[Rhodes22-list] Traditional Mast Backstay problem

Tue Jul 23 07:57:55 EDT 2024

Hi Brian,

Attached below is a post from the archives re an improvement in the OEM backstay adjuster.  The OEM backstay adjuster does not lend itself to rapid and reproducible adjustments.  Especially if you want to race your boat, this is a quick, cheap and effective project.  It doesn't affect your PHRF rating either!

Roger Pihlaja
S/V Dynamic Equilibrium
1978  Sanford, MI

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I mounted a Harken #144 swiveling base with #150 CAM-MATIC cam cleat, #137 eyestrap, #071 stand-up spring, and a 2.25" dia. block just in front of the starboard side backstay chainplate. The standard backstay adjuster line will thread up to this assembly like it was designed to be there. Thru-bolt the Harken swivel base to the gunnel with silicone RTV, four #10-24UNC X 1" stainless steel flat head machine screws and use a #10 stainless steel fender washer under each nut as a backing plate.
Before drilling any holes, thread up the backstay adjuster line and experiment with the position of the swiveling base. You will find there is a sweet spot just in front of the chainplate where the line will run fairly into the block without chafing on the backstay or blocking the boarding ladder. Don't use the smaller Harken #205 swiveling base because the base is right near the boarding ladder & sooner or later, someone is bound to step on the swiveling arm. The Harken 144's swiveling arm can stand up to being stepped on and the 205's can't.
The swiveling arm on the Harken 144 makes trimming the backstay adjuster very easy from either side of the cockpit. Be sure to mount the swiveling base so that the arc of the arm's movement won't allow the adjuster line to flop overboard. I marked my backstay adjuster line at 2" intervals with colored magic marker so I can reproduce the backstay tension.
In order for the backstay adjuster to be able to cause any noticeable difference in lee or weather helm, you need to have the rest of the rig set-up properly. With only the slack taken out of the backstay tension, the inner (lower) shrouds have to be set quite tight. The outer (upper) shrouds just need to have the slack taken up. Sight up the mast and be certain the mast is not bent or leaning side-to-side or bent fore-and-aft.
The mast should have a slight aft rake to it, about 2 deg max. Now when you tighten up the backstay, the forward lower shrouds will restrain the middle of the mast. The head of the mast will be pulled aft. This will simultaneously take up slack in the forestay and induce a slight bend in the mast. (Note: NOT recommended with IMF mainsails!)
Tightening up the forestay is desirable for genoa sail shape when beating to weather. If your mainsail is properly cut and not blown out from old age, the mast bend will cause the mainsail shape to flatten out into an aerodynamic shape that is better for high winds and beating to weather. You will also move the sail plan's center of effort aft, thus inducing weather helm.
This is an inexpensive modification that works so effortlessly that Stan ought to consider it as a factory option. My backstay adjuster has been absolutely bullet proof for 10 hard sailing seasons.
Roger Pihlaja
S/V Dynamic Equilibrium
07 Jul 98
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Thanks for your detailed description. Sounds like a good solution. Did you have any trouble getting to the back ends of the through- bolts? Seems like a long narrow reach. Can you get them from inside the lazarette?
Your mention of IMF mains got me thinking, since that's what we have. Maybe with the furling tube adding stiffness to the spar, I won't be able to induce much bend anyway, so prudence on cranking down the backstay is probably wise. It's also likely to have some ill effect on the performance of the furler, if the IMF furling tube isn't straight. My new forestay has a turnbuckle (required by the CDI furler), so I can do more adjusting there.
Your recommendations for adjusting the upper and lower shrouds will be very helpful, too. Thanks again.
Gary Sanford
s/v Raven
07 Jul 1998
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The Harken 144 swiveling base is mounted on the starboard side gunnel just in front of the backstay chainplate. The job will require 2 people, one down in the lazarette to hold the wrench and a helper up topside to turn the screwdriver. However, the gunnel is wide enough to easily reach up there with a wrench. You were probably thinking the swiveling base mounted on the top of the transom, which would be a very long narrow reach to get at the thru-bolts on the backside. It turns out the top of the transom isn't wide enough to mount the swiveling base.
My roller furler has a turnbuckle as well. This forestay turnbuckle is used to adjust the static rake of the mast when there is no backstay tension. For a conventional mainsail, the proper mast rake is about 2 deg to the rear. I don't know what an IMF mainsail requires for mast rake. You may have to experiment with mast rake until you get neutral helm. You may find the best you can do is have a slight lee helm in light air building up to neutral helm in a moderate breeze & then weather helm in heavy air. With an IMF mainsail, I would adjust the forward lower shrouds somewhat looser. Then, increasing backstay tension would simply increase the rearward rake of the mast without bending the mast. This would get you the forestay tension you need to be able to point to windward. The chances are your IMF mainsail isn't designed to respond to mast bend anyway. Remember, I have a fully battened conventional mainsail & I specified my mast bend parameters to the sailmaker when I ordered the sail. I would imagine bending an IMF mast & then operating the furling mechanism might cause the mainsail to chafe inside the mast & put a lot of stress on the furling mechanism's bearings. Is an IMF mast much stiffer than a conventional mast? I've never seen one off the boat. How much heavier is an IMF mast?
Roger Pihlaja
S/V Dynamic Equilibrium
08 Jul 98
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Had the IMF apart 2 weeks ago. Any rake would be bad news, since the mainsail is wrapping around a tube with roller/spacers top and bottom. If the tube changes distances to the mast wall I do not think the sail would go in (i.e. the whole thing would jam up). The IMF is about two inches more fore/aft and about ½ to 1-inch greater in width, than other masts on boats that size. It’s very stiff, but I have never seen the GB standard mast.
MJM
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The OD of the forestay wire & the rigidity of the headsail foil have very little to do with forestay sag. Forestay sag is primarily controlled by the amount of backstay tension + some secondary & tertiary effects caused by other details related to the way the standing rigging is setup. The use of 3/16" OD wire for the forestay permits the backstay adjuster to be really cranked down hard with no fear of forestay wire stretch or fatigue cycling. The use of the larger diameter wire also introduces an additional safety factor to compensate for corrosion, mechanical damage, etc.
I have my backstay adjuster setup on a Harken 144 swivel base, 150 Cam-Matic cleat, 071 stand-up spring, & 001 single 2.25" block mounted on the starboard side gunnel right at the transom. Backstay tension is quickly adjusted by pulling on the backstay control line thru the Cam-Matic cleat. The 144 swivel base & 150 Cam-Matic cleat allow the backstay tension to be adjusted from virtually any helm position. I used the 144 swivel base because the backstay adjuster is right near the boarding ladder where it might be accidentally stepped on. The large 144 swivel base is rigid enough to step on without damage, while the smaller Harken swivel bases can't take such abuse. The backstay adjuster control line is striped every 2" so that the backstay tension is reproducible.
My standing rigging is setup such that increasing the backstay tension simultaneously reduces headstay sag & bends the mast for flattening the mainsail. Both actions are desirable for sail shaping in heavy air. I have a fully battened conventional mainsail, which is cut very roachy & is designed to respond to mast bend by flattening. I use only one mainsail, but it has 2 jiffy reef points. Needless to say, backstay tension is one of the most important sail shaping controls on Dynamic Equilibrium.
Good grief! I just gave away a couple more racing secrets! Hopefully, no one else is listening.
I guess I don't understand your question re noticing any difference when the sail is fully extended given the weight. The only fully nylon sails are spinnakers. Did you mean, have I ever noticed a difference in light air behavior between a Dacron genoa & my Cruise-Lam genoa? If that's your question, the answer is the bi-radial Cruise-Lam genoa has a better sail shape under all conditions vs. the standard Dacron genoa. In heavy air, the Cruise-Lam + bi-radial construction genoa's sail shape is much better as the standard Dacron + cross-cut construction genoa becomes hopelessly distorted.
The secret of Cruise-Lam's longevity is the Dacron outer skins. The Dacron provides chafe, UV, fatigue resistance, & environmental pollution protection. The reinforcing Kevlar scrims & Mylar film core are buried inside the composite sandwich & are thus protected from the harsh outside world. Unprotected Kevlar & Mylar would be expected to only last one season or less in the marine environment.
Roger Pihlaja
S/V Dynamic Equilibrium
12 Jan 2002
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From: ROGER PIHLAJA <roger_pihlaja at msn.com>
Sent: Monday, July 22, 2024 2:06 PM
To: The Rhodes 22 Email List <rhodes22-list at rhodes22.org>
Subject: Re: [Rhodes22-list] Traditional Mast Backstay problem

Hi Brian,

On S/V Dynamic Equilibrium, my 1978 Rhodes 22, I had a local wire rope rigging shop duplicate what I had when it was time to replace the double backstays.  As you described, it is one piece of cable bent in the middle around a SS thimble.  My backstay adjuster and sockets for the traveler bar are also like yours.  I used this backstay for many years with the GBI gen 2 traveler bar.  When it came time to upgrade to the latest Gen 3 traveler, it slipped right into place using the same backstays and sockets.

Roger Pihlaja
S/V Dynamic Equilibrium
1978. Sanford, MI
Sent from my iPhone

> On Jul 22, 2024, at 1:46 PM, Brian Ferguson <brian.a.ferguson76 at gmail.com> wrote:
>
> To my fellow Rhodes traditional mast-ers,
> My current backstay consists of a single continuous piece of ss cable run
> bent through a thimble to mark the halfway point The thimble is the
> connecting point to the mast head. The two cable ends have stay adjusters.
> There are two single blocks on each side for a total of four, with one of
> which having a becket. Those blocks by the way, are attached to the
> backstay cable with a short piece of cable swaged on to the mainline.
> (Describing it is easier than drawing a picture). I know the blocks are for
> increasing the tension and adjusting underway. Bottom line, everything
> looks very homemade.
> The last time I asked about this, everyone said to purchase a new assembly
> with the traveler bar from GB. Does the latest GB version work for a
> traditional mast? Is there a height difference between the IMF mast and the
> traditional? Or do I just make a copy of what I have?
> Current price of the Backstay assembly is $425 if the webpage prices are
> still accurate. Next email is to Mr Gabriel.
> Thanks all.
> Brian
> NewIn76