Bend on forestay

[bigtyme805]

I was out sailing on saturday and the wind was blowing 15k and I noticed a good bend on my forestay. I have a roller furling and a 150 genoa attached to this. I finally put a roller furling on my rig after much debate. Just for everybody's info I had a professional do the rig.

Is this common? And if it is how much bend should I anticipate? Would a back stay adjuster eliminate this problem?

Thanks for your help.

 

[NateHanson]

It's head-stay sag. In those conditions I'd think you want about 6 inches of sag in the middle of the headstay. If you've got more than that the boat won't point well, and will be overpowered in heavy winds.

You can decrease your sag by adjusting the backstay. you can just take up a few turns on the turnbuckle back at the dock, and check it again when sailing. You don't need a backstay adjuster unless you wish to make adjustments to the rig while sailing (allowing the mast to go forward downwind by loosing the backstay, and tightening the backstay upwind).

I'm sure one of the experienced riggers/sailmakers in the crowd here can give a more complete explanation, but that's the basic gist of it.

Nate

 

[Seth]

That about covers it

Nate has it right-6" of sag in those conditions is OK-much more and you will lose some pointing, and the movement in the headstay as you go through the waves can cause fatigue in the rigging-tightening the BS as he sugests will help-just remember that while too much sag can hurt your pointing ability in breezier conditions, too little sag in light air will give the same result-the genoa needs some sag to have a proper entry-and if the rig is too tight, you won't have enough to perform well in lighter air, and when it is breezy, you are fighting to prevent too much sag from occurring, and you do this by tightening the BS and/or HS.
S

 

[bigtyme805]

That sag is coming in the middle of the rig, just like you pointed to. I just don't remember it when I used a hank on jib.

The main problem I am having is psychological, thinking the rig is being stressed. I guess it is not.

 

[Seth]

Maybe, maybe not

Certainly when you see sag (bend is in the mast) in the HS, it is because the wire is stretching under load, and things ARE stressed. Too much sag and you will start putting loads on hardware in directions they were never meant to take-so it is much more than psychological. If it is only 6", nothing to worry about, but on a boat that small, I would be concerned about 8-10", and take some action.

It will be more visible with the furler than without because the HS is in effect bigger with the extrusions on it, and hence more "visible"-also, it will sag MORE with the furler because you have now added the weight of the furling system to the HS.

The furler is the right way to go, though-just be sure your rig is tuned accordingly-if you feel it(the sag) is too much, tighten the backstay.

One way to tell is when sailing close hauled, trimmed in, etc. Sit on the high side so you can see the telltales. You should see more than 75-80% of the HS in your line of sight. If more than 25% is sagged off and not visible beghind the mast (from this seating position), you have too much and should make the proper adjustments.

Hope this helps,
S

 

[ted_reshetiloff]

How much sag is too much on a 38? I agree with the light air sag being needed and am in the process of installing my hydraulic BS. Is 8-10 too much for this size boat? Obviously I am shooting for a bar straight headstay in breeze but we all know that wont happen perfectly. Seth can you give us a range of acceptable sag for say 0-5 kts. 5-10, 10-15, 15-20 etc? I know it will vary by boat size so any approximation is helpful. What about chop verses flat water? This is a great thread BTW.

 

[Loren Beach]

Keep pumping!

I donno about sag on a 38, but do know that all boats have a practical limit of how much BS tension you can apply...
At some point you have to accept whatever sag is still there and cut the sail to allow for that, IMO.
On our little 34 footer, I have "loaded 'er up" to about 2500# with the Sailtec unit and there was still a little sag. Boat went to weather good. Hull makes some creaking noises as the meter goes over 2K#. We normally use 1500 or so. (On my prior 26 footer the head door would jam with the BS cranked hard for the weather leg.)

A surveyor friend tells me that stretching a tight line between bow and stern rails and then max cranking the BS tension on many low-price production boats can show the bannana effect easily. Owner's eyes show pupil dialation. Just some food for thought...

Cheers,

Loren

 

[Bob in Va]

More, Seth!

Seth, I leave my headstay tensioner in the slackest position at the slip, and ease it to that setting downwind, tensioning it up otherwise as the situation seems to demand on other points of sail. With a masthead rig, is it ever desirable to have it slacked off even more than "parked" position, or to ask it another way, how can I tell if I'm leaving the rig too slack fore and aft when I'm putting the boat up?

 

[Seth]

sag stories

Ted,
For a 38 or similar (which means similar rig configuration and similar structural qualities), I think anything more than about 10" should be corrected to some degree. In anything up to about 5 knots TWS, you want as much sag as you can get without the HS moving around too much each time you hit a wave. Start in these conditions with no backstay tension, trim in and go sailing. Depending on the final cut length of the BS, you might be fine, or you might see the HS swinging around loosely. If so, add just enough BS tension to settle the motion down, yet leave as much sag as you can to get this effect.

From 8-12 KTWS, I would like to see 6-8" of sag-just guessing, but I would guess about 1000 pounds at about 10 KTWS will get you in the 6-7" range.

Beyond 12 kts TWS, you won't be able to get it bone straight (and you never really want that anyway), and keep adding tension so you keep the sag under 8-10"-and I agree-3000lbs should be about all you want to put on the BS adjuster, and 2500 is enough most of the time. If you have the BS adjuster loaded up and still have a lot of sag, you may need to take up a bit on the HS and/or BS using the turnbuckle with the adjuster released.

ALL genoas are designed with the assumption that there will be some sag-that is why a bone straight HS is not fast, and Note: all of these sag estimates assume a genoa with a typical shape and entry. If the genoa has some problems, like too little luff curve, you will need more sag to get it to work well than you would with a "normal" sail. Conversely, if the genoa has too much luff curve, you may be a tighter than normal HS to get the right shape.

Having said all this, the method I like best is what I described before: On the bigger boats with a wheel, trim in and sail close hauled. Steering from the high side (you ALWAYS do that, correct? ), and looking at the telltales. Look at the headstay. In over 12 KTWS, ideally you want to have the majority of the length of the HS in sight, and maybe only upper 10-15% has sagged off behind the mast and out of your line of sight. In 5-10Kts, I would want to see maybe about 80%-allowing a bit more the HS to sag behind the mast.

These are all rough estimates-in flat water you can get away with a slightly straighter HS, and in rough water you want a bit more sag. The age and quality of the sail will make a difference, and finally-don't forget the impact on the mainsail shape- too much BS and the main could becme too flat, and vice versa.You can use these numbers to get in the ballpark, and then "season to taste". Remember that sag is measured by standing at the bow and sighting up along the HS, and lining it up with the mast. The sag is the distance the middle of the HS has "sagged" away from being in line with the front of the mast.

Loren-Spot on as usual-another way to know if you are bending the boat is that you will notice the rudder binding in the shaft. It is acceptable to notice a small amount of binding when at the extreme max amount of loading, but this points out why it is so important to unload the boat when you are done for the day!!! We sometimes refer to the BS adjuster as a poor man's autopilot-since the rudder will barely move (on some boats) when the BS is loaded up. The E-boats are pretty strong, though, and you won't see too much "banana effect" on them.
Bob-When at the slip, ease the backstay mostly off-but leave just a bit on so the rig does not jump around in powerboat wakes, storms, etc. When sailing downwind ease it ALL the way off to get the mast head as far fwd as possible. In fact, take the genny halyard down to the tack fitting and grind it snug and take most of the slack out of the BS-shoving the masthead as far forward as possible-this will reduce weather helm (and hence rudder drag), and get the top of the mainsail a bit higer up and into cleaner, stronger air.

Also Jib/Genoa reaching in big air is another great time to get the mast forward, but it is harder, because if you ease the backstay your wll end up with a deep main, which you don't want....but in theory.....

I need some coffee
S

 

[escapade]

sag (horror) stories

Just a couple things to keep in mind with a hydralic BS. First, you want to leave your aft lower shrouds looser than normal so that the mast (on masthead boats) bends in the proper direction. This will avoid the "inverted mast" trick which is usually catastrophic in nature. If the mast bends "forwards" it will buckle and collapse. Second, regardless of gauge preasure you shouldn't bend the mast beyond the cord length of the spar. Use an old batten taped to the cylinder and mark "full on" & "full off" positions. You can also put reference marks for optium positions for different wind speeds. Makes initial tuning in a race much more accurate and will help to avoid overstressing the hull & rig. You can put TREMENDOUS preasure on with a backstay but I wouldn't sail without one on my E34. They are built for it, just don't overdo it!
Have fun & sail fast
Bud E34 "Escapade"

 

[ted_reshetiloff]

Bud when you say dont bend more than the cord length do you mean if my mast section is say 6" x 4" then I should not put more than 6" of bend in?

 

[Seth]

Have to differ a bit

Very good points, Bud. I'll try to take them a bit further:

Loosening the aft lowers-On days when you want max bend, you should sail with the aft lowers a bit looser-and on days that are light and/or very choppy, tighten them up a bit to reduce the amount of bend for a given tension. This way the main will not get as flat for a given amount of tension/ HS sag as it would with looser aft lowers. As Bud says, in any case, the aft lowers should always be a bit looser than the fwd lowers-to prevent the inverted rig syndrome he describes so well.
Taping a batten to the backstay and marking it in 1" increments (so you can line it up with a mark on the backstay) is a GREAT idea-this way you can have a BS setting for given conditions you can easily reproduce. It is more accurate than using pressure indications, as 3000 pounds one day may not pull the BS to the same point each time-the boat will bend more in some sea conditions than in others, etc. So this is a more accurate method of establishing and being able to duplicate settings for dfferent conditions than just using the pressure guage.

The only item I differ on is the chord length limit for bend. It may be valid, but I have never heard of this, and I can tell you that in the IOR days, it was very common to see 12-15" of bend on an 8" chord section.. I have used over 8" on a 38 in the past, and on the RH 36 10" is not uncommon when the breeze is up. Of course, don't do this unless you have the rig tuned correctly, but I am not aware of any reason to limit bend to chord depth, and it is not something I have ever seen on the race boats I have been a part of..

And that is for masthead rigged boats-the old skinny Frac rigged boats carried 18-24" bend sometimes-in fact the original RH 33 "Outlaw" we discussed yesterday had a VERY spindly little rig-maybe 6" chord, and never had much less than about 8", and often 12-18" when it was breezy.

I would say that once you are sure you have the right HS and BS lengths, and the mainsail has a luff curve of 80% of the available mast bend (a sailmaking rule of thumb), I usually add BS tension until ALL of the draft is removed from the mainsail (assuming there is so much wind I want the sail board flat-anything over about 15 ktws), then I know I can get the boat fully depowered without taking the bend to the absolute limit of available travel..
Sabe?

S

 

[escapade]

yea, right

What Seth said. Using the cord length is probably a bit on the conservative side but I'm a chicken when it comes to bending the living begessus out of a masthead rig. My sailmaker recommended that & the main is cut for that amount of bend. On my old 30+ (which was a frac rig) I used to put a LOT more bend than cord length but it's easier to bend that type of rig. You are putting huge loads on the spar & hull when bending a masthead rig which god intended to be straight! Ericson's are built to take it, just don't get carried away. BTW Ted, to answer your question, the cord length is the fore to aft measurement of the spar section at the base. Otherwise go with Seth's recomendations. I'm learning that to be fast you need to tune your rig for the daily conditions, not just tighten everything up in the spring & run it. That's OK for cruising but to get the max from these boats it takes a little finesse.
Have fun & sail fast
Bud E34 "Escapade"

 

[Emerald]

This has been a great thread to read through. I am sailing a very different rig with the cutter Independence 31, but I can't help but wonder how much of this even us cruisers can play with and benefit from . One of the things I've loved about the Independence 31 is that for a classic cruising style, I've yet to be embarresed sailing against the other boats on what ever point of sail that we coincidentally are on. In fact, I've had quite a few instances where we've beaten much newer, lighter "faster" boats, and have recieved quite a few astonished looks in the process - we've just sat and laughed hard as some have obviously gone nuts trying to keep up as we're kicked back with a malted beverage.

So, with all that exposition, what's the consensus on being able to tweak the cutter rig of the Independence. She does have a bridle on the backstay because of the transom mounted rudder. and I wonder about loading the bowsprit - or does this just make bending easier... I've attached a picture of her rigging for those not familiar.

Thanks for any thoughts, because even us cruisers are often trying to beat the storm or the other boat


-David
Independence 31
Emerald

 

[Seth]

What Bud sez

Bud,

You are right on (again)-I'm with you on everything except the part about God wanting these rigs to be straight. When we designed these rigs, the sections chosen were intended for adjustment if the owner wished it. It is very true that there are some rigs that really are not meant to bend much, if at all-and that would include the I/31 (more on that later). But all of the BK and Olson boats since the late 1970's, and especially everything since 1980 have rigs that are very well suited to bend as a tuning aid.

As for Emerald, all of the sail trim items we have discussed on this site have application for cruisers-those who wish to get a bit more out of their boats will definitely notice the improvements from getting the leads just right, halyard tension right, etc. Lucky for them this is optional!!! For boats like the 31-rig tune IS very important-for safety as well as performance. On a boat with a sprit like that, you certainly could use a block and tackle type backstay-which you would snug up to reduce HS sag when it was windy, and ease it in the light air to induce more sag for better performance. I would stay away from hydraulics, though. But...I really don't think you can get enough bend in this rig to have a real effect on the mainsail depth-so you will be improving things in one dimension-but it would help. For the main, the big thing is to be sure it mathces the mast bend (or lack of same), and is not too full. If you see it backwinding often, it is because either the main is too full, not trimmed in enough, or the genoa leads are too far forward,which will close the leech and force the exhaust from the genoa onto the back of the main-causing backwinding.

Beyond that, in general terms, you want the rig to be straight as you sight up the main track from the windward side-if you see the top falling off to leeward, tighten those uppers (while on the opposite tack so they are loose), if you see the lower/middle section falling off, tighten the lowers (while on the other tack).

The leeward shrouds (once the rig is straight side to side and when loaded), should be slightly loose above about 8-10 knots of wind, but not flapping wildly in the breeze. As you sight up the mast from the windward chainplates, it should not be moving fore and aft more than an inch or so. BTW-when you go out to tune the rig, it must be fully loaded to obtain proper results. To do this do all of your sighting and checking while sailing close hauled-with all sails trimmed right in for upwind sailing-you will need at least 8-10 knots of true wind to get a good result. The helmsperson should get a feel for sailing close hauled, then, when the "rigger" wants to sight up the rig, he/she should bear off 2-5 degrees(without easing the sails). This is called sailing "fat" and if you have telltales, they will be telling you to head up. This will mazimize the loading on the sails and hence the rig. Sail a bit high (pinching), and the rig unloads (bad for tuning), sail way too low, and the same thing happens..Just bear off a couple of degrees so the telltales NEVER indicate you are too close to the wind-and you will know you have fully loaded the rig!!

Good night and good luck!

Seth

 

[Emerald]

Hi Seth,


thanks for all your input on this. Very very helpful.


-David
Independence 31
Emerald

 

[bigtyme805]

Gotta tell you I have learned a lot from the original post I posted. The one thing that came to light for me is that I need to put on a BS adjuster. It gives me more options. With all this talk I had my boat hauled this weekend to get the bottom painted and ran into a guy who sails a 33 hunter who saw me sailing and commented if I had my motor running when I was sailing, I laughed and asked him why he said that. He stated that he came out of the channel with me and he could not catch me.

Ericson's are a good boat, and with all of the captains that participate in this site to help one another i am proud to be an owner of one.

Thanks