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

[Lloyd Crowther]

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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