[Rhodes22-list] shroud tension jokes
Steve
rhodes22-list@rhodes22.org
Thu, 22 Aug 2002 06:16:38 -0700 (PDT)
I also upgraded my headstay wire to 3/16 when I
upgraded to the schafer furler.
Steve
--- Roger Pihlaja <cen09402@centurytel.net> wrote:
> Dear Toad,
>
> First of all, I'm an engineer & I've owned my Rhodes
> 22 since the spring of 1987. Stan @ GBI will never
> be this specific with rig tuning specs. It's just
> not his nature. Early on, I purchased a Loo's
> tension gage, started doing experiments, making
> measurements, & racing my boat. The specs I gave
> you are the lowest static tension settings that
> yield the desired dynamic behavior in the sailing
> rig. By the way, totalling up the lbs of tension in
> the standing rigging doesn't tell you very much.
> Each stay is loaded individually. The ultimate
> tensile strength of those 5/32" OD, 1 X 19, 316
> stainless steel wires is on the order of 2800 lbs.
> At 600 lbs max tension on the loaded windward upper
> sidestay, my suggested rig tension settings leave a
> safety factor of more than 4X.
>
> The only part of the standing wire rigging I've
> upgraded was my forestay wire to 3/16" OD, which has
> an ultimate tensile strength of about 4000 lbs. I
> did this wire size upgrade when I replaced my OEM
> standard roller furler to a Harken Unit 0. 3/16" OD
> wire in the forestay is probably overkill. But,
> 3/16" OD was the largest standard size available for
> the Harken Unit 0. I had to replace the forestay
> anyway as part of the installation, there was no
> good reason not to upgrade, & it seemed like cheap
> insurance.
>
> The breaking strength of the wires & the swaged
> terminals are the limiting factors. The chainplates
> can hold much more than the rest of the rig. You
> could confidently lift the entire boat suspended
> from the upper side chainplates. They don't need to
> be upgraded.
>
> The mast compression post is only loaded to a small
> fraction of its buckling strength. Don't worry
> about it.
>
> Look on page 970 of the WEST Marine 2002 Master
> catalog for a Loo's tension gage. You would need to
> order a Loo's model 91A or PT1.
>
> As I said in my post, I was trying to use the image
> of the ends of the hull bending upward like a "22
> foot long banana" under rig stress as a "greatly
> exagerated" illustration of the effects involved.
> The real hull deflection is subtle, certainly not
> observable without precision measurement
> instruments.
>
> Since I suggested adjusting the length of the
> forestay in 1/2" increments to adjust your weather
> helm/lee helm balance, if you measure the forestay
> length to 1/4 of that increment, or 1/8" accuracy,
> that will be sufficient resolution. You are quite
> correct, I had too many significant figures in my
> forestay length spec. It should have read 333-5/8".
>
> Criticize me if you wish, but did anyone else give
> you anything but qualitative descriptions of rig
> tuning? Why don't you try my rig tuning procedure &
> see what you think?
>
> Roger Pihlaja
> S/V Dynamic Equilibrium
> ----- Original Message -----
> From: Toad the Wet Sprocket
> To: rhodes22-list@rhodes22.org
> Sent: Tuesday, August 20, 2002 3:30 PM
> Subject: Re: [Rhodes22-list] shroud tension jokes
>
>
>
>
>
>
> Roger,
>
> So you have a total of 1800lbs of tension on all
> of your shrouds, not to mention the fore/backstay
> tension? Where did you come up with all of these
> figures? Are these the specs from Stan and the
> guys at GB? This all seems like quite a strain on
> the chain plates and alot of compression down
> through the mast into the hull.
>
> Did you replace your rigging with larger cables or
> beef up the chain plate mountings?
>
> Where can one buy the guage you have and a tape
> measure that measures to three decimal places? Is
> my boat supposed to bend up at the ends like a 22
> foot banana too?
>
> Sorry, I couldn't resist. I was in a goofy
> mood today. Honestly, where did you get these
> specs?
>
>
>
>
> Please respond to sprocket80@hotmail.com
>
> From: "Roger Pihlaja"
> Reply-To: rhodes22-list@rhodes22.org
> To:
> Subject: Re: [Rhodes22-list] shroud tension
> Date: Tue, 20 Aug 2002 07:56:38 -0400
> Jack,
> Here's a copy of the rig tuning procedure I use:
> The 1st thing you want to do is measure the length
> of the forestay on center
> from pin-to-pin. On my 1976, standard mainsail,
> Rhodes 22, this measurement
> is 333.625 inches. Write this number down because
> it is very important.
> If your forestay length is more than a couple of
> inches different than this,
> you might want to reset it 333.625 inches as a
> reasonable starting point.
> Now step the mast. Take the excess slack out of
> the forestay & backstays
> with the backstay adjuster. You don't want things
> real tight at this point.
> All upper & lower sidestays should be slack. Go to
> the base of the mast,
> pull a halyard taut along the mast & sight up the
> mast from the rear & from
> the side. Any deviation from a straight mast will
> show up as a gap between
> the mast & the halyard. There should be no
> observable bend or bowing in the
> mast. If there is, the mast may have been dropped
> & bent at some point or
> may have some other problem. You should call Stan
> at GBI & he will be able
> to help you work out your problem.
> I like to use a Loo's tension gage. The model 91
> is the appropriate range
> for the Rhodes 22. Remember to always measure the
> tension at the same
> relative position on each shroud every time. On
> Dynamic Equilibrium, I
> have marked these measurement points with little
> spots of paint on the
> wire right at my eye level.
> The upper sidestays are adjusted next. Raise a
> tape measure up the mast on
> a halyard. Measure to the same point on each side
> of the boat. I like to
> use the edge of the toerail right next to the
> sidestay. Tighten the
> turnbuckles a little at a time on each side to
> adjust the upper sidestays
> until both sides are the same length +/- 1/4" &
> tensioned to approximately
> 300 lbs +/- 5%. This procedure assures the top of
> the mast is centered in
> the boat & the upper sidestays are tensioned
> equally port & starboard.
> What you do next depends upon whether your boat
> has the IMF mainsail or a
> conventional mainsail.
> On an IMF mainsail boat, I would adjust the 4
> lower sidestays so they were
> all approximately the same tension. I would start
> with approximately 200
> lbs +/- 5% on all 4 lowers. This is not a lot of
> shroud tension. Check for
> mast straightness with the halyard again. You want
> the mast to be straight
> in order for the IMF furling mechanism inside of
> it to be able to turn
> without binding &/or excessive wear on the
> bearings. Minor bending or
> bowing can be taken out with the lower sidestays.
> However, I would call
> Stan at GBI if I couldn't get the mast to
> straighten out with a difference
> of about +/- 15% on lower sidestay tension.
> My Rhodes 22 has a conventional mainsail. I have a
> very roachy fully
> battened mainsail which has been cut to respond to
> mast bend. I have my
> backstay adjuster set-up to adjust quickly from
> the cockpit with calibration
> marks on the line.
> Tighten the turnbuckles equally & a little a time
> on each side to keep
> things reasonably centered. I adjust the forward
> lower sidestays to 400 lbs
> +/- 5% of tension, and the aft lower sidestays to
> 200 lbs +/- 5% of tension.
> Then, check for mast straightness with the
> halyard. Believe it or not, the
> standard mast on the Rhodes 22 is such a stiff
> telephone pole that, at 200
> lbs differential tension on the lowers, there will
> be a barely detectable
> fore/aft bend in the mast with no sails set & the
> backstay adjuster slack.
> At 400 lbs of tension on the lower forward
> sidestays, when the backstay
> adjuster is tensioned, primarily only the upper
> half of the mast is pulled
> towards the stern. The forestay is tightened & the
> mast is bent at the same
> time. Both actions are exactly what you want to
> obtain proper sail shape in
> a high wind situation.
> Now go out sailing. On a close hauled course, put
> up enough sail to heel
> the boat over about 15-20 deg. Make certain the
> rudder blade & centerboard
> are all the way down. On my Rhodes 22, the above
> tension settings cause the
> mast to remain straight & more or less centered in
> the boat. The primary
> thing to check is the upper sidestays. On my
> Rhodes 22 with the above
> unloaded tension settings, at 15-20 deg of heel,
> the windward upper sidestay
> should have about 450 lbs tension & the leeward
> upper sidestay should have
> about 150 lbs of tension. I have my upper
> sidestays set-up such that the
> leeward upper sidestay tension drops to 0 lbs at
> about 30 degrees of heel.
> At this point, the windward upper sidestay will be
> under about 600 lbs
> tension. Note, normally the stays are set-up to
> give proper shroud tension
> & the correct amount of weather helm with full
> sail set. This tends to
> limit the weather window in which you can do this
> sort of tuning.
> When all sails are properly trimmed & the boat is
> "in the groove", there
> should only a slight amount of weather helm. If
> there is a huge weather
> helm, or neutral, or lee helm; then, you need to
> adjust the rake angle of
> the mast. If you have neutral or lee helm; then
> increase the forestay
> length. To get rid of excessive weather helm,
> shorten the forestay. The
> balance of the boat is very sensitive to this mast
> rake angle, so change it
> in increments of about 1/2" at a time. Note, a
> slight amount of weather
> helm
> is desirable because it provides feedback to the
> helmsman, thus allowing
> him to steer a better course. Excessive weather
> helm tends to tire the
> helmsman out.
> Once I'm happy, I lock the adjustment in place by
> taping the lock nuts on
> the turnbuckles. I find I only need to do this
> adjustment once. The
> Rhodes 22 is such a strongly built little boat
> that nothing ever seems to
> stretch or bend. I do check the side-to-side upper
> sidestay length at the
> beginning of every season; but, it's never changed
> in the 13+ seasons I've
> been measuring it. Trailering set-up only involves
> adjusting the lower
> sidestays since the rest are not disturbed.
> As far as rig tension settings on the trailer vs.
> off the trailer, I've
> found the
> only rig tension adjustment that significantly
> changes is the backstay
> tension.
> You can set the tension on the rest of the
> standing rigging according to the
> above procedure on the trailer. It will be very
> close to optimum when you
> get the boat in the water, certainly good enough
> to do the on-the-water
> fine tuning described above.
> FYI, I slack off on the backstay tension when
> Dynamic Equilibrium is not
> being sailed. As I mentioned above, the backstay
> adjuster has sufficient
> power to affect the shape of the hull. Greatly
> exaggerated, imagine the
> ends
> of the hull being pulled upward like a 22 foot
> long banana when the backstay
> adjuster is tight! There is no sense leaving the
> hull & rig under that kind
> of
> stress when the boat is not being sailed.
> Jack, I hope this description of rig tuning helps
> you. Good luck!
> Roger Pihlaja
> S/V Dynamic Equilibrium
> ----- Original Message -----
> From: "Jack Goldberg"
> To:
> Sent: Monday, August 19, 2002 7:47 PM
> Subject: [Rhodes22-list] shroud tension
> > This list has been helpful in the past, so I'll
> come to the trough of
> > knowledge to feed again.
> > I noted with interest the thread about the mast
> plate bolts coming loose
> and
> > the response with regard to the tension of the
> shrouds. My 84' has a
> > standard main. When I bought the boat this
> spring, the shrouds were very
> > loose (obout 3 inches of play from side to side
> at about 3 feet from the
> > deck. The guy I bought the boat from said that
> was OK, but now I'm
> worried.
> > Is there a spec' on how tight (or loose) the
> shrouds should be under no
> > load?
> >
> > Jack Goldberg,
> >
> >
>
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