dialed back
> > > out by adjusting the
> > > static
> > > > > > tilt of the mast such that the mast leans
> > > forward slightly, thus
> > > moving
> > > > > the
> > > > > > CE of the rig forward.  The static tilt of the
> > > mast is adjusted with
> > > the
> > > > > > turnbuckle on the forestay or by shortening
> > > the forestay cable.
> > > > > >
> > > > > > After having installed both a high tech
> > > composite genoa on a Harken
> > > > roller
> > > > > > furler & a fully battened mainsail, I'd say
> > > the genoa returns the
> > > > biggest
> > > > > > performance bang for the buck.  But, the fully
> > > battened mainsail looks
> > > > > > totally cool when hoisted & the sail shape is
> > > much easier to adjust to
> > > > > > exactly what you want for the prevailing
> > > conditions & point of sail.
> > > > > >
> > > > > > You will have a choice between sail slugs and
> > > a bolt rope on the luff.
> > > > I
> > > > > > choose sail slugs & my mainsail almost falls
> > > down the mast when the
> > > > > halyard
> > > > > > is released.  Reefing it under load sometimes
> > > requires the sail be
> > > > hauled
> > > > > > down; but, that was true with the partially
> > > battened mainsail as well.
> > > > > You
> > > > > > will have a choice between loose footed &
> > > footed using a bolt rope.  I
> > > > > > choose a bolt rope on the foot, mainly because
> > > that's what the
> > > standard
> > > > > > mainsail had.  I would order the optional
> > > zippered shelf which will
> > > > allow
> > > > > > you to increase the fullness of the lower 1/3
> > > of the mainsail shape
> > > for
> > > > > > light air.  You zip up the shelf to flatten
> > > the mainsail shape for
> > > heavy
> > > > > > air.  After you've paid the big bucks for this
> > > fully battened
> > > mainsail,
> > > > > > definitely get a leech line & cleat.  The
> > > primary function of the
> > > leech
> > > > > line
> > > > > > is to stop the trailing edge of the sail from
> > > fluttering as the air
> > > foil
> > > > > > sheds its trailing vortices.  This fluttering
> > > subjects the sailcloth &
> > > > > > stitching in the leech to a lot of high
> > > frequency wear cycles, which
> > > can
> > > > > > result in premature fatigue failure of the
> > > material.  You tighten the
> > > > > leech
> > > > > > line just enough to stop the fluttering.
> > > Thus, the leech line extends
> > > > the
> > > > > > life of your expensive new sail & is well
> > > worth the money up front to
> > > > have
> > > > > > it installed.  You will have to specify the
> > > number of reef points in
> > > > your
> > > > > > new mainsail.  I originally ordered just 1 set
> > > & later had a sailmaker
> > > > > > retrofit a 2nd set.  The next time around, I
> > > will order two sets of
> > > reef
> > > > > > points.  My 1st reef point reduces the
> > > mainsail area by 1/3 and the
> > > > second
> > > > > > reef point by 2/3 relative to the full
> > > mainsail area.
> > > > > >
> > > > > > Finally, this new fully battened mainsail will
> > > be substantially
> > > bulkier
> > > > > when
> > > > > > furled on the boom vs. the standard mainsail.
> > > The chances are, your
> > > > > current
> > > > > > mainsail cover will no longer fit.  I modified
> > > my old mainsail cover
> > > to
> > > > > fit
> > > > > > the new sail.
> > > > > >
> > > > > > Roger Pihlaja
> > > > > > S/V Dynamic Equilibrium
> > > > > >
> > > > > >
> > > > > > ----- Original Message -----
> > > > > > From: "Peter Thorn" <pthorn at nc.rr.com>
> > > > > > To: "The Rhodes 22 mail list"
> > > <rhodes22-list at rhodes22.org>
> > > > > > Sent: Thursday, March 18, 2004 5:21 PM
> > > > > > Subject: Re: [Rhodes22-list] Mast Crane (was
> > > Lou Moore)
> > > > > >
> > > > > >
> > > > > > > Roger,
> > > > > > >
> > > > > > > I certainly will try it.  It sounds great!
> > > > > > >
> > > > > > > Where did you acquire your 12" mast crane?
> > > Do you recall Loos
> > > > settings
> > > > > > for
> > > > > > > forwards, uppers and aft shrouds?
> > > > > > >
> > > > > > > With only 4 cord/inches upper mast bend, my
> > > guess is the greatest
> > > > > benefit
> > > > > > is
> > > > > > > headsail luff sag adjustment.   If you can
> > > obtain enough tension to
> > > > keep
> > > > > a
> > > > > > > 150 Genoa close to zero cord/inches in a
> > > blow, you must be putting
> > > > > > 400-500
> > > > > > > pounds on the headstay.   R22 construction
> > > looks like it would take
> > > > > that.
> > > > > > > Stan builds 'em beefy.
> > > > > > >
> > > > > > > Thinking out loud - 1) built the rig first,
> > > 2) measure/verify the
> > > > > > > "reasonable mast bend" above the spreaders,
> > > 3) send numbers to
> > > > > sailmaker.
> > > > > > > Can you think of anything else?
> > > > > > >
> > > > > > > Best,
> > > > > > >
> > > > > > > PT
> > > > > > >
> > > > > > >
> > > > > > > > Peter,
> > > > > > > >
> > > > > > > > With the forestay cable buried inside of
> > > the roller furling foil &
> > > > > > > > impossible to get at with a Loo's Tension
> > > gage, I've never
> > > measured
> > > > > the
> > > > > > > > forestay tension.  I have some calculated
> > > theoretical values; but,
> > > > > they
> > > > > > > > would only apply to my particular boat &
> > > masthead geometry &
> > > > wouldn't
> > > > > be
> > > > > > > of
> > > > > > > > much use to anyone else.  When you refer
> > > to "chord-inches, I
> > > presume
> > > > > you
> > > > > > > > mean the maximum perpendicular distance
> > > from the chord to the
> > > radius
> > > > > of
> > > > > > > > curvature?  Assuming my definition of
> > > chord-inch agrees with
> > > yours,
> > > > > with
> > > > > > > the
> > > > > > > > range of adjustments on Dynamic
> > > Equilibrium as currently
> > > configured,
> > > > > > over
> > > > > > > > the 333-5/8 inch length of the forestay, I
> > > can adjust the
> > > chord-inch
> > > > > > value
> > > > > > > > from nearly 0 to about 6 inches.  The
> > > aluminum extrusions on the
> > > > > > headsail
> > > > > > > > foils won't sag too much more than that
> > > without causing bearing
> > > and
> > > > > > > furling
> > > > > > > > problems.
> > > > > > > >
> > > > > > > > On my current fully battened mainsail, I
> > > went fairly conservative
> > > on
> > > > > the
> > > > > > > > amount of mast bend the mainsail can
> > > respond to.  It is currently
> > > > cut
> > > > > to
> > > > > > > > respond to only about 2 chord-inches,
> > > mostly above the spreaders.
> > > > The
> > > > > > > mast
> > > > > > > > curvature actually trails off
> > > asymptotically to 0 below the
> > > > spreaders
> > > > > > > > because of stretch in the lower sides
> > > stays and the differential
> > > > > > fore/aft
> > > > > > > > static load I put on the lower side stays.
> > >  The forward lower side
> > > > > stays
> > > > > > > are
> > > > > > > > adjusted tighter than the rear lower side
> > > stays to facilitate mast
> > > > > > > bending.
> > > > > > > > I think the amount of mast bend could be
> > > increased to about 4
> > > > > > cord-inches
> > > > > > > > without any trouble.  When the time comes
> > > to replace this
> > > mainsail,
> > > > > > that's
> > > > > > > > the spec I plan to ask for.  With the
> > > current aluminum mast
> > > > extrusion,
> > > > > > > > trying for more bend than about 4
> > > cord-inches is asking for
> > > trouble
> > > > in
> > > > > > my
> > > > > > > > engineering judgement.  The aluminum
> > > extrusion might experience
> > > > > fatigue
> > > > > > > > failure (especially in a salt water
> > > environment) and the loads on
> > > > the
> > > > > > > > forestay & backstays would start to get a
> > > little high for the hull
> > > > > > > structure
> > > > > > > > and chain plates.
> > > > > > > >
> > > > > > > > As you probably already know, you bend the
> > > mast to straighten the
> > > > > > > forestay,
> > > > > > > > thereby reducing headstay sag plus flatten
> > > the mainsail shape.
> > > Both
> > > > > > > actions
> > > > > > > > depower the rig for heavy air.  Yes,
> > > depowering the rig with the
> > > > > > backstay
> > > > > > > > adjuster is much faster than any other
> > > method because it takes
> > > care
> > > > of
> > > > > > > both
> > > > > > > > sails at the same time.  I have my
> > > backstay adjuster setup with a
> > > > > Harken
> > > > > > > 144
> > > > > > > > swivel cam base with 150 cam-matic cleat,
> > > 082 single bullet block,
> > > &
> > > > > 071
> > > > > > > > stand-up spring mounted on the aft
> > > starboard gunnel.  The
> > > swiveling
> > > > > arm
> > > > > > > cam
> > > > > > > > base & cam-matic cleat on the end of the
> > > arm allows me to reach
> > > the
> > > > > > > backstay
> > > > > > > > adjuster from virtually any helm position.
> > >  The backstay adjuster
> > > > line
> > > > > > is
> > > > > > > > marked with calibration marks for quick,
> > > reproducible tension
> > > > > > adjustments.
> > > > > > > > I used the big Harken 144 swivel cam base
> > > because this unit is
> > > > mounted
> > > > > > > right
> > > > > > > > by where people come aboard over the
> > > transom from the boarding
> > > > ladder.
> > > > > > > The
> > > > > > > > 144 is sufficiently stout that you can
> > > stand on the swiveling arm
> > > > > > without
> > > > > > > > damaging it.  I've been sailing with this
> > > backstay adjuster setup
> > > > > since
> > > > > > > > 1988.  It's been absolutely bulletproof so
> > > far.
> > > > > > > >
> > > > > > > > Try it - You'll like it a whole bunch!
> > > > > > > >
> > > > > > > > Roger Pihlaja
> > > > > > > > S/V Dynamic Equilibrium
> > > > > > > >
> > > > > > > >
> > > > > > > > ----- Original Message -----
> > > > > > > > From: "Peter Thorn" <pthorn at nc.rr.com>
> > > > > > > > To: "The Rhodes 22 mail list"
> > > <rhodes22-list at rhodes22.org>
> > > > > > > > Sent: Thursday, March 18, 2004 10:44 AM
> > > > > > > > Subject: Re: [Rhodes22-list] Mast Crane
> > > (was Lou Moore)
> > > > > > > >
> > > > > > > >
> > > > > > > > > Roger,
> > > > > > > > >
> > > > > > > > > Thanks for the detailed explanation.  I
> > > am the child of an ME,
> > > but
> > > > > not
> > > > > > > one
> > > > > > > > > myself.  All my engineering is pants
> > > seat.  I'll add "eccentric
> > > > > > loading"
> > > > > > > > to
> > > > > > > > > my sailing jargon vocabulary.
> > > > > > > > >
> > > > > > > > > So, how much tension can you add to your
> > > forestay by adjusting
> > > > your
> > > > > > > > > backstay?  Can the 12" crane actually
> > > put more tension on
> > > forestay
> > > > > > than
> > > > > > > > std
> > > > > > > > > crane can?  We all know a light beam
> > > straight entry points much
> > > > > > better.
> > > > > > > > >
> > > > > > > > > And, will your Harken furler track allow
> > > the forestay to sag and
> > > > > power
> > > > > > > up
> > > > > > > > > (for light air)?
> > > > > > > > >
> > > > > > > > > For any boat with sail reduction
> > > capacity, mast bending might be
> > > a
> > > > > bit
> > > > > > > > > unnecessary - but  non-the-less
> > > interesting.  After all, one can
> > > > > bend
> > > > > > > the
> > > > > > > > > mast probably quicker than any other
> > > de-powering technique.
> > > > During
> > > > > a
> > > > > > > race
> > > > > > > > > it wouldn't distract from more important
> > > things (like paying
> > > > > attention
> > > > > > > to
> > > > > > > > > the wind) nearly as much as furling
> > > would.  How much mast bend
> > > > (say
> > > > > by
> > > > > > > > > "cord/inches") can you induce in Dynamic
> > > Equilibrium's mast
> > > above
> > > > > the
> > > > > > > > > spreaders?
> > > > > > > > >
> > > > > > > > > As always, I enjoy your posts.
> > > > > > > > >
> > > > > > > > > PT
> > > > > > > > >
> > > > > > > > >
> > > > > > > > >
> > > > > > > > > > Peter,
> > > > > > > > > >
> > > > > > > > > > Michael is talking about Dynamic
> > > Equilibrium's masthead.  I
> > > have
> > > > > my
> > > > > > > > double
> > > > > > > > > > backstay attachment point moved aft
> > > about 6 inches in order to
> > > > > allow
> > > > > > > the
> > > > > > > > > > double backstays to clear the roach of
> > > my fully battened
> > > > mainsail.
> > > > > > > > > >
> > > > > > > > > > Mast bend is highly dependent upon how
> > > you setup the tension
> > > in
> > > > > the
> > > > > > > > > standing
> > > > > > > > > > rigging.  I believe there is there is
> > > a standing rigging
> > > tuning
> > > > > > > > procedure
> > > > > > > > > on
> > > > > > > > > > the FAQ page.
> > > > > > > > > >
> > > > > > > > > > However, if you modify the masthead
> > > geometry, like on my boat,
> > > > the
> > > > > > > mast
> > > > > > > > > > operates a little bit differently than
> > > standard.  The mast can
> > > > be
> > > > > > > > modeled
> > > > > > > > > as
> > > > > > > > > > a column statically loaded by the
> > > standing rigging in
> > > > compression
> > > > > +
> > > > > > a
> > > > > > > > > > cantilever beam point loaded at the
> > > masthead.  The standard
> > > > > masthead
> > > > > > > > > > geometry loads the upper end of the
> > > mast pretty symetrically.
> > > > > > > However,
> > > > > > > > > when
> > > > > > > > > > you move the double backstay
> > > attachment point aft, you are
> > > > > > introducing
> > > > > > > a
> > > > > > > > > > factor called "eccentricity" (e) into
> > > the column loading.
> > > > > > Basically,
> > > > > > > > > think
> > > > > > > > > > of e as the amount by which the
> > > compression force vector is
> > > > moved
> > > > > > off
> > > > > > > > the
> > > > > > > > > > neutral axis of the column.  i.e. when
> > > e = 0, the compression
> > > > load
> > > > > > is
> > > > > > > > > > applied right down the neutral axis of
> > > the column & you have
> > > > pure
> > > > > > > column
> > > > > > > > > > buckling.  As e is increased, the
> > > deflection of the column
> > > under
> > > > > the
> > > > > > > > load
> > > > > > > > > > behaves like a combination of column
> > > buckling + bending of a
> > > > > > > cantilever
> > > > > > > > > beam
> > > > > > > > > > point loaded on the free end.  This
> > > cantilever beam bending
> > > from
> > > > > the
> > > > > > > > > > eccentricity is in addition to the
> > > cantilever beam bending
> > > > induced
> > > > > > by
> > > > > > > > the
> > > > > > > > > > standing rigging.  As far as inducing
> > > mast bend, it's the
> > > total
> > > > > > > > cantilever
> > > > > > > > > > beam deflection we are interested in
> > > because it's reproducible
> > > &
> > > > > > > > > > controllable.  Column buckling is sort
> > > of an on/off
> > > catastrophic
> > > > > > kind
> > > > > > > of
> > > > > > > > > > failure - i.e. virtually no bend up to
> > > some critical load &
> > > > then,
> > > > > > BAM!
> > > > > > > > > > buckled mast.
> > > > > > > > > >
> > > > > > > > > > You might not think that mast bend is
> > > possible in a masthead
> > > > rig.
> > > > > > > > > However,
> > > > > > > > > > you have to think about the behavior
> > > of the mast in a 3-D
> > > world.
> > > > > As
> > > > > > > the
> > > > > > > > > > mast is bent, the height of the
> > > masthead off the deck is also
> > > > > > reduced.
> > > > > > > > > > Although the forestay length attached
> > > to the front of the
> > > > masthead
> > > > > > > > doesn't
> > > > > > > > > > change, because the masthead drops
> > > down as well as moving aft,
> > > > the
> > > > > > > mast
> > > > > > > > > can
> > > > > > > > > > still assume a bent shape.  This bent
> > > shape can be fine tuned
> > > by
> > > > > > > > adjusting
> > > > > > > > > > the tension of the 4 lower sidestays,
> > > which collectively
> > > > restrain
> > > > > > the
> > > > > > > > mast
> > > > > > > > > > from moving from side-to-side as well
> > > as fore-aft at about the
> > > > > > > midpoint.
> > > > > > > > > > The standard double backstay tension
> > > adjuster with the
> > > standard
> > > > > > > masthead
> > > > > > > > > > geometry is also capable of bending
> > > the mast.  However,
> > > because
> > > > e
> > > > > is
> > > > > >  a
> > > > > > > > > very
> > > > > > > > > > small value with the standard masthead
> > > geometry, the required
> > > > > > backstay
> > > > > > > > > > tension to achieve a given amount of
> > > mast bend is much higher,
> > > > > which
> > > > > > > > > > compression loads the mast closer to
> > > the critical column
> > > > buckling
> > > > > > > load.
> > > > > > > > > >
> > > > > > > > > > Note, this discussion is only
> > > applicable for the standard rig.
> > > > > > Never
> > > > > > > > bend
> > > > > > > > > > an IMF mainsail mast.
> > > > > > > > > >
> > > > > > > > > > Roger Pihlaja
> > > > > > > > > > S/V Dynamic Equilibrium
> > > > > > > > > >
> > > > > > > > > >
> > > > > > > > > > ----- Original Message -----
> > > > > > > > > > From: "Peter Thorn" <pthorn at nc.rr.com>
> > > > > > > > > > To: "The Rhodes 22 mail list"
> > > <rhodes22-list at rhodes22.org>
> > > > > > > > > > Sent: Thursday, March 18, 2004 3:27 AM
> > > > > > > > > > Subject: [Rhodes22-list] Mast Crane
> > > (was Lou Moore)
> > > > > > > > > >
> > > > > > > > > >
> > > > > > > > > > > Michael et al,
> > > > > > > > > > >
> > > > > > > > > > > 12" mast crane?  Very interesting
> > > idea..  Would the forestay
> > > > > > tension
> > > > > > > > > boost
> > > > > > > > > > > with that much leverage?  Or just
> > > create mastbend above the
> > > > > > > spreaders?
> > > > > > > > > > Has
> > > > > > > > > > > anyone, in the life of the universe,
> > > ever created upper mast
> > > > > bend
> > > > > > > with
> > > > > > > > a
> > > > > > > > > > std
> > > > > > > > > > > rig?   (You were probably thinking
> > > about clearing a big
> > > > roach).
> > > > > > > > > > >
> > > > > > > > > > > Afterthought- Does a Harken forestay
> > > furler have a soft
> > > track?
> > > > > If
> > > > > > > its
> > > > > > > > > > hard
> > > > > > > > > > > metal, can you somehow belly the
> > > Genoa entry for light air?
> > > > > > > > > > >
> > > > > > > > > > > PT
> > > > > > > > > > >
> > > > > > > > > > > PS - Go fasts are fun, but I'd trade
> > > them for a favorable
> > > > shift.
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > > > well now, I think I have to switch
> > > sides this year,
> > > > > full-batted
> > > > > > > main
> > > > > > > > > > sail
> > > > > > > > > > > with a 12 inch crane are the way to
> > > go, single line
> > > > > > > > > > > > reefing and a soild boom vang, but
> > > IMF is more convent.
> > > > > > > > > > > >
> > > > > > > > > > > > MJM
> > > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > > > >
> > > > > > > > > > > > >
> > > __________________________________________________
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> > > > > > > > > > > >
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