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Split back stay adjuster

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C25BC
Navigator

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Canada
200 Posts

Initially Posted - 04/01/2017 : 05:23:52

I've just ordered the pieces for a split backstay adjuster , went off the owners manual diagram . As I mentioned in a previous post I can't get a rake in my mast when tuning rigging, basically level is about the best I can do with backstay turnbuckle adjusted alll the way in . Logistically I'm trying to sail the summer before oredering new rigging . It appears to be in good condition.
So does anyone have any experience with tuning the rigging with the backstay tensioner? I was reading a article wher it seemed to say you have your fore and aft stays backed right off like 6" of sag , the aft lowers backed off , With the uppers set at about 30 on the loos gauge , with no mention of the lower fore stays , when the wind picks up you tension backstay . Could this be acccurate ? You sail light winds with some of your rigging slack ?

Angus
S.V.Tempus
#4748
1984 Catalina 25 SK/SR/Trad.

Steve Milby
Past Commodore

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USA
5853 Posts

Response Posted - 04/01/2017 : 08:10:20

I've never found instructions for tuning a C25 rig with an adjustable backstay. It took me about 15 years to figure out how to do it, with the help of Derek Crawford.

Most people think the purpose of the backstay adjuster is to make the boat point higher to windward than it can with a fixed backstay, but that isn't correct. A sailboat's ability to point to windward is limited by it's basic architecture. The benefit of a backstay adjuster is that it enables you to ease the tension on the forestay when you're sailing off the wind or in lighter air. By doing so, you create forestay sag, and that powers up the rig. A backstay adjuster doesn't make the boat point higher or sail faster to windward, but it makes it faster off the wind and in light air.

Before you start to tune the rig, you should ensure that you have as much room for adjustment in the forestay and backstay turnbuckles as possible. That might account for your inability to establish any rake in the mast. Use your jib halyard to hold up your mast temporarily while you completely detach the forestay. Completely remove the turnbuckle barrel from the forestay and also from the chainplate tang. Then, put the barrel back on, so that it starts to thread at both ends at the same time. Next, rig the main halyard aft, to hold up the mast temporarily while you do the same with the turnbuckle that attaches the backstay to the backstay adjuster. Remove the turnbuckle barrel and put it back on as before.

Up to a point, you tune a rig with adjustable backstay the same way you tune one with a fixed backstay. In either case, you want the mast to be erect laterally, and I like to start with it plumb fore and aft, and that's also what the owner's manual recommends. Add enough tension to the backstay adjuster so that there is no appreciable sag in the forestay, and so that the forestay will deflect about an inch if you tug on it with about 50 lbs pressure. The forestay should not be bar-tight, ever. Remember, the boat's ability to point to windward is limited by it's architecture, and after it reaches it's optimum pointing ability, it won't point any higher, no matter how much tension you put on the backstay adjuster.

Next, you need to establish the rake (i.e. the amount that the mast leans aft from plumb). The farther the mast is raked aft, the greater the amount of weather helm you'll feel in the tiller when sailing to windward. Your goal is to have a fairly light weather helm. I thought the owner's manual recommended a specific amount of rake, but I just checked, and don't see it. Nevertheless, I'd suggest you begin with a nominal one inch rake. (After you have completely finished tuning the rig, take the boat out and sail it. If the weather helm feels too heavy when sailing to windward in about 10-12 kt winds, adjust the rig forward a wee bit. If the weather helm is too light, adjust it to lean aft a little more.)

Next, loosen all your lower stays just enough to take the tension off them. Then, tighten the uppers snugly by an equal number of turns on each side. Next, take your jib halyard, and use it as a measuring device (you might need to tie a piece of line onto it, to lengthen it), to make sure that the distance from the top of your mast to the chainplate for the upper stay on the starboard side of your boat is the same as the distance from the top of your mast to the chainplate for the upper stay on the port side of your boat. If the distance is not equal, adjust your upper stays until the distance is equal on both sides. That will ensure that your mast does not lean more to one side than the other.

Now, adjust your forward lower stays until the slack is just taken out of them. Then continue tightening them, alternately by an equal number of turns, until they are as tight as you can comfortably get them by hand. Then use a tool to tighten each forward lower stay a little more, about 1-2 turns.

Then do the same with your aft lowers, but leave them slightly slack. You want the aft lowers to be loose so that, when you ease the backstay adjuster, they will allow the mast to lean forward slightly, allowing the forestay to sag, which powers up the rig.

Lie down on the coach roof, and sight up the mainsail track, to see if the mast is still straight. If it is not, then make such adjustments to the forward lower stays as are necessary to make it so.

At this point, your mast will be erect laterally, nearly plumb fore-and-aft, and straight.

Then sail the boat to windward in 10-12 kt winds, pay attention to the amount of it's weather helm, make such fine adjustments as will give it a light feel, and practice adjusting the backstay tension for different windspeeds and points of sail. The general idea is not to have it all the way on or all the way off, but to adjust it so that it has the optimum effect in each windspeed and point of sail.

Re: Your mast rake problem. The only reasons I can think of as to why you can't get the mast to rake aft are (1) your forestay and backstay turnbuckle barrels need to be taken off and re-threaded, as described above; (2) your forestay is too short. If the forestay was cut too short when it was replaced, you can buy extensions of different lengths that are much less expensive than replacing the whole forestay. I'd suggest you measure your forestay and try #1 above first.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

Edited by - Steve Milby on 04/01/2017 08:20:29

Derek Crawford
Master Marine Consultant

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USA
3312 Posts

Response Posted - 04/01/2017 : 08:11:15

As a hardcore racer, I carried what was probably the loosest rig in the Country! Following the advice of my sailmaker (a gold medalist racer) I had 10" sag in the forestay, backstay waving in the breeze, uppers at 30, aft lowers at 20 and the fore lowers at 25. If I cranked on the backstay, the forestay and backstay became tight. It was a very fast rig, especially off the wind, but the leeward shrouds looking like cooked spaghetti when going to weather seemed strange to most people.
If you are not racing, I would recommend a tighter rig.

Derek Crawford
Chief Measurer C25-250 2008
Previous owner of "This Side UP"
1981 C-25 TR/FK #2262 Used to have an '89 C22 #9483, "Downsized"
San Antonio, Texas

Sailynn
Navigator

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USA
178 Posts

Response Posted - 04/01/2017 : 08:54:56

Great explanations from Steve and Derek. I just want to add one more thing. Having the ability to bow the mast with a adjuster in heavy winds on a sailboat will soften the upper leech of your sails, and help spill wind and keep the boat flatter, reduce weather helm while maintaining course as opposed to luffing the sails. As mentioned if your forestay is too short, don't be afraid to add the correct extension. It will also make it easier to pin the forestay if you trailer sail like we do several times a year. I'm prone to checking the rigging, especially now that we just replaced it. After 30 years of rigging/de-rigging and adjusting we have found left and right hand nuts are worth the extra dollar for doing adjustments to the turnbuckles instead of cotter pins or rings IMHO.

Lynn Buchanan
1988 C25 SR/WK #5777
Sailynn
Nevada City, CA

C25BC
Navigator

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Canada
200 Posts

Response Posted - 04/01/2017 : 20:52:48

Just got home and read my messages , Thank you . And I appreciate the input and being lucky enough to have access to the confbined knowledge and experience .
Angus

Angus
S.V.Tempus
#4748
1984 Catalina 25 SK/SR/Trad.

Stinkpotter
Master Marine Consultant

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Djibouti
9017 Posts

Response Posted - 04/02/2017 : 10:10:29

Will you have enough length in the forestay to rake the mast back with the new backstay? If not, you can put a longer toggle or T-bolt at the forestay turnbuckle--all available at WM and elsewhere.

Toggles and Ts

Another thing cranking down a backstay adjuster can do is add bend to the mast (although somewhat limited with a mast-head rig), which flattens the mainsail by pulling forward on the midsection of the luff. That along with the tensioned forestay (flattening the jib) improves windward performance in heavier air and can improve pointing. Derek's rig appeared to be set up for that, and then for powering up both sails in light air and/or downwind by slackening the fore- and backstays. That along with some outrageous racing sails and a semi-professional crew probably made ^This Side Up^ (R.I.P.) the fastest C-25 on the planet!

Dave Bristle
Association "Port Captain" for Mystic/Stonington CT
PO of 1985 C-25 SR/FK #5032 Passage, USCG "sixpack" (expired),
Now on Eastern 27 $+!nkp*+ Sarge

Edited by - Stinkpotter on 04/02/2017 10:11:35

C25BC
Navigator

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Canada
200 Posts

Response Posted - 04/02/2017 : 14:17:24

I seem to have lots of adjustment in forestay , have the turnbukle at about 50% and it's pretty slack, harder to tell with extrusion on but it's far from tight. The backstay is 3 or 4 turns from being all the way in ,( I wonder if I can get shorter turnbuckle for backstay) I'm going to go over the whole thing again next weekend taking into consideration advice given on this thread ... work does get in the way of sailing .

Angus
S.V.Tempus
#4748
1984 Catalina 25 SK/SR/Trad.

cshaw
Captain

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USA
460 Posts

Response Posted - 04/02/2017 : 18:54:03

Totally agree with Steve, Derek and Dave. I learned to set up a rig like Derek described and use an adjustable backstay like Dave described when I was racing my Thistle over 50 years ago. Like Derek, I get laughed at for how loose Confetti's rig is, with the leeward shrouds flopping around when going to weather. (Those are the same guys that usually finish a long way behind me #128526;)...

When I sailed on Galveston Bay, it would develop a short steep chop as the wind increased that killed Confetti's upwind speed. However we would dedicate someone to ease the backstay as we would hit a wave and tighten it back up between them. Made a huge difference in upwind performance. Same person would play the traveller during gusts. Kept him busy on a gusty day with a big chop! <grin>

Derek mentionend 10" of forestay sag. That's also about what we have on Confetti (might be why the light air 155 I bought from Derek work's so well for me?). 10" sounds terrible, but remember the sails are cut to accommodate headstay sag in the shape profile for the luff round. It's also not hard to measure it under sail with an independent very taunt line and streamers with 1" stripes. Then take pictures zoomed in.

As to whether Dave is right about TSU being the fastest 25 on the planet......well....maybe......<big grin!>

Chuck

Chuck Shaw
Confetti
Cat 25, hull#1
1976 FK/TR

Derek Crawford
Master Marine Consultant

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USA
3312 Posts

Response Posted - 04/02/2017 : 19:05:48

Chuck, I so wish that we could have raced against each other (as long as I had my own sails!).
Come on Dave - my crew really weren't semi-pro. My genoa trimmer used to teach sailing at the Naval College and my foredeck guy had been sailing/racing since he was five (on Lake Michigan)...

Derek Crawford
Chief Measurer C25-250 2008
Previous owner of "This Side UP"
1981 C-25 TR/FK #2262 Used to have an '89 C22 #9483, "Downsized"
San Antonio, Texas

C25BC
Navigator

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Canada
200 Posts

Response Posted - 04/02/2017 : 20:27:50

Good to know , never would have had the minerals to go out with forestay that slack , the plastic extrusion from the CDI will add some extra weight as well I guess .

Angus
S.V.Tempus
#4748
1984 Catalina 25 SK/SR/Trad.

Stinkpotter
Master Marine Consultant

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Djibouti
9017 Posts

Response Posted - 04/03/2017 : 16:29:43

Ya, Angus... You're not in the league with Chuck and Derek if you're running with a CD furler (or any furler).

But the forestay can be pretty loose with that plastic foil. As a non-racer, I never went that loose, and if your boat is moored where waves move it, I'd keep it relatively tight to minimize shock-loads on the terminals.

And I do wish Chuck and Derek could have raced--I might have flown in to see that! (But I wouldn't qualify to be on either boat!) What's really cool is Chuck's hull number--0001--still humiliating lots of boats!

Dave Bristle
Association "Port Captain" for Mystic/Stonington CT
PO of 1985 C-25 SR/FK #5032 Passage, USCG "sixpack" (expired),
Now on Eastern 27 $+!nkp*+ Sarge

C25BC
Navigator

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Canada
200 Posts

Response Posted - 04/03/2017 : 18:55:55

Can't argue with that , sailed in may 20's for 5 or 6 years , a 1970 venture 22 on the BC coast knew acbsouley nothing in reflection, but had quite a bit if fun .Started up again a few years ago with the Cat 22 trying to get it right this time . Funny thing about the the furler it was on my list of things I wanted on my new boat , and I'm not even sure if I can use it yet with the wobble in the extrusion from incorrect trailer storage , will find out soon enuf.

Angus
S.V.Tempus
#4748
1984 Catalina 25 SK/SR/Trad.

Stinkpotter
Master Marine Consultant

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Djibouti
9017 Posts

Response Posted - 04/03/2017 : 19:45:29

I recall reading that the CDI foil, which is shipped coiled up, straightens itself out given a little time in the sun. A true kink might be a problem. You can probably get some advice from CDI.

Dave Bristle
Association "Port Captain" for Mystic/Stonington CT
PO of 1985 C-25 SR/FK #5032 Passage, USCG "sixpack" (expired),
Now on Eastern 27 $+!nkp*+ Sarge

Dave5041
Former Mainsheet Editor

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USA
3754 Posts

Response Posted - 04/04/2017 : 12:06:27

I have a flex track on my harken and just run it from the bow to the cockpit with a gentle loop in the cockpit to take up the excess when the mast is down. The slight curve that comes from a couple of months in that position disappears with a couple hours rigged in the sun.

Dave B. aboard Pearl
1982 TR/SK/Trad. #3399
Lake Erie/Florida Panhandle

C25BC
Navigator

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Canada
200 Posts

Response Posted - 04/04/2017 : 17:32:40

So will it still work not straight ? I'm months away from the warm sun , and a couple weeks from sailing .

Angus
S.V.Tempus
#4748
1984 Catalina 25 SK/SR/Trad.

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