[Rhodes22-list] Mast Crane (was Lou Moore)
Richard F Sheehan
dickshee at juno.com
Fri Mar 19 10:11:06 EST 2004
Lloyd;
Try spraying the slugs with silicone. Run the sail up and down a couple
of times, and you should notice a vast difference in performance.
Dick
On Fri, 19 Mar 2004 01:27:08 -0500 "Lloyd Crowther" <lcrowther at cox.net>
writes:
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 you're 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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CPT Richard F. Sheehan
218 Pier D
Naples, FL 34112
dickshee at juno.com
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